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Tektronix 2715 Spectrum Analyzer user manual

1. 1 250MHZ OFFSE 50 25 t 60 70 F f PRESS W 2 ite Figure 5 8 Typical or CSO Measurement Results Display NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 14 Press 4 to print the all results of the measurement A printer must be connected to the 2715 15 Press 9 to exit this mode or continue to the next measurement mode To run the CTB or CSO measurement in the Automatic mode follow these steps 1 Ifyouare taking a CSO measurement press 7 to toggle IN SERVICE basis on or off as desired 2715 User Manual Measurements 2715 User Manual 7 e UV 10 11 12 13 Press 6 1 to select Automatic mode SET UP TEST FREQUENCIES menu item 5 is added to the menu These frequencies represent points where beats are expected to occur relative to the visual carrier Press 0 and enter the first beat frequency either as an offset from the visual carrier or as an absolute frequency Press 1 and enter the second beat frequency Press 2 and enter the third beat frequency Press 3 and enter the fourth beat frequency Press 4 and ente
2. Electrical Characteristics Appendix B Broadcast AM FM and TV Signal Sources Appendix C System Appendix D Global Definitions Reset Cycle Description Reset Categories Appendix E External Input and Output Mains Power J101 TV Sideband Analyzer and External Tracking Generator Interface J102 External Trigger J103 Accessory Connector J104 Digital Communications Port Appendix F Accessories and Options Accessories Options L pTTTTTTTT Wem NNN RB NR Table of Contents List of Figures Figure 2 1 Figure 2 2 Figure 2 3 Figure 2 4 Figure 2 5 Figure 2 6 Figure 3 1 Figure 3 2 Figure 3 3 Figure 3 4 Figure 3 5 Figure 3 6 Figure 3 7 Figure 3 8 Figure 3 9 Figure 4 1 Figure 4 2 Figure 5 1 Figure 5 2 Display with Factory Default Power Up Settings Normal On Screen Data Readouts Typical Measurement Result Display The Primary Calibrator Signal and Harmonics Calibrator Signal Fundamental Layout of the Text Screen in the Spectral Display Mode Layout of the Text Screen in the Menu Display Mode The Frequency Marker Function Block Fundam
3. v es sw CATV APPL CATV Measurements Page 2 Menu Structure OOO ot DEMOD DSPL USER DEF INPUT 0 ADJACENT CHANNEL LEAKAGE 1 VIEW MODULATION FIELD 2 VIEW MODULATION LINE 3 VIEW PICTURE 4 LISTEN 5 CTB 6 CSO 7 CROSS MODULATION 0 RUNCROSS MODULATION 8 IN CHANNEL RESPONSE 1 STORE CURRENT RESULTS 9 MORE 4 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS 4 PRINT STORED RESULTS 5 METHOD FREQUENCY DOMAIN or TIME DOMAIN NCTA __ To CATV APPL 9 LEAVE CROSS MODULATION CATV Measurements Page 1 0 RUN IN CHAN RESP 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS 4 PRINT STORED RESULTS 5 SETUP IN CHAN RESP TEST MODES 6 TEST SIGNAL LINE NUMBER 0 INTERACTIVE 7 IN SERVICE 1 AUTO PAUSE FOR SIGNAL ON 9 LEAVE IN CHAN RESP TEST FREQUENCIES amp 2 User Defined 500 000KHZ Default RS 232 only 3 User Defined 500 000KHZ Default Displayed only when IN SERVICE is On 4 User Defined 1 25000MHZ Default 5 User Defined 42 00000MHZ Default 6 User Defined 43 00000MHZ Default 7 User Defined 3 75000MHZ Default 8 USE DEFAULT TEST FREQUENCIES TEST MODES IN SERVICE 0 INTERACTIVE 1 AUTO TEST FREQUENCIES User Defined 500 000KHZ Default User Defined 500 000KHZ Default User Defined 1 25000MHZ Default User Defined 2 00000MHZ Default User Defined 3 00000MHZ Default User Defined 3 75000MHZ Default USE DEFAULT TEST FREQUENCIES CO
4. 0 1 5 ACCURATE FREQUENCY AND AMPL ACCURATE AMPLITUDE ONLY FAST AMPLITUDE ONLY ON OFF ATTEN AMPL ENTRY VIEW MODULATION MODE TARGET LINE CYCLE DELAY TARGET LINE DURATION TEST MODES INTERACTIVE AUTO MEASUREMENT TIME 2715 User Manual Operating Basics MENUSI CATV SWP TRIG UTIL MKR FREQ APPL DEMOD DSPL USER DEF INPUT CO Un gt C r2 RECENTER CHANNEL xx CARRIER LEVEL AVG POWER CARRIER SURVEY MODULATION DEPTH AURAL FM DEVIATION CARRIER NOISE DESIRED UNDESIRED HUM LFD FREQUENCY RESPONSE CATV MEASUREMENTS SETUP MORE CATV APPL CATV Measurements Page 1 Menu Structure 2 of 3 0 RUN C N D U 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS 4 PRINT STORED RESULTS 5 SETUP CARRIER NOISE TEST MODES 0 INTERACTIVE 7 IN SERVICE 1 AUTO 9 LEAVE C N D U 2 AUTO PAUSE FOR CARRIER OFF 5 NOISE NORM D BW RUN HUM LFD STORE CURRENT RESULTS DISPLAY RESULTS PRINT CURRENT RESULTS PRINT STORED RESULTS POWER LINE FREQ Cn gt r2 9 LEAVE HUM LFD 0 RUNFREQ RESP CURRENT REFERENCE 5 SETUP FREQ RESP TEST MODES 0 REF 9 LEAVE FREQUENCY RESPONSE 1 WITH REF SWEEP RANGE 2 START FREQUENCY 3 STOP FREQUENCY 4 USE DEFAULT START STOP RS 232 only TEST MODES 0 NO REF 1 WITH REF REFERENCE ACQUISITION START FREQUENCY
5. penr goora Figure 6 16 Video Signal Using Continuous Horizontal Line Triggering 2715 User Manual Spectrum Analyzer Menus 2715 User Manual 9 Call up the SETUP TABLE again and choose item 1 KNOB SELEC TABLE 10 Return to the spectral display The tuning knob now controls which pulse is used Pulses are numbered from 1 to 1023 The current line number horizontal video line number and sync pulse number are the same is displayed at the bottom of the right on screen column If more than one sync pulse is displayed the number is that of the pulse nearest the left edge of the screen Turning the knob clockwise increases the line number and counter clockwise decreases it 11 Turn to about line 17 to view several lines including the vertical interval test signal VITS This signal is usually present between lines 15 20 in the U S see Figure 6 17 The display is not as bright as it was in the CONTINUOUS mode because the 2715 is triggering on and displaying only one horizontal line out of every 525 If the display is too dim adjust the INTENSITY control 100 F REF 55 2 4 ATTN 10DB 24 ADBMV VF 10 20 US ZSPAN 1 65MV 7 5MHZ RBW T 20 30 5 40 T 50 2 ES d 60 70 L RE 0 N G eti dB Figure 6 17 Video Signal Using Knob Selectable Horizontal Line Trigger
6. INPUT Menu Structure d WW U92 O9 Ww ede T N 3 21 Table of Contents Dedicated Controls Dedicated Controls 0 cece E c ec eee eee eee eens 4 1 Fundamental Operations 0 0 0 eee ee ete 4 1 SPAN DIV a a areca DEM CIN IERI 42 Frequency Entry Normal 4 5 Frequency Entry NonCATV Mode 4 7 RBEBELBVElLzJjnu E M we 4 9 Enhanced Versatility cec ce Ce BA he o eR RAEN EGRE 4 11 ResBW Lei VERREM ERU ee 4 11 Nideo E aie E E E E texte clad ace 4 14 Vert Scale oU CR CC E GU NE AER CN MS 4 16 SWEEP cei R ee eee ad Ae ease Aa ES CMS 4 17 I evelu i aser Lcid UT 4 20 Display Storage slc LER a ha EGER HERE E ER 4 20 Freq Mkrs s al ea NA eee da ad eee ah 4 26 Miscellaneous Controls 4 33 CATV Measurements CATV Measurements 5 1 Preliminary Information 5 1 General CATV 2715 Mode eens 5 4 CARRIER LEVEL and AVERAGED POWER Measurement 5 20 CARRIER SURVEY Measurement 5 25 MO
7. When the measurement is initiated the instrument does the following m Enables peak acquisition mode W Sets the reference level so that the peaks of the detected test signal are placed in the top major division while the instrument is in the 10 dB div mode W Sets the vertical mode to 1 dB div m If measuring on in service basis enables gating on the specified TV line and performs a slow sweep In interactive mode the instrument prompts you to move the marker to the first location for example the lowest detected burst packet in a Multiburst signal and press W to make the first measurement Then the instrument prompts you to move the marker to the second location for example the highest detected burst packet and press W to make the second measure ment The instrument then calculates the difference between the two 5 63 Measurements 5 64 Interactive Mode Automatic Mode measurements divides the difference by two and presents the quotient as the measurement result The previous example used a Multiburst test signal If the test signal is Line Sweep the procedure is the same with the marker positioned on the highest point in the detected sweep and then on the lowest point or vice versa For this mode the IN CHANNEL RESPONSE is measured at two locations that are chosen by placing a marker at the lowest point in the channel response and taking a measurement then moving the marker to the highest
8. 50 iF 40 50 Figure 5 6 Typical Frequency Response Display Without Reference The instrument returns to the spectral display Note that the FREQUENCY RESPONSE menu is still active If you press CATV APPL the FREQUEN CY RESPONSE menu will be displayed A more definitive display is acquired by comparing the result to a known reference Item 5 in the FREQUENCY RESPONSE menu lets you acquire this reference A reference may be taken at the head end and stored to compare with data taken at any point along the transmission line Storing this data also allows periodic checks over time at the same point To acquire a frequency response reference perform the following steps 1 Press CATV APPL 5 to call up the FREQ RESP SETUP menu 2 Press 1 to select the WITH REF test mode 5 45 Measurements 3 Enter the start and stop frequencies as follows Note that the default start frequency is the visual carrier for the lowest unskipped channel in the selected channel table and the default stop frequency is the visual carrier for the highest unskipped channel in the selected channel table a Ifthe default start stop frequency range is adequate for your measure ments press 4 to select it and go directly to step 4 b Press 2 and enter a start frequency with the keypad c Press 3 and enter a stop frequency with the keypad 4 Pre
9. Measurements 5 26 This gives you the following options 0 RUN CARRIER SURVEY AMPL FAST AMPL FREQ AMPL 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 SET UP CARRIER SURVEY 6 EXTERNAL ATTEN AMPL 9 LEAVE CARRIER SURVEY In this example the accurate amplitude measurement mode ACCUR AMPL is selected see menu item 0 3 Press 5 to select a different measurement mode This displays the TEST MODES submenu with following menu choices 0 ACCURATE FREQUENCY AND AMPL 1 ACCURATE AMPLITUDE ONLY 2 FAST AMPLITUDE ONLY 4 Press 0 to select ACCURATE FREQUENCY AND AMPL FREQ AMPL Note that the asterisk moves to that selection in the menu indicating that it 1s the current selection The CARRIER SURVEY measurement modes are identical to those for CARRIER LEVELS and are described in Carrier Levels Measurement earlier in this section To reduce the run time you may want to tag unwanted channels for omission skipping from the survey To use the Skip Channel selection you must select a channel and then go into the setup menu and mark the channel for skipping The following sequence demonstrates the steps that must be followed to skip channels 1 Press any menu button to acquire a spectral display 2 Select a channel 3 Press CATV APPL 8 2 to skip the selected channel Another way to skip channels is through the
10. 5 56 To run the or CSO measurement in the Automatic mode with Pause for Carrier Off follow these steps NOTE Automatic mode with Pause for Carrier off is not available if the in service CSO measurement basis is selected 9s wm ce 10 11 12 13 Press 5 2 to select the Automatic mode with Pause for Carrier Off The SET UP TEST FREQUENCIES menu item 5 is added to the menu These frequencies represent points where beats are expected to occur relative to the visual carrier Press 0 and enter the first beat frequency either as an offset from the visual carrier or as an absolute frequency Press 1 and enter the second beat frequency Press 2 and enter the third beat frequency Press 3 and enter the fourth beat frequency Press 4 and enter the fifth beat frequency Press 5 to use default frequencies Press BKSP BKSP 0 to run the measurement The instrument measures the visual carrier peak for a reference then prompts you to turn off the carrier Turn off the carrier and press W to continue or Z to abort the measure ment over the spectral display The instrument measures the beats within 100 kHz on either side of each frequency then displays the worst case result with the spectral display Press CATV APPL to display the CTB or CSO menu Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE
11. Press DSPL to return to the spectral display The alarm should be sounding 6 41 Spectrum Analyzer Menus Activating Minimum Hold 6 42 14 Select the LIMIT DETECTOR once again The status indicator changes to OVER UNDER The display line becomes an upper limit and the threshold set using the MKR FREQ 0 becomes a lower limit 15 Press DSPL to return to the spectral display The limits are indicated by the broken horizontal line If signals are within the limits no alarm sounds The alarm will sound if all signals fall below the lower limit or if one signal exceeds the upper limit The limit detecting features are very useful for go no go or yes no type tests They are especially useful for doing vehicular leakage surveys of cable television facilities Set the display line to the desired number of dBUV m and when the alarm sounds note the location and magnitude using the marker readout of the leak for later investigation and correction Further the display line limit detector feature converts the user definable command WAIT FOR END OF SWEEP to a WAIT FOR LIMIT command see USER DEF on page 6 89 This is a handy way to halt the execution of a user defined routine until the alarm condition has been satisfied If you change the reference level while using the display line limit detector feature the line changes position on screen to track the new reference level Press next to REF LEVEL to observ
12. 2 dB at 1000 MHz Note 2 Note 1 Approximate extended limits if is used and mixer input evel is set to 20 dBm Note 2 Normal limits without preselector and mixer input level set to default setting of 30 dBm in a 60 channel flat system Specifications 90 80 10 60 4 dB to 500 MHz Note 1 2 dB to 500 MHz Note 1 CSO Measurement Limit dBc 50 Minimum signal level for gated 4 dB to 500 MHz Note 2 t at 1000 MH aol eee 2 2 dB to 500 MHz Note 2 inimum signal level for gated measurement to 500 4 dB at 1000 MHz Note 2 2 dB at 1000 MHz Note 2 ote 1 Approximate extended limits if preselector is used and mixer Input level is set to 20 dBm Note 2 0 Normal limits without preselector 30 20 10 0 10 20 30 40 50 60 70 and mixer input level set to default setting of 30 dBm in a 60 channel VISUAL CARRIER PEAK dBmV flat system Figure A 3 Typical Accuracy Limits for Nongated CSO Measurement 90 80 T0 cso 9 4 dB to 500 MHz Note 1 Measurement Limit dBc 50 2 dB to 500 MHz Note 1 Minimum signal level for gated measurement at 1000 MHz 4 dB to 500 MHz Note 2 40 S 2 dB to 500 MHz Note 2 inimum signal level for gated measurement to 500 4 dB at 1000 MHz Note 2 30 2 dB at 1000 MHz Note 2 ote 1 Approximate extended limits if preselector is used
13. 4 6 3 Press SPAN DIV 1 0 0 X to set the span to 100 MHz div 4 Press REF LEVEL 3 8 e 8 Y to set the reference level to 38 8 dBmV 5 Press RES BW AUTO 6 Turn the FREQ MKRS knob a few clicks clockwise Each click of the knob increases the center frequency by 2 0 MHz 7 Turn the FREQ MKRS knob counterclockwise and the center frequency decreases by the same amount 8 Reduce the span to 20 MHz div 9 Turn the FREQ MKRS knob a few clicks clockwise The spectral display appears to move sideways at about the same rate as it originally did However it is now moving only 0 4 MHz per click We call this visual behavior constant rate tuning It occurs because the knob normally changes the center frequency at 0 02 of the span div per click Obviously it would take 250 clicks to change the frequency by 100 MHz at 20 MHz div The knob remains active whenever the 2715 is in the spectral display mode Arrow Keys The arrow keys can also be used to change the normal center or start frequency as discussed in the following example 10 Press adjacent to CHAN FREQ The frequency changes by channel allocation width of the currently selected channel table 6 MHz for the STD HRC and IRC channel tables If you had previously selected a channel by entering a frequency value that is not centered about the channel allocation width the first increment will move the center frequency to the center of the next c
14. NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer 12 Press 3 to print results of the last measurement performed A printer must be connected to the 2715 13 Press 4 to print all stored results of the measurement a printer must be connected to the 2715 The following auxiliary operations involve viewing a display Each selection toggles the desired display on and off Press 9 repeatedly until page 2 of the CATV MEASUREMENTS menu CATV MEASUREMENTS PG 2 is displayed Note the following items in the menu 1 VIEW MODULATION FIELD 2 VIEW MODULATION LINE 3 VIEW PICTURE 4 LISTEN These features are selected by pressing the number that applies to each and deselected by pressing the same number or pressing a number that applies to another feature This operation allows you to view a full field of baseband modulation in the analog mode This operation is not available for FM DATA and PILOT signals If this current channel has scrambling on as specified in the channel table you are prompted to turn off scrambling before proceeding The needed trigger modes will not work with scrambling When the operation is invoked the 2715 tunes to the visual carrier and enables the 1 MHz resolution bandwidth filter and zero span
15. 100 mW On the other hand if you have a very weak signal you may need to amplify it 22 Press CATV APPL to enable the CATV mode 23 Ensure the calibrator is turned off 24 Press INPUT to call up the Input menu Item 6 indicates that there is presently no external attenuation or amplifica tion 25 Press 6 to call up the external attenuation and amplification selections 26 Press 1 to allow you to input an attenuation value Suppose you have attenuated an RF transmitter output 40 dB prior to measuring it 27 Following the on screen prompts press 4 0 Z 2715 User Manual Spectrum Analyzer Menus Accommodating a 50 2715 User Manual Source 28 29 30 31 32 This procedure enters an external attenuation value of 40 dB The spectral display does not change but the reference level now indicates 58 dBmV and is followed by the term OFST This indicates that the reference level has been offset in this case by 40 dB Any reference level now entered is offset automatically by the external attenuation or gain Press INPUT 6 Item 0 indicates that the offset is turned on Press 0 to turn off the offset The spectral display will reappear but OFST is gone Press INPUT 6 0 to toggle the offset back on without reentering the external attenuation value Turn off the offset Enter a value of 0 dB for external attenuation The 2715 has a 75 Q input impedance and expects a
16. 11 12 13 14 Choose item 1 from the MKR FREQ menu The Programmed Tuning Increment menu appears Programmed tuning increments can be designated by the center or start frequency the marker or delta marker frequency or numeric keypad entries The current center frequency is approximately 300 MHz as would be the start frequency if you placed the 2715 in that mode Press 0 to select the center frequency as the tuning increment The spectral display reappears Turn the FREQ MKRS knob one click clockwise The frequency is changed 300 MHz Reset the center frequency to 300 MHz Turn on the marker Position the marker at 150 MHz Select item 1 from the MKR FREQ menu Now choose item 1 currently MARKER FREQ from the Programmed Tuning Increment menu to select the marker frequency as the tuning increment Turn off the marker and turn the FREQ MKRS knob one click The frequency should change 150 MHz Reset the frequency to approximately 300 MHz Turn on the marker and position it on the calibration signal fundamental at 100 MHz Enter the delta marker mode and place the movable marker on the second harmonic at 200 MHz From the Programmed Tuning Increment menu select item 1 which now reads DELTA MKR FREQ 2715 User Manual Spectrum Analyzer Menus 15 Turn off the markers and turn the FREQ MKRS knob one click The frequency now changes by one harmonic 100 MHz per click When making distortion measu
17. 6 50 Measuring Signal Bandwidths 6 44 Searching For Signals 6 48 Viewing Instantaneous Frequency Deviation 6 54 Arrow Keys 2 8 2 15 Channel Entry 4 4 CTR MEAS TRKG 4 32 Frequency Entry NonCATV Mode 4 7 Frequency Entry Normal Mode 4 6 Reference Level Operation 4 9 RES BW 3 9 4 12 SPAN DIV 4 2 SWEEP 3 9 4 17 Attenuation Amplification External 6 6 AURAL FM DEVIATION Measurement 5 32 Enable AURAL FM DEVIATION Measurement 5 34 AUTO 3 9 RES BW 3 9 4 13 SWEEP 3 9 Auto Res BW 4 13 Automatic Mode 5 64 Auxiliary Operations 5 68 Line Modulation 5 69 2715 User Manual Listen 5 70 View Modulation Field 5 68 View Picture 5 69 Average Noise Measuring 6 45 AVERAGE POWER Measurement 5 20 B C MINUS A See Subtracting Stored Signals Backspace Key 3 6 Built in Speaker 2 10 C Calibrator Built in 2 10 Calibrator Turning On and Off 6 4 CARRIER LEVELS Measurement 5 20 CARRIER SURVEY Measurement 5 25 Carrier to Noise Ratios Measuring 6 46 CATV Measurement Results Files 6 76 CATV Measurements ADJACENT CHANNEL LEAKAGE Measurement 5 47 AURAL FM DEVIATION Measurement 5 32 AVERAGE POWER Measurement 5 20 CARRIER LEVELS Measurement 5 20 CARRIER SURVEY Measurement 5 25 CROSS MODULATION Measurement 5 60 CTB CSO Measurement 5 49 Desired to Undesired Measurement 5 35 FREQUENCY RESPONSE 5 43 General CATV 2715 Mode 5 4 HUM LFD Measure
18. Auto Test Locations items 2 through 8 are added to the menu These locations are points relative to the visual carrier where measurements are to be made Press 2 and enter the first measurement location Press 3 and enter the second measurement location Press 4 and enter the third measurement location Press 5 and enter the fourth measurement location Press 6 and enter the fifth measurement location Press 7 and enter the sixth measurement location Press BKSP 0 to run the measurement If measuring in service the instrument measures the visual carrier peak for a reference then enables gating on the specified TV line and measures the test signal amplitudes at the specified frequencies If measuring on the normal basis the instrument pauses and prompts you to switch to the appropriate full field test signal before continuing It then measures the visual carrier peak and the test signal amplitudes Press CAT V APPL to display the INLCHANNEL RESPONSE menu Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed Press 2 to display the results of the last measurement performed A display resembling Figure 5 8 on page 5 54 appears You can view other previously stored results by pressing W or stop viewing the results by pressing Z 5 67 Measurements Auxiliary Operations View Modulation Field 5 68
19. Do not physically abuse the spectrum analyzer It can withstand a fair amount of rough handling but dropping it off a workbench or bouncing it around the trunk of a car or the back of a truck may cause damage Protect the instrument while transporting it and use it where it cannot be accidentally hit kicked or dropped W Provide proper ventilation 2715 User Manual 2 3 Getting Started A System Checkout Turning On the Spectrum 2 4 Analyzer CAUTION To prevent damage from over heating you must ensure that the clearance provided by the feet is maintained on the bottom and that there are at least 2 in 50 80 mm of clearance around the other sides DO NOT block the air intake areas on the sides bottom or the exhaust area at the rear Never operate the instrument inside a carrying case After you have observed the foregoing precautions you are ready to perform the initial system checkout Checkout consists of normalizing the spectrum analyzer and then measuring the frequency and amplitude of the built in calibration source In the process you will become acquainted with the front panel and the display Before applying power make sure there is no signal source connected to the spectrum analyzer 1 Plugin the power cord 2 Press the POWER switch The green LED adjacent to the power switch lights indicating that power is turned on The LED indicators flash and you hear a few beeps as the 2715 performs
20. Index F Factory Default Settings 2 4 2 6 Field Triggering TV Video 6 88 File System 6 75 Antenna Table Files 6 76 CATV Measurement Results Files 6 76 Channel Table Files 6 76 Curve Files 6 76 Flatness Correction Data Files 6 76 Normalization File 6 76 Settings Files 6 76 User Defined Program UDP Files 6 76 Files Protection 6 77 First Mixer Input Level Setting 6 8 Flatness Correction Data Files 6 76 FM Deviation See Frequency Deviation Viewing FM DEVIATION Measurement See AURAL FM DEVIATION Measurement FM Transmissions Listening to 6 56 FM VOL 3 8 FREQ MKRS 3 3 4 5 4 26 MKR Delta OFF 4 26 Frequency Corrections On and Off 6 73 Frequency Deviation Viewing 6 54 Frequency Entry Non CATV Mode Keypad Entry 4 8 Frequency Entry NonCATV Mode 4 7 Arrow Keys 4 7 Frequency Entry Normal Mode 4 5 Arrow Keys 4 6 FREQ MKRS 4 5 Keypad Entry 4 7 Frequency Measurement Process 2 13 Frequency Offsets 6 26 FREQUENCY RESPONSE Measurement Acquire a Frequency Response Reference 5 45 Enable FREQUENCY RESPONSE 5 44 FREQUENCY RESPONSE 5 43 Mode 1 5 43 Mode 2 5 43 Function Blocks 2 8 Fundamental Controls 2 8 Fundamental Operations Channel Entry 4 4 Frequency Entry NonCATV Mode 4 7 Frequency Entry Normal Mode 4 5 REF LEVEL 4 9 SPAN DIV 4 2 2715 User Manual G General CATV 2714 Mode Channel Tables 5 6 5 10 Selecting a Chann
21. Specifications Table A 3 Frequency Amplitude Related Characteristics Cont Characteristic Performance Requirement Center Measure Supplemental Information When activated the signal nearest center screen or nearest marker if marker is on and above a preset threshold level is moved to center screen The frequency and amplitude values are preceded by the letter C Readout Resolution 1kHz or 1Hz Readout resolution is selectable Signal Tracking Table A 4 Amplitude Related Characteristics Characteristic Performance Requirement Vertical Display Mode Reference Level Range Log Mode Linear Mode Steps Log Mode Linear Mode FINE REF LVL STEP Activated When activated the centered signal is held at center screen Signal tracking requires a signal strength greater than the threshold level If the strength of a signal being tracked decreases below the threshold level the instrument displays the message NO SIGNAL FOUND ABOVE THRESHOLD Supplemental Information 10 dB div 5 dB div 1 dB div and Linear Top of graticule 21 2 dBmV to 468 8 dBmV 41 2 dBmV to 448 8 dBmV with the PREAMP enabled 10 83 uV div to 342 33 mV div 1 08 nV div to 34 23 mV div with the PREAMP enabled 1dB or 10 dB 1 2 5 sequence 10 83 uV div to 342 33 mV div 20 2 division per increment Accuracy Dependent on m Normalizations m Calibrator accuracy m Frequency response A 14 2715 User Manual Spe
22. The 2715 then finds and centers the peak of the visual carrier and places it at the reference level The display storage and readouts are turned off and short holdoff is selected for an analog display The 2715 sets the sweep time to 2 ms div and the trigger mode to TV Field trigger 2715 User Manual Measurements Line Modulation View Picture 2715 User Manual To view field modulation press 1 The center frequency is set to the visual carrier frequency of the selected channel zero span is enabled the sweep rate is set to 2 ms division the resolution bandwidth is set to 1 MHz and the readouts are turned off You should see at least one field of the video signal This operation allows you to view one line of demodulated video for the current channel in the analog mode The setup is the same as for field modulation except that the 2715 sets the sweep time to 10 us div and the trigger mode to TV Line trigger The line to trigger on is set to the VITS line specified in the channel table If no VITS line is specified then line 17 is selected The FREQ MKRS knob is assigned to video line This lets you select the line to trigger on Thus you can display any line in the field for viewing by using the knob To view line modulation press CATV APPL 2 The center frequency is set to the visual carrier frequency of the selected channel zero span is enabled the sweep rate is set to 10 us division the resoluti
23. Un gt 3 18 2715 User Manual Operating Basics MENUS SWP TRIG MKR FREQ CATV APPL DEMOD DSPL USER DEF INPUT BANDWIDTH MODE CARRIER TO NOISE NOISE NORM D SIGNAL SEARCH MENU OCCUPIED BW gt QU MJ C FM DEVIATION MODE CATV MEASUREMENT MODE 9 SETUP TABLE IMENUS CATV A SWP TRIG UTIL MKR FREQ APPL DEMOD DSPL USER DEF INPUT OFF AM DEMODULATOR FM DEMODULATOR BROADCAST AM VIDEO C29 c 9 VIDEO MONITOR SETUP 2715 User Manual CATV APPL Applications Menu Structure BEGIN FREQ END FREQ START TEST DISPLAY RESULTS c DB DOWN FOR BW MODE NORM BW FOR C N NOISE NORM D BW PERCENT OCCUPIED BW MJ c DEMOD Menu Structure 0 VIDEO DETECT MODE 1 SYNC POLARITY 2 VIDEO POLARITY 3 19 Operating Basics MENUSI SWP TRIG UTIL MKR FREQ rod DSPL Menu Structure DEMOD DSPL USER DEF INPUT 0 DIGITAL ANALOG 1 ENSEMBLE AVERAGING 1 INITIATE AVERAGING 2 B CMINUSA 2 TERMINATE AVERAGING 3 B C MINUS A OFFSET TO 3 MAX 4 ACQUISITION MODE 4 MEAN 5 TITLE MODE 5 MIN 6 GRATICULE ILLUMINATION 6 MAXMIN 7 DISPLAY SOURCE AM 7 NUMBER OF AVERAGES 8 DISPLAY LINE 8 SAVE RESULTS IN DISPLAY 9 MIN HOLD 1 TITLE MODE 2 TITLE MODE EDIT 3 PLOTLABELING 4 PLOT LABELING EDIT 1 ON OFF 2 VALUE ENTRY 3 DISPLAY LINE TO MARKER 4 LIMIT DETECTOR IMENUS SWP TRIG UTIL MKRIFREQ AP
24. COMMUNICATION PORT CONFIG SCREEN PLOT CONFIGURATION PRINTER CONFIGURATION INSTRUMENT CONFIGURATION REAL TIME CLOCK SETUP STORED SETTINGS PROTECT FILE SYSTEM DIRECTORY PROTECT FILE Un gt CJ r2 9 INSTALLED OPTIONS DISPLAY Expands to registers 10 18 20 28 and 30 39 0 AUTO 1 FIXED AUTO FIXED rA LOG 1DB DIV LOG 5 DB DIV LOG 10 DB DIV LINEAR LP c 0 GPIB 2 RS 232 c COMM PORT PLOTTER LANGUAGE PLOT SPEED PLOTS PER PAGE CJ c Cn GRATICULE LINES ON PLOT AUDIO ALERT MINIMUM SIGNAL SIZE WAVEFORM TO PRINTER WAVEFORM OUTPUT FORMAT PHASELOCK FREQUENCY CORRECTIONS SPECTRAL DISPLAY IN MENUS SWEEP HOLDOFF Un gt QU L2 SET DAY SET MONTH SET YEAR SET HOUR SET MINUTE SET SECONDS TO 00 DISPLAY DATE TIME CO Un gt L2 Displayed when selected plotter language is HPGL PUNEO STATUS GPIB ADDRESS POWER ON SRQ EOI LF MODE TALK ONLY MODE STATUS BAUD RATE DATA BITS PARITY EOL FLOW CONTROL ECHO VERBOSE 2715 User Manual Operating Basics MENUSI SWP TRIG UTIL MKR FREQ EPL UTIL Menu Structure CJ 2 of 2 DEMOD DSPL USER DEF INPUT 1 STORED SETTINGS DISPLAYS 2 KEYPAD ENTERED SETTINGS 3 NORMALIZATIONS 4 SYSTEM CONFIGURATION 5 INSTR DIAGNOSTICS ADJ USTMENTS 0 DIAGNOSTICS 6 SERVICE
25. Figure 3 5 The Keypad Numeric keys are used to enter numerical values in the immediate entry mode or in response to menu prompts They are also used to select the numbered items from menus The terminator keys signify the end of an entry and supply the appropriate units for the entry They are context sensitive if you press X the spectrum analyzer automatically interprets it as MHz ms or mV depending on the parameter being entered The dot key supplies the decimal point in numeric entries and can be used as a period in label and title entries The backspace key erases the last character pressed in data entry modes and backs up one menu level when menus are active DISPLAY STORAGE HOLD ENABLE OSPR ROH Figure 3 6 Display Register Control Pressing A B C or D when SAVE ENABLE is not armed turns its respective register on and off for display When the register is displaying data saved or current the red LED to the lower right of the key is lighted When SAVE ENABLE is armed press A B or C to store the current sweep if the register is cleared or clear the register if it contains saved data 2715 User Manual Operating Basics SAVE ENABLE MAX HOLD A amp B VERT SCALE 2715 User Manual PLOT The saving or clearing action occurs whether the register is displaying data or not The green LED to the lower left of the key lights when the register contains
26. IN SERVICE CSO ONLY LEAVE CTB or CSO 0 RUN CTB or CSO 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 SET UP CTB or CSO 6 DIGITAL ANALOG 7 9 2715 User Manual Measurements 2715 User Manual To run the CTB or CSO measurement in the Interactive mode follow these steps 2 If you are making a CSO measurement press 7 to toggle IN SERVICE basis on or off as desired Press 5 0 to select the Interactive mode Press BKSP 0 to run the measurement The instrument measures the visual carrier peak then prompts you to move the marker to the first beat If you are using the CSO in service basis in the interactive mode the instrument first finds quiet lines if none were specified in the channel table Then the algorithm that performs the earnest beat amplitude measurements will reset the RF attenuator preamp combination to appropriate settings The algorithm has its own means of adequate averaging for the measurement Press CAT V APPL 6 to enable the Analog display with short holdoff since it might be easier to visually detect beats in the analog mode Turn the FREQ MKRS knob to place the first beat on a graticule line Make a note of this graticule line Press CAT V APPL 6 to enable the Digital display and move the marker to the graticule line noted in the preceding step Press W to continue with the meas
27. STOP FREQUENCY USE DEFAULT START STOP ACQUIRE NEW REFERENCE STORED REFERENCE MENU EDIT CURRENT REFERENCE NAME LO Un Displayed only if a reference has been acquired 2715 User Manual 3 15 Operating Basics es CATV APPL CATV Measurements Page 1 Menu Structure 3013 DEMOD DSPL USER DEF INPUT RECENTER CHANNEL xx CARRIER LEVEL AVG POWER CARRIER SURVEY MODULATION DEPTH AURAL FM DEVIATION CARRIER NOISE DESIRED UNDESIRED HUM LFD FREQUENCY RESPONSE CATV MEASUREMENTS SETUP MORE 34 VU lt CATV APPL CATV Measurements 2 2 Option 50 and Option 75 only 3 16 EXIT CATV MEASUREMENT MODE CHANNEL TABLE SKIP CHANNEL ALL CHANNELS SITE OPERATOR REF LEVEL UNIT EDIT CHANNEL TABLES REMOVE ALL STORED RESULTS LEAVE CATV MEASUREMENTS SETUP CO Un gt CU E23 STD HRC IRC User Defined User Defined User Defined User Defined User Defined User Defined User Defined 2715 User Manual Operating Basics MENUSI SWP TRIG UTIL DEMOD CATV MKR FREQ APPL CO Un gt CU CATV APPL CATV Measurements Page 2 Menu Structure 1 of 2 DSPL USER DEF INPUT ADJACENT CHANNEL LEAKAGE 0 RUN ADJACENT CHANNEL LEAKAGE VIEW MODULATION FIELD 1 STORE CURRE
28. The acquisition mode must be exited before any routine can be activated FUNC NOT AVAIL ON THIS CHAN TYPE A function was invoked on a signal which the channel table thinks is of an inappropriate type to be performed on this signal FUNCTION NOT AVAIL IN LIN MODE Switch to LOG mode vertical scale to obtain proper functioning This error message may appear upon the invocation of instrument functions such as carrier to noise noise normalized bandwidth and antenna correction factors FUNCTION NOT AVAIL IN MAX SPAN Signal track mode incompatible with MAX SPAN Try smaller span ILLEGAL COMMAND Firmware error Contact your local Tektronix service center or representative if message persists ILLEGAL PARAMETER PASSED Firmware error Contact your local Tektronix service center or representative if message persists ILLEGAL START STOP INC VALUES Illegal Start Stop or Increment values are present for the antenna correction factor table the user is attempting to edit Either the initial non usable values are present the user has not attempted to enter his own values or the values entered have some inconsistency such as the start value being greater than the stop value 2715 User Manual Appendix System Messages 2715 User Manual INACTIVE MARKER OFF SCREEN The frequency value of the inactive marker has been retained The marker itself is out of the range of the display and is not visible INSUFFICIENT MEMORY AVAILABLE Not
29. The width of the narrowest filter in the IF stages of a spectrum analyzer The RBW determines how well the analyzer can resolve or separate two or more closely spaced signal components Save A function which inhibits storage update saving existing data in a section of multiple memory for example Save A 2715 User Manual Glossary Scanning Spectrum Analyzer See heterodyne spectrum analyzer Scanning Velocity Frequency span divided by sweep time and expressed in hertz per second Secondary Marker The second marker displayed only in the Delta Marker mode Sensitivity Measure of a spectrum analyzer s ability to display minimum level signals expressed in volts or decibels Internal frequency IF bandwidth display mode and any other influencing factors must be given Shape Factor Skirt Selectivity The ratio of the frequency separation of the two 60 dB 6 dB down points on the response curve to the static resolution bandwidth Single Sweep Operating mode in which the sweep generator must be reset for each sweep Especially useful for obtaining single examples of a signal spectrum Signal Identifier A means to identify the spectrum of the input signal when spurious responses are possible Span Per Division Span Div Frequency difference represented by each major horizontal division of the graticule Spectrum The frequency domain representation of a signal wherein it is represented by displaying its frequen
30. This method provides a visually intuitive approach to span control enabling you to designate only that portion of the displayed spectrum that is of particular interest 8 Turn on the marker and place it just to the left of the calibration signal harmonic at 300 MHz 6 17 Spectrum Analyzer Menus 9 Enter the delta marker mode and place the active marker just to the right of the harmonic at 400 MHz 10 Select item 6 MARKER START STOP from the Marker Frequency menu The spectral display reappears and brackets the calibration signal third and fourth harmonics The marker start stop selection automatically adjusts the starting frequency of the display and the span div so that what is displayed is what was between the markers If you are not in the delta marker mode when you select MARKER START STOP the 2715 will enter zero span at the current center or marker frequency 11 Turn off the markers Notice that the resolution BW has also changed in response to the changed span div because RES BW was in AUTO mode Transposing Markers 300 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF WIDE 50 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR Suppose you want to measure the difference in frequency between the peaks at 300 MHz and 500 MHz and between 500 MHz and 200 MHz The following steps show how to make these measurements 12 Enter marker mode and position the marker on the 300 MHz peak 13 Enter delta marker mode and place the active
31. X to set the center frequency to 100 MHz 3 Press SPAN DIV 2 0 X to set the span div to 20 MHz 4 Press REF LEVEL 3 8 8 Y to set the reference level to 38 8 dBmV 5 Press INPUT 9 to enable the calibrator 6 Press AUTO to set the resolution bandwidth to 5 MHz 7 Press MKR A OFF twice to disable the markers Arrow Keys Until now resolution bandwidth has been left in the AUTO mode which enables you to make measurements without worrying about where the resolution bandwidth is set The 2715 s default is a fixed resolution bandwidth of 300 KHz AUTO mode is available but it is not the normal operating mode There are circumstances in which you will want to control the resolution bandwidth yourself For instance if you look at the time domain representation of a TV video signal using zero span you will want to use the 5 MHz maximum bandwidth filter to ensure enough bandwidth for the video signal In other cases you may want to select a very narrow resolution bandwidth in order to resolve signal sidebands or intermodulation distortion products The RES BW arrow keys enable you to select resolution bandwidths of 300 Hz 1 kHz 3 kHz 10 kHz 30 kHz 100 kHz 300 kHz 1 MHz and 5 MHz in the 2715 It is important to know how far signals must be separated before we can see them as separate The answer depends on the particular filters bandwidths signal levels and other factors but the following rules app
32. done by keying in a permissible channel number according to the selected channel table followed by W Enter the desired channel number with the front panel keypad to select a channel NOTE In the CATV mode frequency can be entered by terminating the entry with the X Y or Z In the nonCATV mode CHAN FREQ the associated and and all the terminator keys exclusively control frequency The nonCATV mode is enabled by pressing CATV APPL 8 0 For instance to select channel 8 in the specified table do the following steps 4 Press 8 IW The numbers appear on the screen to the right of CHAN If you make a mistake correct it any time prior to pressing W by repeatedly pressing BKSP the backspace key until the incorrect number disappears and then type the correct number Pressing W ends the entry and the 2715 interprets the currently displayed value as Channel 8 The other terminators are used for channel frequency entry For example if you enter a certain frequency the displayed channel number defaults to the channel within whose limits the entry falls The frequency controls set the 2715 normal center or start frequency in the normal or CATV mode FREQ MKRS This procedure shows how to adjust the center frequency using the FREQ MKRS knob 1 Press INPUT 9 to turn on the calibration signal 2 Press 1 0 0 X to set the center frequency to 100 MHz 4 5 Dedicated Controls
33. internal memory Delete and resave the affected program PROTECTED FILE Occurs when attempting to delete a file that is protected QUERY NOT AVAILABLE Query attempted on function for which there is no query response QUIET LINE VERIFICATION FAILED The 2715 was unable to find the quiet line used to take in service Carrier to Noise and Composite Second Order measurements REAL TIME CLOCK HW FAILURE Firmware hardware error Contact your local Tektronix service center or representative if message persists REAL TIME CLOCK NOT INSTALLED 2715 cannot detect presence of real time clock REFERENCE LEVEL HAS NEW RANGE LIMITS The reference level range limits have changed because the preamp or external ATTEN AMPL mode is activated The reference level itself does not change REFERENCE NORMALIZATION FAILED Perform the reference normalization again checking for the presence of the correct external reference frequency and its correct entry from the keypad if required Contact your local Tektronix service center or representative if message persists REGISTER VALUE NOT ALLOWED A storage register value was utilized that is not legal for the requested function For example the register value 1 was used with the GPIB command STOre This attempts to store settings in the factory default power up register a reserved register REMOVE PROTECTION FIRST The selected user defined program cannot be deleted until its file protection is removed RU
34. mean minimum etc of a number of signal spectra If the nature of the signal does not change during the period over which the average is compiled the parameter being averaged rapidly approaches its mean value This results in an enhance ment of the signal to noise ratio without reducing the bandwidth or slowing the sweep speed This does not mean you cannot ensemble average continuous narrowband signals However in those cases you can also use video filtering which may prove faster and more convenient The result of the ensemble average is an estimate of the mean value of the parameter being averaged Successive estimates or averages will vary from each other in a random fashion The larger the number of sweeps averaged the more accurate an estimate of the spectral characteristic that is obtained 19 Select ENSEMBLE AVERAGING by pressing DSPL 1 The Ensemble Averaging menu appears Items 1 and 2 start and stop the averaging process The remaining items specify which values to average how many sweeps to average and where to store the result If you are going to store just the one ensemble average it makes little difference where you put it You can use registers A B or C but you cannot store the average in a register that already contains data Register D is not available because it always contains the current trace If you plan to use the stored average as a reference and perhaps intend to subtract it from other spectra you
35. the 2715 is in MAX SPAN The dedicated front panel key is provided to conveniently enter and exit this mode 11 Press MAX to obtain the largest span available on the 2715 The span div readout now indicates 150MHz MAX 4 3 Dedicated Controls 44 Channel Entry 12 Press MAX a second time to return to 20KHZ Many of the keys on the 2715 are toggle action The ability to undo an action by pushing the same button that carried out the action is typical MAX is a toggle action key taking you from the current span div to 180 MHz div and back ZERO The following example demonstrates the effects of using zero span 13 Set the center frequency to 100 MHz Notice that the calibration signal is centered in the display 14 Press ZERO The signal is a straight horizontal line In the zero span mode the 2715 remains at a fixed frequency What you see is the variation in time of the signal power coming through the RBW filter at that frequency Since the calibration signal has constant amplitude the display is constant 15 Turn the FREQ MKRS knob to slowly increase the center frequency The signal amplitude decreases and the noise increases as you tune away from the calibration signal The noise generated internally by the 2715 has a time varying random amplitude In the zero span mode the 2715 does not sweep the frequency spectrum Rather the local oscillator remains at a fixed frequency so that the resolution bandw
36. 00MHZ n M 181 27MH2 68 8DBMV M 9 6DBMVo 600 0KHZ E 10 DB 7 300KHZ RBW i STD CH 8 i 10 dB T 30 50 40 Noise Floor 600 kHz Figure 2 1 Display with Factory Default Power Up Settings The displayed spectrum represents the noise floor of the spectrum analyzer The noise floor is the amplitude of the noise generated internally by the spectrum analyzer itself and passed through the resolution bandwidth filter Narrowing the resolution bandwidth lowers the noise floor because noise power is directly proportional to the resolution bandwidth The noise appears as a thick irregular band across the bottom portion of the screen To achieve this appearance digital display storage is used The unique max min display shown here is designed to resemble the analog spectra that the spectrum analyzer inherently produces 2715 User Manual Getting Started 2715 User Manual 5 Press D to see the analog display This turns off the D storage register the only one currently enabled When all registers are turned off the analog display appears 6 Repeatedly press D to toggle the D register on and off several times Notice the similarity between displays 7 Turn the D register on To obtain the max min display the maximum and minimum amplitudes of the analog spectrum are each sampled at 256 points Plotting the two interleaved sets of 256 points produces the 512 point graph of the spectrum that you see
37. 1 Temperature Operating Nonoperating Humidity Operating Nonoperating Altitude Operating Nonoperating Electrostatic Discharge 8 kV IEC 801 2 Radiated Immunity 27 MHz 500 MHz IEC 801 3 Performance Requirement No responses above 90 dBm in a 3 V meter field Fast Transients Capacitive Clamp 1 kV Power Leads 500 V Control Leads IEC 801 4 Power Line Surge 1 kV Differential Mode 2 kV common mode IEC 801 5 0 C to 50 C 55 C to 475 C 95 RH 5 30 C and below 75 RH 5 31 C through 40 C 45 RH 5 41 C through 50 C Five cycles 120 hours in accordance with MIL STD 28800E class 5 15 000 ft 4 57 km 50 000 ft 15 24 km 1 After storage at temperatures below 15 C the instrument may not reset when power is first turned on If this happens allow the instrument to warm up for at least 15 minutes then turn power off for 5 seconds an back on 2 NVRAMis lost below 10 C 2715 User Manual A 21 Specifications Table A 9 Environmental Characteristics Cont Characteristic Vibration Operating Instrument secured to a vibration platform during test Description MIL T 28800E Method 514 Procedure X modified 15 minutes along each of 3 major axes ata total displacement of 0 015 in 0 38 mm peak to peak 2 4 g at 55 Hz with frequency varied from 10 Hz to 55 Hz in 1 minute sweeps Hold for 10 minutes at 55 Hz All major resonances must be
38. 1 dB 12 0 dB within limits shown in Figure 5 on page 9 Standard vertical interval test signal line sweep ghost canceller multiburst is measured within gate which excludes active video resultis expressed as dB P P 0 2 dB tX 0 5 dB assuming test signal is flat at head end 2715 User Manual Specifications 90 80 10 X 4 dB to 500 MHz 60 C N Measurement 2 dB to 500 MHz t 4 dB at 1000 MHz Limit dBc 50 u 40 Minimum C N for gated 30 measurements level for gated measurement at 1000 20F 10 Pe Minimum signal level for gated measurement to 500 0 30 20 10 0 10 20 30 40 SUAL CARRIER PEAK dBmV 50 V Figure A 1 Typical Accuracy Limits for Carrier to Noise Measurement 60 70 2 dB at 1000 MHz Note 60 channel flat system 4 dB to 500 MHz Note 1 2 dB to 500 MHz Note 1 4 dB to 500 MHz Note 2 2 dB to 500 MHz Note 2 4 dB at 1000 MHz Note 2 90 80 10 Ga Ss A 60 Se ee a CTB N Measurement 2 Limit dBc 50 I Minimum signal level for gated W A measurement at 1000 MHz N 40 inimum signal level for gated measurement to 500 Hz N 30 20 10 0 30 20 10 0 10 20 30 40 50 60 70 VISUAL CARRIER PEAK dBmV Figure A 2 Typical Accuracy Limits for CTB Measurement 2715 User Manual
39. 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 9 Press 4 to print all stored results of the measurement Again a printer must be connected to the 2715 10 Press 9 to leave the HUM LFD measurement and return to the CATV MEASUREMENTS menu 2715 User Manual Measurements FREQUENCY RESPONSE Running The Mode 1 Test 2715 User Manual The FREQUENCY RESPONSE test displays the difference between spectra taken at different times or places in the system mode 1 or a raw spectrum of the entire channel table mode 2 The modes are selectable from the FREQ RESP SETUP menu A mode 1 frequency response test has two parts The first part is acquisition of the reference and the second is comparing the current spectrum with the stored reference spectrum The reference may be acquired either by measurement or by recalling a previously stored reference from NVRAM A mode 2 frequency response test sets the instrument up into a mode that sweeps between specified frequency limits in a 5 MHz resolution bandwidth When the FREQUENCY RESPONSE test is initiated the start and stop frequency limits default to the minimum and maximum frequencies in the selected channel table If a mode 1 test has been selected a reference must be acquired A referen
40. 4 14 Normal Mode Frequency Entry 4 5 Normalization File 6 76 Normalization Initial 2 5 Normalizing the 2715 6 65 Numeric Keys 3 6 NVRAM If You Lose 6 81 2715 User Manual O Occupied Bandwidths OBW Measuring 6 50 Offsets Frequency 6 26 Options Confirming Installed 6 77 Oscillator YIG See YIG oscillator Oscilloscope Trigger Modes 6 83 P Packaging 2 1 Parameter Value Enter 6 3 PEAK FIND 3 4 4 33 Phaselock Turning On and Off 6 72 PLOT 3 7 4 33 Plotter Configuration See Selecting the Screen Plotter Configuration Plotter Output Typical 4 34 POWER 3 8 Power Mains 2 3 Power Down Settings Recall 6 62 Power Up Settings User Defined 6 62 Preamplifier Turning ON OFF 6 9 Precautions Handling 2 2 RF INPUT 2 2 Printer Configuration 6 71 Printing the On Screen Readouts 6 82 Programmed Tuning 6 24 Protecting Files 6 77 R Rackmount Adapter Installation 2 2 Range CHAN FREQ Control 3 4 REF LEVEL Control 3 5 SPAN DIV Control 3 4 READOUT 3 8 4 34 Recall and Save Settings and Displays 6 62 Recall Last Power Down Settings 6 62 Receiving 2 1 REF LEVEL 3 5 Arrow Keys 3 5 STEP 3 5 ZERO and MAX Keys 3 5 REF LVL STEP 3 5 4 10 Reference Level Operation Arrow Keys 4 9 Keypad Entry 4 10 REF LVL STEP 4 10 Index 5 Index Reference Level Units Changing 6 5 Register Priority 4 23 Register Select and Sav
41. 4 Turn inner LEVEL control knob slowly from fully counter clockwise to fully clockwise and watch the screen update This feature enables you to carefully examine a small portion of the spectrum It is also convenient for manually scanning a broadcast or communications band while listening to demodulated signals the 2715 acts like a radio receiver The operator can stop at any station since the sweep is being manually controlled 5 Toggle the manual scan mode off by selecting item 7 again 100 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF WIDE 20MHz 10 DB 5MHz RBW AUTO The User Definable menu enables you to store and execute user definable sequences of keystrokes called routines or programs The routines are intended to permit a series of operations to be carried out with only two keystrokes Press the USER DEF menu button and select the routine you want to run This feature is particularly useful when you have to make a series of repetitious measurements Before you can use routines they must be created and each routine must have a well defined starting point One good way to ensure the routine starts with the correct instrument settings is to begin by recalling a specific group of settings 6 89 Spectrum Analyzer Menus 6 90 Another way is to start with a known group of settings for example the factory or user defined power ups and manually change them to the configuration at which your routine begins this can
42. 6 74 Turning Phaselock On and Off 6 72 INTENSITY 3 8 4 35 Interactive Mode 5 64 K Keypad Entry Channel Entry 4 5 Frequency Entry NonCATV Mode 4 8 Frequency Entry Normal Mode 4 7 Reference Level Operation 4 10 SPAN DIV 4 3 Keys Backspace 3 6 Dot 3 6 Numeric 3 6 Register Select and Save 3 6 SAVE ENABLE 3 6 Terminator 3 6 Toggle Action 2 9 L Labels and Titles Adding 6 36 LEVEL 3 8 LEVEL Control 4 20 Limit Detector and Display Line 6 40 LIN Vertical Scale 4 16 Line Modulation Operation 5 69 Line Number Test Signal 5 63 Line Trigger TV 6 85 Listen Operation 5 70 Listening to AM or FM Transmissions 6 58 Mains Power 2 3 Manually Scanning 6 89 Marker Control 4 26 Index 4 Marker Peak Find 3 4 Marker to the Reference Level 6 21 Marker Moving to the Next Higher or Lower Peak 6 20 Markers Transposing 6 18 Markers to Set Start and Stop Frequencies 6 17 MAX HOLD A amp B 3 7 4 26 MAX Key 3 5 Max Span 4 3 Maximum Signal Levels 5 2 Measurement ADJACENT CHANNEL LEAKAGE 5 47 AURAL FM DEVIATION 5 32 AVERAGE POWER 5 20 CARRIER LEVELS 5 20 CARRIER SURVEY 5 25 CROSS MODULATION 5 60 CTB CSO 5 49 DESIRED to UNDESIRED 5 35 FREQUENCY RESPONSE 5 43 HUM LFD 5 40 In Channel Response 5 62 MODULATION DEPTH 5 28 Typical CATY 2 12 Measurement Process 2 13 Amplitude 2 13 Frequency 2 13 Verifying 2 13 Measuring Carr
43. 71 505 25 509 75 Measurements Table 5 4 STD Cont Channel Visual Carrier Aural Carrier 72 511 25 515 75 13 517 25 521 75 74 523 25 521 15 75 529 25 533 15 76 535 25 539 75 77 541 25 545 75 78 547 25 551 75 79 553 25 557 15 80 559 25 563 75 81 565 25 569 75 82 571 25 515 15 83 511 25 581 75 84 583 25 581 15 85 589 25 593 75 86 595 25 599 75 87 601 25 605 75 88 607 25 611 75 89 613 25 617 75 90 619 25 623 75 91 625 25 629 75 92 631 25 635 75 93 637 25 641 75 94 643 25 647 15 Table 5 5 HRC Channel Visual Carrier Aural Carrier 2 54 00 58 5 3 60 00 64 5 4 66 00 70 5 1 72 00 76 5 5 78 00 82 5 6 84 00 88 5 95 90 00 94 50 96 96 00 100 50 97 102 00 106 50 98 108 00 112 50 99 114 00 118 50 2715 User Manual Measurements 2715 User Manual Table 5 5 HRC Cont Channel Visual Carrier Aural Carrier 14 120 00 124 50 15 126 00 130 50 16 132 00 136 50 17 138 00 142 50 18 144 00 148 50 19 150 00 154 50 20 156 00 160 50 21 162 00 166 50 22 168 00 172 50 7 174 00 178 50 8 180 00 184 50 9 186 00 190 50 10 192 00 196 50 11 198 00 202 50 12 204 00 208 50 13 210 00 214 50 23 216 00 220 50 24 222 00 226 50 25 228 00 232 50 26 234 00 238 50 27 240 00 244 50 28 246 00 250 50 29 252 00 256 50 30 258 00 262 50 31 264 00 268 50 32 270 00 274 50 33 276 00 280 50 34 282 00 286 50 35 288 00 292 50 36 294 00 298 50 37 300 00 304 50 38 306 00 310 5
44. 75 Q signal source impedance However a 50 source impedance is typically associated with some applications that use dBm as a standard amplitude measurement unit The 2715 provides two ways to make 50 Q measurements When making narrowband measurements for example carrier to noise ratios relative amplitudes of signals close together in frequency interference levels relative to a nearby signal you can generally connect the 2715 directly to a 50 Q source If a 50 Q source is connected to the input of a 50 Q instrument the voltage will be 1 6 dB lower than it is with the same source connected to the 75 input of the 2715 We can also calculate that 0 dBmV dissipated in 75 Q is equal to 48 8 dBm across 50 Q The total difference is therefore 50 4 dB For these cases use item 6 of the INPUT menu EXTERNAL ATTEN AMPL to enter a 1 6 dB offset to the reference level See Accommodating External Amplification Attenuation on page 6 6 When making broadband measurements or measurements of absolute amplitude for example antenna system or amplifier sweeps absolute carrier amplitude comparison of signals widely separated in frequency you may want to present a matched load to the source to provide maximum flatness and to minimize standing wave ratios You can do so by inserting the matching minimum loss pad shown in Figure 6 3 between the source and the 2715 To obtain correct dBm readings set the INPUT menu measure ment para
45. 89 75 2 55 25 59 75 3 61 25 65 75 4 67 25 71 75 1 73 25 71 15 5 79 25 83 75 6 85 25 89 75 95 91 25 95 75 96 97 25 101 75 97 103 25 107 75 98 109 25 113 75 99 115 25 119 75 14 121 25 125 75 15 127 25 131 75 16 133 25 137 75 17 139 25 143 75 18 145 25 149 75 19 151 25 155 75 20 157 25 161 75 21 163 25 167 75 22 169 25 173 75 2715 User Manual 5 15 Measurements Table 5 6 IRC Cont Channel Visual Carrier Aural Carrier 7 175 25 179 75 8 181 25 185 75 9 187 25 191 75 10 193 25 197 75 11 199 25 203 75 12 205 25 209 75 13 211 25 215 75 23 217 25 221 75 24 223 25 227 15 25 229 25 233 75 26 235 25 239 75 27 241 25 245 75 28 247 25 251 75 29 253 25 257 15 30 259 25 263 75 31 265 25 269 75 32 211 25 215 15 33 211 25 281 75 34 283 25 287 75 35 289 25 293 75 36 295 25 299 75 37 301 25 305 75 38 307 25 311 75 39 313 25 317 75 40 319 25 323 15 41 325 25 329 75 42 331 25 335 75 43 337 25 341 75 44 343 25 341 15 45 349 25 353 15 46 355 25 359 75 47 361 25 365 75 48 367 25 371 75 49 373 25 311 15 50 319 25 383 75 51 385 25 389 75 52 391 25 395 75 53 397 25 401 75 54 403 25 407 75 55 409 25 413 75 56 415 25 419 75 57 421 25 425 75 58 427 25 431 75 2715 User Manual Measurements 2715 User Manual Table 5 6 IRC Cont Channel Visual Carrier Aural Carrier 59 433 25 437 75 60 439 25 443 75 61 445 25 449 75 62 451 25 455 75 63 457 25 461 75 64 463 25 467 7
46. 9 Table E 2 9 Pin Female to 25 Pin Female Null Modem Cable E 10 Table E 3 9 Pin Female to 25 Pin Male Extension Cable E 11 Table F 1 Standard Accessories F 1 Table F 2 Optional Accessories F 1 Table F 3 Power Cord Identification F 2 vii Table of Contents viii 2715 User Manual I Ii General Safety Summary To Avoid Fire or Personal Injury 2715 User Manual Review the following safety precautions to avoid injury and prevent damage to this product or any products connected to it To avoid potential hazards use this product only as specified Only qualified personnel should perform service procedures While using this product you may need to access other parts of the system Read the General Safety Summary in other system manuals for warnings and cautions related to operating the system Use Proper Power Cord Use only the power cord specified for this product and certified for the country of use Connect and Disconnect Properly Do not connect or disconnect probes or test leads while they are connected to a voltage source Ground the Product This product is grounded through the grounding conductor of the power cord To avoid electric shock the grounding conductor must be connected to earth ground Before making connections to the input or output terminals of the product ensure
47. A OFF to enter the delta marker mode 23 Place the movable marker near the calibration signal fundamental at 100 MHz 24 Press CTR MEAS TRKG This mode of operation centers the signal peak nearest the movable marker and measures the difference between the centered signal and the signal at the fixed marker In this case the fundamental is recentered and the markers appear on top of it and the third harmonic Readings of approximately 200 MHz and 12 dB appear at the top of the left column preceded by the letters DC delta counter The center measure feature with the delta marker mode provides a convenient method of determining precise signal differ ences without manual tuning or interpolation of graphical data 25 Turn off the markers 2715 User Manual Dedicated Controls 2715 User Manual The center measure feature can perform still another function When center measure is used in the zero span mode the counter measures the frequency at the output of the 2715 detector Because the output varies only if the signal is modulated the counter is actually measuring the frequency of the modulation if none is present you receive a message saying so Normally AM detection is used but you can select FM detection Whichever detector is selected the center measure feature provides a quick method of determining the frequency of the modulating signal Of course the modulation frequency must fall within the bandwidth of the reso
48. C The title will vanish from the screen if any register is turned on that contains a current sweep but will remain in storage register C until waveform C is unsaved with SAVE ENABLE C There are several other title or text information entry functions available In each case with the exception of plot labeling text is entered just the same as for title editing Plot labeling is similar 16 Press DSPL 5 4 to select PLOT LABELING EDIT Since plot labels can use all 16 display lines instead of just one most of the instructions are on a separate screen so that they do not cover the label being entered 2715 User Manual Spectrum Analyzer Menus The buttons and the FREQ MKRS knob work the same as for other text editing In addition any of the up or down arrow buttons move the cursor vertically between lines Labeling information may be entered on any or all lines As the cursor moves between lines the list of available characters shifts so that the line being edited is always visible 17 Press W to display the label editing screen The W button toggles between the label editing screen and the instruction screen The editing screen displays the label being edited if any exists the cursor and the display of available characters This screen also displays the waveform so that you can see how the label will plot with respect to the waveform 18 Move the cursor one division to the right of center screen and two divi
49. External Video Input pin 1 m Sweep Gate pin 2 m Chassis and Signal Ground pin 3 m Sweep Ramp pin 4 m Video Output pin 5 2715 User Manual Appendix E External Input and Output Pin 1 External Video Input 2715 User Manual The remaining signals see Figure E 1 are used by the 2707 External Tracking Generator and are not discussed in this manual Refer to the 2707 External Tracking Generator Instruction Manual if you need more information about these signals 5 4 3 2 1 1019181 716 Pin Signal 1 External Video Input O 2 Sweep Gate 3 Chassis Signal Ground 1 4 Sweep Ramp 5 Video Out 1514 13 12 11 6 CLKO Input Figure E 1 Accessory Connector J103 7 DATA Output 8 DATAO Input 9 EXTGLATCH Input 10 23 38 MHz Output 11 VLVL Input 12 SWPSLOPE Input 13 Not Used 14 Not Used 15 Not Used Bulleted instructions in the signal discussions guide you through applications using the Accessory Connector signals The instructions are designed to be used consecutively as provided The signals are discusssed in logical sequence not in pin number order 100 0MHZ 28 8DBMV AUTO SWEEP ATTN 10DB VF WIDE 10 DB CALIBRATOR 20 0MHZ 5MHZ RBW AUTO Pin 1 enables you to introduce an external video signal to the 2715 in effect giving it limited oscilloscope capabilities It is also used to introduce the frequency markers from the 1405 TV Sideband Analy
50. One remains at the original marker position while the position of the second is controlled by the knob The right column indicates the difference denoted by the letter D preceding the readouts in frequency and amplitude between the two marker positions 9 Increase the span to 50 MHz div 10 Use the tuning knob to place the movable marker at the top of the first signal peak to the right of center the calibration signal second harmonic The right column now reads as follows D 100MHz D 13 0 DB NOTE The values displayed by your instrument may not exactly match those illustrated You are measuring the difference in frequency and amplitude between the fundamental and second harmonic of the calibration signal Your instrument may not read these values exactly but it should be close If you attempt to move the movable marker past the edge of the display you will see that the spectral display behaves almost the same as it did for the single 2715 User Manual Dedicated Controls 2715 User Manual marker The difference is that the stationary marker remains fixed with respect to the spectrum You can even force the stationary marker off screen and the readout will continue to indicate the difference between the two marker positions In this way you can make difference measurements across the whole input range of the 2715 11 Turn the tuning knob clockwise until the readout indicates the movable marker is 900 MHz to the
51. Pin Female to 25 Pin Male Extension Cable Table E 3 and Figure 7 show the connections for this type of cable A cable with this configuration is available as an optional accessory Refer to Appendix F Accessories and Options for the part number Table E 3 9 Pin Female to 25 Pin Male Extension Cable 9 Pin Female to 25 Pin Male Pin signal Pin signal 1 DCD to 8 DCD 2 RXD to 3 RXD 3 TXD to 2 TXD 4 DTR to 20 DTR 5 GND to 7 GND 6 DSR to 6 DSR 7 RTS to 4 RTS 8 CTS to 5 CTS 9 not used 9 Pin Female 25 Pin Male C 1 e 1 2 2 3 3 4 4 2715 lt 5 5 6 6 7 7 e e 10 e 11 12 To PC e13 gt or e 14 Modem e 15 e 16 e 17 e 18 e 19 20 21 22 23 24 25 J Figure E 7 9 Pin Female to 25 Pin Male Extension Cable 2715 User Manual 11 Appendix E External Input and Output E 12 2715 User Manual a ee a a Appendix F Accessories and Options Accessories 2715 User Manual The 2715 is shipped with the standard accessories listed in Table F 1 Optional accessories are listed in Table F 2 Also optional AC mains power cords are available meeting various international standards see Table F 3 Table F 1 Standard Accessories Tektronix Part Number Description 070 9115 XX User Manual 2715 070 8533 XX Programmer Manual 2714 amp 2715 070 8535 XX Pocket Reference 2714 amp 2715 070 9611 XX User M
52. RBW AUTO ATTN 6DB VF WIDE 10 DB Channel Name CH nn CALIBRATOR AUTO SWEEP 10 5 1 The VERT SCALE function block contains a three way toggle key labeled 10 5 1 This label expresses the three logarithmic vertical scale factors available on the 2715 10 5 and 1 decibels per major vertical division Press the key to cycle the vertical scale factor through the three values in a 10 dB 5 dB dB 10 dB sequence 1 Press 10 5 1 The signal peak is now one division down from the reference level Also the vertical scale factor readout now indicates 5dB The noise also seems to have disappeared the signal to noise difference is the same but the scale factor change has moved the noise below the bottom of the screen Press 10 5 1 again The signal peak is now five divisions down and the readout says 1 dB The primary use for this feature is to more accurately read displayed signal peaks Press 10 5 1 once again to restore the 10dB setting LIN The second key in the VERT SCALE function block is also toggle action It converts the vertical scale from logarithmic to linear and back again 4 Ensure that the calibration signal is centered and the reference level is set to 23 8 dBmV Press LIN The vertical scale readout now indicates 1 94MV When the LIN mode is initially selected the 2715 converts the vertical scale so the bottom graticule line is V and the scale factor is converted from dB to
53. STAND BY A delay is required in the use of the instrument until this message disappears START FREQUENCY CHANGED A change in the stop frequency necessitated a change in the start frequency STOP FREQUENCY CHANGED Change in start frequency necessitated a change in stop frequency STORAGE REGISTER EMPTY No data yet stored in the register accessed TABLE CURRENTLY IN USE The table is currently in use but the user may still delete it if desired TABLE IS TOO LARGE TO EDIT The current combination of start stop increment setup frequencies results in a correction table with too many elements TIMER INTERRUPT FAULT Firmware hardware error Possible malfunction of interrupt timer on processor board indicated Contact your local Tektronix service center or representative if message persists after normalization C 13 Appendix System Messages TOO MANY FILES OPEN Firmware hardware error Indicates that the maximum number of files is already open Cannot open any more files at this time Contact your local Tektronix service center or representative if message persists after normalization UNCAL Indicates the 2715 is operating in an uncalibrated state Occurs under the following conditions W Sweep speed is too fast for a specified resolution BW video filter and span combination m One or more critical normalizations have not been completed successfully UNCAL OFF A change of state indicator briefly displayed when an uncali
54. VERBOSE is an on off toggle When VERBOSE is ON a response is returned to the controller following each command or query The response may be an event code the correct query response or a simple OK for a completed command not normally requiring a response When VERBOSE is OFF only responses to queries are generated The default is OFF GPIB Configuration 5 Press 0 to select GPIB from the COMMUNICATION PORT CONFIG menu The GPIB Port Configuration menu appears Several choices are offered in all cases the 2715 settings must match those used by the controller or printer plotter m Item 0 STATUS enables you to toggle the GPIB port on and off line The port must be on line to communicate with any other device m Item 1 GPIB ADDRESS specifies the primary address the 2715 does not support secondary addresses that can be any value from 0 to 30 When the 2715 is used with a system controller the value must match that used to configure the controller Address 0 is usually reserved for the controller itself When the 2715 is used in the TALK ONLY mode with a plotter any address can be used The address you set is read immediately by the 2715 and retained in NVRAM until you change it m Item 2 POWER ON SRQ determines whether a service request SRQ is generated at power up Because there normally is no need for a SRQ at power up the default setting of item 2 POWER ON SRQ is OFF However in some cases you may want to sense that
55. above 1 8 GHz All except Option 50 and Option 75 excursion in 2 4 KHz ion in 20 ms Performance Requirement Supplemental Information All except Option 50 and Option 75 100 Hz peak to peak total excursion in Short term after 1 hr warm up and with PHASELOCK in AUTO mode Resolution Bandwidth 6 dB down Resolution bandwidth selections are 5 MHz 1 MHz 300 kHz 100 kHz 30 kHz 10 kHz 3 kHz 1 kHz and 300 Hz for the spectrum analyzer Shape Factor 60 dB 6 dB Noise Sidebands 7 1 or less for all resolution bandwidths lt 1 MHz All except Option 50 and Option 75 lt 70 dBc at 30X Resolution Bandwidth for all resolution bandwidths lt 100 kHz lt 69 dBc at Option 50 and Option 75 30X Resolution Bandwidth for all resolution bandwidths lt 100 kHz Video Filter A 12 Reduces video bandwidth to about 1 of the selected resolution bandwidth or one of 12 video filters 3 Hz 10 Hz 30 Hz 100 Hz 300 Hz 1 kHz 3 kHz 10 kHz 30 kHz 100 kHz 300 kHz or WIDE can be selected from the UTIL menu 2715 User Manual Specifications Table A 2 Frequency Related Characteristics Cont Performance Requirement Characteristic Resolution Bandwidth 6 dB down Supplemental Information Resolution bandwidth selections are 5 MHz 1 MHz 300 kHz 100 kHz 30 kHz 10 kHz 3 kHz 1 kHz and 300 Hz for the spectrum analyzer Shape Factor 60 dB 6 dB 7 1 or less for all resol
56. affect printing time when using a dot matrix printer READOUT You can toggle the standard on screen readouts on and off There are two reasons for doing so First it prevents the readouts from overlapping the signal spectrum The following steps illustrate the second reason 1 Initialize the 2715 to the factory power up defaults 2 Enter the analog display mode 3 Press SWEEP Notice the regularly spaced dark areas in the sweep 4 Press READOUT below the VERT SCALE function block to turn off the readouts The dark areas are gone now The dark areas represent time when the CRT beam is writing the on screen readouts Their appearance changes with sweep speed By eliminating the readouts you eliminate the dark areas You will also notice that the trace has intensified This is because the 2715 does not have to take time out from each sweep to write the on screen data 2715 User Manual Dedicated Controls 2715 User Manual 5 Press READOUT activate register D and press AUTO in the SWEEP function block to turn the data readouts back on INTENSITY The intensity control is a rotary knob that works exactly like any oscilloscope intensity control Twist the INTENSITY knob slowly back and forth Notice the display grow brighter and dimmer as you turn the control Leave the intensity set to a level sufficient for good contrast in your ambient light conditions If you have to turn it to full intensity try reduc
57. again Contact your local Tektronix service center or representative if message persists AMPLITUDE NORMALIZATION FAILED Perform amplitude normalization again Contact your local Tektronix service center or representative if message persists AMPLITUDE OUT OF CALIBRATION The spectrum analyzer amplitude may be out of calibration This message may be generated by the auto sweep rate measurement routine Appendix System Messages C 2 AVERAGE NOISE TOO LOW The average noise level in the Carrier to Noise or Noise Normalization measurement is below the bottom of the screen and cannot be digitized To correct the problem reduce the reference level to bring the noise level onto the screen AVERAGE IN PROCESS An ensemble average not CONTINUOUS is in process Used to report event over GPIB CALIBRATOR DOESN T MATCH READOUT The calibrator is enabled and an external attenuation or external frequency offset is enabled CAN T COUNT WITH CORRECTIONS OFF Turn Frequency Corrections ON The location of this selection is UTIL 4 3 CANNOT CALC VERT SENSITIVITY Perform amplitude normalization Contact your local Tektronix service center or representative if message persists CANNOT COUNT VCO IF Perform frequency normalization Either the VCO counter input or the IF counter input failure can cause this error to occur Contact your local Tektronix service center or representative if message persists CANNOT COUNT BEAT FREQ
58. again Contact your local Tektronix service center or representative if message persists NO SIGNAL FOUND ABOVE THRESHOLD There is no displayed signal exceeding the marker threshold value Thresh old can be reset using the MKR FREQ menu NO SIGNAL AT CENTER OF DISPLAY Firmware hardware error Contact service center if message displays repeatedly NO SIGNAL AT COUNTER INPUT Perform normalizations again Contact your local Tektronix service center or representative if message persists 2715 User Manual Appendix System Messages 2715 User Manual NO TEST LINE NUMBER SPECIFIED An in service measurement of the in channel response was attempted without entering a test signal line number Enter a test signal line number at the menu prompt and then take the in service in channel response measure ment NOISE LEVEL LESS THAN 2DB Measured system noise level is less than 2 dB above the 2715 noise floor Noise power correction has been made by NOISE NORM D or C N mode algorithms in the 2715 NON COMPATIBLE NVM FORMAT The firmware version was not compatible with the non volatile memory Consequently the NVM was re initialized Contact service center if message displays repeatedly NONE OF THE TRACES ARE ACTIVE A digitized waveform must be on to employ desired function NORMALIZATION COMPLETE Normalization routine successfully finished NORMALIZATION SUGGESTED Frequency normalization needed Contact your local Tektronix
59. an example the following procedure creates a new title TEST123 3 Press 2 to start the title mode edit 4 Rotate the FREQ MKRS knob until the letter T appears 5 Press MKR 9 to move the cursor one place to the right 6 37 Spectrum Analyzer Menus 6 38 6 Rotate the FREQ MKRS knob until E appears 7 Continue this process until you have spelled TEST You can enter numbers and advance the cursor automatically without rotating the knob by using the numeric keypad 8 Press 1 2 3 to complete the title 9 Press X to store the result in the display title buffer You can also exit from the title edit mode without saving the title or any changes by pressing Z The following steps show how to make the title visible on screen or on a plot 10 Press 1 to toggle on TITLE MODE Pressing 1 again turns off the title 11 Leave the title on and return to the spectral display Your title is visible in the upper left corner of the screen At this point the title is associated with the highest priority waveform Perma nently attach it to a waveform C 12 Press SAVE ENABLE and C 13 Press DSPL 5 2 Y to delete the title from the display title buffer 14 Return to the spectral display The title is gone but the readouts are displaced downward one line because TITLE MODE is still enabled 15 Turn off the D register and turn on C The title is back it has become part of the saved waveform in
60. and mixer Input level is set to 20 dBm Note 2 0 limits MT z E and mixer input level set to default n a 20 30 40 50 60 20 setting of 30 dBm in a 60 channel VISUAL CARRIER PEAK dBmV flat system Figure A 4 Typical Accuracy Limits for Gated CSO Measurement A 8 2715 User Manual Specifications 500 MHz to 1000 MHz 65 55 Measurement Limit dBc 35 25 20 10 0 10 20 30 40 50 60 70 INPUT LEVEL dBmV FOR SINGLE SIGNAL TEST ENVIRONMENT Figure A 5 Typical ACL Measurement Limits for 2 dB Accuracy To 500 MHz using preselector 500 MHz to 1000 MHz using preselector To 500 MHz in 60 channel flat system dominated by analog signals 10 dB stronger than average power of channel under test _ 500 MHz to 1000 MHz in 60 channel flat system dominated by analog signals 10 dB stronger than average power of channel under test Measurement Limit dB 20 10 0 10 20 30 40 50 60 70 CHANNEL UNDER TEST INPUT LEVEL dBmV Figure A 6 Typical D U Measurement Range Limits for 2 dB Accuracy 2715 User Manual A 9 Specifications To 500 MHz using preselector 500 MHz to 1000 MHz using preselector To 500 MHz in 60 channel flat system dominated by analog signals 10 dB stronger than average power of channel under test r 500 MHz to 1000 MHz in
61. are protected only the saved waveforms are deleted ONLY WAVEFORMS SAVED When saving settings in a location containing previously protected settings only the waveforms are saved OUT OF RANGE A value has been entered that is outside the permitted range The instrument will default to the closest permissible value If the message appears at times other than data entry a firmware hardware error is probable Contact your local Tektronix service center or representative if message persists PLOT ABORTED A new plot request has caused the currently running plot to be aborted A new plot must be requested again in order to restart plot process PLOT COMPLETE A plot operation has been finished PLOT IN PROCESS Signifies for GPIB reporting that a plot is in progress POLYNOMIAL HAS NO SOLUTION Firmware hardware error Contact your local Tektronix service center or representative if message persists PORT OFFLINE Select ONLINE in proper port configuration submenu PRINTER ERROR Check the printer Some printers return Printer Error for all conditions that need attention offline out of paper etc refer to the printer manual 2715 User Manual Appendix System Messages 2715 User Manual PRINTER IS NOT CONNECTED Connect printer to appropriate port Check printer cable PRINTER OUT OF PAPER Reload printer paper PROGRAM NOT EXECUTABLE The selected user defined program is corrupted or too big to fit into available
62. be done within the routine but it uses up additional memory In the following example we shall create a user defined routine to perform CARRIER LEVELS measurements on 10 channels at six hour intervals The resultant UDP will execute a 24 hour test The result over 24 hours will be five sets of 10 stored results representing a set for each time the UDP is repeated and the set stored when the UDP was first created To create the user defined routine 1 Press USER DEF and select item 9 USER DEF PROG UTILITIES Select item 1 TITLE EDIT and press W to begin editing Enter a title of 24 HOUR LEVELS The procedure is the same used to title a display see Adding Titles and Labels in this section The title can be up to 28 characters long Remember to press X to store the title Titling the routine is not mandatory if you do not supply a title the routine is named PROGRAM by default but does help you to recall what a routine is supposed to do 2 Select item 0 ACQUIRE EXIT KEYSTROKES from the USER DEF PROG UTILITIES This begins the accumulation of keystrokes The spectral display reappears with the routine name superimposed and the following message ACQUIRE KEY STROKES 0 BYTES Each key that you press will now be recorded in the order in which it was pressed This sequence of key strokes constitutes the bulk of the user defined routines The function of that key is also carried out as you watch You can return to the USER DE
63. being used with a vertical scale factor of 175 mV div m Press 10 5 1 three times and notice that the scale changes to 87 5MV 17 5MV back to 175MV Turn off all registers to view the analog signal and then turn the D register back on The VERT SCALE and DISPLAY STORAGE function blocks remain operation al You can alter the display scaling view analog or digital signals compile ensemble statistics or select other items from the DSPL menu Pin 3 of the Accessory Connector is chassis and signal ground 100 0MHz AUTO SWEEP ATTN 10DB 28 8DBMV VF WIDE 20 0MHZ 10 DB 5MHZ RBW AUTO CALIBRATOR Pin 5 of the Accessory Connector is the analog video output from the 2715 The analog video output is a 0 to 1 6 V signal representing the vertical deflection of the display on the 2715 with all registers turned off 0 volts is the top graticule line and 1 6 V is the bottom line The output signal range remains constant 2715 User Manual Appendix E External Input and Output regardless of reference level attenuation and vertical scale The signal can be used to drive an external oscilloscope or other video display unit For example in certain applications a device with a low or high persistence phosphor may be particularly useful Connect pin 5 to an input channel of an oscilloscope At the oscilloscope select 0 2 V div and 50 ms div scale factors invert the input and trigger internally You may have trouble
64. circumstances number of analog channels on the system and how far down the digital signal is from the general level of the analog channels Note that even when the preselector is used the maximum signal level input for most of the digital tests is depicted as being below the 70 dBmV burnout limit This is because of specific measurement dependent hardware limits of the instrument Violating the depicted limit can result in inaccurate measurement results CAUTION To avoid overloading the 2715 and possibly damaging it do not place AC or DC power supply voltages on the input of the 2715 At power up the 2715 comes up in the CATV mode tuned to the default power up channel The power up channel is the last active channel when power was turned off or channel T 7 labeled 907 in STD Table 5 4 if was erased before the last power down Upon entering the CATV MEASUREMENT MODE the instrument software searches for the visual carrier signal associated with the default power up channel and places a marker at the visual carrier peak The instrument then configures itself as follows Frequency Center of default power up Channel Band Reference Level 68 8 dBmV Span Div Channel Band 10 RF Attenuation 50 dB Resolution Bandwidth 300 kHz Sync amp Video Polarity From current channel table Vertical Mode Log Vertical Scale 10 dB div Sweep Auto Trigger Free Run Marker On Marker Frequency Apparent Visual Carrier P
65. comfortable viewing The cycle delay values can range from 0 ms to 30 000 ms With TARGET LINE DURATION selected you can adjust how much of the cycle delay is used to display the target line and its associated readouts You can use the target line duration with the cycle delay discussed in the previous text to adjust the display times for comfortable viewing The target line duration values can range from 0 to 100 2715 User Manual Measurements 2715 User Manual Table 5 7 shows examples of the interactions between cycle delay time target line duration and the display times for the target line and channel field or line displays Table 5 7 Examples of Cycle Delay Target Line Duration Interaction Target Additional Target Additional Channel Cycle Delay Line Duration Line Display Time Field Line Display Time 1000 ms 95 950 ms 50 ms 1000 ms 50 500 ms 500 ms 1000 ms 30 300 ms 700 ms 500 ms 95 475 ms 25 ms 500 ms 50 250 ms 250 ms 500 ms 30 150 ms 350 ms When you select ENTER ADJUSTMENT MODE from the MODULATION DEPTH menu the following is displayed m Target Line appears at the position representing the selected target line percentage value 0 to 100 The position of the target line is relative to the top of the screen which is 0 m Target line percentage value appears in the lower right hand corner of the screen m Current Sync Tip Voltage value appears in the upper left hand c
66. ensemble mean in register A Press MAX HOLD B Press SAVE ENABLE B to save the max hold values in register B Press INPUT 9 to turn off the calibrator Press UTIL to call up the Utility menu Press 1 to select STORED SETTINGS DISPLAYS 6 63 Spectrum Analyzer Menus Notice that settings 3 through 8 are blank and item 9 indicates MORE There are in fact 34 fields in addition to last power down and user defined power up contained on 4 menu pages in which you can save stored settings and displays 19 20 21 22 23 24 25 26 4 6 64 Repeatedly press 9 to advance to page 4 Press BKSP three times to back up to the first page The register locations currently being displayed are indicated at the top right of each page R00 R08 R10 R18 R20 R28 R30 R39 Press 3 X to store the settings you entered earlier in the register 3 location Gf there is a setting already present delete it or use another location Unsave the A and B registers and turn them off If you do not the CANNOT OVERWRITE SAVED DISPLAY message is displayed when you try to recall settings Press MAX HOLD to turn it off Press UTIL 1 2 W to reinitialize the 2715 to your user defined power up settings Press UTIL 1 Item 3 reads as follows AB 90MHZ 38 8DBMV 20MHZ This message shows the primary control settings that are saved in that location and tells you register A and B waveforms a
67. entry can contain up to 25 characters but regardless of how many you enter the 2715 attempts to control frequency to the nearest hertz The frequency is displayed at the top of the left hand data column to 1 of the span div 12 Press 1 e 2 5 X to set the center frequency to 1 25 MHz The numbers you type appear on screen to the right of CHAN If you make a mistake correct it any time prior to pressing the MHz terminator by repeatedly pressing BKSP until the incorrect number disappears and then enter the correct value Pressing a terminator key X Y Z determines the units and enters the data X can represent units of MHz ms or mV Because the frequency immediate entry mode requires a frequency the 2715 interprets the currently displayed value as 1 25 MHz when you press X If a time or voltage unit had been required the 2715 would have interpreted your entry as 1 25 ms or 1 25 mV respectively when you pressed X On the other hand had you wanted the entry to represent a frequency of 1 25 GHz you would have pressed 1 2 5 0 X Use the correct multiple and X to select GHz while the 2715 is in the CATV mode Now use the direct entry method to set the center frequency to 100 MHz 13 Press CHAN FREQ 1 0 0 X The following procedures demonstrate how to change the frequency when operating in the nonCATV mode Arrow Keys You can adjust the frequency using the arrow keys as shown in the
68. errors messages lt UNDO CHAN gt lt ABORT ALL gt USE KNOB TO SELECT PARAMETER X STORE TABLE AND EXIT Figure 5 3 Channel with FINISH selected The FINISH selection shown in Figure 5 3 ends the editing session and goes back to the CATV MEASUREMENTS SETUP menu The table of edited data is copied into NVRAM and becomes the master copy Upon returning to the spectral display if the channel displayed currently was edited during the session the screen will reflect the changes The UNDO CHAN selection repaints the screen with all the values that were there before the channel was selected and the CHANNEL element is automati cally selected for further editing The ABORT ALL selection copies the original table from back to RAM the channel table reverts to its original state and the parent menu is displayed A confirmation prompt is displayed before this complete loss of all edits can occur 5 9 Measurements Selecting a Test Channel While in the spectral display enter the desired test channel by pressing keypad numbers corresponding to the channel and terminate the entry by pressing W or enter any frequency within the channel band of the channel and terminate with X Y Z Refer to Tables 5 4 through 5 6 for factory loaded channel tables Table 5 4 STD Channel Visual Carrier Aural Carrier 907 7 00 11 5 908 13 00 17 5 909 19 00 23 5 910 25 00 29 5 911
69. expressed in hertz or hertz per division 2715 User Manual Glossary 2715 User Manual Full Span Maximum Span A mode of operation in which the spectrum analyzer scans an entire frequency band Gain Compression Effect seen at an input level where the analyzer circuits have less gain than their small signal values This is usually specified at the 1 dB compression point in terms of the input level required to reduce the gain by 1 dB Graticule The calibrated grid overlaying the display screen of spectrum analyzers oscilloscopes and other test instruments Harmonic Distortion The distortion that results when a signal interacts with itself often because of nonlinearities in the equipment to produce sidebands at multiples or harmonics of the frequency components of the original signal Harmonics Frequency components of a signal occurring at multiples of the signal s fundamental frequency Heterodyne Spectrum Analyzer A type of spectrum analyzer which scans the input signal by sweeping the incoming frequency band past one of a set of fixed RBW filters and measuring the signal level at the output of the filter Hum Modulation Modulation distortion at power frequencies hum is the amplitude distortion of the desired signal caused by the modulation of these signals at the frequency of the power source Hum Sidebands Undesirable responses created within the spectrum analyzer appearing on the display that are separated f
70. filter is turned off and the LED goes out Sounds The 2715 can emit tones under the following conditions m During power on self test m When an abnormal condition occurs m When a message appears m When a key is pressed The instrument emitted self test beeps when it was powered up The beep can be set to sound when an error occurs when a key is pressed when either happens or it can be set to never sound If the error alert is turned on and an abnormal condition exists such as a request to extend a measurement parameter beyond its range the 2715 emits a high level beep A message is simultaneously displayed on screen describing the abnormal condition 2715 User Manual 2 9 Getting Started The 2715 is equipped with AM and FM demodulator circuits that extract the audio signals on amplitude or frequency modulated RF signals The demodulated audio is reproduced on the built in speaker This feature can be used to identify most voice channels based on their content or call signs and can help to identify others by enabling you to determine the type of modulation frequency shift keying pulsed CW For better quality audio or private listening use the headphone jack on the right side of the 2715 The AM FM demodulators are discussed in detail in DEMOD on page 6 56 The Built In Calibrator The 2715 is equipped with a built in calibration source The calibrator for the 2715 has no external Cal Signal output Instead the calibr
71. following procedure 1 Press CATV APPL 8 0 to exit CATV mode 2 Press 1 0 3 However neither is a permissible value at this menu level and your entry would have been rounded to the nearest allowable value 4 7 Dedicated Controls 4 8 3 Press adjacent to CHAN FREQ The frequency changes by 10 MHz It would take ten presses of the arrow key to change the frequency by 100 MHz The frequency arrow keys change the frequency by one division 4 Change the span div to 100 MHz 5 Press adjacent to CHAN FREQ The frequency changes by one division 100 MHz At large span div settings the arrow keys can change the frequency very rapidly Keypad Entry For very large frequency changes or to preset a known center or start frequency the direct entry mode using the keypad is faster To set the center or start frequency to a predetermined value press CHAN FREQ to place the center or start frequency in immediate entry mode The abbreviation FREQ appears at left center of the 2715 screen The abbreviation FREQ indicates that you can enter the center frequency directly from the keypad This is done by keying in a permissible value followed by an appropriate terminator key You can enter any value from 0 Hz to 1 8 GHz even though the 2715 low frequency specification is 9 kHz Your entry can contain up to 25 characters but regardless of how many you enter the 2715 attempts to control frequency to th
72. for the RS 232 connector are shown in Figure E 4 Signal levels handshaking protocols and other matters of importance to digital communica tions are detailed in the 27 4 amp 2715 Programmer Manual and the pertinent standards RXD DCD ie D E 5 Cts Figure E 4 RS 232 C Connector Pin Assignments The RS 232 connector J104 on the 2715 is typically used to connect the 2715 to a PC that is running the Cable TV RF Measurements Software The RS 232 connector on the PC interface card may be one of three types m 9 pin female m 25 pin female m 25 pin male Check which type of connector your PC interface card has and refer to the following tables and illustrations to determine which cable you need 2715 User Manual Appendix E External Input and Output 2715 User Manual 9 Pin female to 9 Pin Female Null Modem Cable Table E 1 and Figure 5 show the wiring configuration for this type of cable A cable with this configuration is available as an optional accessory Refer to Appendix F Accessories and Options for the part number NOTE Pins 1 and 8 are connected together on each 9 pin female connector Both pins connect to pin 7 on the opposite 9 pin connector Table E 1 9 Pin Female to 9 Pin Female Null Modem Cable 9 Pin Female to 9 Pin Female Pin signal Pin signal 18 DCD CTS to 7 RTS 2 RXD to 3 TXD 3 TXD to 2 RXD 4 DTR to 6
73. from noise introduced by the distribution system Noisy video can limit the sensitivity for both C N and CSO measurements taken in service When measuring ICR noise is not a concern but the 2715 assumes that the test signal in the specified line is spectrally flat at the head end If this is not true the 2715 s flatness will be misstated A technique for assessing flatness and compensating for a nonflat video source is suggested in the section on ICR measurement details 2715 User Manual Measurements 2715 User Manual The successful application of gated measurements therefore depends on good quality video signals In particular you should avoid attempting to make in service measurements on channels carrying video from low quality sources such as consumer grade VCRs and camcorders In addition to the noise and flatness problems most low quality video sources produce head switching glitches or other disturbances which tend to disrupt the timing of the 2715 s gate operation Such disruptions may cause measurement errors ranging from subtle to dramatic When performing in service tests the instrument routine checks for quiet lines at lines 10 through 20 and 272 through 282 on NTSC systems or at lines 6 through 20 and 318 through 332 on PAL systems If the only quiet lines available are beyond this range then you must specify the quiet line in the channel table using the Cable TV RF Measurements Software for Windows provide
74. front panel lights the spectral display reappears and you may hear the 2715 sweeping 7 Ifyou hear nothing turn the outer barrel of the LEVEL control clockwise to increase the volume 8 Press ZERO SPAN to hear whatever is being transmitted by the station 9 Leave the 2715 in zero span and turn the FREQ MKRS knob to tune it as you would a radio receiver The signal level rises as you tune in stations and falls to the noise floor when no station is present 10 Press DEMOD 0 to turn off the FM demodulator 11 Press ZERO SPAN to return to the normal spectral display To listen to AM transmissions connect an antenna to the 2715 as outlined in Appendix B Broadcast AM FM and TV Signal Sources The antenna will probably need to be much longer than for FM 12 Press CHAN FREQ 1 X to set the center frequency to 1 MHz 13 Press SPAN DIV 1 0 Y to set span to 10 kHz div 14 Ensure RES BW and SWEEP are set to AUTO 15 Ensure that the calibrator is turned off 16 If necessary adjust the reference level until you can see signal peaks in the 500 kHz to 1 6 MHz area this is the medium wave broadcast band 17 Tune the 2715 until a strong signal is centered 18 Press DEMOD The DEMOD TG menu appears 19 Press 1 to select AM DEMODULATOR The LED adjacent to AM VOL on the front panel lights and the spectral display reappears 20 Press ZERO SPAN and adjust the LEVEL control as needed until you h
75. given in Table 5 1 Table 5 1 Safe Maximum Signal Levels Number of Signals Input Safe Maximum Amplitude to Spectrum Analyzer per Signal dBmV 1 70 0 10 60 0 30 4552 50 453 0 70 51 5 100 50 0 Remember two 68 dBmV signals total more than 70 dBmV Higher signal levels should be externally attenuated With the exception of Adjacent Channel Leakage ACL these tests are characterized for use in a multichannel environment no preselector or in a single channel environment preselector used ACL is characterized for the single channel environment only since it is used only at the head end prior to the system combiner In the multichannel environment digital signals are typically 10 dB lower in level than analog TV signals on the same system In this case the maximum safe input level per channel may be unexpectedly far below the maximum safe total power for the attenuator 70 dBmV For example in a 150 channel flat system dominated by analog TV signals the maximum safe input level for a digital signal 10 dB below the analog levels is only about 37 dBmV 2715 User Manual Measurements A Initial Setup 2715 User Manual For this reason the maximum signal input level for the digital tests except for ACL is depicted as 37 dBmV for the multichannel environment In specific cases the safe limit may be higher but it is your responsibility to correctly make that determination based on your specific
76. horizontal scale factor in zero span mode and has units of time division in the spectral mode view the sweep rate by pressing SWP TRIG The sweep rate readout indicates 5 0MS ZSPAN 50 ms div in zero span and the internal noise is displayed 2 Press The LED below AUTO in the SWEEP function block turns off indicating the sweep rate is no longer being automatically selected 3 Press continuously until the sweep rate readout changes to 1MS ZSPAN The SWEEP down arrow key decreases the sweep rate in a 1 2 5 sequence The noise on the trace is no longer visible Variations in the noise waveform can be seen occurring in a millisecond or less Even faster sweep rates are possible 1 us div with display storage disabled 4 17 Dedicated Controls 4 18 4 Press several times The noise is compressed to a grass like appearance and the indicated sweep rate increases The SWEEP key increases the sweep rate in a 1 2 5 sequence The and keys perform reciprocal actions they decrease or increase the time required to sweep one division Pressing either key removes the 2715 from the automatic sweep rate selection mode and or thereafter function like the sweep rate selector on a conventional oscilloscope NOTE Because sweep rate is the inverse of sweep speed decreasing sweep rate increases sweep speed 5 Resetthe sweep rate to 50 ms div and the span div to 50 KHz 6 Setthe
77. how to name an antenna 11 Press 1 to select TITLE EDIT 12 Press W to begin editing If an old antenna table is being modified its name appears at the upper left with an underscore cursor beneath the first letter If the antenna table is new only the cursor appears 13 Press Y to delete an old name entirely You can press Z to abort the title editing process without changes 14 Turn the FREQ MKRS knob to select letters to change the title 15 Use MKR or MKR 4 to move the cursor back and forth 6 15 Spectrum Analyzer Menus 6 16 16 Press X when the title is complete 17 Press 2 to select STORE 18 Choose any unused antenna number The new or modified antenna table will be stored under that number Its name is displayed adjacent to the number If you do not name the antenna it is given aname of ANTENNA If all five antenna tables are already in use you will have to delete an existing antenna before you can store the new or modified table For instance suppose you have modified an existing antenna table and wish to store the modified version in the place of the original table using the same antenna name Even though the name and location are the same you must first delete the original antenna table Deleting the original antenna from the antenna list does not delete the edited version in the local buffer After you delete the original store the edited version in the original location Yo
78. is being used and the bandwidth of the filter is indicated on screen Notice how much less noisy the lower portion of the spectral display appears By filtering the noise it is sometimes possible to reveal low level signals that are in the noise This is the primary reason for using a video filter The signal peaks at 700 MHz 800 MHz and 900 MHz the seventh eighth and ninth harmonics of the calibration signal should now be visible There are small differences from instrument to instrument but you should be able to spot the peaks above the noise Video filtering works well for continuous wave and other narrow band signals but when examining pulsed or wideband signals such as television video especially the sync pulses a video filter may prevent you from accurately seeing signal characteristics in much the same way that using a resolution bandwidth that is too narrow does Although it may not have been apparent the sweep speed also decreased in order to accommodate the longer time constant of the video filter Just as with the resolution bandwidth filter a signal needs more time to reach its peak amplitude when propagating through a narrow video filter 3 Press VID FLTR again to toggle the video filter off 2715 User Manual 4 15 Dedicated Controls Vert Scale 4 16 The Vert Scale controls select from the available logarithmic vertical scale factors or convert to the linear mode 100 0MHz 23 8DBMV 20 0MHz 5MHz
79. is a conventional spectral display of signal power vs frequency However by selecting FM DEVIATION MODE you can view instantaneous frequency variations vs time 1 Connect a short antenna or tap to the 2715 input as outlined in Appendix B Broadcast AM FM and TV Signal Sources 2 Ensure that the calibrator is turned off 3 Adjust the reference level until you can see individual FM broadcast or TV sound carrier signal peaks 4 Tune the 2715 until a strong signal is centered Your display might resemble Figure 6 12 on page 6 52 5 Press SPAN DIV 1 0 0 Y to change the span to 100 kHz div 6 Press CATV APPL 7 to select FM DEVIATION MODE from the Applications menu The 2715 reverts to a waveform display mode in zero span The bottom line of the right column reads as shown below FM 10 KHz 2715 User Manual Spectrum Analyzer Menus This indicates that FM demodulation is now being used and that the vertical scale factor has changed to 10 kHz division The vertical axis now measures frequency deviation The sweep being displayed should resemble the upper trace in Figure 6 14 It is an approximate indication of the instantaneous frequency deviation The vertical scale can be changed in a 10 5 1 kHz div sequence 7 Repeatedly press 10 5 1 to cycle through the frequency deviation scales set the vertical scale to 10 kHz div 8 Press DSPL 9 W to select MIN HOLD IN WFM A Let the
80. kHz 0 1 6 V 200 mV div signal input for vertical deflection of the CRT beam The signal is processed through the video filters and the 1 dB 5 dB and 10 dB scale factor circuits on the Log board Display storage may be by passed TTL compatible signal that goes to a logic high level while the CRT beam is Sweeping Provides a nominal 1 3 V to 1 3 V negative going ramp proportional to the horizontal sweep output impedance lt 50 Provides 0 V to 41 6 V of video signal inversely proportional to the vertical display amplitude 0 V is the top ofthe screen Impedance is 1 kO Clock output to Option 05 External Tracking Generator CMOS logic levels typically 3 5 V high 1 5 V low Pin 7 Data I Input Data input from Option 05 External Tracking Generator Typically 45 V high 30 1 V low Pin 8 Data O Output Data outputto Option 05 External Tracking Generator CMOS logic levels typically 3 5 V high 1 5 V low mo in 9 EXTGLATCH Logic output to Option 05 External Tracking Generator CMOS logic levels typically 3 5 V high 1 5 V low mo in 10 26 38 MHz Input A 18 Input from Option 05 External Tracking Generator typically a 0 5 Vp p sine wave centered at 43 7 VDC 2715 User Manual Specifications Table A 5 Input Output Signal Characteristics Cont Characteristic Pin 11 VLVL Output Performance Requirement Pin 12 SWPSLOPE Output Supplementa
81. measurement records and displays the following parameters for the current channel Peak visual carrier level averaged power if measuring a digital channel m Visual carrier frequency not available when measuring a digital channel Intercarrier frequency not available when measuring a digital channel m Visual to aural carrier amplitude ratio not available when measuring a digital channel Three measurement modes allow you to select the trade off between measure ment time and accuracy that best fits your needs m FREQ AMPL accurately measures carrier frequencies and amplitudes ACCUR AMPL accurately measures carrier amplitude but does not measure carrier frequency m FAST AMPL less accurately measures carrier amplitude and does not measure carrier frequency NOTE When measuring a digital channel all measurements are made in a mode similar to ACCUR AMPL In conjunction with the CARRIER LEVELS measurement you can set up the 2715 so that the above parameters are measured for a second aural carrier for the current channel These measurements are also recorded and displayed 5 20 2715 User Manual Measurements CARRIER LEVEL 2715 User Manual When the CARRIER LEVELS measurement is initiated on an analog channel the 2715 performs the following steps that are common to all CARRIER LEVELS measurement modes Recalls base settings if necessary Base settings are the standard settings fro
82. must store it in register A Whichever register is used it must be cleared before you attempt to store new data in it or you will receive an error message Item 8 of the ENSEMBLE AVERAGING sub menu is a three way toggle that switches among registers in the sequence A B C A 20 Ensure that register A is clear and then repeatedly press 8 until the last character on the line is You can average a fixed number of spectra or choose continuous averaging Continuous averages are used when the mean value of the signal you are viewing can change slowly with time when you want to watch a mean value estimate change in real time or when you simply wish to continuously monitor a process If you select a fixed ensemble size you can average up to 1024 sweeps The parameter being averaged can be the maximum minimum max min or mean of the spectral display Averaging begins when item 1 is selected from the Ensemble Averaging menu and ends when the sweep has been completed You can also stop the averaging by selecting item 2 from the menu Continuous averaging weights older sweeps so that they have a progressively smaller effect on the average Each step back in time reduces the impact of a sweep to 90 per cent of its previous value 6 29 Spectrum Analyzer Menus 6 30 The factory default setting is a 16 sweep fixed average Do the following steps to change the number of averages to 24 21 Press 7 from the Ensemble Averagi
83. obtain continuous counter readings in the signal track mode 4 31 Dedicated Controls 4 32 28 Press MKR FREQ 9 1 2 to turn on the counter see Counter Resolution on page 6 23 for additional information The following steps show how to continuously monitor a frequency difference 29 Press CTR MEAS TRKG again to exit from tracking mode 30 Reset the span to 50 MHz div 31 Enter the delta marker mode 32 Place the movable marker near the third harmonic 33 Reenter the tracking mode You are using the delta counter feature in the signal track mode The third harmonic is centered and the frequency difference between the fundamental and third harmonic is being constantly monitored 34 Exit from the tracking mode and turn off the markers Arrow Keys You can use the arrow keys to move the marker from one peak to another 35 Center the calibration signal 36 Turn on the marker 37 Press MKR The marker jumps to the second harmonic peak 38 Press 9 again 39 The marker jumps to the third harmonic 40 Now press MKR 4 The marker jumps in the other direction MKR 4 and MKR move the marker to the next signal peak in the indicated direction and above the preset threshold but they will not go beyond the edge of the display or lower than 0 Hz Further the readouts and center measure tracking behave as if you had manually moved the marker 41 Enter the delta marker mode a
84. off the D register 8 Press A to turn on the A register Notice that the display does not change with time The contents of the A register are not being updated You are viewing a saved sweep 9 Now save a waveform into the B register 10 Activate the B register and ensure the A register is turned off 11 Set the resolution bandwidth to 30 kHz 12 Press SAVE ENABLE B The current sweep is saved and the B green LED lights The register remains active but because it is now saved it is no longer updated NOTE Status of the red LED is not changed by the save operation 2715 User Manual Dedicated Controls 13 Deactivate all registers all red LEDs extinguished 14 Set the resolution bandwidth to 5 MHz 15 Press SAVE ENABLE C The green C LED lights 16 Activate the C register The digitized and saved version of the analog sweep is displayed The digitizer is continuously updated whether it is being displayed or not Further it is always the current digitizer output that is saved You cannot for instance save one register into another However nonvolatile RAM does make it possible to permanently save the contents of the display registers by transferring them to stored settings registers see Other User Defined Settings on page 6 63 17 Press SAVE ENABLE A to deactivate the C register and activate A The A green LED turns off indicating there is nothing stored in the A register The regist
85. peak should drop to almost one division below the reference level The reference level readout should indicate 28 3 dBmV 8 Press REF LVL STEP again REF LVL STEP is another toggle action key The LED goes out indicating that the reference level is back in 10 dB per press mode 9 Press w Confirm that the reference level returns to 18 3 dBmV 10 Reset the reference level to 38 8 dBmV The first part of this section covered the fundamental controls of the 2715 This second part covers the remaining controls and how they enhance your ability to make accurate spectral measurements easily and conveniently We cover how to control the resolution bandwidth vertical scale factor and sweep speed We show how to use display storage and marker controls to quickly measure signal amplitude and frequency with maximum accuracy and we show how to make direct spectral comparisons and to save important results for future reference in nonvolatile RAM NVRAM 100 0MHz 38 8DBMV 20 0MHz 5MHz RBW AUTO AUTO SWEEP ATTN 20DB VF WIDE 10 DB Channel Table Name CH nn CALIBRATOR The Res BW controls select the 2715 resolution bandwidths of 300 Hz to 5 MHz and allow time to be automatically selected to match the selected bandwidth 4 11 Dedicated Controls 4 12 Set the 2715 parameters as follows to match the preceding settings box 1 Press UTIL 1 1 to recall factory default settings 2 Press CCHAN FREQ 1 0 0
86. power up channel center of currently selected channel or selected frequency nn Channel number This is most easily done by pressing UTIL 1 1 to recall the factory default settings Dedicated Controls 4 2 SPAN DIV The span controls change the total display frequency span range symmetrically about the center frequency select channel table entries and set the 2715 in the maximum span or zero span modes 1 Press INPUT 9 to turn on the calibration signal 2 Press MKR A OFF twice to turn off the markers 3 Press CHAN FREQ 4 0 0 X to set the 2715 center frequency to 400 MHz 4 Press MAX and AUTO RES BW Remember that in MAX SPAN the marker changes position and not the frequency at screen center 5 Press REF LEVEL 3 8 e 8 Y to set the reference level to 38 8 dBmV Arrow Keys The arrow keys to the right of SPAN DIV change the frequency span represented by one horizontal division on the screen The arrows directly increase or decrease the span per division 6 Beginning with maximum span press to the right of SPAN DIV several times to decrease the span div to 20 MHz This causes the 2715 to zoom in on the spectral display 7 Now press until the span div increases to 180 MHz Watch the spectral display zoom out just as though it was moving away from you The up arrow increases the span div compressing or squeezing the spectrum together The down arrow de
87. rate to 2 msec div and deactivate all storage registers 5 The screen displays one field of video information The dark vertical spaces in the waveform are caused by the time taken to write the on screen readouts 6 Turn off the readouts The waveform on screen should resemble Figure 6 15 except it will be sliding across the screen because the sweep generator is free running 100 NNI RUMP NR Rezo Figure 6 15 Video Field Using Internal or TV Field Triggering 6 84 2715 User Manual Spectrum Analyzer Menus TV Line Trigger 2715 User Manual 7 Select item 1 INTERNAL from the SWP TRIG menu 8 Slowly rotate the LEVEL control until the display is stationary The sweep is now being triggered by the vertical sync pulse External triggering is usually chosen for pulsed signal analysis when there is an externally available gate signal signifying that the signal to be examined is present at the 2715 input for example the keying signal from an RF transmitter or the squelch signal in a receiver if the gating signal is not available you might trigger internally The External trigger signal is applied through a BNC connector J102 on the back of the 2715 its amplitude can be from 100 mV to 50 V See Appendix E External Input and Output for additional information 9 Without changing any other control settings select item 3 LINE fro
88. reference level to 38 8 dBmV and turn on the calibrator 7 Press repeatedly to reduce the time div A beep sounds and the word UNCAL appears 8 Continue to press to increase the sweep speed and notice the signal peak decrease and shift to the right This condition occurs when sweeping too fast for a given resolution BW and demonstrates how measurement errors can occur The resolution filter is sweeping so fast that its output does not have time to reach steady state 9 Reselect ZERO SPAN The UNCAL message disappears because in the zero span mode the filter is not being swept at all 10 Reset the displayed sweep speed to 1 ms div AUTO The AUTO key in the SWEEP function block serves two purposes First it is used in much the same way as the AUTO key in the RES BW function block as a toggle action key that switches the 2715 between automatic and manual selection of sweep rate When AUTO sweep rate selection is active the sweep rate selected by the 2715 depends on the span div resolution bandwidth and video filter in use Second pressing the SWEEP AUTO key when the 2715 is in the single sweep mode exits from that mode 11 Press ZERO to exit the zero span mode Notice how distorted the calibration signal is 2715 User Manual Dedicated Controls 2715 User Manual 12 Press AUTO in the SWEEP function block The LED below the key lights indicating that the sweep rate is being automatically s
89. right of the stationary marker 12 Turn on the video filter if the sixth or seventh harmonics of the calibration signal near center screen are not visible The peaks should now be visible 13 Place the moveable marker on either peak to measure its difference in amplitude and frequency relative to the fundamental 14 Press MKR A OFF one press if in A marker mode two if in single mark er mode to exit the marker mode and return to the normal RF attenuation and video filter readouts 15 Turn off the video filter CTR MEAS TRKG 140 0MHz AUTO SWEEP ATTN 40DB 28 8DBMV VF WIDE 50 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR The center measure feature detects the signal peak nearest the marker and above a preset amplitude threshold changing the threshold is discussed in MKR FREQ on page 6 17 When the marker is turned off the signal peak nearest center screen is used The 2715 then measures the signal frequency and makes it the new center frequency This feature allows you to bypass tuning to measure a signal frequency just place the marker close to the signal of interest and press CTR MEAS TRKG Press the key twice to enable the signal track feature to keep drifting signals centered by continuously repeating the center measure feature NOTE CTR MEAS TRKG provides the easiest and most accurate method of determining a signal s frequency 16 Press MKR A OFF to activate the marker 4 29 Dedicated Contro
90. saved data Pressing D when SAVE ENABLE is armed toggles the spectrum analyzer in and out of waterfall display mode All registers must first be cleared Individual sweeps cannot be saved in D Arms the save clear function Press SAVE ENABLE and then press the key corresponding to the register to be saved cleared The LED below the key lights when SAVE ENABLE is armed Enables max hold mode When MAX HOLD is enabled the A and B registers retain the largest signal observed unless they contain saved waveforms The LED below the key lights when MAX HOLD is active N VERT SCALE LIN 10 51 LEVEL PLOT READOUT AM VOLCI INTENSITY FM VOLL OPTION POWER ON OFF Figure 3 7 Vertical Scale and Other Controls This area of the front panel contains the following controls 10 5 1 Press repeatedly to cycle the vertical scale in 10 5 1 10 sequence in LOG logarithmic display mode LIN Toggles the vertical display mode from LOG logarithmic to LIN linear and back again Scale factor is controlled by the reference level controls in the LIN mode and by 10 5 1 in the LOG mode Initiates a screen plot on an optional printer or plotter Plotter and interface must be correctly configured see System Configuration on page 6 67 Operating Basics READOUT POWER INTENSITY LEVEL AM VOL and FM VOL VID FLTR 3 8 Toggles the on screen readouts on and o
91. service center or representative if message persists NORMALIZED RESULT OUT OF RANGE Perform normalizations again Contact your local Tektronix service center or representative if message persists NORMALIZING Normalization routine running NOT AVAILABLE WITH DBUV M IDLE The selected function is not available with DBUV M mode idled Select new reference unit to enable operation NOT AVAIL IN SHORT HOLDOFF MODE Certain functions that require end of sweep processing are not available when in the Short Holdoff mode NOT AVAIL IN WATERFALL MODE The selected function is not available in waterfall mode NOT AVAIL W DISPLAY STORAGE ON Function not compatible with digital display Use analog display NOT INSTALLED Feature not installed on this instrument C 9 Appendix System Messages C 10 NVM CHECKSUM ERROR Nonvolatile memory has been corrupted and consequently re initialized Contact the local Tektronix service center or representative if message persists NVM FRAGMENTATION ERR Firmware hardware error Contact your local Tektronix service center or representative if message persists NVM SEGMENTATION ERROR Firmware hardware error Contact your local Tektronix service center or representative if message persists NVM VERSION MIS MATCH Firmware hardware error Contact your local Tektronix service center or representative if message persists ONLY WAVEFORMS DELETED When settings you are attempting to delete
92. slightly below the selected beat frequency sets 30 kHz RBW and turns the video filter off The instrument begins gating the signal path so that the path is on only during quiet lines in the vertical interval It then internally acquires and averages a reasonable number of readings during gate on times for each of a series of closely spaced frequencies bracketing the selected beat frequency The highest reading for the collection of averaged submeasure ments is reported as the amplitude of the selected beat The 2715 then verifies the quiet lines After the measurement has been made or Z is pressed the instrument returns to the spectral display Automatic Mode In the Automatic mode the instrument measures the level of the signals at frequencies specified in the setup table Up to five 5 frequencies can be specified For each table entry the instrument measures the beat using the same settings as specified for the interactive case Automatic With Pause The Automatic With Pause mode is identical to the Automatic mode except that Mode after measuring the video carrier the instrument pauses and prompts you to turn off the carrier The Automatic With Pause mode is not available when in service basis is selected 5 50 2715 User Manual Measurements Single Sweep Mode Continuous Mode 2715 User Manual The Single Sweep mode is designed to minimize the time that the carrier must be turned off The Single Sweep mode is no
93. spurious responses and possibly even damaging the mixer 4 Press INPUT 9 to turn on the built in calibrator NOTE The amplitude of the internal calibrator is 18 8 dBmV This places the peak level at the top graticule line with the reference level set at 18 8 dBmV and 0 dB internal attenuation To measure the calibration signal you are going to use the three primary controls on the spectrum analyzer These are located in the central dark gray function block and are shown in Figure 2 4 The three primary controls and the FREQ MKRS knob to the left are the controls you will use most often In general you can make most measurements with only these controls although you will find that other controls and menu features enable you to make many measurements more quickly and conveniently Selects Change frequency in frequency for designated step size immediate entry Decrease Increase Ean Selects span div for od Decrease Change span div in 1 2 immediate keypad entry SPANN Increase Selects reference level for immediate REF LEVEL eerieve f J Increase Change reference level in 1 dB or keypad entry Geno 1 Decrease 10 dB steps Figure 2 4 The Primary Controls First raise the displayed signal height by reducing the reference level The reference level represents the signal power needed to deflect the displayed spectrum to the top graticule line The 27
94. stored results for the Carrier Survey measurement beginning with the last stored results After all the results have been displayed the 2715 reverts to the CARRIER SURVEY menu 5 27 Measurements 9 Press 3 to print results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 10 Press 4 to print all stored results of the measurement A printer must be connected to the 2715 11 Press 9 to leave the Carrier Survey measurement and return to the CATV MEASUREMENTS menu MODULATION DEPTH Measurement 5 28 The MODULATION DEPTH measurement records and displays the depth of modulation for the current channel Test results can be displayed and stored Stored or current results can be printed if you have an RS 232 interface installed in the 2715 You make selections and run the modulation depth test using the CATV MEASUREMENTS submenu MODULATION DEPTH which provides the following choices 0 RUN MODULATION DEPTH 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 SET UP ADJUSTMENT MODE 6 ENTER ADJUSTMENT MODE 9 LEAVE MODULATION DE
95. that is mixed with an incoming signal to produce the IF signal Markers The instrument uses three types of markers Update Marker Marks the current sweep position in a digital storage display as the display is being updated Video Markers Marker signals applied to the external VIDIMARKER input from a Tektronix 1405 Television Sideband Analyzer The Video Markers mark frequencies of interest on the television signal Waveform Markers When the Marker function is enabled it provides a movable cursor with readout of frequency and amplitude at the marker position When the delta marker mode is enabled a second marker allows operations and readout between the two marker positions MAX HOLD Peak Mode Digitally stored display mode which at each frequency address compares the incoming signal level to the stored level and retains the greater In this mode the display indicates the peak level at each frequency after several successive sweeps 2715 User Manual Glossary 2715 User Manual MAX MIN A display mode on the spectrum analyzer that shows the maximum and minimum signal levels at alternate frequency points its advantage is its resemblance to an analog display MIN HOLD A spectrum analyzer feature which captures the minimum signal amplitude at all displayed frequencies over a series of sweeps Modulate To regulate or vary a characteristic of a signal Modulating Signal The signal which modulates a carrier The sig
96. the SWEEP arrow keys slow the sweep rate to 2 ms div The display resembles Figure 6 15 on page 6 84 You can now see an entire frame of video information with the start of the frame at the left of the display The frame does not slip sideways as it does in the LINE trigger mode because the sweep generator is locked to the displayed signal itself You can eliminate the dark vertical spaces in the display by turning off the readouts Slow the sweep rate without using SWEEP and 15 Call up the Sweep Trigger menu and choose item 6 SWEEP RATE 16 Following the prompt enter 5 ms div The 2715 reverts immediately to the display mode and you can see three whole video frames This feature enables you to conveniently set sweep rate when you are already working in the Sweep Trigger menu and may have turned off the readouts 17 Return to the FREE RUN mode by pressing SWP TRIG 0 2715 User Manual Spectrum Analyzer Menus Manually Scanning USER DEF 2715 User Manual 100 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF 300KHz 1 0MHz 10 DB 300KHz RBW AUTO 1 Center a strong video carrier 2 Callup the Sweep Trigger menu and select item 7 MANUAL SCAN The spectral display reappears but it does not appear to be updating 3 Turn the inner LEVEL control knob and watch the screen carefully A portion of the display updates as you turn the knob In this mode the knob controls the horizontal sweep position
97. the case of pure amplitude modulation as is assumed by the Time Domain method This is done to preserve continuity with previous history So the indicated cross modulation reading is 9 9 dB worse than the sideband amplitude that produced it For example if sidebands are found at 60 dBc an equivalent cross modulation level of 50 1 dBc is displayed and stored For another example suppose the test carrier is cross modulated such that the carrier amplitude varies 1 peak to peak Both the Time Domain and Frequency Domain methods would report a cross modulation level of 40 dBc The closest in sidebands would then be 49 9 dB below the carrier As a final example suppose that instead of being amplitude modulated the test carrier is phase modulated to an extent that produces closest in sidebands 65 dB down from the carrier The Frequency Domain method would report a cross modulation level of 55 1 dBc but the Time Domain method would detect no cross modulation and would display CROSS MOD lt 48 DBC indicating that the cross modulation level was below its measurement limit If the cross modulation is the result of amplitude and phase effects the sidebands will be unequal in amplitude The Frequency Domain method reports the higher of the two sideband amplitudes to ensure the most conservative result with respect to compliance with legal limits on coherent disturbances The following procedure shows how to take a cross modulation measu
98. the factory default value of 5000 ms to the value you entered This value is permanently stored until you change it using the above procedure 6 79 Spectrum Analyzer Menus Service Normalizations 6 80 The 2715 contains a set of frequency and amplitude normalization values when it is shipped from the factory The normalizations are based on reference values called reference normalizations determined at the time of manufacture The reference normalizations specify the 2715 gain step sizes and the frequency and amplitude of the internal calibrator signal The references are determined by comparison with an accurate external attenuator and signal source If NVRAM is ever lost for instance because the battery runs down the factory reference normalizations are lost with it and you must perform a service reference normalization to achieve maximum accuracy from the 2715 If you have signal sources available that are more precise than the on board calibration signal they can be used to achieve added accuracy when normalizing the 2715 Using the REFERENCE NORMALIZATIONS selection from the Service Normalizations menu you can measure new reference values for the on board calibration signal and attenuator with respect to more precisely known alternate sources The alternate sources must exceed the following specifications frequency 5 parts in 107 10 Hz amplitude 18 8 0 1 dBmV 100 1 MHz attenuation gain step 10 0 5 dB 10
99. the protection press BKSP 8 3 You can now delete the routine if you wish 13 To execute the UDP press USER DEF 3 The display will return to the spectral display and also display the message WAITING FOR Date Time PROG 3 PRESS USER DEF TO ABORT NOTE In creating the UDP you actually stored data from each measurement as the UDP was being defined If you want to retain only the data from the 24 hour test be sure to remove all stored results prior to executing the UDP Also the SITE and OPERATOR NAMES should be defined prior to the UDP execution so the stored data will be properly nomenclated 2715 User Manual 6 91 Spectrum Analyzer Menus 6 92 2715 User Manual Appendices MU rey Appendix A Specifications This section lists the electrical physical and environmental characteristics of the spectrum analyzer specifies the performance requirements for those characteris tics and provides supplementary information Electrical Characteristics 2715 User Manual Unless otherwise stated the following tables of electrical characteristics and features apply to the spectrum analyzer after a 15 minute warm up period within the environmental limits and after all normalization procedures have been carried out Information in the Performance Requirement column of Tables A 2 through 8 is guaranteed and verifiable unless otherwise noted Supplemental Information is intended to further explain a characterist
100. the screen display is the collection of noise peaks This does not affect the accuracy of the earnest measurement nor does it affect your ability to locate a low amplitude region for the earnest measurement In this particular situation there is no need for concern when the visual noise level appears to be excessively high In Auto Test Mode you will not be required to do any settings In Auto with Pause for Carrier Off Test Mode you will be prompted to turn off the carrier at some time during the measurement If measuring an analog channel the spectrum analyzer then measures the noise at 2 7 MHz above the video carrier If measuring a digital channel the spectrum analyzer measures the undesired power across the whole channel In addition to the three test modes you are given the option of resetting the normalized noise bandwidth The default bandwidth is 4 MHz This is not used for digital channels 5 Press BKSP to return to the CARR NOISE DESIRED UNDESIRED measurement menu 6 Press 0 to run the CARR NOISE DESIRED UNDESIRED measure ment After the measurement is complete the instrument displays the current results the offset frequency from the carrier at which the noise was measured and the normalization bandwidth superimposed on the spectral display 5 39 Measurements 7 Press CATV APPL to display the CARR NOISE DESIRED UNDE SIRED menu 8 Press 1 to store the results of the las
101. to select ALL PARAMETERS Typically you will see a number of changing waveforms and messages on screen telling you which normalizations are being carried out However if NVRAM is ever lost the factory reference normalizations are lost with it see f You Lose NVRAM on page 6 81 Then regardless of which normalizations you are carrying out you will receive the following message ONE OR MORE REFERENCE NORMALIZATIONS HAS NOT BEEN PERFORMED FOR OPTIMUM ACCURACY REFERENCE NORMALIZATIONS MUST BE DONE CONSULT MANUAL FOR PROCEDURE PRESS W TO CONTINUE PRESS Z TO ABORT 5 If you have facilities to carry out the reference normalizations see Service Normalizations on page 6 80 abort this process and perform the reference normalizations before continuing Otherwise press W to continue A recently normalized instrument is more accurate than one that is not normal ized even if the references have not been normalized 2715 User Manual Spectrum Analyzer Menus System Configuration Configuring the Communications Port 2715 User Manual The normalization process completes without further operator intervention When it is complete a beep sounds if the audio alert is enabled see The Audio Alert on page 6 71 and the following message appears NORMALIZATION COMPLETE If you receive a message that either frequency or amplitude normalization failed try the procedure again The spectral display reappear
102. to select the AURAL FM DEVIATION measurement menu 3 Press 5 to select SET UP AURAL FM DEVIATION 4 Press 0 to select interactive mode if not already selected as indicated by an asterisk 5 Press 5 and use the keypad to enter and 5 6 Press W to enter selected time sets the measurement time to 0 50 minutes 7 Press BKSP to return to the AURAL FM DEVIATION measurement menu 8 Press 0 to run the interactive aural FM deviation measurement After the measurement is complete the instrument displays the current results and the message RESUME OR ACCEPT CURRENT MEAS W TO RESUME Z TO ACCEPT 9 Press W to run the measurement again or Z to accept the current measurement If you press W to run the measurement again waveform C continues to accumulate peak deviation data for the measurement time you selected 30 seconds 10 Press CATV APPL to display the AURAL FM DEVIATION menu 2715 User Manual Measurements 11 Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed 12 Press 2 to display results of the last measurement performed A display resembling Figure 5 4 on page 5 24 appears showing FM deviation At this point you can choose to either go ahead and view other previously stored results for this measurement by pressing W or stop viewing the results by pres
103. triggering because of the multiple signal peaks and blanking period of the video signal but there should be a spectrum on the oscilloscope similar to the one on the 2715 If not adjust your oscilloscope trigger and vertical position controls Pin 2 Sweep Gate Pin 2 of the Accessory Connector contains the sweep gate The sweep gate is a 5 V pulse whose leading edge is synchronous with the start of the 2715 s sweep The trailing edge marks the end of sweep See Figure E 2 The signal is usually used in conjunction with the video output pin 5 to indicate when a new sweep is beginning Volts f Analog Video 5 Sweep Gate 0 1 3 Sweep Ramp 0 13 Time Figure E 2 Sweep Gate and Ramp Timing 2715 User Manual E 5 Appendix E External Input and Output Pin 4 Sweep Ramp E 6 m Continuing with the setup from the video output discussion connect pin 2 to the external trigger input of your oscilloscope and select the external trigger mode positive slope Adjust the oscilloscope trigger level control until the spectral display locks in place Now turn off all the analyzer s registers Compare the spectrum analyzer and oscilloscope displays If the image is as desired follow the next step this can be especially important when you are trying to view time varying analog spectra m Turn on MAX HOLD in all the 2715 registers Notice the analog tr
104. use three of the most important controls on the spectrum analyzer and to confirm that the major functions of the spectrum analyzer are operating correctly 1 Press UTIL 1 1 to recall FACTORY DEFAULT POWER UP settings The factory defaults set the RF attenuation to 50 dB This affords the most protection to the spectrum analyzer because any signal at the input undergoes maximum attenuation before reaching the power sensitive mixer circuit We recommend that you use this setting when connecting unknown signals to the spectrum analyzer 2 Press CATV APPL 8 0 to disable the CATV mode 3 Press MAX then AUTO in the RES BW block to enable maximum span and AUTO RES BW The span goes to 180 MHz per division and the resolution bandwidth goes to 5 MHz This is maximum span and is indicated by the word MAX in the span readout This is the safe setting for introducing new signals It enables you to view the entire measurement range 1 8 GHz of the spectrum analyzer If a smaller span is used large signals can be present off screen 2715 User Manual 2 13 Getting Started 2 14 A CAUTION The total signal power that is all signals on screen or off added together not just the signal of interest must remain below 70 dBmV With a small span it is also possible to reduce the attenuation to view a low level on screen signal while inadvertently allowing an off screen high level signal to saturate the mixer causing
105. volts The display is similar to what you see on an oscilloscope Thereafter the REF LEVEL arrow keys change the scale factor in a 1 2 5 sequence Consequently the reference level changes by 6 or 8 dB when changing scale factors If the FINE reference level step size is selected while in the LIN mode the arrow keys change the scale factor at a rate of approximately 0 02 division per step and the corresponding reference level changes approximately 0 2 dB 2715 User Manual Dedicated Controls 2715 User Manual Sweep 6 Press LIN to toggle back to logarithmic mode When switching back to logarithmic from linear the last selected log scale is implemented 100 0MHz AUTO SWEEP ATTN 21 2DBMV VF 3KHz 50 0KHz 10 DB 10KHz RBW AUTO The Sweep function block controls the 2715 normal sweep rate auto sweep and single sweep feature other trigger modes are discussed in SWP TRIG on page 6 83 The rate at which the CRT beam sweeps across the screen is known as the sweep rate It is also the rate at which the displayed spectrum is swept Arrow Keys Normally sweep rate is automatically selected by the 2715 However in some cases such as when looking at the time domain representation of a signal in zero span you may want to vary the sweep rate for a better view of the signal 1 Ensure that the calibrator is turned off and enter the zero span mode The currently selected sweep rate is displayed on screen as the
106. waveform B Enable HUM LFD The following procedure shows how to make a HUM LFD measurement Measurement 1 Press CATV APPL to call up the CATV MEASUREMENTS menu See Figure 5 1 2 Press 6 to select the HUM LFD measurement menu 2715 User Manual 5 41 Measurements 5 42 This gives you the following options 0 RUN HUM LFD 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 POWER LINE FREQ 9 LEAVE HUM LFD Press 5 to select the desired power line frequency 60 Hz or 50 Hz The 5 key toggles between the two line frequencies Press 0 to run the Hum LFD measurement After the measurement is complete the instrument displays the measured hum at the selected power line frequency and the time domain waveform in waveform B Press CAT V APPL to display the HUM LFD menu Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed Press 2 to display the results of the last measurement performed A display resembling Figure 5 4 appears showing the current result You can press W to view other previously stored results for this measurement or press Z to stop viewing the results Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement results only when the RS
107. you attempt to recall settings with or without corresponding displays you will receive the message CANNOT OVERWRITE SAVED DISPLAY The settings will be recalled along with any displays saved in registers A B or C that are not currently saved but currently saved registers will not be overwrit ten To recall a previously saved display first unsave its destination register The following example demonstrates the ability the 2715 has to recall the last settings in effect before the power was turned off 14 Turn off the 2715 and then turn it on again 15 Press UTIL call up the Utility menu 16 Press 1 to select STORED SETTINGS DISPLAYS 17 Press 0 to select LAST POWER DOWN 18 The settings that were in effect the last time power to the 2715 was turned off are immediately recalled 100 0MHz AUTO SWEEP ATTN 0DB 18 8DBMV VF WIDE 20 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR The following examples describe using the user defined power up settings 1 Press UTIL to call up the Utility menu 2 Press 1 to select STORED SETTINGS DISPLAYS 3 Press 2 to select USER DEFINED POWER UP 4 Following the prompt press X to store the current settings 2715 User Manual Spectrum Analyzer Menus Other User Defined 2715 User Manual Settings You are warned if other settings are already stored as the user defined power up If there are old settings you must delete them before you can store the current setti
108. you measure a digital channel the 2715 executes these steps for each carrier Recalls base settings if necessary Base settings are the standard settings from which each test is run equivalent to selecting 0 RECENTER CHANNEL xx from the CATV Measurements menu page one Sets sweep to single sweep mode acquisition mode to sample detect and selects 30 Hz video filter bandwidth Sets the resolution bandwidth to 100 KHz in channels wider than 4 MHz otherwise sets it to 30 KHz Sets span div so that the screen covers 15 more than one channel width Sets time div to AUTO mode Takes a sweep and adjusts the reference level up in 10 dB steps if max signal is off the top of the screen Finds the edges of the signal Integrates the power spectral density of all screen locations between the edges of the signal Stores the resulting amplitude as an averaged power amplitude NOTE If the preselector is used you should allow or correct for its insertion loss The input level limit with preselector can be extended to 62 dBmV but this can cause significant additional inaccuracy 2715 User Manual Measurements Enable CARRIER LEVELS Measurement 2715 User Manual You use the CATV MEASUREMENTS menu to access the CARRIER LEVEL AVG POWER measurement menu The CATV MEASUREMENTS menu resides on two pages see Figure 5 1 on page 5 4 You can toggle between the pages by pressing 9 1 Press CATV APPL to d
109. 0 1 MHz We will not give examples for all reference normalizations but we will show you how to determine a new frequency reference 1 Connect an external frequency source to the 2715 input meeting the frequency specification given above Various sources are available for example WWV in the U S some broadcast television carriers assorted frequency standards A frequency of 100 to 500 MHz would be very good but signals as low as 5 MHz can be used 2 Return to the spectral display and perform a center measure to ensure the external reference is centered 3 Press UTIL 5 5 to select SERVICE NORMALIZATIONS 4 Press 1 to select REFERENCE NORMALIZATIONS 5 Press 1 to select INTERNAL REF FREQ from the resulting Reference Normalizations menu On screen prompts appear for each of the reference normalizations 6 Press 1 to select EXTERNAL FREQ and enter the frequency of the external source 2715 User Manual Spectrum Analyzer Menus If You Lose NVRAM 2715 User Manual A 7 Press 2 to select CONNECTED MEASURE and press W when you are ready to have the 2715 determine the new reference After a few seconds you will receive a NORMALIZATION COMPLETE message 8 Determining new gain step and amplitude references is done in a similar fashion follow the prompts 9 Press UTIL 3 0 to complete the process of optimizing the 2715 s accuracy by performing a complete normalization The remainin
110. 0 39 312 00 316 50 40 318 00 322 50 35 288 00 292 50 36 294 00 298 50 37 300 00 304 50 38 306 00 310 50 39 312 00 316 50 40 318 00 322 50 41 324 00 328 50 42 330 00 334 50 43 336 00 340 50 44 342 00 346 50 45 348 00 352 50 46 354 00 358 50 5 13 Measurements Table 5 5 HRC Cont Channel Visual Carrier Aural Carrier 47 360 00 364 50 48 366 00 370 50 49 372 00 376 50 50 378 00 382 50 51 384 00 388 50 52 390 00 394 50 53 396 00 400 50 54 402 00 406 50 55 408 00 412 50 56 414 00 418 50 57 420 00 424 50 58 426 00 430 50 59 432 00 436 50 60 438 00 442 50 61 444 00 448 50 62 450 00 454 50 63 456 00 460 50 64 462 00 466 50 65 468 00 472 50 66 474 00 478 50 67 480 00 484 50 68 486 00 490 50 69 492 00 496 50 70 498 00 502 50 71 504 00 508 50 72 510 00 514 50 73 516 00 520 50 74 522 00 526 50 75 528 00 632 50 76 534 00 538 50 TI 540 00 544 50 78 546 00 550 50 79 552 00 556 50 80 558 00 562 50 81 564 00 568 50 82 570 00 574 50 5 14 2715 User Manual Measurements Table 5 5 HRC Cont Channel Visual Carrier Aural Carrier 83 576 00 580 50 84 582 00 586 50 85 588 00 592 50 86 594 00 598 50 87 600 00 604 50 88 606 00 610 50 89 612 00 616 50 90 618 00 622 50 91 624 00 628 50 92 630 00 634 50 93 636 00 640 50 94 642 00 646 50 Table 5 6 IRC Channel Visual Carrier Aural Carrier 2 55 25 59 75 3 61 25 65 75 4 67 25 71 75 1 73 25 71 15 5 79 25 83 75 6 85 25
111. 15 provides several methods of directly changing the reference level The most convenient method is to press the arrow keys 2715 User Manual Getting Started 5 Press to the right of REF LEVEL three times to reduce the reference level 30 dB For numeric entry the W key terminates any channel number whereas the X Y or Z keys terminate channel frequency entry On channel frequency the 2715 selects the channel closest to the new channel frequency Figure 2 5 shows what the resulting display should look like although some of the signal peaks on your spectrum analyzer may have slightly different ampli tudes than those shown Notice that both the reference level and RF attenuation readouts have decreased 30 dB the reference level is 38 8 dBmV and the RF attenuation is 20 dB Normally the arrow keys change the reference level 10 dB per press but in FINE mode the value changes 1 dB per press Another method is to set the reference level to 20 8 dBmV less than half a division above the expected signal ampli tude We choose this value for the following reasons m Signal amplitudes are read out and displayed most accurately when they are near the reference level m 2 dB provides a small amount of headroom in case the signal should be slightly larger than anticipated Fundamental Le E N 2nd 3rd 4th 10th 100 ake REF 900 0MHZ ATTN 20DB 38 8DBMV T VF WIDE 180MHZ MAX i 10 DB z5bMHZ RBW
112. 2715 13 Press 4 to print all stored results of the measurement A printer must be connected to the 2715 14 Press 9 to return to the CATV MEASUREMENTS menu CARRIER SURVEY Measurement The CARRIER SURVEY measurement makes a carrier levels measurement on all active unskipped channels in the current channel table and makes a record of the following parameters Peak visual carrier amplitude or averaged power if measuring a digital channel m Visual carrier frequency not available when measuring a digital channel Intercarrier frequency not available when measuring a digital channel m Visual to aural carrier amplitude ratio not available when measuring a digital channel When the CARRIER SURVEY measurement is initiated the 2715 performs the following steps W Advances to the next unskipped channel in the channel table Executes CARRIER LEVELS measurement refer to Carrier Levels Measurement on page 5 20 using the measurement mode selected for CARRIER SURVEY measurement execute AVG PWR if measuring a digital channel W Sets RF attenuation mode back to auto and vertical mode back to 10 dB div before measuring the next channel Enable CARRIER SURVEY To make a CARRIER SURVEY measurement do the following steps Measurement 1 Press CATV APPL to call up the CATV MEASUREMENTS menu See Figure 5 1 on page 5 4 2 Press 2 to select the CARRIER SURVEY measurement menu 2715 User Manual 5 25
113. 3 Reference Level Vid Fltr BW Marker amplitude 4 Horizontal Scale TRKG Indicator Vert Scale 5 Resolution BW Blank TV Channel Video Line 6 UNCAL Indicator Single Sweep Messages 7 Error Message 8 User Defined Program Title 9 Displayed Message 10 UDP Status 11 Keypad entry WFM to Save 12 Real time Clock Display 13 14 15 CALIBRATOR Indicator 16 WARMUP TIME 15 MIN Message GPIB amp RS 232 Status May also contain C N NOISE NORM D BW amp OBW results Figure 3 1 Layout of the Text Screen in the Spectral Display Mode 3 1 Operating Basics Figure 3 2 shows the text screen for the menu display mode The menu footer area contains prompts general information and additional data entries shown below m Which key to press to return to the spectral display m Which key to press to back up one menu level m Which menu key was pressed to enter this menu m What data to enter m Data that has already been entered m Which terminator key to press LINE SCREEN CONTENT 1 Menu Title 2 3 Up To 10 4 Items 0 9 Displayed 5 Here 6 7 8 9 10 11 12 13 Error Message 14 Data Entry 15 Footer area containing prompts 16 general information and data entries Figure 3 2 Layout of the Text Screen in the Menu Display Mode Connectors Controls and Menus Most of the spectrum analyzer front panel controls are located in function blocks that are denoted by their borders or background colors Each block c
114. 300MHz indicating that the start frequency is now 300 MHz Some users prefer to run the 2715 in this mode This feature can be useful for viewing sidebands or performing harmonic distortion measurements 5 Toggle back to center frequency control by pressing MKR FREQ 9 0 As discussed earlier there is a threshold below which the 2715 will not automatically detect signal peaks Normally the 2715 estimates the peak amplitude of the minimum displayed signal which usually represents the noise floor and sets the threshold one division higher However when the displayed signal is greater everywhere than the noise the 2715 sets the threshold in proportion to the signal peaks rather than the noise floor The threshold is then 2715 User Manual Spectrum Analyzer Menus Counter Resolution 2715 User Manual artificially high and may result in other signals being ignored that rise only slightly above the threshold Item 0 of the MKR FREQ menu enables you to set the threshold to a fixed amplitude suitable for detecting the signals present in your particular application The fixed threshold is also handy when you simply want to exclude low level signals while jumping the marker among high level peaks The following steps show how to set the threshold 6 Choose Item 0 from the MKR FREQ menu 7 Enter a value of 45 dBm following the prompts 8 Press any menu button to return to the spectral display 9 Using either the MOVE MARK
115. 31 00 35 5 912 37 00 41 5 913 43 00 41 5 2 55 25 59 75 3 61 25 65 75 4 67 25 71 75 5 77 25 81 75 6 83 25 87 15 95 91 25 95 75 96 97 25 101 75 97 103 25 107 75 98 109 25 113 75 99 115 25 119 75 14 121 25 125 75 15 127 25 131 75 16 133 25 137 15 17 139 25 143 75 18 145 25 149 75 19 151 25 155 75 20 157 25 161 75 21 163 25 167 76 22 169 25 173 75 7 175 25 179 75 8 181 25 185 75 9 187 25 191 75 10 193 25 197 75 11 199 25 203 75 12 205 25 209 75 13 211 25 215 75 23 217 25 221 75 24 223 25 221 15 25 229 25 233 15 26 235 25 239 75 21 241 25 245 15 28 247 25 251 75 29 253 25 251 15 5 10 2715 User Manual Measurements 2715 User Manual Table 5 4 STD Cont Channel Visual Carrier Aural Carrier 30 259 25 263 75 31 265 25 269 75 32 211 25 215 15 33 211 25 281 75 34 283 25 287 75 35 289 25 293 75 36 295 25 299 75 37 301 25 305 75 38 307 25 311 75 39 313 25 317 75 40 319 25 323 15 41 325 25 329 75 42 331 25 335 75 43 337 25 341 75 44 343 25 341 15 45 349 25 353 15 46 355 25 359 75 47 361 25 365 75 48 367 25 371 75 49 373 25 311 15 50 319 25 383 75 51 385 25 389 75 52 391 25 395 75 53 397 25 401 75 54 403 25 407 75 55 409 25 413 75 56 415 25 419 75 57 421 25 425 75 58 427 25 431 75 59 433 25 437 75 60 439 25 443 75 61 445 25 449 75 62 451 25 455 75 63 457 25 461 75 64 463 25 467 75 65 469 25 413 15 66 475 25 479 75 67 481 25 485 75 68 487 25 491 75 69 493 25 497 75 70 499 25 503 75
116. 5 65 469 25 413 15 66 475 25 479 75 67 481 25 485 75 68 487 25 491 75 69 493 25 497 15 70 499 25 503 75 71 505 25 509 75 72 511 25 515 75 73 517 25 521 75 74 523 25 521 15 75 529 25 533 75 76 535 25 539 75 77 541 25 545 75 78 547 25 551 75 79 553 25 557 75 80 559 25 563 75 81 565 25 569 75 82 571 25 515 15 83 511 25 581 75 84 583 25 581 15 85 589 25 593 75 86 595 25 599 75 87 601 25 605 75 88 607 25 611 75 89 613 25 617 75 90 619 25 623 75 91 625 25 629 75 92 631 25 635 75 93 637 25 641 75 94 643 25 647 75 5 17 Measurements In Service Measurement 5 18 Capability In service measurement capability includes measurement of C N CSO and ICR on negative modulation polarity signals only Gating hardware in the 2715 Spectrum Analyzer allows these measurements to be made on normal modulated TV signals without disruption of programming This is done by interrupting the signal processing path of the spectrum analyzer during times when active video and or undesired test signals would interfere with the measurement The advantage of using gating techniques is that you can perform more measurements without interrupting service to your subscribers Also carrier to noise may be measured within the video band of the channel which allows you to make meaningful measurements through a set top converter without using extra equipment or complicated procedures NOTE In service measurements are not available w
117. 5 and the plotter from the bus Place the plotter in the listen only mode usually done with controls on the plotter You can then send screen data from the 2715 to the plotter by pressing PLOT Whichever communications port is installed in your 2715 the spectral display and its attendant information can be sent to a printer or plotter by pressing PLOT but you must first correctly configure the interface To configure the port in your 2715 for use with your particular printer or plotter select item 1 of the System Configuration menu SCREEN PLOT CONFIGU RATION Item 0 COMM PORT on the Screen Plot Configuration menu indicates to which communications port the plot is sent Make the choice based on whether RS 232 or GPIB is installed See Configuring the Communications Port on page 6 67 for more information However your print plot device must also be equipped with a corresponding interface GPIB or RS 232 Item 1 PLOTTER LANGUAGE cycles through the supported printer and plotter models Repeatedly select item 1 from the menu Each time you press 1 the printer or plotter displayed at the end of the line changes EPSON FX the default refers to FX series printers produced by Epson and HPGL stands for Hewlett Packard Graphics Language Stop when the model of your printer plotter or the one yours emulates is displayed 2715 User Manual Spectrum Analyzer Menus m Item 2 PLOT SPEED only appears if a plotter is selected fo
118. 60 channel flat system dominated by analog signals 10 dB stronger than average power of channel under test 65 Em 55 Measurement Limit dBc 49 35 25 20 10 0 10 20 30 40 50 60 70 INPUT LEVEL dBmV Figure A 7 Typical Digital Signal CSO Measurement Range Limit for 2 dB Accuracy To 500 MHz using preselector 500 MHz to 1000 MHz using preselector To 500 MHz in 60 channel flat system dominated by analog signals 10 dB stronger than average power of channel under test 500 MHz to 1000 MHz in 60 channel flat system dominated by analog signals 10 dB stronger than average power of channel under test Measurement Limit dBc 20 10 0 10 20 30 40 50 60 70 INPUT LEVEL dBmV Figure A 8 Typical Digital Signal CTB Measurement Range Limit for 2 dB Accuracy A 10 2715 User Manual Specifications Table A 2 Frequency Related Characteristics Characteristic Performance Requirement Supplemental Information Channel Tuned with keypad CHAN FREQ J or CHAN FREQ according to the selected channel table Frequency Range All except Option 50 and Option 75 Tuned with keypad CHAN FREQ 9 kHz to 1 8 GHz CHAN FREQ FREQ MARKERS Option 50 and Option 75 9 kHz to knob UTIL menu or MKR FREQ menu 2 15 GHz Accuracy 5 x 1077 of center frequency 10 Hz 1 Assumes zero drift since last least signifi
119. 8 dBmV ref level 0 2 div x 10 dB div 18 8 dBmV Using only the frequency span and reference level controls you have verified the basic operation of the 2715 and determined the frequency and amplitude of its calibrator signal 2 19 Getting Started 2 20 2715 User Manual EX d EE Operating Basics Br si Operating Basics Display Screen 2715 User Manual This section provides an overview of the spectrum analyzer display menus controls and connectors The experienced spectrum analyzer user will find it a handy guide The spectrum analyzer display consists of an 8 division high by 10 division wide graphical sweep screen with a 16 row by 32 character text screen overlay In the spectral display mode both the graphic and text data are normally present although the text screen can be toggled on and off by pressing READOUT In the menu display mode only the text screen is normally present but the sweep display can be turned on see The Spectral Display in Menus on page 6 74 The entire screen area is available for the sweep display but contents of the text screen are placed in predetermined locations Figure 3 1 shows the text screen layout used in the spectral display mode When the optional Display Title line is not used rows 2 through 11 and rows 13 14 and 15 move up one LINE SCREEN CONTENT 1 Display Title optional 2 Center Freq Start Freq RF Atten Mkr Freq Counter Freq
120. AT V APPL to display the INLCHANNEL RESPONSE menu Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed Press 2 to display the results of the last measurement performed A display resembling Figure 5 8 on page 5 54 comes up At this point you can choose to either go ahead and view other previously stored results by pressing W or stop viewing the results by pressing Z NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer 12 13 14 Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 Press 4 to print the all the results of the measurement Again a printer must be connected to the 2715 Press 9 to exit this measurement 2715 User Manual Measurements Running The Automatic When taking an In Channel Response measurement in Auto mode you have a Measurement choice between using the in service basis or the normal basis use menu item 7 to choose the basis If you choose in service you must also use item 6 to specify the TV line number containing the desired test signal 1 90s X Ge ee 113 10 2715 User Manual Press 5 1 to select Auto mode
121. ATV mode The resolution bandwidth RES BW is set to 300 kHz allowing you to see most of the detail in the channel band 1 2 Connect a cable TV feed to the RF INPUT Press CAT V APPL 8 1 to call up a menu of channel tables Initially there are three factory installed tables in this menu You may choose to add other tables to this menu using the PC based software that comes with the 2715 Press 0 to select the standard STD table The reference level is then set so the peak of the visual carrier is approxi mately one division down from the top graticule line and the center frequency and span are set so the channel band is centered on the screen horizontally Press any menu button to return to the spectral display The abbreviation CHAN appears at left center of the screen The CHAN indicator tells you that you can enter the channel number directly from the keypad This is done by keying in a permissible number followed by the W terminator key labeled CHAN Select an active channel channel 8 for this exercise 5 Press keypad numbers corresponding to the desired channel The numbers you press appear on screen to the right of CHAN If you make a mistake you can correct it by repeatedly pressing the backspace key until the incorrect number disappears and then entering the correct number Press W after the channel number has been entered This key can represent units of CHAN GHz SEC or V Because y
122. COM PLETE is displayed Press 2 to display results of the last measurement performed A display resembling Figure 5 8 comes up You can either view other previously stored results by pressing W or stop viewing the results by pressing Z Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 2715 User Manual Measurements 2715 User Manual NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 14 Press 4 to print all stored results of the measurement A printer must be connected to the 2715 15 Press 9 to exit this mode or continue to the next measurement mode To run the CTB or CSO measurement in Single Sweep mode follow these steps NOTE Single Sweep mode is not available if the in service measurement basis is selected s vb mw Uv oce Press 5 3 to select the Single Sweep mode The SET UP TEST FREQUENCIES menu item 5 is added to the menu These frequencies represent points where beats are expected to occur relative to the visual carrier Press 0 and enter the first beat frequency as an offset only from the visual carrier Press 1 and enter the second beat frequency Press 2 an
123. Cable TV RF Measurements Software Use the front panel buttons to make the changes and back space button BK SP to remove the changes one character at a time Use lt ABORT ALL to undo all changes back to when FINISH was last executed and use UNDO CHAN to undo all changes back to when the channel was selected NOTE The FINISH selection and the ABORT ALL selection ends the editing session and goes back to the CATV MEASUREMENTS SETUP menu EDIT CHANNEL TABLE STD CHANNEL 2 TYPE CATV VISUAL FREQ 55 25000MHZ CHAN WIDTH 6 000000MHZ CHAN EDGE 1 25000MHZ 2ND OFFSET NONE NO SKIP NO QUIETLINE AUTO ICR LINE 19 WHITE LINE NONE POLARITY VIDEO SYNC NEG POS warnings errors messages lt FINISH gt lt UNDO CHAN gt lt ABORT ALL gt USE KNOB TO SELECT PARAMETER USE MARKER ARROWS TO EDIT Figure 5 2 Channel 2 of the STD channel table selected for edit with menu set to change SCRAMBLED toggles between YES NO Measurements Table 5 3 shows the element selected selection options if applicable and front panel key assignments for making changes Table 5 3 Menu Selections Element Selected CHANNEL Selection Options All Channels Edit Keys USE KEYPAD CHAN FREQ ARROWS TO EDIT TYPE VISUAL FREQ CENTER FREQ CHAN WIDTH CHAN EDGE 2ND OFFSET CATV PILOT DIGITAL and FM4 N A N A N A N A NONE offset frequency USE MKR ARROWS TO EDIT U
124. DESTINATION WAVEFORM CONFLICT An attempt was made to enable two functions that use the same destination waveform The display line ensemble average min hold dBmV M and waterfall mode use destination waveforms DIRECTORY ERROR IN FILE Firmware hardware error Contact your local Tektronix service center or representative if message persists DISCONNECT INPUT SIGNAL Input signal needs to be removed in following step DISPLAY LINE OFF SCREEN The display line is out of range either at the top or bottom of the CRT display EDITING BUFFER IS EMPTY The local editing buffer for either the UDP or antenna tables is empty If you are attempting to delete the editing buffer the error message is simply to inform the you that the selected action is invalid END OF FILE Firmware hardware error Contact your local Tektronix service center or representative if message persists ENSEMBLE AVERAGE COMPLETE Signifies completion of an ensemble average process ERROR Firmware error Contact your local Tektronix service center or representative if message persists FATAL ERROR IN FILE Firmware hardware error Contact your local Tektronix service center or representative if message persists FILE NOT FOUND Occurs when attempting to access a file that does not exist 2715 User Manual Appendix System Messages 2715 User Manual FILE SIZE ERROR Occurs when attempting to create a new file in NVRAM and the size of the new file is not the
125. DSR 5 GND to 5 GND 6 DSR to 4 DTR 7 RTS to 1 8 DCD CTS 8 see pin 1 9 not used 9 P in Female 9 Pin Female 1 11 2 2 4 4 To2715 4 5 es 5 S ToPC 6 e 6 7 7 8 8 9 9 so P Figure E 5 9 Pin Female to 9 Pin Female Null Modem Cable 9 Pin Female to 25 Pin female Null Modem Cable Table E 2 and Figure E 6 show the wiring configuration for this type of cable A cable with this configuration is available as an optional accessory Refer to Appendix F Accessories and Options for the part number E 9 Appendix E External Input and Output NOTE Pins 1 and 8 are connected together on the 9 pin female connector these connect to pin 4 on the 25 pin female connector Pins 5 and 8 are connected together on the 25 pin female connector these connect to pin 7 on the 9 pin female connector Table E 2 9 Pin Female to 25 Pin Female Null Modem Cable 9 Pin Female to 25 Pin Female Pin signal Pin signal 18 DCD CTS to 4 RTS 2 RXD to 2 TXD 3 TXD to 3 RXD 4 DTR to 6 DSR 5 GND to 7 GND 6 DSR to 20 DTR 7 RTS to 5 8 CTS DCD 8 see pin 1 9 not used 9 Pin Female 25 Pin Female 1 2 3 3 4 4 dr cc eH 6 6 7 7 8 8 L 9 9 13 amp ToPC 20000806 008800808880880 0 Figure E 6 9 Pin Female to 25 Pin Female Null Modem Cable E 10 2715 User Manual Appendix E External Input and Output 9
126. DULATION DEPTH Measurement 5 28 AURAL FM DEVIATION Measurement 5 32 CARRIER TO NOISE DESIRED to UNDESIRED Measurement 5 35 HUM LFD Measurement s pooo erneta 00 cece E E 5 40 FREQUENCY RESPONSE ee E a AE E E 5 43 ADJACENT CHANNEL LEAKAGE 5 47 and CSO Measurements 5 49 CROSS MODULATION Measurement 5 60 In Channel Response 5 62 Auxiliary Operations esse es ee he Re AE eU IUe AREE 5 68 Spectrum Analyzer Menus Spectrum Analyzer Menus 6 1 Using the Menus beens eae teas Kote ates 6 1 ao RP PR SUPR NORRIS s 6 4 MKR EREQ ceo E ER 6 17 DSPL was cast hee aA 6 27 Ensemble Averaging esee 6 28 APPS eid r dee ee a dahon UE 6 43 DEMOD EE 6 56 UTILE yan tte hadnt ee a PERRA RUE RIDE RATED aA 6 60 The Audio Al rt cee deeded te ead a A EE Se es 6 71 SWP TRIG iil nea bees ee eR pee pede REE eels 6 83 USER DEP kae e n edad adel ach wae dak ia Ae nd CERES d 6 89 il 2715 User Manual Table of Contents Appendices Glossary and Index 2715 User Manual Appendix A
127. EF LEVEL by a specified amount They are always active in the spectral display mode even if the parameter is not selected for immediate entry CHAN Change CATV mode changes by one channel in the channel table skipping the SKIPPED channels FREQUENCY change equivalent of 50 knob clicks or 1 major division in the AUTO tuning increment mode and by the designated tuning increment in other modes SPAN DIV change in a 1 2 5 sequence from 1 kHz to 180 MHz REF LEVEL change 1 dB or 10 dB per step depending on REF LVL STEP setting ZERO and MAX Keys Shortcuts respectively to the zero span and maximum span settings The keys are toggles one press activates the setting the second returns to the span used prior to the first press ZERO SPAN no frequency sweep horizontal axis calibrated in time div and the display is a time domain representation of the signal at the indicated center or start frequency MAX SPAN 180 MHz div often used to view full input range of 0 1 8 GHz REF LVL STEP Toggles the amount by which the REF LEVEL arrow keys change the reference level between 1 dB and 10 dB per press The adjacent FINE indicator is illuminated when 1 dB is selected 2715 User Manual 3 5 Operating Basics Numeric Keys 0 9 Terminator Keys W X Y 2 Dot Key e BKSP Key Register Select and Save Keys A B C D 3 6 KEYPAD CHAN W c GG CF CO GJ OR cago BK SP D s
128. ER selection from the MKR FREQ menu or the marker arrow keys attempt to move the marker from peak to peak It will only jump to the peaks above 45 dBm in amplitude 10 Turn off the marker 11 Press MKR FREQ 0 Z to restore automatic threshold selection 12 Press any menu button to return to the spectral display The 2715 enables you to change the resolution of its built in counter It is possible to specify its resolution as 1 kHz or 1 Hz or to turn off the counter when the Signal Track mode is in use Be aware that this feature only changes the counter resolution to 1 Hz not the accuracy 13 Press MKR FREQ 9 1 14 Under COUNTER RESOLUTION select item 0 COUNTER OFF WHEN TRKG 15 Press CTR MEAS TRKG and notice the counter reads out to 1 Hz 16 Enter the TRKG mode and note that there is no counter reading 17 Return to COUNTER RESOLUTION and select 1 kHz Notice the counter is now reading in TRKG mode When you select items 1 or 2 the counter reads out to the indicated resolution in either CTR MEAS or TRKG Because it takes longer to update the display when the counter is reading out turning it off speeds up the signal tracking capability 18 Reselect item 0 from COUNTER RESOLUTION and then turn off the TRKG mode 6 23 Spectrum Analyzer Menus 6 24 Programmed Tuning 300 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF WIDE 50MHz 10 DB 5MHz RBW AUTO CALIBRATOR 9e A ms GUN gt 10
129. F 20 18 8 dBmV Figure 2 5 Calibrator Signal and Harmonics 2715 User Manual 2 15 Getting Started 2 16 To specify a predetermined value press REF LEVEL to place the reference level in the immediate entry mode The abbreviation REFL will appear at left center of the screen The REFL indicator tells you that you can enter the reference level directly from the keypad by typing a value followed by an appropriate terminator key NOTE In the spectral display mode the abbreviation for the control last placed in the immediate entry mode remains on screen until another control is chosen When a control is in the immediate entry mode repeated settings for that control can be entered without having to press CHAN FREQ SPAN DIV or REF LEVEL again Only primary controls can be placed in immediate entry mode 6 Press 2 0 e 8 to set the reference level to 20 8 dBmV The numbers you type appear on screen to the right of REFL If you make a mistake you can correct it by repeatedly pressing BKSP the backspace key until the incorrect number disappears and then entering the correct value 7 Press Y after the correct number has been entered The Y key can represent units of kHz or dB Because you selected an entry mode immediate reference level entry that requires decibels and because the factory default unit is dBmV the spectrum analyzer correctly interpr
130. F PROGRAM UTILITIES at any time by pressing USER DEF Press UTIL 1 1 to recall the FACTORY DEFAULT POWER UP Select a channel table Select a channel Run a CARRIER LEVELS measurement on the selected channel Store the current CARRIER LEVELS measurement results in NVRAM Repeat steps 4 through 7 for the other nine channels dB M ET EO Press USER DEF 9 9 to select TIME DELAY SETUP 2715 User Manual Spectrum Analyzer Menus 10 Set the following m Day of the week on which you want the UDP to run the 0 key cycles through the days of the week m Time hour and minute when the first measurement will start m Set REPEAT INTERVAL to 6 HRS UDP will repeat after every six hours m Set RUN N TIMES to 5 the number of times you want the UDP to repeat over a 24 hour period 11 Store the routine in one of nine locations registers by pressing USER DEF 6 and selecting a storage location For this exercise assume that no UDP has already been stored in Slot 3 Store the routine in Slot 3 You cannot store a routine in a location in which another routine is already stored You must first delete the prior routine 12 To prevent your routine from accidental erasure press USER DEF 9 and select item 8 PROTECT and then press 3 Select item 7 DELETE and notice the next to your routine indicating that it is protected Press 3 W The following message appears REMOVE PROTECTION FIRST To remove
131. FF WHEN TRKG 1 HZ 1 1H 2 1KHZ 3 13 Operating Basics FD x CATV APPL CATV Measurements Page 1 Menu Structure DEMOD DSPL USER DEF INPUT C Un gt CU I2 C5 RECENTER CHANNEL xx 1 of 3 CARRIER LEVEL AVG POWER CARRIER SURVEY MODULATION DEPTH AURAL FM DEVIATION CARRIER NOISE DESIRED UNDESIRED HUM LFD FREQUENCY RESPONSE CATV MEASUREMENTS SETUP MORE 3 14 CO Un gt Un Un HL CO Un gt HL 9 RUN LEVELS POWER STORE CURRENT RESULTS DISPLAY RESULTS PRINT CURRENT RESULTS PRINT STORED RESULTS SET UP CARRIER LEVELS EXTERNAL ATTEN AMPL LEAVE CARRIER LEVEL AVG PWR RUN CARRIER SURVEY STORE CURRENT RESULTS DISPLAY RESULTS PRINT CURRENT RESULTS PRINT STORED RESULTS SET UP CARRIER SURVEY EXTERNAL ATTEN AMPL LEAVE CARRIER SURVEY RUN MODULATION DEPTH STORE CURRENT RESULTS DISPLAY RESULTS PRINT CURRENT RESULTS PRINT STORED RESULTS SET UP ADJUSTMENT MODE ENTER ADJUSTMENT MODE LEAVE MODULATION DEPTH RUN FM DEVIATION STORE CURRENT RESULTS DISPLAY RESULTS PRINT CURRENT RESULTS PRINT STORED RESULTS SET UP AURAL FM DEVIATION ENTER ADJUSTMENT MODE LEAVE AURAL FM DEVIATION RS 232 only TEST MODES ACCURATE FREQUENCY AND AMPL ACCURATE AMPLITUDE ONLY FAST AMPLITUDE ONLY ON OFF ATTEN AMPL ENTRY TEST MODES
132. FM Pilot and Digital signals in the CATV mode 5 4 2715 User Manual Measurements NOTE Previous versions of Cable RF Measurements Software allowed you to use a Data signal type The new Cable TV RF Measurements Software for Windows replaces the Data signal type with a Digital signal type If desired you can use the FM signal type to simulate a Data signal type with the new software Table 5 2 shows the measurements that can be made on each signal type Table 5 2 Signal Type Measurements Signal Types Measurements TV Digital Carrier Level X X X Avg Power Carrier Survey X X Modulation Depth Aural FM Deviation gt lt gt lt gt lt gt lt x gt lt gt lt Carrier To Noise Desired Undesired o X Frequency Response X X X X View Field Modulation X View Line Modulation X View Picture X PT Listen X X CTB X X X X CSO X X X X Cross Modulation gt lt Adjacent Channel Leakage 2715 User Manual 5 5 Measurements 5 6 Channel Tables Channel tables are the central data that controls the actions of the measurements The 2715 uses channel tables to tune to different channels in any one CATV system Thus the resident firmware provides three commonly used factory loaded channel tables STD HRC and IRC In addition you can create your own customized channel table s using the Cable TV RF Measurements Software for Win
133. IBM compatible PC software that is provided as an accessory Refer to the Cable TV RF Measurements Software for Windows manual for more information 2715 User Manual Measurements 2715 User Manual 4 If you have skipped channels press BKSP 2 to return to the CARRIER SURVEY menu 5 Press 0 to run the CARRIER SURVEY measurement After the measurement is complete the instrument displays the message RESULTS AVAILABLE VIA DISPLAY IN THE CARRIER SURVEY MENU 6 Press CATV APPL to display the CARRIER SURVEY menu 7 Press 1 to store the results of the last measurement After a short period the message RESULTS STORAGE COMPLETE is displayed 8 Press 2 to display the results of the last measurement performed A display resembling Figure 5 5 comes up CARR SURVEY CURRENT CHAN 8 06 JAN 94 12 00 00 CHANNEL 2 10 5 DBMV 55 250000MHZ 15 8DBC 4 500000MHZ CHANNEL 3 VISUAL 9 8 DBMV 61 250000MHZ 15 4DBC 4 500000MHZ CHANNEL 4 VISUAL 9 5 DBMV 67 250000MHZ AURAL 15 1DBC 4 500000MHZ W CONT Y NEXT Z ABORT Figure 5 5 Typical Carrier Survey Report Screen You can choose to either go ahead and page through all the stored results for the last measurement by repeatedly pressing W or stop viewing the results by pressing Z After all of the current results have been displayed as you continue pressing W or if you press Z the 2715 starts displaying
134. MHz but you can change it to suit your application For this example you need to change the bandwidth to 5 MHz to obtain an approximation of the 2715 s noise floor 1 Press 9 2 2 Press 5 X to enter a value of 5 MHz 2715 User Manual 6 45 Spectrum Analyzer Menus Measuring Carrier to Noise Ratios 6 46 3 Press BKSP to return to the Applications menu 4 Press 2 again The spectral display reappears and the marker is turned on The first two items in the right on screen column read approximately as follows N 44 2DBMV 5 0MHZ The reading may vary somewhat and is the average internal noise in a 5 MHz band at the marker frequency You may also receive the following warning NOISE LEVEL LESS THAN 2DB This is because the 2715 recognizes when the noise it is measuring approaches its own noise floor It knows that it cannot accurately measure external signals too close to that value 5 Press DSPL and ensure that item 4 is set to MAX MIN display mode 6 Press DSPL to return to the spectral display 7 Turn the FREQ MKRS knob to reposition the marker at the bottom of the displayed noise Notice that the noise amplitude readout does not change significantly The noise amplitude appears to be approximately halfway between the maximum and minimum values of the spectral display This is because the 2715 does not compute the arithmetic mean of the minimum and maximum values usi
135. Memory allocation firmware hardware error Contact your local Tektronix service center or representative if message persists MARKERS ARE OFF Marker s must be turned on to obtain desired function C 7 Appendix System Messages C 8 MARKER WOULD OVERWRITE NOISE VALUE Enabling the marker would overwrite the saved Carrier to Noise or Normalized Noise value Markers cannot be placed on a display saved with Carrier to Noise or Noise Norm d modes enabled MUST BE IN DELTA MARKER MODE Turn on Delta Markers to obtain desired function NO CSO BEATS ARE DEFINED This message appears when a continuous CSO test terminates because no beats were specified in the CSO setup menu NO LISTENER A screen plot front panel operation was attempted to the GPIB port but no listen addressed devices were available Place a listen addressed device on the bus and reselect the operation NO MODULATION ON SIGNAL Occurs in zero span when CTR MEAS is attempted and there is no constant frequency modulation on the carrier NO QUIET VIDEO LINES FOUND Quiet lines are retrace lines where no modulation is present The Carrier to Noise and Composite Second Order tests use quiet lines to take in service measurements The 2715 was unable to automatically find quiet lines to use for the tests NO REFERENCE DEFINED A function was invoked which requires a valid current reference but no such reference exists NO SIGNAL NORMALIZATIONS Perform normalizations
136. NCY menu Press 0 and enter the first beat frequency as an offset from the visual carrier Press 1 and enter the second beat frequency Press 2 and enter the third beat frequency Press 3 and enter the fourth beat frequency Press 4 and enter the fifth beat frequency Press 5 to use default frequencies Press 6 to specify the frequency of the carrier to be measured This is usually the next channel down in frequency Press 7 to enter the test interval Minimum interval and default is 15 seconds The maximum test interval is 21600 seconds 6 hours Press 8 to enter how often the instrument normalization will be run Minimum interval and default is 1 hour and the maximum interval 15 24 hours Press BKSP BKSP 0 to run the measurement The instrument normalizes itself for about 12 minutes It then measures the specified carrier frequency within 200 kHz on either side for a peak to use as an amplitude reference Next it measures the amplitudes of the beats within 50 kHz on either side of the specified beat frequencies It then waits for the interval to expire so the cycle can be repeated 2715 User Manual Measurements 2715 User Manual 13 14 15 16 Press W or Z to stop the test It will stop when the current cycle finishes When the measurement is complete it displays the number of beats that were measured the number of times they were measured and the number of seco
137. NOTE The stability and frequency accuracy specifications of the spectrum analyzer are guaranteed only for the factory default YIG settling delay time In service measurement capability includes measurement of C N CSO and ICR on NTSC and PAL signals only Gating hardware in the 2715 Spectrum Analyzer allows these measurements to be made on normal modulated TV signals without disruption to the TV program in progress Since gated measurement techniques have advantages and disadvantages the 2715 Spectrum Analyzer is designed so that you always have a choice of whether or not you use gated in service measurement techniques If you follow the In Service menu selections for C N CSO or ICR you will be making a gated measurement otherwise you will be making a measurement in the conventional way without gating For more information about in service measurements refer to In Service Measurement Capability on page 5 18 The instrument is very durable but rough handling or liquids dust or other contaminants inside the case can cause damage The optional Travel Line package provides additional protection during transportation Optional capabilities result in even greater performance Refer to Appendix F Accessories and Options for information on options currently available for the 2715 Cable TV Spectrum Analyzer 2715 User Manual 1 3 Introduction 1 4 2715 User Manual Getting Started Getting Started This section describe
138. NT RESULTS VIEW MODULATION LINE 2 DISPLAY RESULTS VIEW PICTURE 3 PRINT CURRENT RESULTS LISTEN 4 PRINT STORED RESULTS CTB 0 RUNCTB CSO 1 STORE CURRENT RESULTS 5 MEASURE SIDE CROSS MODULATION 2 DISPLAY RESULTS IN CHANNEL RESPONSE 3 PRINT CURRENT LEVELS 9 LEAVE ACL MORE 4 PRINT STORED RESULTS 5 SETUP TEST MODES 6 DIGITAL ANALOG 0 INTERACTIVE 1 AUTO 9 LEAVE 2 AUTO PAUSE FOR CARRIER OFF 3 SINGLE SWEEP 5 SETUP TEST FREQUENCIES TEST FREQUENCIES 0 User Defined 1 User Defined 2 User Defined 0 00000HZ Default 3 User Defined 4 User Defined 5 USE DEFAULT TEST FREQUENCIES 0 RUNCSO 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT LEVELS 4 PRINT STORED RESULTS 5 SETUP CSO TEST MODES 6 DIGITAL ANALOG 0 INTERACTIVE 7 IN SERVICE 1 AUTO 9 LEAVE CSO 2 AUTO PAUSE FOR CARRIER OFF 3 SINGLE SWEEP RS 232 only 4 CONTINUOUS 5 SETUP TEST FREQUENCIES AND CONTINUOUS MODE PRMTRS TEST MODES IN SERVICE 0 INTERACTIVE 1 AUTO 5 SETUP TESTFREQUENCIES TEST FREQUENCIES 2715 User Manual Not displayed in INTERACTIVE mode 0 User Defined 1 25000MHZ Default 1 User Defined 750 000KHZ Default 2 User Defined 3 User Defined 750 000KHZ Default 4 User Defined 1 25000MHZ Default 5 USE DEFAULT TEST FREQUENCIES CONTINUOUS MODE PARAMETERS 6 CARRIER FREQ 7 TEST INTERVAL 8 NORMALIZATION INTERVAL Displayed only if CONTINUOUS mode is selected 3 17 Operating Basics
139. NTASK CANNOT START PROCESS Firmware error Contact your local Tektronix service center or representative if message persists C 11 Appendix System Messages C 12 SATELLITE VIDEO MNTR NOT INSTLD 2715 cannot sense presence of optional satellite FM video detector SEARCH TERMINATED MAX SIGNALS Signal search is terminated if it detects more than 50 signals SELECT TALK ONLY MODE FIRST Screen plot front panel operation requires the GPIB address mode to be talk only when the plot port is set to GPIB SELECTED PROGRAM IS EMPTY The selected user defined program is empty No action is taken SELECTED STORED SETTING IS EMPTY Setting must be stored before it can be recalled SELECTED TABLE IS EMPTY The selected antenna correction factor table is empty SETTING CORRUPTED Requested stored setting has been deleted because of a corrupted data value This message may also occur in general instrument operation if Settings Verify UTIL 5 4 is turned ON This selection checks all data transac tions involving the instrument settings No deletions occur in the general operation Contact your local Tektronix service center or representative if message persists SHORT HOLDOFF MODE NOT INSTLD 2715 cannot detect presence of Short Holdoff feature SHORT YIG DELAY GO TO UTIL 5 4 The YIG oscillator settling delay time has been changed from the factory default setting of 5000 ms Use the Utility Menu UTIL 5 4 2 to change t
140. O Meas rement eene eR erect rre ed A 8 Figure A 5 Typical ACL Measurement Limits for 2dB AccUEAECY venen eeRe here rhe ee E VERRE CE E MEE A 9 Figure 6 Typical D U Measurement Range Limits for 2 dB ACCUFACY chess sers mee eet ee medo WERE A 9 Figure A 7 Typical Digital Signal CSO Measurement Range Limit for 2 dB A 10 Figure A 8 Typical Digital Signal CTB Measurement Range Limit for 2 dB A 10 Figure E 1 Accessory Connector J103 E 3 Figure E22 Sweep Gate and Ramp Timing E 5 V Table of Contents vi Figure E 3 IEEE Standard 488 GPIB Connector Pin Assignments E 7 Figure E 4 RS 232 C Connector Pin Assignments E 8 Figure E 5 9 Pin Female to 9 Pin Female Null Modem Cable E 9 Figure E 6 9 Pin Female to 25 Pin Female Null Modem Cable E 10 Figure E 7 9 Pin Female to 25 Pin Male Extension Cable E 11 2715 User Manual Table of Contents List of Tables 2715 User Manual Table 5 1 Safe Maximum Signal Levels 5 2 Table 5 2 Signal Type Measurements 5 5 Table 5 3 Menu Selections 5 8 Table 5 4 STD MERERI NE SERU Me E A EET e 5 10 Table 5 5 uet
141. OTE Any control settings can be used Normalization is a set of procedures contained in ROM that calculate gain and frequency characteristics of the circuits in the 2715 based on the built in 100 MHz 18 8 dBmV calibrator signal The characteristics must be accurately known to correctly scale and display the analyzed signal The normalization values are stored in non volatile memory Using external signals to achieve even greater measurement accuracy or to renormalize the reference if NVRAM should ever be lost is described later in Service Normalizations on page 6 80 If the 2715 self test routine detects that the present 2715 gain or frequency characteristics differ significantly from those determined during the previous normalization the NORMALIZATION SUGGESTED message is displayed on the screen You should then perform a normalization although the 2715 remains useable for relative measurements The NORMALIZATION SUGGESTED message may also appear while the 2715 is warming up especially if the user defined power up settings include a narrow span This is normal and you need not perform a normalization unless the message persists beyond the warm up period Any time you require the utmost accuracy we recommend a normalization first Normalization may be required because of any of the following W Circuit or component variation with time drift m Large temperature difference from that at which previous normalization was c
142. PL to call up the CATV MEASUREMENTS menu See Figure 5 1 2 Press 9 to select MORE which displays the second page of the CATV MEASUREMENTS menu 3 Press 0 to select ADJACENT CHANNEL LEAKAGE 5 47 Measurements 5 48 This gives you the following options 0 RUN ADJACENT CHANNEL LEAKAGE 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 MEASURE SIDE BOTH 9 LEAVE ACL Press 5 to select the frequency channel on which you want the test to run the upper frequency channel UPPER the lower frequency channel LOWER or both the upper and lower frequency channels BOTH Press 0 to run the adjacent channel leakage measurement After the measurement is complete the instrument displays the measured adjacent channel leakage Press CAT V APPL to display the ADJACENT CHANNEL LEAKAGE menu Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed Press 2 to display the results of the last measurement performed A display resembling Figure 5 4 appears showing the current result You can press W to view other previously stored results for this measurement or press Z to stop viewing the results Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement res
143. PL USER DEF Menu Structure DEMOD DSPL USER DEF INPUT 0 User Defined 1 User Defined 2 User Defined 3 User Defined 4 User Defined 5 User Defined 6 User Defined 7 User Defined 8 User Defined 9 USER DEF PROGRAM UTILITIES 0 ACQUIRE KEY STROKES 1 TITLE EDIT 2 WAIT FOR END OF SWEEP 3 DISPLAY MESSAGE 4 PAUSE FOR USER DEF KEY 5 CONTINUOUS EXECUTION 6 STORE 7 DELETE 8 PROTECT 9 TIME DELAY SETUP 3 20 Cn P GJ NJ SET DAY SET HOUR SET MINUTE REPEAT INTERVAL RUN NTIMES CLEAR TIME 2715 User Manual Operating Basics MENUSI SWP TRIG UTIL MKR FREQ DEMOD DSPL USER DEF INPUT CATV APPL 1 PREAMP REF LEVEL UNIT 1ST MXR INPUT LVL RF ATTENUATION CO gt w 2715 User Manual EXTERNAL ATTEN AMPL CAL SIG 100MHZ 18 8DBMV INPUT Menu Structure DBM DBMV DBV DBUV DBUW Cn ROC I3 9 DBUV M SETUP 0 ON OFF 1 ATTEN AMPL ENTRY DBUV M IN WFM x EDIT ANTENNA TABLE User Defined User Defined User Defined User Defined User Defined MEASUREMENT DIST SAVE RESULTS IN WFM MARKER DISPLAY Not available in CATV Measurements Mode BEGIN EDIT TITLE EDIT STORE LOAD DELETE PRINT ANTENNA SETUP 1 2 3 4 START FREQUENCY STOP FREQUENCY INC FREQUENCY REFERENCE DISTANCE 3 21 Operating Basics 3 22 2715 User Manual AO O Dedicated Controls Dedicated Controls This section describes in de
144. PTH When you initiate the MODULATION DEPTH measurement the 2715 performs the following 1 Tunes to the carrier frequency finds the peak value and moves the signal to top of screen The 2715 then enables zero span linear vertical scale and 1 MHz RBW filter 2 If VITS is present in the selected channel table data for this channel the 2715 uses the VITS line to determine depth of modulation The VITS line must include a 100 white signal for this method to work In this case the sweep time is set to 100 us div and the trigger mode to TV line trigger The VITS line is defined in the channel table using the IBM compatible PC software 2715 User Manual Measurements Enable MODULATION DEPTH Measurement 2715 User Manual If VITS is not present the sweep time is set to 2 ms div and the trigger mode to FREE RUN In either case VITS or no VITS 10 sweeps are taken and modulation depth is computed for each sweep The final result is the average of all 10 sweeps For each sweep modulation depth is computed as follows MaX 100 max min NOTE This measurement does not work well on a scrambled channel where the sync tip is not present The following procedure shows how to make a modulation depth measurement Press CATV APPL to call up the CATV MEASUREMENTS menu See Figure 5 1 on page 5 4 2 Press 3 to select the MODULATION DEPTH measurement menu 3 This gives you the followi
145. REQ m CATV APPL m DEMOD m DISPL m USER DEF m INPUT Some of the submenus are used for servicing information about these submenus is in the optional 27 5 Spectrum Analyzer Service Manual Refer to Table F 2 Optional Accessories on page F 1 for the part number of the service manual e MNS ay SWP TRG Menu Structure LD DEMOD DSPL USER DEF INPUT FREE RUN INTERNAL EXTERNAL LINE TV LINE TV FIELD SWEEP MENU 6 SWEEP RATE 7 MANUAL SCAN 8 SYNC POLARITY 9 SETUP TABLE HORIZONTAL LINE TRIGGERING CONTINUOUS KNOB SELECTABLE KEYPAD ENTERED LINE KEYPAD ENTRY TV LINE STANDARD Cn GJ NJ L2 gt MJ L3 2715 User Manual 3 11 Operating Basics MENUS UTIL CATV SWP TRIG MKR FREQ APPL 1 of 2 DEMOD DSPL USER DEF INPUT STORED SETTINGS DISPLAYS KEYPAD ENTERED SETTINGS NORMALIZATIONS SYSTEM CONFIGURATION INSTR DIAGNOSTICS ADJ USTMENTS SERVICE REQUEST eV 9 MORE 3 12 o UTIL Menu Structure LAST POWER DOWN FACTORY DEFAULT POWER UP USER DEFINED POWER UP User Defined User Defined User Defined User Defined User Defined User Defined MORE CO Un gt CU E23 FREQUENCY REFERENCE LEVEL SPAN DIV RF ATTENUATION RESOLUTION BW VIDEO FILTER VERTICAL SCALE SWEEP RATE ALL PARAMETERS FREQUENCY ONLY AMPLITUDE ONLY Nr
146. REQUEST 1 EXTENDED DIAGNOSTICS 2 MANUAL ADJUSTMENTS 9 MORE 4 3 DEBUG MENU 4 INTERNAL PARAMETERS 5 SERVICE NORMALIZATIONS 6 DIGITAL OPTIONS DIAGNOSTICS 0 PRINT READOUTS 8 CALIBRATION MODE 8 EDIT CHANNEL TABLE i shortcut Factory troubleshooting aids not 9 MORE discussed in this manual 1 Option 50 and Option 75 only MENUSI SWP TRIG UTIL MKR FREQ pond MRK FREQ Menu Structure DEMOD DSPL USER DEF INPUT 0 THRESHOLD 1 PROGRAMD TUNING INC 0 CENTER FREQ 2 KNOBFUNCTION 1 MARKER FREQ 3 MARKER TO REFERENCE LEVEL 2 KEYPAD ENTRD INC 4 MOVE MARKER TO NEXT PEAK 3 KEYPAD ENTRY 5 TRANSPOSE MARKERS 4 RETURN TO AUTO 6 MARKER START STOP 7 FREQUENCY START STOP 0 FREQUENCY 8 TUNING INCREMENT 1 MARKER 9 SETUP TABLE 2 VIDEO LINE 0 FREQ START ENTRY 1 FREQ STOP ENTRY 0 CENTER START FREQ 1 COUNTER RESOLUTION 3 FREQ OFFSET 4 FREQOFFSET MODE 2715 User Manual Displayed only if KNOB SELECTABLE is se lected in the SWEEP MENU SETUP TABLE NRO 0 DEFLECTION AMP CAL DISPLAY STORAGE CAL SWEEP CAL CFCV1 ADJ USTMENTS TOGGLE VD DAC LO HI VD DAC TO VIS CARR AFC TOGGLE GATE TOGGLE QUERY LOCK STATUS SETTINGS VERIFY FILE SYSTEM MENU YIG SETTLE DELAY FREQUENCY NORMALIZATIONS REFERENCE NORMALIZATIONS AMPLITUDE NORMALIZATIONS NORMALIZATION VALUES PRINT ALL NORM VALUES NORM DEBUG TO PRINTER Factory troubleshooting aids not discussed in this manual COUNTER O
147. RM SUGGESTED SET BEAT Perform frequency normalization Contact your local Tektronix service center or representative if message persists FREQ NORM SUGGESTED SET VCO Perform frequency normalization Contact your local Tektronix service center or representative if message persists C 5 Appendix System Messages C 6 FREQ NORM SUGGESTED SPAN DAC Perform frequency normalization Contact your local Tektronix service center or representative if message persists FREQUENCY NORMALIZATION FAILED Perform frequency normalization again Contact your local Tektronix service center or representative if message persists FUNC NOT AVAIL IN DBUV M MODE Selected function is not available with the dBuV m measurement mode enabled Functions not available include LIN vertical mode FM and EXTernal display sources and attempting to unsave the selected destination waveform Choose new reference units to enable the selected operation FUNC NOT AVAIL IN CURRENT MODE Refer to manual for proper instrument settings This error message may appear for instance upon the invocation of instrument functions such as carrier to noise noise normalized bandwidth and antenna correction factors while in linear scaling mode In these particular cases the vertical scaling mode would have to be changed to logarithmic before invoking the functions Another case would be the invocation of a user defined routine while in the user defined routine acquisition mode
148. SE KEYPAD TO EDIT USE KEYPAD TO EDIT O NONE SCRAMBLED SKIP QUIET LINE ICR LINE YES NO AUTO any line number NONE any video line number USE MKR ARROWS TO EDIT USE KEYPAD W ENTER Z AUTO USE KEYPAD W ENTER Z NONE WHITE LINE POLARITY VIDEO SYNC NONE any video line number NEG NEG NEG POS POS NEG POS POS USE KEYPAD W ENTER Z NONE USE MKR ARROWS TO EDITS lt FINISH gt N A X STORE TABLE AND EXIT lt UNDO CHAN gt N A Y UNDO CHANNEL CHANGES lt ABORT ALL gt W CONFIRM ABORT Z ABORT ALL TABLE Z CANCEL CHANGES The last line of text on the screen identifies the front panel button used for editing the selected element 4 If the channel TYPE selected is CATV or PILOT the next line reads VISUAL FREQ If the channel TYPE selected is DIGITAL or FM the next line reads CENTER FREQ 5 The tight MKR arrow toggles the SYNC polarity and the left MKR arrow toggles the VIDEO polarity 5 8 2715 User Manual Measurements 2715 User Manual Figure 5 3 shows a channel with the menu set to store the changes and exit the menu FINISH It has a second aural carrier 4 7MHz above the video carrier EDIT CHANNEL TABLE ED S TV CHANNEL 907S TYPE CATV CENTER FREQ 7 25000MHZ CHAN WIDTH 3 000000MHZ CHAN EDGE 1 50000MHZ 2ND OFFSET 4 70000MHZ SCRAMBLED NO SKIP NO QUIET LINE 15 ICR LINE 19 WHITE LINE 14 POLARITY VIDEO SYNC NEG POS warnings
149. Signal Line Number 5 63 Text 3 1 Text Screen In the Menu Display Mode 3 2 Text Screen In the Spectral Display Mode 3 1 Time and Date Setting 6 75 Titles and Labels Adding 6 36 Total Input Power Limitations 5 2 Trace Adjustments 4 35 Trace Rotation Adjustment 4 35 Transposing Markers 6 18 Trigger Modes Oscilloscope 6 83 Tuning Increment Selecting 6 21 Tuning Programmed 6 24 Turning On the Spectrum Analyzer 2 4 Turning the Calibrator On and Off 6 4 TV Line Trigger 6 85 TV Video Field Triggering 6 88 U Unpacking 2 1 USER DEF Menu 6 89 User Defined Power Up Settings 6 62 Program UDP Files 6 76 Routine Create 6 90 Settings 6 63 Using Markers to Set Start and Stop Frequencies 6 17 2715 User Manual UTIL Menu 6 60 V Diagnostics and Adjustments 6 78 Generating a Service Request 6 82 Instrument Configuration Sending Waveforms To a Computer 6 72 Settings the MInimum Signal Size 6 72 Manual Adjustments Aligning the Display 6 78 Menu Entered Control Settings 6 60 Normalizing the 2715 6 65 Other User Defined Settings 6 63 Recall Last Power Down Settings 6 62 Save and Recall Settings and Displays 6 62 Service Normalizations 6 80 System Configuration 6 67 Configuring the Communications Port 6 67 Instrument Configuration See Instrument Config uration Selecting the Printer Configuration 6 71 Turning Phaselock On and Off 6 72 Use
150. TUP TABLE from the Applications menu 2715 User Manual Spectrum Analyzer Menus Press 0 from the Setup Table to display the prompt for a new value Press 6 Z to enter a value of 6 dB Press BKSP to return to the Applications menu Press 0 to implement BANDWIDTH MODE The 2715 returns automatically to the spectral display after you press 0 The delta markers have been activated and bracket the calibration signal peak If the signal peak is not centered the 2715 selects the peak nearest center screen The first two items in the right on screen column read as follows BW 300KHZ 6DBC You are measuring the bandwidth of the resolution bandwidth filter The indicated bandwidth will not be exactly 300 kHz it will vary slightly about 300 kHz 8 Press next to SPAN DIV until the span readout is 10 0KHZ 9 Press RES BW until RBW readout is 30KHZ The bandwidth should now read approximately 30 kHz The 2715 remains in bandwidth mode until you call up the Applications menu and toggle it off make an alternate selection or until you turn off the markers 10 Press APPL 0 to turn off bandwidth mode Measuring Average Noise 100 0MHz AUTO SWEEP ATTNODB 18 8DBMV VF WIDE 20 0MHz 10 DB 5MHz RBW AUTO Item 2 of the Applications menu causes the 2715 to measure the average noise at the marker location and normalize it to a specified bandwidth The default bandwidth is 4
151. The counter readout still indicates the true center frequency 8 Turnon the marker and turn the FREQ MKRS knob clockwise The marker frequency is also increased by 5 15 GHz 9 Press MKR FREQ to call up the Marker Frequency menu 10 Press 9 to select the SETUP TABLE 2715 User Manual Spectrum Analyzer Menus DSPL 2715 User Manual 11 Press 4 to toggle FREQUENCY OFFSET MODE to ON MINUS 12 Return to the spectral display The center frequency now reads 4850 0 MHz and the marker reads progres sively lower frequencies as it moves to the right The frequency axis appears reversed because any time the local oscillator in the frequency converter is above the frequency of the original signal the output frequencies are reversed That is the higher the input signal frequency the lower the output frequency This is exactly the process that occurs in C band block down converters Therefore you use ON MINUS when viewing their output Ku band converters on the other hand have local oscillator frequencies below the input signal frequency and you use ON PLUS when viewing their output signals 300 0MHz AUTO SWEEP ATTN 12DB 8 8DBMV VF WIDE 20 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR The Display menu enables you to change the appearance of the display screen and the signals presented on it From the Display menu you can do the following m Switch between analog and digital display modes m Ensemble average spectra D
152. This display not only imitates the analog spectrum but can also assist in detecting low level signals by more effectively showing the characteristic void they produce under the noise floor The spectral display is overlaid by a 32 character wide by 16 character high text screen Not all of the text fields are displayed all the time and you can turn the text screen on and off by pressing READOUT The top portion of the text screen contains two data readout columns that are present whenever the text screen is turned on The readouts show spectrum analyzer settings or measurement results Figure 2 2 shows the data normally displayed in the readout columns Center frequency Marker frequency Reference level Marker amplitude Horizontal scale factor Vertical scale factor Resolution bandwidth Channel table and number Various messages may appear as needed below the data readout columns Figure 2 2 Normal On Screen Data Readouts With the spectrum analyzer in the MAX SPAN mode indicated by MAX following the horizontal scale factor the resulting spectrum spans the entire input frequency range In this mode the first item in the left column lists the frequency at the location of the frequency marker the intensified spot on the display 2 7 Getting Started Control Panel Basics 2 8 The types of information in the right column may change depending on operating mode You will learn when to expect alternate information as we
153. UENCY Perform frequency normalization Contact your local Tektronix service center or representative if message persists CANNOT DELETE FILE WHILE IN USE Occurs when attempting to delete a file that is in use CANNOT NORMALIZE PLL VCO Perform frequency normalization Contact your local Tektronix service center or representative if message persists CANNOT OVERWRITE SAVED DISPLAY Old data must be deleted or transferred to STORED SETTINGS before new data can be saved CANNOT OVERWRITE STORED REF An attempt was made to overwrite a stored reference CANNOT OVERWRITE STORED SETTING An instrument setting is already stored in this register Old setting must be deleted first 2715 User Manual Appendix System Messages 2715 User Manual CANNOT OVERWRITE STORED WAVEFORM A waveform is already stored in this register Old waveform s must be deleted first CANNOT STORE NV MEMORY FULL Must delete other settings if further storage is desired CATV MEASUREMENT FAILURE A measurement function failed CHAN DOESN T EXIST IN CHAN TABLE A channel has been selected that does not exist in the current channel table CNTR SIGNAL OUT OF IF PASSBAND The signal in zero span is not above the threshold Perform CTR MEAS again or use a wider resolution bandwidth filter Performing a frequency normalization may also facilitate a count Because of span and display storage inaccuracies the signal may not be exactly centered in the di
154. User Manual Tektronix 2715 Spectrum Analyzer 070 9115 05 This document supports firmware version 2 14 97 and above ce Copyright Tektronix Inc All rights reserved Tektronix products are covered by U S and foreign patents issued and pending Information in this publication supercedes that in all previously published material Specifications and price change privileges reserved Printed in the U S A Tektronix Inc P O Box 1000 Wilsonville OR 97070 1000 TEKTRONIX and TEK are registered trademarks of Tektronix Inc Tektronix warrants that this product will be free from defects in materials and workmanship for a period of one 1 year from the date of shipment If any such product proves defective during this warranty period Tektronix at its option either will repair the defective product without charge for parts and labor or will provide a replacement in exchange for the defective product In order to obtain service under this warranty Customer must notify Tektronix of the defect before the expiration of the warranty period and make suitable arrangements for the performance of service Customer shall be responsible for packaging and shipping the defective product to the service center designated by Tektronix with shipping charges prepaid Tektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the Tektronix service center is lo
155. Utility menu item 6 SERVICE REQUEST enables you to manually generate a service request SRQ whenever required for testing or other purposes See the 2714 amp 2715 Programmer Manual for detailed information about SRQs and their uses To generate a SRQ press UTIL 6 If the communications port is on line the request is generated immediately and reflected on screen by the message REQUEST at bottom center if the port is off line nothing happens The message remains on screen until serviced by the controller or until the commu nications port is cycled on and off line using UTIL 4 0 0 0 GPIB or UTIL 4 0 2 0 RS 232 NOTE The techniques for reporting the event causing an SRQ are different for RS 232 and GPIB See the 2714 amp 2715 Programmer Manual The Utility menu also enables you to print the on screen readouts on an FX series printer The 2715 must be equipped with the RS 232 port and the printer must be connected directly to the port Each on screen line is terminated with a linefeed regardless of the terminator selected from the RS 232 configura tion menu Further the RS 232 port must be on line to use this feature 2715 User Manual Spectrum Analyzer Menus SWP TRIG Free Running the Sweep Generator Oscilloscope Trigger 2715 User Manual Modes Printing the on screen readouts can be handy if you wish to print results during a user defined program UDP sequence For instance suppo
156. XR INPUT LEVEL 30DBM 5 RF ATTENUATION AUTO 50DB 6 EXTERNAL ATTEN AMPL NONE 9 CAL SIGNAL 100MHz 18 8DBMV OFF PRESS ANY MENU KEY TO EXIT PRESS BKSP FOR PREVIOUS DISPLAY Figure 6 1 The INPUT Menu Depending on the parameter or feature there are three ways the status may be changed each uses the numeric keypad m When only two or three values or conditions are permitted pressing the keypad key corresponding to the item number cycles through the acceptable values At each step the new status appears at the end of the line m Ifthe 2715 accepts a smaller range of values it presents a secondary menu consisting of a list of the values that may be selected by pressing their corresponding keypad keys m parameter can have a wide range of numerical values two things happen First the selected item number is preceded by an asterisk to ensure there is no confusion about which item was selected Then you are prompted to enter the new value This is illustrated in Figure 6 2 where item 6 from the SWP TRIG menu has been selected TRIGGER MENU O FREE RUN 1 INTERNAL 2 EXTERNAL 3 LINE 4 TV LINE 5 TV FIELD SWEEP MENU 50MS DIV 6 SWEEP RATE OFF 7 MANUAL SCAN POSITIVE 8 SYNC POLARITY 9 SETUP TABLE ENTER NEW VALUE INPUT MENU 1 2 5 SEQUENCE Figure 6 2 Sweep Trigger Menu with SWEEP RATE Selection Chosen 2715 User Manual Spectrum Analyzer Menus 2715 User Manual To enter a setting or parameter value pre
157. a few sweeps There is a slight pause about every fourth sweep This is the period during which the corrections are computed and implemented 2 Press SPAN DIV 5 0 Y to reduce the span to 50 0 kHz div Watch the signal peak for several minutes Notice how the signal peak drifts relative to screen center and then is recentered as the 2715 computes and implements the corrections 3 Press UTIL 4 3 to call up the INSTRUMENT CONFIGURATION menu FREQUENCY CORRECTIONS from the Instrument Configuration menu is a toggle that enables you to turn the corrections off and on 4 Press 5 to turn off the frequency corrections feature 5 Press UTIL to return to the spectral display 6 73 Spectrum Analyzer Menus The Spectral Display in 6 74 Menus Changing the Sweep Holdoff Notice how the signal now drifts continuously Press UTIL 4 3 5 again to turn the frequency corrections back on Press UTIL to return to the spectral display Note that the signal is again centered Some people prefer to have the display present when working with menus others do not 8 10 Press UTIL 4 3 to activate the INSTRUMENT CONFIGURATION menu Repeatedly press 6 to toggle SPECTRAL DISPLAY IN MENUS off and on Note how the spectral display is superimposed on the menu For now leave the display turned on There is a holdoff period between the end of one sweep and the start of the next to give th
158. able 6 13 Equipment Setup for Field Strength Measurements 6 11 Equivalent Decibel Voltage Values 6 12 Procedure 6 12 Using 6 10 Dedicated Controls 2 8 Default Settings restoring 2 6 Index 2 DEMOD Menu 6 56 Listening to AM or FM Transmissions 6 58 Listening to AM Transmissions 6 57 Listening to FM Transmissions 6 56 Video Demodulation 6 58 DESIRED to UNDESIRED measurement 5 35 Diagnostics and Adjustments 6 78 Display Line and Limit Detector 6 40 Display Registers 4 21 Analog Display 4 21 D Register 4 24 MAX HOLD A amp B 4 26 Register Priority 4 23 Display Screen 3 1 Display Storage 4 20 Display Registers 4 21 SAVE ENABLE 4 22 Display Aligning 6 78 Display Initial 2 6 Displaying an External Source 6 40 Displays and Settings Save and Recall 6 62 Dot Key 3 6 DSPL Menu 6 27 Activating Minimum Hold 6 42 Adding Titles and Labels 6 36 B C MINUS A 6 32 Changing Acquisition Mode 6 36 Changing the Display Mode 6 28 Display Line and Limit Detector 6 40 Displaying an External Source 6 40 Ensemble Averaging 6 28 Subtracting Stored Signals 6 32 Turning Graticule Illumination On and Off 6 39 E Edit a Channel Table 5 7 Edit a Title 6 37 Ensemble Averaging 6 28 Enter Parameter Value 6 3 Equipment Returning 2 1 Exit From a Menu 6 3 External Amplification Attenuation 6 6 External Source Displaying 6 40 2715 User Manual
159. able values Selecting item 6 VERTICAL SCALE calls up another menu that enables you to select any of the normal values of 10 dB div 5 dB div 1 dB div or Linear Sweep rate can be set from 1 us div to 2 s div in a 1 2 5 sequence Other values will be converted to the nearest allowable value Rates faster than 100 us div can be used only with analog displays that is with display storage turned off Press UTIL to return to the spectral display and view the screen you have created Press UTIL 2 to return to the KEYPAD ENTERED SETTINGS menu Press 2 2 0 X to enter a span div of 20 MHz Press 1 21 8 8 Y to enter a reference level of 28 8 dBmV Press any menu button to restore the spectral display 6 61 Spectrum Analyzer Menus Save and Recall Settings and Displays Recall Last Power Down Settings User Defined Power Up 6 62 Settings The 2715 enables you to save and recall up to 36 sets of control settings and any saved displays that accompany them These are in addition to the factory default power up settings that are permanently stored in the instrument The 2715 also automatically saves the settings displays in use in location 0 when it is powered down You can manually save up to 35 additional setting display groups and designate one group as the power up settings A general word of caution the 2715 will not allow you to destroy a display currently saved in registers A B or C If
160. above 55 Hz resonance is defined as an excursion greater than 2X the input displacement Shock Operating and Nonoperating Three guillotine type shocks of 30 g one half sine 11 ms duration each direction along each major axis total of 18 shocks no drops allowed on the front surface and front corners Transit Drop Free Fall 8 in 203 2 mm one per each of 5 faces and 4 corners instrumentis tested and meets drop height of 12 in 304 8 mm Table A 10 Physical Characteristics Characteristic Weight With Standard Accessories Without Standard Accessories Dimensions Height with Feet and Handle Width With Handle Without Handle Depth With Front Panel Cover Without Front Panel Cover With Handle Extended Performance Requirement 25 Ibs 11 34 kg 22 5 lbs 10 21 kg 5 4 in 137 16 mm 14 2 in 360 68 mm 12 9 in 327 66 mm 17 5 in 444 50 mm 16 85 in 427 99 mm 20 1 in 510 54 mm A 22 2715 User Manual Specifications Table A 11 Certifications and Compliances Category EC Declaration of Conformity EMC Description Meets intent of Directive 89 336 E EC for Electromagnetic Compatibility Compliance was demonstrated to the following specifications as listed in the Official J ournal of the European Communities EN 50081 1 Emissions EN 55022 Class B Radiated and Conducted Emissions EN 60555 2 AC Power Line Harmonic Emissions EN 50082 1 Immunity IEC 801 2 Electrostatic D
161. ace is still displayed on the oscilloscope By using the video output to view the analog display all four registers remain available for digital storage and display You can have an analog display and four different digital traces m If your oscilloscope has a sweep magnifier or delayed sweep facility use either one to obtain an enhanced view of the central signal peak on the oscilloscope without altering the spectrum analyzer settings The oscilloscope horizontal scale factor equals the 2715 span division times the ratio of the 2715 and oscilloscope sweep speeds Pin 4 of the Accessory Connector is the sweep ramp The sweep ramp varies linearly from 1 3 V to 1 3 V and is proportional to the horizontal position of the sweep as it crosses the screen The start of the ramp is synchronous with the start of the 2715 sweep The bottom of the ramp marks the end of sweep see Figure E 2 The signal is usually used in conjunction with the video output to generate the horizontal deflection for an external video unit such as an XY oscilloscope or recorder m Continuing with the setup from the Sweep Gate paragraph connect pin 4 to the X axis input of your oscilloscope and the video output to the Y axis Place the oscilloscope in XY mode Adjust the X axis gain on the oscillo scope until the sweep just fills the screen If the sweep is backwards invert the X axis input to reverse it The advantage in using the ramp to control the oscilloscope
162. al point to see the stored value press UTIL 2 9 Press 3 3 e 3 X to set the span division to 33 3 MHz The numbers you type appear on screen to the right of SPAN If you make a mistake you can correct it any time prior to pressing X by repeatedly pressing BKSP the backspace key until the incorrect entry disappears and then entering the correct value Pressing a terminator button W X Y or Z determines the units and enters the data X can represent units of MHz ms or mV Because the immediate span div entry mode requires a frequency the 2715 correctly interprets the currently displayed value as 33 3 MHz when you press X If a time or voltage unit had been required the 2715 would have interpreted your entry as 33 3 ms or 33 3 mV respectively when you pressed X On the other hand had you wanted the entry to represent a span div of 33 3 kHz you would have pressed Y instead of X 10 Press The span div changes to 20 MHz the nearest span div value in the down ward direction in the normal 1 2 5 sequence Had you pressed the span div would have changed to 50 MHz the nearest value in the upward direction The span readout now indicates 20MHZ and the 4 harmonic of the calibration signal is at the center frequency of 400 MHz MAX There is often a need to view the entire input frequency range of the 2715 such as when connecting new signals to the 2715 input In this mode
163. alibration signal on and off The following procedure shows how to turn the calibrator on and off Press INPUT to call up the Input menu The word OFF following item 9 of the INPUT menu indicates the calibrator signal is turned off 2 Press 9 to turn on the calibrator signal The spectral display appears and the word CALIBRATOR is now displayed at the lower right of the screen indicating the calibrator signal is on The calibrator signal is the peak at center screen Turning on the calibrator also internally disconnects the RF input path from the RF Attenuator and prevents viewing external signals 3 Press INPUT again The word following item 9 now is ON In this way the menu enables you to toggle between the two possible settings and displays the current setting 4 Press 9 again to turn the calibrator off You get the spectral display back but without the word CALIBRATOR displayed 5 Press INPUT 9 once again to turn the calibrator back on The following steps show how to set the RF attenuation 6 Press REF LEVEL 4 8 e 8 Y to set the reference level to 48 8 dBmV 2715 User Manual Spectrum Analyzer Menus Changing Reference Level 2715 User Manual Units 7 8 Press to the right of REF LEVEL twice Notice that the signal peak rises but the noise floor does not This is because the RF attenuation decreased each time you pressed the key The increased signal height is ach
164. amplifier turned on may create spurious signal components and produce unreliable amplitude measurements Note the level of the noise floor and then press INPUT 1 Item 1 of the INPUT menu toggles the preamplifier on and off The preamplifier is now turned on as indicated by the term PRE following the reference level readout Again note the noise floor It should be approximately 12 dB lower than before The 2715 has automatically reduced its internal gain thus lowering the normal noise floor to compensate for the added gain of the preamplifier The result is that you can now see signals that are up to 12 dB below the normal 2715 noise floor Toggle the preamplifier off 6 9 Spectrum Analyzer Menus 6 10 Using the DBUV M The decibel relative to a microvolt per meter dBuV m is an electric field strength unit that characterizes the intensity of radiated RF energy Typically the radiated signal amplitude is measured at the terminals of a calibrated antenna to determine the field strength With most spectrum analyzers you then correct the measured signal amplitude for any external gain or attenuation convert signal amplitude to radiated intensity using the antenna factor often referred to as the K factor for your antenna and scale the field strength for the difference between the measurement distance and the required reference distance However the 2715 performs the correction conversion and scaling for you Input the
165. an from the remaining data 8 Displays the cumulative aural FM deviation Interactive mode runs until the user selected time elapses or you terminate or abort it and then displays the measurement results and a prompt for the operator to resume or accept the current measurement When you initiate an interactive aural FM deviation measurement and do not terminate or abort it the 2715 performs the following 1 Executes step 1 through step 8 as discussed earlier in Auto Mode 2 Loads Waveform B with a straight line halfway across the screen horizontal ly to mark the position of the completed mean 5 33 Measurements Adjustment Mode Enable AURAL FM DEVIATION Measurement 5 34 3 Prompts you to either resume or accept the current measurement If you select RESUME the 2715 makes another measurement The min hold register is not cleared between measurements to allow further accumulation of the peak deviation When you select ENTER ADJUSTMENT MODE from the AURAL FM DEVIATION submenu the 2715 computes and displays the instantaneous aural FM deviation for each sweep This allows you to use a constant test tone to adjust the level of modulation on a sweep by sweep or real time basis No measurement results are stored in this mode The following procedure shows how to make an aural FM deviation measurement 1 Press CATV APPL to display the CATV MEASUREMENTS menu See Figure 5 1 2 Press 4
166. an in the immediate entry mode Notice that the abbreviation SPAN appears at the left center of the screen The SPAN indicator tells you that you can enter the span div directly from the keypad This is done by keying in a permissible value followed by an appropriate terminator key 10 Press 6 to set the span div to 6 MHz Any number you type appears on screen to the right of SPAN If you make a mistake you can correct it by repeatedly pressing BKSP the backspace key until the incorrect number disappears and then entering the correct value 11 Press X after the correct number has been entered This key can represent units of MHz ms or mV Because you selected an entry mode that requires a frequency the 2715 correctly interprets the currently displayed entry as 6 MHz If a time or voltage unit had been required the 2715 would have interpreted your entry as 6 ms or 6 mV respectively The span now is set to 6 MHz and the ninth harmonic of the calibrator signal is centered on screen at 900 MHz You may have noticed that the resolution bandwidth changed to 1 MHz This demonstrates the AUTO resolution bandwidth selection mode of the 2715 The spectrum analyzer reduces its resolution bandwidth as you reduce the span div so the resolving power of the instrument automatically increases as you look at the spectrum more closely To look at the calibrator signal fundamental you must change the center frequency The spectrum analyz
167. and 2715 If the filter is used its gain or attenuation should be included in this number If balun losses are not included in the antenna factor they should be included here Cable loss if significant can also be included here K antenna factor supplied by manufacturer or calculated as follows 20logf G 10 log 19 X Rant G antenna gain as a function of frequency f frequency of signal in MHz Rant output resistance of the antenna or the balun if the balun is treated as part of the antenna 2715 User Manual Spectrum Analyzer Menus 2715 User Manual Homemade Twin Lead Antenna 5600 1 425 f MHz f MHz inches meters 300 Twin Lead Folded Cut Dipole Non Metallic Mounting Board Masonite lt 300 75 TV Balun Figure 6 4 Equipment Setup for Field Strength Measurements With the 2715 you enter the attenuation using the EXTERNAL ATTEN AMPL feature from the INPUT menu and the antenna factor measurement distance and reference distance using the DBUV M SETUP under the REFERENCE LEVEL UNITS of the INPUT menu Note that many commercial antenna suppliers include the balun losses in the antenna factor For the most accurate results use an antenna calibrated at the specified reference distance and perform the measurement at that distance If possible measure the return loss of the antenna to make certain it is properly tuned to the desired frequency See Tek
168. and aural carriers When the measurement is finished the 2715 returns to the spectral display Two lines near center screen display the measurement results One line displays the visual carrier amplitude and frequency in absolute values and the second line displays aural carrier amplitude and frequency as offsets from the visual carrier values 9 Press CATV APPL to recall the CARRIER LEVELS measurement menu 10 Press 1 to store the measurement results 11 Press 2 to display the measurement results See Figure 2 3 for a typical display 12 Press W to display the last stored results if they exist 13 Press 3 to print the measurement results The spectrum analyzer must be connected to a printer that is capable of printing text 14 Press 4 to print the stored measurement results 15 Press 9 to deselect the CARRIER LEVELS measurement 16 Disconnect the cable TV feed from the RF INPUT 2715 User Manual Getting Started CARRIER LEVEL CURRENT CHAN 8 24 OCT 91 19 33 08 TEKTRONIX JOHN SMITH VISUAL 8 7DBMV 181 240072MHZ AURAL 16 4DBC 4 499988MHZ PRESS W TO CONT Z TO ABORT Figure 2 3 Typical Measurement Result Display Making Your First This procedure shows you how to verify the frequency and amplitude of the NonCATV Measurement calibration signal Although the calibration signal is used the measurement technique is the same for any continuous signal In the process you will learn to
169. and level measurements frequency is counted only if ACCURATE FREQUENCY AND AMPL is on Accurate Fre Amplitude quency and Visual carrier frequency measurement Visual to aural carrier frequency measurement Visual carrier peak level measurement Visual to aural carrier level difference measurement Accurate Am plitude Only Visual carrier peak level measurement Visual to aural carrier level difference measurement Fast Amplitude Only Carrier amplitudes are measured using marker values in 10 dB div vertical scale Visual Carrier Amplitude Range 18 dBmV to 58 8 dBmV for C N lt 30 dB 300 kHz RBW Frequency Range 15 MHz to 1015 MHz Resolution 0 3 dB Absolute Accuracy 2 7 dB for visual C N 230 dB 300 kHz RBW and for FM signal C N 233 dB 100 kHz RBW assumes flatness corrections are present Relative Accuracy 0 8 dB relative to adjacent channel 11 5 dB relative to all other channels Aural Carrier Difference Range Resolution Accuracy Aural FM Deviation Typical Range Accuracy Cross Modulation Typical Range Resolution 0 to 30 dB for C N 215 dB 300 kHz RBW 0 3 dB 1 1 dB for C N 215 dB 300 kHz RBW Peak FM deviation measured for the selected channel 10 kHz to 50 kHz usable to 80 kHz 4 kHz The third order distortion at the horizontal sync frequency AM measured on the unmodulated visual carrier as corrected to the NCTA recommended synchronous square wave modula
170. annot unsave the destination register or use the LIN FM DEMODULATOR or EXTERNAL SOURCE features To disable the dBuV m measurement mode select any other reference unit If you are using an antenna for the first time you need to create an antenna table From time to time you may also need to alter an existing table Whether creating new antenna tables or changing old tables all editing takes place in the local buffer or editing buffer using the EDIT ANTENNA TABLE selection from the DBUV M SETUP on the Input menu New antenna data is written directly to the buffer prior to permanent storage old data is loaded into the buffer prior to editing and restorage If you wish to enter new antenna data or change old data use the following procedure 1 Press INPUT to call up the Input menu 2 Press 9 to select DBUV M SETUP from the INPUT menu 3 Press 0 to select item EDIT ANTENNA TABLE 6 13 Spectrum Analyzer Menus 6 14 To create a new antenna entry press 6 ANTENNA SETUP Enter the start stop and frequency steps at which measurements will be made Enter the reference distance The reference distance is the distance to which you want the field strength referred For maximum accuracy your antenna should be calibrated at the reference distance and your measurement made at that distance However if you require another distance enter it here For instance if you are making measurements at 10 meters but want the field streng
171. anual Cable TV RF Measurements Software 161 0104 00 U S Power Cord 200 2520 00 Front Cover 103 0045 00 Adapter Connector Male to BNC Female 50 103 0301 00 Adapter 75 O Female F to Female BNC 103 0310 00 Adapter 75 Female to Female F Table F 2 Optional Accessories Tektronix Part Number Description 012 1339 00 Coaxial cable 75 BNC to BNC 24 in 609 6 mm 012 0074 00 Coaxial cable 75 BNC to BNC 42 in 1066 8 mm 012 0057 01 Coaxial cable 50 BNC to BNC 42 in 1066 8 mm 012 0991 01 GPIB cable 39 4 in 1 m 012 0991 00 GPIB cable 78 8 in 2 m 012 1380 00 RS 232 cable 9 pin female to 25 pin female 76 in 1930 mm 012 1379 00 RS 232 cable 9 pin female to 9 pin female 76 in 1930 mm 012 1241 00 RS 232 cable 9 pin female to 25 pin male 180 in 4572 mm 016 0848 00 Rain Cover 016 0677 03 Accessory Pouch 016 0566 00 Viewing Hood 346 0199 00 Carrying Strap Appendix F Accessories and Options Table F 2 Optional Accessories Cont Tektronix Part Number Description 606 0110 02 Service Kit 337 2775 01 CRT Light Filter clear 337 2775 02 CRT Light Filter gray 070 9096 00 Service Manual 016 0792 02 Transit Case Table F 3 Power Cord Identification Plug Configuration Normal Usage Option Number North America Standard 125V Europe 230V United Kingdom 230 V North America A4 230 V Switzerland A5 230 V F 2 2715 User Manual Appen
172. arried out m Nonvolatile memory is lost for any reason 6 65 Spectrum Analyzer Menus 6 66 Always perform the normalizations in environments especially temperatures like those in which the subsequent measurements will be carried out Also remove any input signals from the 2715 before performing amplitude or frequency normalizations Although we recommend that you wait a full 15 minutes after power up before making measurements with the 2715 it is within advertised specifications by then it is possible to make them shortly after power up If you must make measurements immediately after the instrument is turned on and the NORMALIZATION SUGGESTED message is on screen carry out a normalization directly Note however that if you do so the 2715 may require renormalization after it is fully warmed up 1 Press UTIL to call up the Utility menu 2 Press 3 to select NORMALIZATIONS The Normalizations menu enables you to normalize amplitude parameters AMPLITUDE ONLY the frequency parameters FREQUENCY ONLY or both ALL PARAMETERS It takes longer for amplitude normalization than for frequency normalization and several minutes for both Routinely select ALL PARAMETERS to ensure the 2715 measures amplitude and frequency as accurately as possible but if you are in a hurry you can select only the parame ters that are most important to your measurements 3 Disconnect all signals from the 2715 input 4 Press 0
173. at display the whole channel across the screen Selects 100 kHz RBW and turns the video filter off Enables gating and peak acquisition mode Initially places the marker at 2 MHz above the visual carrier and if necessary changes the reference level setting so that the low point of the trace is at least 10 dB above the bottom of the screen 4 Ifin interactive mode prompts the user to adjust the marker to the desired position for the noise measurement If in auto mode with pause for carrier off prompts the user to turn off the carrier 5 Measures the noise at the location shown in Table 5 8 using the applicable built in noise measurement routine which applies the noise measurement corrections for filter BW detector errors and instrument noise floor proximity If measuring on the in service basis the routine includes switching to zero span and averaging for a substantial number of TV vertical sweep periods 5 36 2715 User Manual Measurements 2715 User Manual Table 5 8 Locations of Noise Measurement Mode Measurement Location In service interactive At marker In service auto At 42 7 MHz above carrier Interactive Atmarker Auto Atlowest channel edge Pause At 42 7 MHz above carrier Digital Average whole channel 6 Subtracts the noise level from the previously measured carrier level both expressed in log dB units and displays the result as C N in dB 7 lf in service basis is selected verifies that the qu
174. ation of the 2715 ensure that no external signals connected to the 2715 2 Press UTIL and 3 This calls up a menu that offers you a choice of normalization processes 3 Select ALL PARAMETERS by pressing 0 Normalization should begin immediately and continue without interruption until it is completed Normalizing all parameters requires several minutes During the process you will see various displays and messages which keep you informed of progress but do not require action The process ends with an audible beep and the message NORMALIZATION COMPLETE indicating satisfactory operation If you receive any other message terminating this initial normalization repeat the procedure If the message persists contact your Tektronix Service Center 2 5 Getting Started Restoring the Factory Default Settings The Initial Display 2 6 To ensure a common starting point for the calibration signal measurement you must restore the factory default power up settings 4 Press UTIL 1 1 This restores the factory default settings whenever the 2715 is in normal spectral display mode and most other modes It is a handy method of returning to a fixed set of conditions if you get lost Figure 2 1 shows what the spectrum analyzer screen looks like after initializing the instrument settings Center Frequency 180 MHz 183 MHz 186 MHz Reference Level gt r 68 8 dBmV 483
175. ations Table A 4 Amplitude Related Characteristics Cont Performance Requirement Supplemental Information Characteristic Sensitivity without P reamp Resolution Bandwidth 110MHz 1 8GHz 2 15 GHz 5 MHz 36 dBmV 28 dBmV 26 dBmV 85 dBm 77dBm 75 dBm 1 MHz 43 dBmV 35dBmV 33 dBmV 92 dBm 84dBm 82dBm 300 kHz 48 dBmV 40dBmV 38 dBmV 97 dBm 89dBm 87 dBm 100 kHz 53 dBmV 45dBmV 43 dBmV 102dBm 94dBm 92dBm 30 kHz 58 dBmV 50dBmV 48 dBmV 107 dBm 99dBm 97dBm 10 kHz 63 dBmV 55dBmV 53 dBmV 112dBm 104dBm 102 dBm 3 kHz 68 dBmV 60dBmV 58 dBmV 117 109dBm 107 dBm 1 kHz 73 65dBmV 63 dBmV 122dBm 114dBm 112 dBm 300 Hz 78 dBmV 70 dBmV 68 dBmV Sensitivity with Preamp Resolution Bandwidth 127 dBm 119dBm 117 dBm 110 MHz 1 8 GHz and 2 15 GHz Not Specified 5 MHz 48 dBmV 95 dBm 1MHz 55 dBmV Not Specified 104 dBm 300 kHz 60 dBmV Not Specified 109 dBm 100 kHz 65 dBmV Not Specified 114 dBm 30 kHz 70 dBmV Not S pecifi 119 dBm 10 kHz 75 dBmV Not Specifi 124 dBm 3 kHz 80 dBmV Not Specifi 129 dBm 1 kHz 85 dBmV Not Specifi 134 dBm 300 Hz 90 dBmV Not Specifi 139 dBm A 16 Equivalent maximum input noise for each resolution bandwidth P erformance measurements above 1 8 GHz refer to the Option 50 and Option 75 instruments only Sens
176. ations by changing the YIG oscillator settling delay time from the factory default value The factory YIG oscillator settling delay time default is 5000 ms The indicated YIG oscillator settling time for example the default of 5000 ms represents the longest delay that will occur Typically most operations of the spectrum analyzer will result in shorter delay times The default settling time was chosen to ensure compliance with published specifications for all instruments over a variety of conditions such as temperature aging wide frequency steps calibration variations YIG oscillator variations and other component variations All 2715 spectrum analyzer stability and frequency accuracy specifications are guaranteed only at the 5000 ms setting However in many applications faster settling delay time may be successfully used Determination of the suitability of 2715 User Manual Spectrum Analyzer Menus 2715 User Manual settings other than the factory default of 5000 ms must be made by the user of the specific 2715 spectrum analyzer The best way to verify operation is to compare measurement results using the factory default YIG oscillator settling delay time and your reset time You may then choose to use and store the reset time The minimum acceptable settling time may vary from instrument to instrument as well as application to application You are encouraged to verify acceptable performance on an instrument by instrument basis wh
177. ator resides in the 2715 and can be connected to the input path without the need for external cabling by selecting the proper Input Menu option 10 Press the MAX SPAN key located below the REF LEVEL key 11 Press the AUTO RES BW key 12 Press INPUT to call up the Input Menu Item 9 specifies a CAL SIG 100MHz 18 8DBMV The calibrator is a CW signal with a fundamental frequency of 100 MHz at an amplitude of 18 8 dBmV 30 dBm Higher order harmonics at lower levels are also present Item 9 toggles the calibrator on and off 13 Press 9 to turn the calibrator on The screen reverts immediately to the spectral display The word CALIBRA TOR now appears near the bottom right of the screen signifying that the calibrator is enabled You should see a few signal peaks towards the left of the display These are the fundamental and harmonics of the calibrator signal If you do not see them it is because the amplitudes of the harmonics may be lower than the noise floor of the 2715 NOTE When the calibrator is enabled the normal RF input is disconnected internally from the input attenuator and cannot be viewed 14 Press INPUT 9 to disable the calibrator Making Your First Measurement The following two types of measurements can be made with the 2715 m CATV measurements NonCATV measurements 2 10 2715 User Manual Getting Started Selecting a Channel Table The factory defaults set the 2715 in the normal C
178. available signals are AM and FM broadcasts To receive AM or FM broadcast radio stations you can plug a piece of wire directly into the center terminal of the input connector and hang the other end out a nearby window If your building is not metal framed you can probably use a length of wire that fits within the same room as the spectrum analyzer The required length of wire will depend on the strength location and frequency of the transmitter among other variables 50 kW FM stations 40 miles distant have been received with a wire paper clip straightened and inserted directly into the input connector CAUTION The spectrum analyzer can be damaged by static discharge or high level signals Remove any static charge before connecting a wire or antenna to the spectrum analyzer Remove any static charge by first momentarily grounding the wire to the case of the instrument If the wire may be carrying AC or DC power measure it with a high impedance voltmeter or oscilloscope to be sure that it does not exceed the DC input rating of the spectrum analyzer If you are close to a transmitter be sure to set a reasonably high value of RF attenuation before connecting the wire or antenna to the spectrum analyzer Use the spectrum analyzer to measure the signal amplitude at the frequency of the transmitter before going to lower attenuator settings If you have an accessible antenna such as a wire or whip connected ground yourself to the case of the
179. band excluding the region within about 1 MHz of the visual carrier while normal program material is being broadcast 5 35 Measurements CARRIER TO NOISE When the CARRIER TO NOISE measurement is initiated on an analog channel the 2715 performs the following NOTE When you are measuring C N on an in service basis at a test frequency within the video band the useful sensitivity may be limited by noise on the video signal being carried 1 If in service basis is selected finds a group of quiet lines if none are specified in the channel table 2 Tunes to the visual carrier frequency and sets the following RBW to 300 kHz with no video filter span to 200 kHz div sweep speed to 50 ms div 200 ms div if the modulation polarity is positive as in the French L system The 2715 makes a single sweep and then does a peak search with the marker and records the marker value as the carrier level 3 Performs one of the following unless in auto in service basis a If normal basis in service not selected returns to frequency and span settings that display the whole channel across the screen Selects 30 kHz RBW and turns the video filter on Initially places the marker on the minimum point of the waveform and if necessary changes the reference level setting so that the low point is at least 10 dB above the bottom of the screen b If interactive in service basis is selected returns to frequency and span settings th
180. bel Voltage Values dBpV M 0 microvolt per 20 meter 40 60 millivolt per 80 meter 100 0 398 0 631 volt per me 120 3 98 E 6 12 2715 User Manual Spectrum Analyzer Menus 2715 User Manual 8 Select the antenna number 1 through 5 that matches the antenna you are using 9 Press 4 to return to REFERENCE LEVEL UNITS 10 Press 5 to select DBUV M IN WFM x 11 Press INPUT 6 and enter any external gain or attenuation skip this step if none is present This number should include the gain or attenuation of any external amplifier or filter and the losses of any balun that are not included in the manufactur ers K factor table for your antenna 12 Connect your antenna and proceed with your measurement To obtain a measure of the maximum signal strength save the measurement in the A or B register and select MAX HOLD Rotate the antenna until the maximum reading is obtained 13 Turn on the marker and use it to read out the field strength directly in dBuV m or V m While using the dBuV m unit you cannot unsave the destination register or use the LIN FM DEMODULATOR or EXTERNAL SOURCE features you also cannot select the dBuV m unit while using these features Attempting to do so will result in an error message If you turn off the destination register while using dBuV m the message DBUV M MEASUREMENT MODE IDLE is displayed The dBuV m measurement is not made while idling and you still c
181. bove 350 MHz Typically lt 21 dBmV lt 70 dBm Table A 5 Input Output Signal Characteristics Characteristic RF Input VSWR with RF Attenuation gt 10 dB VSWR with 0 dB RF Attenuation Maximum Safe Input Performance Requirement Supplemental Information Type F male connector or type N female connector 1 5 1 maximum Checked to 1 GHz All except Option 50 and Option 75 2 1 maximum up to 1 GHz 3 5 1 maximum up to 1 8 GHz Option 50 and Option 75 4 1 maximum up to 2 15 GHz 70 dBmV 0 1 W or 2 2 V continuous peak 100 VDC blocking capacitor Caution Do not apply more than 100 VDC or 100V peak AC to the RF Input 1 dB Compression Point minimum With no RF Attenuation and 15 mixer at 19 dBmV 30 dBm 34 dBmV 15 dBm 2715 User Manual A 17 Specifications Table A 5 Input Output Signal Characteristics Cont Characteristic Performance Requirement Supplemental Information Ext Trig J 102 BNC connector 10 kQ DC coupled for external trigger signals Voltage Range Minimum Typically atleast 100 mV pear 15 Hz to 1 MHz Maximum 50 V DC peak AC Pulse Width 0 1 us minimum Accessory Connector 103 DB 15 female connector Pin 1 External Video Input Pin 2 Sweep Gate 42 0 V minimum high ER 0 8 V maximum low Pin 3 Chassis and Signal Ground Pin 4 Sweep Output 1 3 V Pin 5 Log Video Output Pin 6 CLKO Output Typically 100 ohm DC coupled 0 50
182. brated state has been corrected and exited UNCAL ON A change of state indicator briefly displayed when an uncalibrated state has been entered UNDEFINED ERROR CODE Firmware hardware error Returned error code has overrun established limits Contact your local Tektronix service center or representative if message persists UNDEFINED EVENT CODE Firmware hardware error Returned error code has overrun established limits Contact your local Tektronix service center or representative if message persists USE ANTENNA SETUP MENU FIRST The antenna start stop increment frequencies must be set prior to editing the correction table USER DEFINED PROGRAM IN PROCESS A UDP is in progress Reported primarily for GPIB purposes USER DEFINED PROGRAM COMPLETE A UDP has finished USER REQUEST A user request SRQ has been initiated C 14 2715 User Manual Appendix System Messages VERT MODE SCALE MISMATCH ON DIFF B minus A function attempted with mixed vertical modes LOG LIN display AM FM demodulator or mixed scales 10 5 1 dB 10 5 1 kHz 17 5 87 5 175 MV Reset the vertical modes or scales to be consistent Amplitude mode scale choices are found with UTIL 2 6 with scale choices also available from the front panel VERT SCALE function block Demodulator choices are found with DEMOD 1 and DEMOD 2 WAIT ABORTED SWEEP NOT ARMED Requested WAIT FOR END OF SWEEP was aborted immediately to avoid an endless wait loop Th
183. by IEEE and IEC Abbreviations used in the instrument and in the documentation are consistent with ANSI Y 1 1 1972 Copies of the ANSI and IEEE standards can be ordered from the Institute of Electrical and Electronic Engineers Inc Change History Information Changes to the 2715 may occur or manual errors may be found that make some of the information in the manual inaccurate When this happens Manual Change Information notices containing the corrected information are inserted at the rear of the manual This ensures that the manual contains the latest and most accurate information available when the product is sold Contact any Tektronix Service Center for information 2715 User Manual xi Preface Manual Organization General Sections 1 through 3 contain material that enables the beginning or experienced operator to safely power up and initially normalize the spectrum analyzer Sections 4 through 6 provide detailed explanations and some measurement examples that may be especially useful The examples should be read while interactively using the spectrum analyzer and carrying out the instructions In this way you quickly acquire the knowledge and skills necessary to make accurate measurements The end of one example and start of the next are indicated by a settings box that looks like this 8 75MHZ AUTO SWEEP M 11 45 MHZ 23 5DBMV M 13 8 DBMV 600KHZ 10 DB 300KHZ RBW STD CH2 The box shows what the control settings of the sp
184. by plotting the display you can first title the display If you are plotting the display you can also label significant points 1 Ensure that only the D register is active 2 Press DSPL 5 to select title mode Item 2 reads TITLE MODE EDIT if one or more registers contain a current sweep as now or TITLE MODE EDIT WFM X if only saved data is displayed saving a waveform also saves its title 2715 User Manual Spectrum Analyzer Menus 2715 User Manual In either case the title to be edited is always associated with the highest priority displayed waveform see register priority chart on page 4 23 This means for instance that to create a title for the B waveform the C and D registers must be turned off or to edit the title of a saved waveform in the C register all registers containing a current sweep must be turned off Although you can edit the title of a saved waveform for display or plotting only the originally saved waveform title is retained You can circumvent this restriction by saving the waveform and its new title as part of a stored settings group see Save and Recall Settings and Displays on page 6 62 the edited title is then retained as part of the newly saved settings waveform and you can delete the original or not as you choose When performing a screen plot the title being edited is attached to the highest priority waveform even if it has a previously saved title However if lower priority saved wave
185. cally a sine wave upon which modulation is impressed Carrier Frequency The frequency of the carrier signal Carrier to Noise Ratio C N The ratio of carrier signal power to average noise power in a given band width surrounding the carrier usually expressed in decibels Center Frequency That frequency which corresponds to the center of a frequency span expressed in hertz Clear Erase Presets memory to a prescribed state usually that denoting zero Composite Second Order CSO Second order distortion products generated by the direct addition or subtraction of fundamental visual carrier frequencies Glossary 1 Glossary Glossary 2 Composite Triple Beat CTB Cross modulation third order distortion product resulting from the addition and subtraction of fundamental visual carriers with the co channel interfer ence harmonic of other visual carriers or the addition and subtraction of a combination of three visual carriers dBc Decibels referenced to carrier level dBm A unit of expressed power level in decibels referenced to 1 milliwatt dBmV A unit to express voltage levels in decibels referenced to 1 millivolt dBuV A unit to express voltage levels in decibels referenced to 1 microvolt Decibel dB Ten times the logarithm of the ratio of one electrical power to another Deflection Coefficient The ratio of the input signal magnitude to the resultant output indication The ratio may be expressed in terms
186. cant digit normalization procedure Drift Long Term One Year 2 PPM year Short Term SPAN DIV x20 kHz All except Option 50 and Option 75 400 Hz up to 1 8 GHz Option 50 and Option 75 500 Hz above 1 8 GHz With frequency corrections enabled Readout Resolution Frequency Span Div Range Accuracy Linearity Flatness Relative to the Reference Level at 100 MHz Within 3 All instruments 2 dB 9 KHz to 1 8 GHz Option 50 and Option 75 3 dB above 1 8 GHz 1 kHz or 1 Hz counter readout menu selectable Using SPAN DIV and SPAN DIV buttons selections in a 1 2 5 sequence Using the keypad or UTIL menu select any value from 100 MHz div to 1 kHz div In MAXSPAN 180 MHz div All except Option 50 and Option 75 or 215 MHz div Option 50 and Option 75 In ZERO SPAN 0 Hz div Measured over the center 8 divisions Measured with 10 dB of RF Attenuation and PREAMP off Flatness is affected by m Input voltage standing wave ratio VSWR m Gain variation m Mixerconversion z 2715 User Manual Specifications Table A 2 Frequency Related Characteristics Cont Characteristic Residual FM With SPAN DIV lt 20 kHz 20 ms up to 1 8 GHz Option 50 and Option 75 peak to peak total excurs above 1 8 GHz lt 120 Hz on in 20 ms With SPAN DIV gt 20 kHz lt 2 kHz peak to peak tota 20 ms up to 1 8 GHz Option 50 and Option 75 peak to peak total excurs
187. case is 38 Hz 325 25 MHz Ch 41 worst case is 173 Hz 643 25 MHz Ch 94 worst case is 332 Hz Aural carrier measured relative to the visual carrier Internal Counter 1 MHz to 10 MHz for an amplitude difference of lt 30 dB and aural C N 215 dB 300 kHz RBW 1Hz 15 Hz for visual to aural carrier difference lt 8 MHz Absolute peak amplitude of visual carrier measured with PREAMP OFF Visual carrier frequency measurement Visual to aural carrier frequency measurement Visual carrier peak level measurement Visual to aural carrier level difference measurement Visual carrier peak level measurement Visual to aural carrier level difference measurement Carrier amplitudes are measured using marker values in 10 dB div vertical scale 18 dBmV to 458 8 dBmV for visual C N 230 dB 300 kHz RBW 1 Configured using Cable TV RF Measurements Software Dependent on selected channel table Frequencies above 1 8 GHz are not supported by the Cable TV RF Measurements Software 3 Dependent on selected channel table Total input power all signals included cannot exceed 70 dBmV A 2 2715 User Manual Specifications Table A 1 CATV Characteristics Cont Characteristic Frequency Range Resolution Absolute Accuracy Description 15 to 1015 MHz 0 1 dB 12 5 dB for visual C N 230 dB 300 kHz RBW and for FM signal C N 233 dB 100 kHz RBW assumes flatness corrections are present Relative Accuracy 0 5 dB relativ
188. cated Customer shall be responsible for paying all shipping charges duties taxes and any other charges for products returned to any other locations This warranty shall not apply to any defect failure or damage caused by improper use or improper or inadequate maintenance and care Tektronix shall not be obligated to furnish service under this warranty a to repair damage resulting from attempts by personnel other than Tektronix representatives to install repair or service the product b to repair damage resulting from improper use or connection to incompatible equipment or c to service a product that has been modified or integrated with other products when the effect of such modification or integration increases the time or difficulty of servicing the product THIS WARRANTY IS GIVEN BY TEKTRONIX WITH RESPECT TO THIS PRODUCT IN LIEU OF ANY OTHER WARRANTIES EXPRESSED OR IMPLIED TEKTRONIX AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE TEKTRONIX RESPONSIBILITY TO REPAIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED TO THE CUSTOMER FOR BREACH OF THIS WARRANTY TEKTRONIX AND ITS VENDORS WILL NOT BE LIABLE FOR ANY INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES IRRESPECTIVE OF WHETHER TEKTRONIX OR THE VENDOR HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES Table of Contents Introduction Getting Started Operating Basics 2715 U
189. ce is acquired by using the ACQUIRE A REFERENCE selection in the FREQ RESP SETUP menu The default start and stop frequency limits may be changed prior to acquiring the reference if desired Whenever the start or stop frequencies are changed the current reference is marked as invalid The instrument will sweep between the start and stop limits specified in this menu apply a digital filter to the resultant sweep and retain the resultant waveform and instrument setup The digital filter is used to smooth the reference to reduce sensitivity to slight frequency errors and differences in program material between the reference sweep and the subsequent frequency response peaks During reference acquisition the reference name is assigned by linking the site name current date the start frequency and the stop frequency The name may be changed with the EDIT CURRENT REFERENCE NAME selection This selection can only be used if there is a currently valid reference The reference is acquired with the 5 MHz RBW filter The goal is to capture the video carrier peaks throughout the frequency range If a valid reference exists the mode 1 test WITH REF may be run The first step is to recall the reference settings into the 2715 hardware Then after each sweep the raw sweep data is filtered using the identical digital filter used to filter the reference data The reference waveform is then subtracted from the current waveform and the difference written int
190. ces 14 Press DSPL 0 Notice that only the analog signal remains 15 Press DSPL 0 again Both the saved C digital display and the current D digital display return the same register configuration that was in use prior to entering the analog mode by selecting item 0 16 Turn on the B register and then turn off all registers in the order D C B 17 Press DSPL 0 Notice that the B register the last one turned off is the only one reactivated 18 Reset the center frequency to 300 MHz and turn on only the D register In general ensemble averaging techniques are used for the same reason as filters to enhance the desired signal to noise ratio Narrow resolution BW or video filters reduce the noise by reducing the 2715 s bandwidth Unfortunately they also require slower sweep speeds and in the cases of broadband signals the filters may limit the signal energy For these applications we can use ensemble averaging However if ensemble averaging is used with pulsed waveforms without taking special care to synchronize the 2715 to the signal erroneous measurements result This is because of the way scanning spectrum analyzers determine the spectrum of pulsed signals See Tektronix application note 26W 7037 1 Spectrum Analyzer Fundamentals for more information about pulse measurements 2715 User Manual Spectrum Analyzer Menus 2715 User Manual Ensemble averaging computes the average value of some parameter peak
191. ch generator output m Flatness response of modulator or other cable TV system components is not within 3 5 dB 2715 User Manual Measurements Running the Interactive Measurement 2715 User Manual To achieve the best amplitude measurement accuracy your test generator must produce a signal whose spectral density is the same at each test frequency Ideally all signals should have equal amplitude and burst duration for multi burst signals or uniform sweep rate for swept signals Many generators do not meet standards for flat spectral density Further test signals carried on program video may not be flat Therefore if in channel response measurements yield excessive response deviations check the flatness of the test signal being used if possible This might be done either at RF or at baseband depending on circumstances at the head end of the cable system If such a check reveals a problem it is reasonable to use the head end data to compensate the field data for the in channels errors measured at the head end The following procedure shows how to make an interactive in channel response measurement 1 Press CATV APPL to call up the CATV MEASUREMENTS menu See Figure 5 1 2 Press 9 7 to select the INLCHANNEL RESPONSE measurement menu This gives you the following options RUN IN CHAN RESP STORE CURRENT RESULTS DISPLAY RESULTS PRINT CURRENT RESULTS RS 232 Only PRINT STORED RESULTS RS 232 Onl
192. channel type is FM FM modulation is always used If the channel type is TV the modulation type depends on the video polarity as described in Channel Tables on page 5 6 To listen to channel audio press CATV APPL 4 Use the outer LEVEL knob to set the audio level When the carrier has FM modulation the display shows the instantaneous FM deviation Top Screen 0 kHz Deflection Factor 10 kHz division The other bright trace waveform accumulates peak deviation in MIN HOLD mode When the carrier has AM modulation the display shows the demodulated audio You can disable the LISTEN mode by pressing CATV APPL 4 again or DEMOD 0 However if you use the DEMOD 0 selection to disable LISTEN mode the active channel will not be recentered on the screen you merely turn off demodulation 2715 User Manual Spectrum Analyzer Menus D Spectrum Analyzer Menus Using the Menus 2715 User Manual This section describes the menu selected firmware driven features of the 2715 The menus provide a high degree of sophistication without a complicated control panel Press any key in the front panel MENU function block to cause a menu to be displayed on the screen The menus enable you to perform a variety of tasks as listed below some of which are not convenient using the front panel dedicated controls m Displaying and center
193. cifications Table A 4 Amplitude Related Characteristics Cont Performance Requirement Supplemental Information All except Option 50 and Option 75 80 dB maximum Log 8 divisions Linear Characteristic Display Dynamic Range Log Mode Display Dynamic Range is dependent upon the selected R esolu tion Bandwidth The accuracy specifications apply for amplitude measurements done with the marker only since marker measure ments are corrected for logging errors Option 50 and Option 75 Baseline will rise to indicated value typically 10 dB to 20 dB below signal level applied near frequency of 2 11 GHz Display Dynamic Range is reduced if there is signal energy at or near 2 11 GHz Accuracy 10 dB div Mode 5 dB div Mode 1 dB div Mode Linear Mode 1 0 dB 10 dB to a maximum cumulative error of 2 0 dB over the 70 dB range and a maximum cumulative error of 4 0 dB over the 80 dB range 1 0 dB 10 dB to a maximum cumulative error of 2 0 dB over the 40 dB range 1 dB maximum error over the 8 dB range 5 of full scale 10 dB div accuracy and range is affected by the signal to noise ratio of the selected Resolution Bandwidth filter See following table for maximum specified range Resolution Bandwidth dB Down 5 MHz 40 1MHz 40 300 kHz 50 100 kHz 50 30 kHz 60 10 kHz 60 3 kHz 80 1 kHz 80 300 Hz 80 RF Attenuator Range 0 to 50 dB in 2 dB steps 2715 User Manual A 15 Specific
194. controls can be conveniently set using either the arrow keys or immediate entry mode The arrow keys enable you to instantly change control settings and move according to the channel table selection The arrow keys are active whenever the spectrum analyzer is in the spectral display mode 2715 User Manual Getting Started In immediate entry mode you press the key corresponding to the parameter you wish to set CHAN FREQ SPAN DIV or REF LEVEL type the parameter value on the keypad and press the appropriate terminator key to complete the entry The value appears on screen as you type Each of the terminators W X Y and Z can represent more than one unit as indicated by the legend to the right of each key however the keys are context sensitive If an entry represents a frequency the indicated frequency unit is selected automatically when you press the key If dBs are required the indicated dB unit is selected and so on for all of the units Many keys are toggle action The ability to undo an action including menu selection by pushing the same button or sequence of buttons that carried out the action is typical of operations performed on the 2715 8 Press VID FLTR to observe the toggle action The red video filter LED illuminates and the trace shrinks vertically as the filter turns on and averages the noise 9 Press VID FLTR again The noise spectrum expands to its original size as the
195. creases the span div and expands or stretches the spectrum The arrow keys are active whenever the 2715 is in the spectral display mode Experiment by pressing each arrow key until the span div no longer changes You will notice two characteristics of the 2715 m Span div changes in a 1 2 5 sequence between 1 kHz and 100 MHz plus 180 MHz div in maximum span m Resolution BW changes automatically as the span changes later we show how this can be changed 1 If you request a narrow span before the 2715 is completely warmed up you may get a NORMALIZATION SUGGESTED message This message should not appear after the 2715 warms up 2715 User Manual Dedicated Controls 2715 User Manual Keypad Entry The preset span div values are sufficient for most measurement needs However other span div settings can be specified to the nearest tenth of a unit To set the span div to an arbitrary value do the following steps 8 Press SPAN DIV to place span in the immediate entry mode Notice that the word SPAN appears at left center of the 2715 screen The word SPAN indicates that you can enter the span div directly from the keypad immediate entry mode by keying in a permissible value followed by an appropriate terminator key Any value from 1 kHz div to 180 MHz div is acceptable You can enter up to 25 characters but the 2715 rounds the value to three decimal points and stores it In the spectral display the value is shown rounded to one decim
196. cy distribution Spectrum Analysis The technique or process of determining the frequency distribution of a signal Spectrum Analyzer A device for determining the frequency components of a signal Spurious Response A response to a spectrum analyzer wherein the displayed frequency is not related to the input frequency 2715 User Manual Glossary 9 Glossary Glossary 10 Static Amplifier Resolution Bandwidth The specified bandwidth of the spectrum analyzer s response to a continuous wave CW signal if sweep time is kept substantially long This bandwidth is the frequency separation of two points on the response curve usually 6 dB down if it is measured either by manual scan true static method or by using a very low speed sweep quasi static method Sweep Speed Sweep Rate The speed or rate expressed in time per horizontal division at which the electron beam of the CRT sweeps the screen Vertical Scale Factor Vertical Display Factor The number of dB volts etc represented by one vertical division of a spectrum analyzer display screen Video The term is used here generally to mean a signal after the detector stage It can also be used more specifically to mean a base band zero carrier frequency television signal Video Filter A postdetection low pass filter View Display Enables viewing of contents of the chosen memory section e g View A displays the contents of memory a View B displays the co
197. cycles between NONE ODD and EVEN The default is NONE Item 4 EOL sets the end of message designator when a message is sent by the 2715 When a message is transmitted over RS 232 the instrument sending the message signifies that the message has been completed Item 4 enables you to select CR carriage return LF line feed or CR LF both used to terminate messages sent to the 2715 The default is CR Item 5 FLOW CONTROL specifies the type of handshaking that will be used The following three choices are possible see the Programmer manual for expanded information on these selections HARD RTS CTS The RTS CTS DTR lines are used The DCD and DSR lines are ignored This mode facilitates binary transfers SOFT XON XOFF XON XOFF CTRL Q CTRL S protocol is used Only transmit and receive lines are needed but RTS and DTR must be forced true Suitable for use with a modem However code conflicts make binary transfers unreliable 2715 User Manual Spectrum Analyzer Menus NONE No flow control is used but RTS and DTR must be forced true This is suitable for use with a modem However the user is responsible to ensure that data buffers do not overflow The default is NONE m Item ECHO is a toggle intended for use with unsophisticated terminals When ECHO is ON the 2715 sends the character it has just received back to the terminal screen CTRL Q and CTRL S are not echoed The default is OFF m Item 7
198. d enter the third beat frequency Press 3 and enter the fourth beat frequency Press 4 and enter the fifth beat frequency Press 5 to use default frequencies Press BKSP BKSP 0 to run the measurement The instrument measures the visual carrier peak for a reference then prompts you to turn off the carrier Turn off the carrier and press W to continue or press Z to abort the measurement Single Sweep mode searches the Auto Test table for the lowest and highest frequencies relative to the visual carrier and sets the instrument s span div and center frequency to sweep from 0 25 MHz below the lowest frequency to 0 25 MHz above the highest frequency The instrument then makes a sweep within these constraints and prompts you to turn on the carrier 5 57 Measurements 5 58 10 Turn on the carrier and press W to continue Z to abort the measure ment The instrument searches the single sweep record for beats within 50 kHz of offset locations specified in the test table and displays the worst case result To run the CSO measurement in Continuous mode follow these steps NOTE Continuous mode is not available if the in service CSO measurement basis is selected 7 woe clo m uU R 11 12 Press 5 4 to select the Continuous mode The SET UP TEST FREQUENCIES AND CONTINUOUS MODE PARAMETERS menu item 5 is added to the menu Press 5 and enter the SET UP TEST FREQUE
199. d with your instrument In this case the in service test is run on the specified line even though it is outside the normal range but there is no verification that the line is still quiet after the test The 2715 firmware includes an algorithm which automatically sets the RF attenuator and RF preamplifier states to values based on a measurement of the signal levels on the system throughout the frequency range This is done for the same reason that the overall operating level in a CATV system needs to be controlled to make a suitable compromise between noise and distortion In some instances this may cause an unexpected result The gating hardware used for some of the in service measurements needs a strong signal to perform reliably In a nonflat system weaker signals on the system may fail to meet this requirement because the optimum RF attenuator and preamplifier settings are based on the levels of the stronger signals present causing the weaker signals to have excessively low levels at the 1st mixer of the 2715 In this case the 2715 automatically increases the 1st mixer input level by the minimum amount required However increasing the 1st mixer input level may cause the measure ment to be corrupted by instrument generated distortion products Although this technique will sometimes give an inaccurate test result the error is in the conservative direction That is if the test result reports that the CATV system passes it most likely
200. data accumulate for two to three minutes A ragged horizontal waveform develops indicating the maximum frequency excursions during the observation period Instantaneous Deviation Maximum Deviation 100 REF 100 2949MHZ ATTN 10DB z VE 0 50MS ZSPAN FM 10 KHZ 75 30KHZ RBW 20 30 sj 40 FREQ Figure 6 14 Instantaneous Frequency Deviation and Maximum Observed Deviation The following steps show how to read out the frequency deviation with the marker 9 Press MKR A OFF to turn the marker on 10 Turn off all registers except register A 11 Use the FREQ MKRS knob to move the marker to the point where you want the measurement 2715 User Manual 6 55 Spectrum Analyzer Menus DEMOD 6 56 Listening to FM Transmissions NOTE Because of the FM demodulator bandwidth the modulating signal used in the deviation monitor mode should consist of normal program material or a single tone in the audio frequency range The foregoing technique provides a quick look at unidirectional frequency deviation The carrier frequency is at the reference level and a downward excursion represents a deviation below the carrier If the FM spectrum is symmetrical the peak to peak deviation is twice the unidirectional amount In the example above 7 divisions is 70 kHz at 10 kHz div and the peak to peak deviation is approximately 140 kHz To see
201. deo band width to 300 kHz and sweep speed to 20 ms div Then it sweeps the carrier frequency and measures the amplitude Beat frequencies are then measured by setting the span to 300 kHz div resolution bandwidth to 30 kHz video band width to 300 Hz and sweep speed to 200 ms div After these settings are complete it sweeps the frequency and measures the beat amplitude After one cycle of the test is complete it waits for the test interval to expire then repeats the test During the test the 2715 display shows the current time the time when the next cycle will start the time when the complete test will finish and the time the next normalization will occur The test may be stopped at any time by pushing the W or Z key When the test is stopped all results data acquired to that time is retained The results may only be viewed on an external computer The 2715 display shows how many beats were measured how many times they were measured the interval between measurements and if the DISPLAY RESULTS button was pushed the amplitude of the measurement floor The measurement floor is the absolute amplitude below which the instrument noise floor is interfering with the measurement to such an extent that accurate amplitude corrections are not possible The following procedure shows how to make a CTB or CSO measurement 1 Press 9 5 or 9 6 to select the or CSO measurement menu This gives you the following options
202. describes the 2715 menu selectable firmware driven features Appendix A Specification lists the 2715 electrical physical and environmental specifications Appendix B Broadcast AM FM amp TV Signal Sources describes connecting the 2715 to various signal sources to do the examples shown in the manual Appendix C System Messages describes abnormal instrument operating situations and the recommended resolution or correction Appendix D Global Resets provides the definitions descriptions and categories of the various reset procedures for the instrument settings Appendix E External Input and Output explains the procedure to get signals in and out of the back panel of your spectrum analyzer Configurations for interconnect cables are also discussed Appendix F Accessories amp Options describes all standard and optional accessories and options currently available for the 2715 If you are already familiar with the spectrum analyzer this manual can serve as a how to reference Check the index or table of contents for the location of the subject of interest Then set the spectrum analyzer according to the correspond ing settings box and refresh your memory by carrying out the example following the box xiii Preface xiv 2715 User Manual ay Introduction Introduction This section introduces you to the basic concepts of an RF spectrum analyzer and its uses This section also briefly describes t
203. discuss the various modes Below the readout columns messages and indicators appear as warranted and numeric instrument settings can be entered The control panel has several characteristics included to make it easy and convenient to operate m Controls with related functions are generally grouped together the groupings Function Blocks are defined by the borders or background color surrounding the controls Dedicated controls permit quick selection of important measurement functions the controls are defined by background color Arrow keys directly increase and decrease critical control settings m Menu keys located in the MENUS function block call up lists of operator selectable features m A numeric keypad permits selection of menu options and entering of critical measurement parameters m Terminator buttons in the keypad block designate the units for numeric entries with a single keystroke m An immediate entry mode that enables you to enter arbitrary values for the channel frequency span and reference level directly from the keypad m Red LED function status indicators adjacent to certain buttons indicate when the functions are active m Green LED register status indicators illuminate when any storage register contains a saved waveform The controls most fundamental to spectrum measurements CHAN FREQ SPAN DIV and REF LEVEL are located in a single central function block with a dark gray background These
204. dix Accessories and Options Options Options B1 and B2 Option M1 Option M3 Extended Service and Warranty Options Option 03 GPIB Communications Port Option 05 External Tracking Generator Option 07 Inverter Battery Pack 2715 User Manual This section describes the options for the 2715 All options are factory installed Option B1 This option adds a service manual for the Spectrum Analyzer Option B2 This option adds a reference manual a user manual a programmer manual and a service manual for the Spectrum Analyzer There are three extended service and warranty options offered for the 2715 that go beyond the basic one year coverage Contact your local Tektronix Field Office or representative for details m Option Two routine calibrations to published specifications in years two and three respectively of warranty coverage plus two years remedial service m Option M2 Four years remedial service m Option Four routine calibrations to published specifications in years two three four and five respectively of product ownership plus four years of remedial service Option 03 supplies a GPIB communications port that conforms to the IEEE Standard 488 General Purpose Interface Bus It also supplies a Programmer Manual The port is activated and configured with the UTIL menu The 24 pin port connector is located on the rear panel of the 2715 Connector terminations can be
205. djust the reference level until the signal peak is at the top line The signal level is very important for proper performance and must also be well above the noise floor Press DEMOD 3 to select BROADCAST AM VIDEO When item 3 is activated the 2715 presets a number of measurement parameters in order to generate a TV picture You may be able to obtain a slightly better picture by changing some settings Experiment with the following controls m REF LEVEL use the 1 dB step size adjust for best display m INTENSITY adjusts contrast m LEVEL outer knob changes vertical size and adjusts for a flicker free display m SWEEP arrow keys changes horizontal size Press DEMOD 3 to turn off the BROADCAST AM VIDEO When the monitor is disabled the settings used prior to entering monitor mode are restored any changes you have made while using the video monitor are overwritten Press UTIL 1 1 to initialize your instrument This can be conveniently done by placing the marker on top of the video carrier and selecting item 3 MARKER TO REFERENCE LEVEL from the MKR FREQ menu 6 59 Spectrum Analyzer Menus UTIL Menu Entered Control Settings 6 60 The Utility menu provides access to system configuration and initialization features front panel settings and waveform storage facilities instrument normalization and diagnostics and miscellaneous other functions Some of the selections within the Utilit
206. dows and an IBM compatible PC or you may choose to modify any of the channel tables directly from the 2715 front panel These two features creating and editing customized channel tables allows the technician to accommodate all nonstandard channel frequencies and operating conditions in a unique system The following defaults are common to all channels in the factory loaded channel tables Color System NTSC Channel Allocation Width 6 MHz Aural Carrier Offset 4 5 MHz Channel Edge Visual Carrier 21 25 MHz Signal Type TV Video Polarity Negative Sync Polarity Positive Skip Status False Scrambling Status False VITS None Channels 907 through 913 in the STD factory loaded channel table Table 5 4 represent channels T 7 through T 13 There are a number of different television standards worldwide that differ in video modulation polarity In negative video modulation maximum carrier power occurs during the sync tips In positive video modulation maximum carrier power occurs during white program material All defined systems use negative modulation except for the A C E and L systems which use positive modulation When modifying or creating a channel table be sure to select the correct video polarity for your system The sync polarity will always be the opposite of the video polarity In defined systems if the video polarity is positive the aural modulation type is AM instead of FM The 2715 automatically selects AM aural
207. e the 2715 stores the new value m True analog display in addition to digital storage with 1 us div sweep speed that lets you see beats down in the noise Low input signal sensitivity with the built in preamplifier activated m Signals as large as 70 dBmV 20 dBm can be accommodated m Automatic selection of both sweep speed and resolution bandwidth m Digital and time domain functions AM FM detection m User definable modes m 300 Hz to 5 MHz resolution bandwidths 2715 User Manual Introduction Post detection digital sampling and storage is used with a unique max min display mode that provides a close approximation of analog displays Peak detection is also provided It is possible to display up to four traces simulta neously and to perform ensemble statistics A continuously updated waterfall display mode can be used to compare the four most recent spectral sweeps 124 Kbytes of nonvolatile random access memory NVRAM is provided to enable saving front panel configurations and spectral sweeps for later review or operation The exact storage capability depends on what else you are storing in the instrument such as user defined keystroke sequences You may improve the center frequency setting time in some applications by changing the YIG oscillator settling delay time from the factory default value The new setting value is saved automatically See Changing the YIG Settle Delay on page 6 78 for more information
208. e 2715 still controls the frequency to the nearest hertz specified The number of decimal places in the on screen readout is commensurate with the screen resolution at the selected span You can also enter decimal values for the reference level and span 2715 User Manual Spectrum Analyzer Menus 2715 User Manual Press 1 to select REFERENCE LEVEL Press 2 4 5 2 Y to enter 24 52 dBmV The 2715 rounds and stores the reference level to one decimal place 0 1 dB Press 2 to select SPAN DIV Press 2 21 6 8 3 2 X to enter 22 6832 MHz division The span is rounded and stored to three decimal places but in the spectral display the span is shown rounded to one place Leave the remaining parameters set as they are but note the following settings 10 11 12 13 RF attenuation can be set to AUTO the default or fixed from 0 to 50 dB in 2 dB step The resolution bandwidth can be set to AUTO the default 300 Hz 1 kHz 3 kHz 10 kHz 30 kHz 100 kHz 300 kHz 1 MHz or 5 MHz if you enter another value the 2715 will convert it to the nearest available value This menu provides the only method of manually setting the video filter bandwidth The video filter bandwidth can be set to AUTO in which case it is 1 100 of the resolution bandwidth in normal mode or fixed from 3 Hz to 300 kHz in a 1 3 sequence 3 Hz 10 Hz 100 kHz 300 kHz other values will be converted to the nearest allow
209. e Keys 3 6 Registers A B C 4 22 RES BW 4 11 Arrow Keys 4 12 AUTO 4 13 RF Attenuation Setting 6 4 RF INPUT 2 2 RS 232 BAUD RATE 6 68 Configuration 6 68 DATA BITS 6 68 ECHO 6 69 EOL 6 68 FLOW CONTROL 6 68 PARITY 6 68 Printing the On Screen Readouts 6 82 STATUS 6 68 VERBOSE 6 69 Running the Automatic Measurement 5 67 S Safe Maximum Signal Levels 5 2 Save and Recall Settings and Displays 6 62 SAVE ENABLE 3 7 4 22 A B C Registers 4 22 Save Keys 3 6 Scanning Manual 6 89 Screen Intensity 4 35 Screen Plotter Configuration Communication Port 6 70 Plotter Language 6 70 Screen Readout 4 34 Selecting a Channel Table 2 11 Selecting the Screen Plotter Configuration 6 70 COMM PORT 6 70 GRATICULE LINES ON PLOT 6 71 PLOT POSITION 6 71 PLOTTER LANGUAGE 6 70 SCREEN PLOT CONFIGURATION 6 71 Selecting the Tuning Increment 6 21 Self Test 2 9 Service Normalizations 6 80 Service Request Generating 6 82 Set the Reference 2 15 Setting Start and Stop Frequencies 6 17 Setting the RF Attenuation 6 4 Setting the Signal Threshold 6 22 Settings and Displays Save and Recall 6 62 Settings Files 6 76 Index 6 Settings Factory Default 2 4 Signal Bandwidths Measuring 6 44 Signal Search 6 48 Signal Threshold Setting 6 22 Signal Track 4 31 Signal Track Mode 3 3 Signal Type Measurements 5 5 5 8 Signal Types 5 4 SINGLE 3 9 Si
210. e MAX HOLD feature yields an estimate of the maximum signal values It can also be very useful for determining maximum signal amplitude during transient condi tions or for making low level fluctuating signals more apparent by saving their peak value You can observe as many sweeps as you wish You could equally as well have used the B register for MAX HOLD 37 Press MAX HOLD A amp B when you are ready to exit MAX HOLD mode The red LED goes out and only the D register sweep remains A feature called MIN HOLD similar to MAX HOLD and activated by pressing DSPL 9 saves the minimum signal values Using both MIN HOLD and MAX HOLD you can measure a signal s total excursion The Freq Mkrs controls select single and delta markers select center measure tracking and control the marker peak find features MKR A OFF The MKR A OFF key is a three way toggle that enables you to control one or a pair of markers A marker is a bright spot that appears on the digitized waveform Markers can be used only with the digital display When the 2715 User Manual Dedicated Controls 2715 User Manual marker mode is turned off the spot on the display indicates either the center or starting frequency of the display When a single marker is turned on it can be moved to any point along the displayed waveform using the FREQ MKRS knob The corresponding signal amplitude and frequency are displayed on screen The marker amplitude readout re
211. e display now consists of a much reduced and totally flat noise floor and some intermittent peaks similar to Figure 6 5 The zero frequency and calibration signal peaks have almost disappeared You have subtracted the average max min spectrum stored in the A register from the active sweep in the B register you can also use the C register and are displaying the result that consists only of the sweep by sweep variations The vertical center of the screen represents zero amplitude difference between the waveforms Waveform subtraction can be used as a sensitive detector of signal changes Suppose you were trying to measure a weak signal which you could turn on and off in the presence of interfering noise and signals You could turn the signal off compile the ensemble average and subtract it as above Then when you turn the weak signal back on it would show up because it was not part of the stored average 6 32 2715 User Manual Spectrum Analyzer Menus 100 REF 400MHZ T ATTN 10DB L 28 8DBMV Ed VF WIDE 100 OME 10 DB 5 27 R T 2 HE 40 FREQ P s 40 CALIBRATOR y L L Figure 6 5 Average Signal Plus Noise and Average Signal Plus Noise Subtracted from the Current Sweep 6 Decrease the reference level 10 dB The calibration signal peaks appear 7 Increase the reference level 20 dB The techniqu
212. e internal circuits time to stabilize For faster response time when continuous observation of signals is necessary the delay can be minimized by entering the short holdoff mode When using short holdoff in the AUTO sweep mode a fictitious signal sometimes appears at the left edge of the screen NOTE Turning on SHORT HOLDOFF disables frequency corrections and most marker measurement modes 11 12 13 14 15 Ensure the spectral display is turned on Press 7 to select SWEEP HOLDOFF from the INSTRUMENT CONFIGU RATION menu Messages appear to indicate which features are sacrificed when using short holdoff Read the messages and press W to continue The SWEEP HOLDOFF status switches from NORMAL to SHORT HOLDOFF and a signal peak may appear at the left edge of the screen Press 7 to reset the sweep holdoff to NORMAL Press 6 to turn off SPECTRAL DISPLAY IN MENUS 2715 User Manual Spectrum Analyzer Menus Setting the Date and Time Protecting Stored Settings The File System 2715 User Manual The 2715 contains a real time clock with battery backup power The clock is used to display the date and time stamp on measurement results The clock is also used to trigger user defined programs and to label printer plotter outputs The following steps show how to set the real time clock 1 Press UTIL 4 select the System Configuration menu 2 Press 4 to select REAL TIME CLOCK SETUP 3 Select item
213. e level of the display and increment and decrement the reference level step size Following is a review of the reference level adjustment Arrow Keys You can adjust the reference level using the arrow keys as shown in the following procedure 1 Notice the height of the signal peak and then press adjacent to REF LEVEL The signal peak appears to increase 10 dB when you press the key Actually the calibration signal amplitude does not change when you change the reference level Instead the reference level decreases changes in the direction indicated by the arrow key to 28 8 dBmV and the attenuation to 10 dB The signal only appears larger because the reference level has been lowered 10 dB and now represents a signal level of 28 8 dBmV 10 dB or one division greater than the calibration signal 2 Press adjacent to REF LEVEL to reduce the on screen signal height one division The reference level readout increases 10 dB to 38 8 dBmV changes in the direction indicated by the arrow and RF attenuation changes to 20 dB The signal peak drops one division but its amplitude is still 18 8 dBmV The up arrow increases the reference level and the down arrow lowers it The keys remain active whenever the 2715 is in the spectral display mode NOTE The direction of the arrows always represents the direction of change of the 2715 setting adjacent to REF LEVEL increases the reference level and lowers the displayed
214. e nearest hertz and the frequency is displayed at the top of the left hand data column to 1 of the span div 6 Press CHAN FREQ to enter the immediate entry mode 7 Press 1 e 2 5 X to set the center frequency to 1 25 MHz The numbers you type appear on screen to the right of FREQ If you make a mistake correct it any time prior to pressing MHz by repeatedly pressing BKSP until the incorrect number disappears and then enter the correct value Pressing a terminator key W X Y Z determines the units and enters the data X can represent units of MHz ms or mV Because the frequency immediate entry mode requires a frequency the 2715 interprets the currently displayed value as 1 25 MHz when you press X If a time or voltage unit had been required the 2715 would have interpreted your entry as 1 25 ms or 1 25 mV respectively when you pressed X On the other hand had you wanted the entry to represent a frequency of 1 25 GHz you would have pressed W instead of X 8 Press CATV APPL 8 to return the 2715 to CATV mode 9 Press INPUT 9 to turn on the calibrator 2715 User Manual Dedicated Controls 10 Press REF LEVEL 3 8 e 8 Y to set the reference level to 38 8 dBmV 11 Press MKR A OFF twice to turn off markers 12 Press CHAN FREQ 1 0 0 X to use the direct entry method to set the center frequency to 100 MHz REF LEVEL The Ref Level controls adjust the referenc
215. e this However the line cannot be moved off screen Continue pressing until the line reaches the top of the screen You will receive the message DISPLAY LINE OUT OF RANGE Lower the line and the message will disappear 16 Press DSPL 8 4 to turn off the limit detector 17 Press 1 to turn off the display line 400 0MHz AUTO SWEEP ATTN 8 8DBMV VF WIDE 20MHz 10 DB 5MHz RBW AUTO CALIBRATOR The following procedure describes how to determine the approximate upper and lower bounds on a spectrum by using the MIN HOLD and MAX HOLD features While MAX HOLD is accessible by dedicated key MIN HOLD can be accessed only from the Display menu 2715 User Manual Spectrum Analyzer Menus APPL 2715 User Manual Press DSPL 9 You will be offered a choice of storage registers for the result of the MIN HOLD process Press W to simultaneously start the MIN HOLD process and select the A register for the result pressing X or Y would select the B or C register respectively for the result This feature is analogous to the MAX HOLD function Minimum hold compares the amplitude of the current sweep point for point with the stored minimum value of previous sweeps If the current amplitude is less the current value becomes the new stored minimum 3 Press MAX HOLD B to accumulate the maximum spectrum amplitude in register B With the A B and D registers displayed you have an upper and
216. e to adjacent channel 1 2 dB relative to all other channels Visual to Aural Carrier Level Difference Measurement Aural carrier level measured relative to the visual carrier Difference Range 0 to 30 dB for aural C N 215 dB 300 kHz RBW Resolution Accuracy Averaged P ower Typical Accuracy Resolution Modulation Depth Measurement Typical AM Range Resolution Accuracy HUM LFD Measurement Typical AM Range Resolution Accuracy Carrier to Noise C N Measurement Typical 0 1 dB 0 75 dB for aural C N 215 dB 300 kHz RBW Averaged amplitude measured with preamp off 2 5 dB for input levels above 30 dBmV up to 37 dBmV multichannel or 52 dBmV preselector in use 0 1 dB Percent AM measured from sync tip to lowest white level found in 10 sweeps the VITS line is used if itis defined in the channel table 50 to 95 0 1 2 for visual C N 240 dB 300 kHz RBW Power line frequency is measured on an unmodulated visual carrier and low frequency disturbance LFD is measured on the modulated carrier 1 to 10 peak to peak 0 1 1 for Hum lt 5 and visual C N gt 25 dB 300 kHz RBW 2 for Hum 1096 and visual C N 225 dB 300 kHz RBW Default noise floor is a normalized 4 MHz bandwidth measured relative to the visual carrier peak Optimum Input Range See Figure 1 on page 7 Maximum Range See Figure 1 on page 7 Resolution 0 3 dB Accuracy S
217. e works no matter the direction of the signal change 8 Reset the reference level to 18 8 dBmV and change the center frequency slightly Again the calibration signal peaks appear Any change from the average either amplitude or frequency becomes obvious 2715 User Manual 6 33 Spectrum Analyzer Menus 6 34 If the waveform in B gets so much larger than that in A that the result goes off screen subtract the average MEAN noise from the MAX HOLD signal plus noise This provides a measure of the maximum signal variations about the mean noise level 9 Press DSPL 2 to disable B C MINUS A mode 10 Ensure the center frequency is set to 400 MHz and the reference level to 18 8 dBmV 11 Turn off the calibrator and store a 24 sweep MEAN average of the noise in register A you need to overwrite the display currently stored in register A 12 After the average is complete turn the calibrator back on and activate MAX HOLD in register The resulting traces are shown in Figure 6 6 400 REF 400MHZ TTN 008 L 18 8DBM T VF WIDE 100 OMHE i 10 DB 725M 2 RB 20 30 40 MAX HOLD plus noise Average MEAN noise CALIBRATOR gt L o Figure 6 6 Average MEAN Noise and MAX HOLD Signal Plus Noise 13 Turn off the A register 14 Press DSPL 2 to enter the B C MINUS A mode The resulting noise floor is appr
218. ear whatever is being transmitted by the station 6 57 Spectrum Analyzer Menus 6 58 Listening to AM or FM Transmissions Video Demodulation 21 Leave the 2715 in zero span and turn the FREQ MKRS knob to tune it as you would a radio receiver The signal level rises as you tune in stations and falls to the noise floor when no station is present 22 Press DEMOD 0 to turn off the FM demodulator 23 Press ZERO SPAN to return to the normal spectral display To hear AM and FM stations select AM DEMODULATOR and FM DEMODU LATOR simultaneously both AM VOL and FM VOL LEDs will light This approach is convenient if you do not know whether the signal is AM or FM or for simply finding audio modulated signals and then switching on only the AM or FM demodulator to determine which type of modulation is being used 100 0MHz AUTO SWEEP ATTN 18 8DBMV VF 300KHz 1 0MHz 10 DB 300KHz RBW AUTO The video demodulator enables you to view broadcast or satellite video transmissions This is useful for identifying signals and determining the nature of interference 1 Press DEMOD to call up the DEMOD TG menu Item 3 is an on off toggle that may indicate BROADCAST AM VIDEO or SATELLITE FM VIDEO depending on the mode that was last selected The BROADCAST mode is used for off air or cable TV signals SATELLITE is used for example when viewing FM video signals at the output of a block down converter LNB In the
219. easurement A printer must be connected to the 2715 11 Press 9 to leave the Modulation Depth measurement and return to the CATV MEASUREMENTS menu The modulation depth adjustment mode allows you to make real time adjust ments of modulation depth You select SET UP ADJUSTMENT MODE to display the SET UP MOD DPTH ADJ MODE menu Using this menu you can select whether or not you view a full field or a single line You also use this menu to set the target line cycle delay and target line duration The SET UP MOD DPTH ADJ MODE menu choices are listed below 0 VIEW MODULATION MODE FIELD LINE 1 TARGET LINE 87 5 2 CYCLE DELAY 1000MSEC 3 TARGET LINE DURATION 30 0 The VIEW MODULATION MODE provides two choices FIELD or LINE If you select FIELD you view a full field if you select LINE you will view line 17 unless you have specified a VITS line for the channel in the channel table With TARGET LINE selected you can set the target line to the depth of modulation for which you want to adjust The target line can be set to represent values from 0 to 100 with 87 5 the default setting With CYCLE DELAY selected you can change the duration of the adjustment cycle The adjustment cycle consists of a display of the channel field or line that alternates with a display of the target line and its associated readouts You can use the cycle delay with the target line duration discussed in the following text to adjust the display times for
220. ector on the rear of the 1405 or J101 IN on the rear of the 2207 and J101 on the rear of the 2715 You can also superimpose frequency markers generated by the 1405 on the sweep produced by the 2715 The markers consist of variable width dips in the 2715 sweep and are in addition to the intensified frequency markers internally generated by the 2715 To superimpose the markers connect the Z AXIS OUT signal from the 1405 to the 2715 external video input pin 1 of accessory connector J103 use pin 3 of J103 for signal ground Turn the markers on or off with the push buttons on the 1405 and control their width and depth using the WIDTH and INTEN controls on the 1405 front panel Consult the 1405 User Manual or Tektronix publication 26 7043 Antenna To Tap No Loose Ends for instructions on making measurements with the 1405 271x combination treat the 2715 as though it is a 2710 2715 User Manual E 1 Appendix E External Input and Output J102 External Trigger AN The shell of this BNC input connector is at chassis ground If you plan to use an external trigger see SWP TRIG in Spectrum Analyzer Menus this is where the trigger signal is input to the 2715 The trigger signal must be positive going and rise above 100 mV for at least 0 1 us CAUTION To avoid damaging the 2715 combined AC plus DC trigger signal levels must not exceed 50 V peak An external trigger signal starts a new sweep each time it rises above a t
221. ectrum analyzer should be to continue with the example that follows it The contents of the box resemble the spectrum analyzer s on screen data readouts Each example begins with the sweep control in AUTO mode To remind you of this AUTO SWEEP is shown in the top center of the box The parentheses mean the enclosed item is not part of the normal on screen readouts Six appendices a glossary and an index contain information about a number of topics useful but not essential to spectrum analyzer operation Specific Introduction contains a brief description of spectrum analysis and reviews the characteristics of the Tektronix 2715 Cable TV Spectrum Analyzer Getting Started enables you to safely apply power and signals to the spectrum analyzer You become acquainted with the fundamental controls of the instru ment and make your first measurements using a firmware based CATV measurement routine and the built in calibration signal Operating Basics provides most of the information needed for routine operation Dedicated Controls explains the features of the spectrum analyzer and the benefits you gain from each control and menu option as you go through examples You learn to easily obtain accurate spectral and time domain measurements CATV Measurements describes CATV requirements and offers step by step procedures to conduct automated measurement routines xii 2715 User Manual Preface 2715 User Manual Spectrum Analyzer Menus
222. ed when the reference is acquired You can modify the reference name by selecting item 7 EDIT CURRENT REF ERENCE NAME in the FREQ RESP SETUP menu shown below 5 FREQ RESP SETUP TEST MODES NO REF WITH REF START FREQUENCY STOP FREQUENCY USE DEFAULT START STOP2 ACQUIRE NEW REFERENCE STORED REFERENCE MENU EDIT CURRENT REFERENCE NAME LEAVE FREQUENCY RESPONSE SANA on 3 Press 5 0 BKSP 0 to run the frequency response measurement without a reference The instrument sets the 2715 to sweep between the specified start and stop frequencies with a 5 MHz resolution bandwidth and returns to normal user control The instrument shows a display similar to that shown in Figure 5 6 Lowest and highest frequencies in the selected channel table 2715 User Manual Measurements 2715 User Manual You can then modify the display by various means for example changing the reference level changing vertical sensitivity or using MARKER START STOP to zoom in on any portion of the display A line drawn through the peaks of the waveform shown in Figure 5 6 represents the frequency response The slope of this line suggests that the higher frequency channels have been provided with a little more gain compensation than the lower frequency channels to compensate for frequency dependent losses in the transmission line This display is useful only when frequency dependent losses in the transmission line are known
223. ee Figure 1 on page 7 In Service C N typical Noise density is measured at 2 MHz offset by default from visual carrier during quiet lines in the vertical interval then normalized to 4 MHz BW and expressed as dBc Optimum Input Range See Figure 1 on page 7 Maximum Range See Figure 1 on page 7 Resolution 0 3 dB 2715 User Manual A 3 Specifications Table A 1 CATV Characteristics Cont Characteristic Accuracy Desired to Undesired Ratio Typical Resolution Accuracy CTB Measurement Typical Description See Figure A 1 on page A 7 Channel averaged power is divided by total noise plus distortion in the channel 0 1 dB 2 dB within the limits shown in Figure A 6 on page A 9 Composite triple beat CTB is measured relative to the visual carrier peak according to the NCTA recommended spectrum analyzer settings SINGLE SWEEP mode does not use all the NCTA recommended settings Maximum Range See Figure A 2 on page A 7 Resolution 0 3 dB Accuracy See Figure A 2 on page A 7 Digital Channel CTB Typical Measured relative to the averaged power of the test channel Resolution 0 3 dB Accuracy 2 dB within the limits shown in Figure A 8 on page A 10 CSO Measurement Typical Optimum Input Range Maximum Range Resolution Accuracy In Service CSO Typical Optimum Input Range Maximum Range Resolution Accuracy Digital Channel CSO Typical Re
224. el Table 5 6 5 7 Signal Types 5 4 General CATV 2715 Mode 5 4 GPIB Configuration 6 69 MODE 6 70 GPIB ADDRESS 6 69 POWER ON SRQ 6 69 STATUS 6 69 TALK ONLY MODE 6 70 Graticule Illumination 6 39 H Headphone Jack 2 10 Holdoff Sweep 6 74 Horizontal Position Adjustment 4 35 HUM LFD Measurement 5 40 Immediate Entry Mode 2 9 3 4 In Channel Response Measurement 5 62 Initial Display 2 6 Initial Normalization 2 5 Initial Setup 5 3 INPUT Menu 6 4 Accommodating 50 Ohm Source 6 7 Accommodating External Amplification Attenua tion 6 6 Changing Reference Level Units 6 5 Setting the First Mixer Input Level 6 8 Setting the RF Attenuation 6 4 Turning the Calibrator ON and OFF 6 4 Turning the Preamplifier ON OFF 6 9 Using the DBUV M 6 10 Input Power Limitations 5 2 In Service Measurements Advantages and Disadvantages 5 18 Capability 5 18 CARRIER TO NOISE 5 35 CSO 5 50 5 53 5 54 In channel response 5 62 5 65 5 67 Successful Application of 5 19 Index 3 Index Installation Rackmount Adapter 2 2 Installed Options Confirming 6 77 Instrument Configuration 6 71 AUDIO ALERT 6 71 Changing the Sweep Holdoff 6 74 ERROR ONLY 6 72 Frequency Corrections On and Off 6 73 KEYCLICK amp ERROR 6 72 KEYCLICK ONLY 6 71 OFF 6 71 Setting the Minimum Signal Size 6 72 The Spectral Display In Menus
225. elected by the 2715 The sweep rate is now 50 ms div the UNCAL message has disappeared and the calibration signal is correctly indicated as 18 8 dBmV at 100 MHz 13 Press AUTO again in the SWEEP function block The LED turns off but the display does not change Toggling out of the AUTO mode maintains the automatically selected rate until you change it with or 14 Reactivate the AUTO sweep mode SINGLE SWEEP 100 0MHz AUTO SWEEP ATTN 20DB 38 8DBM VF 300KHz 1 0MHz 10 DB 300KHz RBW AUTO The 2715 is equipped with a single sweep feature When activated by pressing SINGLE the 2715 makes only one sweep Other controls except AUTO in the SWEEP function block operate normally and signals at the input to the 27715 are treated just as they would be otherwise Pressing AUTO in the SWEEP function block exits from the single sweep mode When a sweep begins will depend on how the 2715 is triggered The factory default mode is free run this is the mode the 2715 currently should be in 15 Set the resolution BW to 3 kHz The sweep now takes two seconds 16 At midsweep press SINGLE The current sweep is aborted and the message SGLSWP MODE appears on screen under the right readout column The message means the sweep circuit is in the single sweep mode and halted 17 Press SINGLE again This prepares the sweep to begin as soon as it receives the next trigger signal which occurs automatically in the
226. en changing the default settling time NOTE If the YIG oscillator settling delay time has been reset from the factory default of 5000 ms and any error messages occur as the center frequency or span div is being reset such as NORMALIZATION SUGGESTED or if any aspect of frequency related performance of your instrument appears to be inappropriate the YIG oscillator settling delay time should be increased or returned to 5000 ms If the YIG oscillator settling time is changed from the factory default a message indicating this case is displayed during instrument power up This is a reminder to you that the factory default value is no longer being used Instruments returned to Tektronix for repair and or calibration will have the YIG oscillator settling time returned to the factory default value 5000 ms and the factory default value will be used during repair and calibration Any repair involving replacing or repairing the YIG oscillator may result in acceptable settling times different from those originally selected To change the YIG oscillator settling delay time do the following steps 1 Press UTIL to call up the UTILITY menu Press 5 to select INSTR DIAGNOSTICS ADJUSTMENTS Press 4 to select INTERNAL PARAMETERS Press 2 to select YIG SETTLE DELAY THEE E E Use the keypad to enter the new delay value in milliseconds press X to terminate the entry You now have changed the YIG oscillator settling delay time from
227. enough memory NVRAM is available for the operation INTERNAL REF AMPL TOO INACCURATE Perform reference amplitude normalization again checking for the presence of the correct external reference frequency and amplitude Contact your local Tektronix service center or representative if message persists INTERNAL REF FREQ TOO INACCURATE Perform reference frequency normalization again checking for the presence of the correct external reference frequency and its correct entry from the keypad Contact your local Tektronix service center or representative if message persists INTERRUPT FAULT AT FF Firmware hardware error Contact your local Tektronix service center or representative if message persists INTERRUPT FAULT Firmware hardware error Contact your local Tektronix service center or representative if message persists INVALID DEVICE NUMBER Firmware hardware error Contact your local Tektronix service center or representative if message persists INVALID FILE NUMBER Firmware hardware error Contact your local Tektronix service center or representative if message persists LAST PWR DOWN REG CHECKSUM ERR Last power down settings bad defaults used Contact your local Tektronix service center or representative if message persists LEAVE INTERACTIVE MODE FIRST An attempt was made to do something illegal in interactive beats or carrier to noise mode such as run another test or try to invoke a UDP MALLOC RAN OUT OF MEMORY
228. ental Analyzer Controls The Keypad e Ee ET re Display Register Control Vertical Scale and Other Controls Resolution BW and Sweep Control The 2715 Back Example of a Waterfall Display Typical Plotter Output Showing TV Channel Spectrum CATV MEASUREMENTS Menu Channel 2 of the STD channel table selected for edit with menu set to change SCRAMBLED toggles between YES NO Figure 5 3 Channel with FINISH selected Figure 5 4 Carrier Level Averaged Power Measurement Results Figure 5 5 Typical Carrier Survey Report Screen Figure 5 6 Typical Frequency Response Display Without Reference ees exe aues suse ete ree Savoie Figure 5 7 Typical Frequency Response Display With Reference Figure 5 8 Typical CTB or CSO Measurement Results Display Figure 5 9 Typical Continuous Mode Results Display Figure 6 1 The INPUT Menu Figure 6 2 Sweep Trigger Menu with SWEEP RATE Selection Chosen 25 6 0 4 n RE DRESS RN RE de 2715 User Manual Table of Contents 2715 User Manual Figure 6 3 75 50 W Matching Minimum Loss Pad 6 8 Figure 6 4 Equipment Setup for Field Strength Measurements 6 11 Figure 6 5 Av
229. er Ensure the signal peak is close to the reference level Call up the Sweep Trigger menu and select SETUP TABLE item 9 Repeatedly select item 4 TV LINE STANDARD until the TV line standard appropriate to your signal appears Use the OPEN 1024 line setting for nonstandard systems Items 0 through 3 of the SETUP TABLE determine which sync pulse s is used Choosing any of them also selects item 4 TV LINE mode from the Sweep Trig ger menu 6 7 Select item 0 CONTINUOUS and then return to the spectral display Turn off digital storage and select zero span Enter LIN mode and change the sweep rate to 20 usec div sweep rate is indicated in the left hand readout column The screen should resemble Figure 6 16 In CONTINUOUS mode the sweep generator is triggered by the first pulse that occurs after the 2715 enters the ready to be triggered state In other words after the 2715 completes the current sweep it enters the ready to be triggered state and is retriggered by the first horizontal sync pulse that comes along Thus a different sync pulse generally triggers each sweep The video signals following each sync pulse are not quite the same but are nevertheless displayed on top of each other The result is an intense but fuzzy display T ATTN 10DB REF 24 4DBMV VF WIDE 10 20 Us ZSPAN i 1 65MV 5MHZ RBW i 20 30 MP OY
230. er provides three direct methods of doing so each appropriate under different circumstances 12 Press to the right of CHAN FREQ twice Notice that the center frequency readout now indicates approximately 894 0 MHz The frequency arrow keys change the center or start frequency by the same as the span div but you can change the tuning rate See Selecting the Tuning Increment on page 6 21 You could continue pressing until the correct frequency is reached but this would require a large number of presses 2 17 Getting Started 2 18 This method of changing frequency is very useful for scanning relatively small bands To change by larger amounts use the immediate entry mode to set the center or start frequency to a predetermined value 13 Press CHAN FREQ to place the center or start frequency in the immediate entry mode Notice that the abbreviation FREQ appears at left center of the screen The FREQ indicator tells you that you can enter the center frequency directly from the keypad by keying in a permissible value followed by an appropriate terminator key 14 Press 1 0 1 to set the center frequency to 101 MHz The numbers you press appear on screen to the right of FREQ If you make a mistake you can correct it by repeatedly pressing the backspace key until the incorrect number disappears and then entering the correct value 15 Press X after the correct number has been entered This key can re
231. er remains active but the displayed spectrum is now updated during each sweep The on screen readouts are stored along with the sweep Since the 2715 displays only one group of readouts at a time the readouts for the highest priority register are displayed when multiple registers are active Register priority is shown in the following chart Priority Highest Register D register current waveform C register current waveform B register current waveform A register current waveform D register saved waveform C register saved waveform B register saved waveform Lowest A register saved waveform To see how register priority works view some spectra 18 Turn off A turn on B and note the on screen readouts The indicated resolution bandwidth should read 30 kHz 19 Turn on C 2715 User Manual 4 23 Dedicated Controls 4 24 The resolution bandwidth should read 5 MHz C has a higher priority than B so its readouts are displayed 20 Turn on the A register and set the resolution bandwidth to AUTO Notice the RBW readout change Any register containing a current sweep has a higher priority than a register containing a saved sweep so the A register readouts are now displayed 21 Clear and deactivate the B and C registers Leave only the D register active The SAVE ENABLE key changes the function of the D key SAVE ENABLE D places the 2715 in the waterfall mode symbolized by t
232. er remains fixed on top of the cal signal peak while the other remains fixed at center scale Consequently the difference frequency also increases 7 Continue turning the knob until the second harmonic approaches center scale 8 Press MEAS TRKG The second harmonic is automatically centered The amplitude and frequency difference between the fundamental and the harmonic are displayed at the top of the right column preceded by DC delta count 9 Repeat this procedure for the third harmonic Notice that although the reference peak the cal signal fundamental is now far off screen to the left you are still accurately measuring the difference frequency 6 19 Spectrum Analyzer Menus Moving the Marker to the 6 20 Next Higher or Lower Peak 10 Continue this process all the way to 1 8 GHz 11 Exit from this mode by turning off the markers This feature is particularly useful when you want to measure the differences between two or more signals so widely separated in frequency that they do not fit on screen at the span division at which you wish to view them If you are already using the Marker Frequency menu item 2 also conveniently turns on the marker mode when it is set to If you trigger the 2715 with a TV video sync pulse by choosing KNOB SELECTABLE from the Sweep Trigger menu Setup Table the Knob Function menu offers another choice VIDEO LINE Selecting VIDEO LINE lets you use the FREQ MKRS knob
233. erage Signal Plus Noise and Average Signal Plus Noise Subtracted from the Current Sweep 6 33 Figure 6 6 Average MEAN Noise and MAX HOLD Signal Pl s NOISe ve ennt hee S E lee Wa Os 6 34 Figure 6 7 B C Minus A Offset to Center 6 35 Figure 6 8 B C Minus A Offset to Top 6 35 Figure 6 9 2715 Plot with Title and Plot Labels 6 40 Figure 6 10 The SIGNAL SEARCH Frequency Range 6 49 Figure 6 11 Illustration of Occupied BW Measurement 6 51 Figure 6 12 Portion of U S Broadcast FM Band 6 52 Figure 6 13 OCCUPIED BW Mode with MAX HOLD 6 53 Figure 6 14 Instantaneous Frequency Deviation and Maximum Observed Deviation 6 55 Figure 6 15 Video Field Using Internal or TV Field Triggering 6 84 Figure 6 16 Video Signal Using Continuous Horizontal Line Triggering 1 ecan rex tr hr rm tne vis 6 86 Figure 6 17 Video Signal Using Knob Selectable Horizontal Line Triggering VITS Visible eek rm emnt htm m e I nein ie e 6 87 Figure A 1 Typical Accuracy Limits for Carrier to Noise Meas rement 27 Vu emer SEE UE A 7 Figure A 2 Typical Accuracy Limits for CTB Measurement A 7 Figure 3 Typical Accuracy Limits for Nongated CSO Measurement 5 RE REIR E IE A 8 Figure A 4 Typical Accuracy Limits for Gated CS
234. erface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 10 Press 4 to print the last stored results of the measurement A printer must be connected to the 2715 11 Press 9 to leave the Cross Modulation measurement and return to the CATV MEASUREMENTS menu In Channel Response Measurement 5 62 You can measure the in channel response interactively or automatically There are two types of automatic mode If the in service basis is not selected Auto Pause for Signal On mode is used If in service basis 1s selected Auto mode is used With in service basis selected the measurement is made using a specific test signal multiburst line sweep or ghost cancelling embedded in the vertical retrace interval The measurement basis is selected from the main INLCHANNEL RESPONSE menu item 7 You also need to specify the TV line number containing the desired test signal by selecting choice 6 in that menu 2715 User Manual Measurements 2715 User Manual The test signal line number is the number of the field line on which the test signal is inserted for in service testing For television systems using the National Television System Committee NTSC standard this typically is on line 10 through line 20 of field 1 and line 9 through line 19 of field 2 However the 2715 counts field lines consecutivel
235. es for the last executed passed normalizations are always restored during the POWER DOWN UP and the POWER UP DIAG AND REBOOT cycles The other cycles do not affect the normalization values 2715 User Manual Pp _ Appendix E External Input and Output The rear panel of the 2715 contains several input and output I O connectors One or more may not be used on your instrument depending on which options you have installed Mains Power For safety be sure to use a 3 wire AC power cord and be certain the ground conductor is properly connected Adjacent to the power receptacle is the mains fuse with its size marked If the fuse repeatedly blows it is likely you have a hardware problem If you suspect a problem contact your local Tektronix Field Office or representative J101 TV Sideband Analyzer and External Tracking Generator Interface This output connector provides the first local oscillator 1st LO signal to the Tektronix 1405 TV Sideband Analyzer or the 2707 External Tracking Generator The connector is provided as part of Option 15 The 1405 is designed for testing video modulators transmitters and head ends The sideband analyzer provides standard video signals to the input of the modulator whose output is accurately measured using the 2715 The 2707 External Tracking Generator allows you to make swept frequency measurements on devices such as filters Simply insert an SMA to SMA cable between the LO IN conn
236. essage is present AUTO Pressing AUTO in the RES BW function block toggles between manual and automatic selection of the resolution bandwidth When the resolution bandwidth is selected automatically by the 2715 the LED below the key is illuminated 4 13 Dedicated Controls Video Filter 4 14 11 Press AUTO to place the resolution bandwidth in the automatic mode The red LED lights You can take the 2715 out of AUTO mode by pressing a RES BW arrow key or by pressing AUTO 12 Set the span div to 50 MHz 13 Note the indicated resolution bandwidth 14 Press in the RES BW function block The LED turns off and the resolution bandwidth goes to 300 kHz 15 Press AUTO The LED lights and the resolution bandwidth is switched back to 5 MHz 16 Press AUTO again The LED turns off but the resolution bandwidth is still 5 MHz Toggling out of the AUTO mode with AUTO maintains the automatically selected resolution bandwidth until you change it with a RES BW arrow key 700 0MHz 28 8DBMV 50 0MHz 5MHz RBW AUTO AUTO SWEEP ATTN 20DB VF WIDE 10 DB Channel Name CH nn CALIBRATOR A video filter is a postdetection filter sometimes referred to as a noise averaging filter used to reduce noise in the displayed spectrum to its average value making low level signals more easily detectable Normally the 2715 uses a video filter about as wide as the resolution bandwidth This limits postdetection noi
237. ets the currently displayed entry as 20 8 dBmV If the currently selected reference level units had been dBm or dBW the 2715 would have interpreted your entry correctly when you pressed the terminator key The RF attenuation is reduced to 2 dB and the reference level readout indicates the desired 20 8 dBmV For the parameters established for this example this entry method enabled you to specify a reference level that could not be achieved with the arrow keys unless you switched to the FINE mode You can also enter fractional reference levels to the nearest 0 1 dB with this method The spectrum analyzer is still in the MAX SPAN mode which means that the harmonics of the calibrator signal are barely more than one half division apart Spread them out by reducing the span div As in the case of the reference level the spectrum analyzer provides two direct entry methods 8 Press to the right of SPAN DIV twice to reduce the span to 50 MHz division Notice that the readout now indicates 50 MHz and the harmonics are two divisions apart 2715 User Manual Getting Started 2715 User Manual Suppose that you want to view just a single harmonic and the 30 MHz band to either side of it You can do this by setting the span to 6 MHz division This is not a value obtainable with the arrow keys but you can to get it in the immediate entry mode 9 To set the span division to a predetermined value first press SPAN DIV to place sp
238. ettings on page 6 60 Automatic Selection 1 100 of the resolution BW Fixed Range 3 Hz to 300 kHz and WIDE in a 1 3 sequence Press SINGLE to place the 2715 in a single sweep mode similar to a conven tional oscilloscope SGLSWP MODE appears on the screen With the 2715 s sweep in free run mode default press the key again to start a sweep In other trigger modes the sweep begins with the first trigger signal following entry into single sweep SGLSWP ARM appears briefly at the start of each sweep Pressing AUTO in the SWEEP function block exits the single sweep mode but preserves the current auto or manual sweep rate selection mode The AUTO keys in the RES BW and SWEEP function blocks toggle the spectrum analyzer into and out of automatic resolution bandwidth and sweep rate selection modes respectively Pressing SWEEP AUTO also exits single sweep mode but preserves the sweep rate selection mode The LEDs below the keys are lit when the automatic mode is selected When toggling out of the automatic mode the resolution BW and sweep rate remain as they were until manually changed When toggling into the automatic mode the spectrum analyzer selects the resolution bandwidth and sweep rate appropriate to the currently selected span The RES BW and SWEEP arrow keys increase and decrease the resolution bandwidth and sweep rate time div in a specified sequence They are always active in the spectral display mode but
239. everal times and watch the marker jump to progressive ly lower peaks If you try to jump the marker above the highest peak or below the lowest the message NO SIGNAL FOUND ABOVE THRESHOLD is displayed You cannot jump the marker to off screen signals MARKER TO REFERENCE LEVEL is an item on the MKR FREQ menu that can be used to quickly and easily determine signal amplitudes 8 Using any method for instance the MOVE MARKER TO NEXT PEAK feature place the marker on top of the signal to be measured In this case use the calibration signal fundamental 9 With the marker at the signal peak press MKR FREQ 3 The reference level is changed to the signal amplitude to place signals at the reference level to make relative measurements It is also a convenient method of setting the video carrier to the reference level when using the video monitor option 10 When you are finished turn off the marker NOTE Signal amplitudes are always determined most accurately when the signal is within one division of the reference level 300 0MHz AUTO SWEEP ATTN 10DB 28 8DBMV VF WIDE 50 0MHZ 10 DB 5MHZ RBW AUTO CALIBRATOR The instrument tuning increment amount per click by which the tuning knob changes frequency is 0 02 of the span division The following steps show how to change the tuning increment 1 Call up the Marker Frequency menu Item 8 is a two way toggle function indicating that the tuning increment is present
240. external gain or attenuation antenna factor and measurement distance using the INPUT menu Then select the dBu V m reference unit and the 2715 does the rest The signal intensity is read out on screen using the marker and corrected for distance in either dBuV m or V m Using the DISPLAY menu you can have the 2715 sound an alert if the measured signal exceeds a threshold that you set This feature facilitates go no go or present absent tests Figure 6 4 shows how to set up your equipment A balun can be included as part of your antenna The filter and external matching network are optional The filter is intended primarily to prevent off the air signals such as radio and television from swamping the 2715 The matching network may be necessary for maxi mum accuracy If in doubt try the measurement with and without the network If there is no difference omit the network for maximum sensitivity The following formula relates the radiated field strength in dB relative to a microvolt per meter dBuV m to the measured signal amplitude in dB relative to a millivolt dBmV and scales the result measured at a distance dmeas to a reference distance dref The reference distance is often specified by the regulatory agencies Papuv m 13 A K ref dmeas distance from radiation source at which the measurement is carried out dref reference distance at which the intensity is desired A attenuation or gain between antenna
241. ference signal source Used to ensure frequency stability in spectrum analyzers Primary Controls Those controls of fundamental importance to spectrum analyzer operation frequency control span div and reference level Primary Marker The marker displayed in the Single Marker mode whose frequency and or position is changed when tuning with the CENTER MARKER FREQUEN CY control When two markers are displayed the brightest marker is the primary marker Pulsed Carrier Waveforms Signal types wherein the carrier is turned on and off or pulsed as in radar sonar and continuous wave CW code Pulse Stretcher A pulse shaper that produces an output pulse whose duration is greater than that of the input pulse and whose amplitude is proportional to that of the peak amplitude of the input pulse Reference Level The signal level required to deflect the CRT display to the top graticule line Relative Display Flatness The display flatness measured relative to the display amplitude at a fixed frequency within the frequency span expressed in decibels Residual FM Incidental FM Short term displayed frequency instability or jitter due to instability in the spectrum analyzer local oscillators Given in terms of peak to peak frequency deviation and expressed in hertz or percent of the displayed frequency Residual Response A spurious response in the absence of an input signal Noise and zero pip are excluded Resolution Bandwidth RBW
242. ff Use when readouts overlay data or to eliminate blanking intervals in analog display Toggles spectrum analyzer power on and off Green LED next to key is illuminated when power is on Turning the knob clockwise increases CRT brightness The inner knob sets trigger level in INT EXT and AC LINE trigger modes as on a conventional oscilloscope horizontal position in manual scan mode and picture framing in video monitor mode Outer knob controls volume of the AM and FM demodulators Lights when the AM or FM demodulators are active to indicate that the outer knob of the LEVEL control sets the audio volume See DEMOD on page 6 56 Normally the spectrum analyzer smooths the detected signal with a video filter having a bandwidth equal to the resolution bandwidth The filter bandwidth is indicated in the right hand readout column However pressing VID FLTR see Figure 3 8 toggles an alternate automatically selected or user designated video filter on and off Its bandwidth replaces the normal video filter readout RES BW SWEEP w 0G 1 AUTO VID FLTR SINGLE AUTO RF INPUT 70dBmV 100mW MAX 22 SS 1 22 Figure 3 8 Resolution BW and Sweep Control 2715 User Manual Operating Basics SINGLE AUTO e 2715 User Manual You can designate the video filter bandwidth using the UTIL Menu see Menu Entered Control S
243. following example we will use the AM monitor mode to view an off air or cable TV signal First here is some information to keep in mind W The carrier to noise ratio must be sufficiently large at least 30 dB in a 4 MHz bandwidth in BROADCAST mode 10 dB in a 30 MHz bandwidth in SATELLITE mode but it is possible to get a poor quality display at slightly lower C N s W You will not be able to satisfactorily monitor scrambled or sync less signals in either mode m The video carrier in either mode should be placed at the reference level for satisfactory operation W Energy dispersal dithering is generally not a problem in the SATELLITE mode 2715 User Manual Spectrum Analyzer Menus 2715 User Manual 10 11 12 13 Press 9 to select VIDEO MONITOR SETUP from the DEMOD TG menu Press 0 to toggle VIDEO DETECT MODE to BROADCAST Toggle items 1 and 2 to the proper polarities If you do not know the polarity set SYNC POLARITY to POSITIVE and VIDEO POLARITY to NEGATIVE These are the standards for normal U S broadcast television You can change them later to accommodate other standards if the video is inverted or sync cannot be achieved Press DEMOD to return to the spectral display Ensure that the calibrator is turned off Connect a short antenna or CATV tap to the 2715 input as outlined in Appendix B Broadcast AM FM and TV Signal Sources Tune to a strong video carrier choose an unscrambled channel A
244. formation 6 77 Spectrum Analyzer Menus Diagnostics and Adjustments Aligning the Display Changing the YIG Settle 6 78 Delay NOTE Any control settings can be used Many of the items on the Utility menu are intended for servicing of the 2715 However we will describe a few used to verify instrument performance Items not discussed are reserved for service personnel or for use under factory supervision NOTE This procedure will overwrite saved waveforms without warning 1 Press UTIL to call up the UTILITY menu Press 5 to select INSTR DIAGNOSTICS ADJUSTMENTS Press 2 to select MANUAL ADJUSTMENTS 9 jm Press 2 to select DISPLAY STORAGE CAL This selection creates a checkerboard display used to adjust trace position and rotation The trace rotation vertical and horizontal alignment controls are located on the back of the 2715 see Miscellaneous Controls on page 4 33 5 Turn the TRACE ROT control until the checkerboard test pattern is rotationally aligned with the graticule 6 Adjust the VERT POS control until the the top line of the pattern coincides with the top graticule line 7 Last turn the HORIZ POS control until the vertical center line of the display coincides with the center vertical line of the graticule 8 After completing the alignment repeatedly press UTIL until the spectral display reappears You may improve the center frequency setting time in some applic
245. forms exist their titles are correctly attached to them The title can be up to 31 characters on a single line and you can only title one display at a time When the title mode is turned on the left hand readouts move down one row to accommodate the title even 1f the title field is blank Select item 2 to edit an existing title or to enter a new title If the display is already titled the title appears in the upper left with an underscore cursor beneath the first letter If the display is untitled just the cursor appears The characters that can be used in the title are listed below the title in three lines arranged as follows m Alphabetic characters m Numbers m Punctuation and special characters The selected character appears in reverse video in the list and also appears above the cursor In the list SP indicates the space or blank character To enter or edit a title use the FREQ MKRS knob to select a character As you turn the knob the selected character moves through the list wrapping between the end of one line and the start of the next and between the end of the last line and the beginning of the first Move the cursor left or right to a new character position with the MKR 4 and MKR 9 buttons When done editing leave the cursor in its last position to avoid an unwanted character Delete the character to the left of the cursor by pressing the BKSP button on the keypad Delete the entire line by pressing Y As
246. found in Appendix E External Input and Output or in the Programmer Manual For programming instructions refer to the Programmer Manual To configure the GPIB port see System Configuration in Section 6 of this manual Option 05 supplies a Tektronix 2707 Tracking Generator for swept measure ments from 100 Hz to 1 8 GHz and at least 100dB dynamic range to see filter ultimate rejection or circuit isolation characteristics Option 07 supplies a Tektronix 2704 DC to AC Inverter 2705 Battery Pack Instruction Manual and necessary mounting hardware This option allows operation of the 2715 in locations where AC power is not available The 2705 provides approximately one hour of operation when used with the 2704 Inverter and 2715 Operating time can be extended by using additional 2705 Battery Packs or alternate 12 VDC sources The Inverter also contains a charger and an auxiliary 18 VDC output to power external devices such as Low Noise Block Down Converters LNB used in satellite downlink applications F 3 Appendix F Accessories and Options Option 08 RS 232 Communications Port Option 15 TV Sideband Analyzer External Tracking Generator Interface Option 30 Rackmount Adapter Option 33 Travel Line Package Option 34 Cradle Type Rackmount Adapter Option 50 Option 75 F 4 Option 08 provides an RS 232 serial communications port and a Programmer Manual This port conforms closely to the IEEE P1174 232 Dra
247. free run mode A message reading SGLSWP ARM momentarily appears and a single sweep is carried out The sweep will progress across the screen as a new spectral display is created 4 19 Dedicated Controls 4 20 Level Display Storage When the sweep is completed the SGLSWP MODE message reappears indicating the 2715 has completed the sweep and is ready to be rearmed If the 2715 is not in the free run trigger mode see SWP TRIG on page 6 83 to change modes behavior is much the same Pressing SINGLE causes the current sweep to abort and the SGLSWP MODE message to appear If you press the key again the SGLSWP ARM message appears This time however the 2715 waits for the first designated trigger signal when detected a single sweep begins After the sweep is complete the SGLSWP MODE message reappears You can start a new single sweep in any trigger mode as often as you wish by pressing SINGLE after the SGLSWP MODE message appears 18 Press AUTO in the SWEEP function block to exit from the single sweep mode The single sweep mode is useful when you want to prevent a succeeding sweep from overwriting a trace you just acquired or to capture the characteristics of intermittent signals There is a dual concentric shaft LEVEL control below the FREQ MKRS knob The inner knob controls the triggering level when the 2715 is in internal external or line trigger modes just as the equivalent control does on a conven tiona
248. ft Standard that defines the features and functions of the RS 232 interface as it applies to instrument systems However it does not necessarily comply with the three level protocol The port is activated and configured with the UTIL Menu The port connector is located on the rear panel of the 2715 Connector terminations can be found in Appendix E External Input and Output or in the Programmer Manual For programming instructions refer to the Programmer Manual To configure the RS 232 port see System Configuration in Section 6 of this manual Option 15 provides an interface for the Tektronix 1405 TV Sideband Analyzer and the 2707 External Tracking Generator The 1 LO is buffered routed to J101 on the 2715 rear panel and terminated in 50 The 2715 1405 combination enables you to measure TV modulator transmitter frequency responses The 2715 2707 combination allows you to take swept frequency measurements on devices such as filters Option 30 provides the hardware for installing the 2715 in a standard 19 in 426 6 mm rack The rackmount adapter requires minimum vertical space of 5 25 in 133 35 mm An alternate cradle mount adapter is also available see Option 34 The 2715 meets all electrical and environmental specifications when it is mounted according to the procedures accompanying Option 30 Option 33 is a Travel Line package that includes a rain cover accessory pouch gray CRT filter and carrying strap Option 34 consist
249. g items on the Service Normalizations menu are normally used only by service personnel However menu item 4 can be used to view selected normalization values and item 5 sends the normalization values to a printer These can be handy for future reference Item 6 sends any messages that occur during normalization to the printer If your 2715 has RS 232 installed you can obtain a hard copy of the normaliza tion values by doing the following 10 Place your Epson FX compatible printer on line a plotter will not work unless it can emulate an FX series printer with the paper in the correct position 11 Select item 5 from the Service Normalizations menu Printing starts immediately Control of the 2715 is returned following printout NOTE If NVRAM is lost the flatness correction data will also be lost This data can be reloaded by a Tektronix service center or by using the procedure described in the 2715 Service Manual The NVRAM in the 2715 is powered by lithium batteries Battery life is limited to a few years WARNING Handling and disposing of lithium cells can be hazardous Refer all battery maintenance to a Tektronix service center When the batteries run down NVRAM and all of its contents are lost All stored settings tables and waveforms disappear as well as all normalization data To prevent inadvertent loss of the reference normalizations routinely return your 2715 to Tektronix for battery replacement When a Te
250. ggering Internal Trigger Level 1 division or more of signal External Trigger Level Supplemental Information Normal Single Sweep and Manual Scan Free Run Internal External Line TV Line and TV Field See EXT TRIG in Table A 5 Nonvolatile Memory Battery Backed Up Instrument settings waveforms and normalization results are stored in NVRAM Battery Life Lithium At 455 C Ambient Temperature 1 to 2 years At 25 C Ambient Temperature Atleast5 years Temperature Range for Retaining Data 10 C to 75 C Internal Calibrator Provides 100 MHz marker for amplitude calibration and comb of 100 MHz markers for frequency and span calibra tion Amplitude and Accuracy 18 8 dBmV 30 dBm 0 3 dB at 100 MHz 2 kHz Drift 2 PPM year IF Gate Rise and Fall Times Off Isolation A 20 7 us nominal 60 dB 2715 User Manual Specifications Table A 9 Environmental Characteristics Characteristic Description The Description column describes how most characteristics were derived and a description of the characteristic This instrument meets MIL T 28800E Type Class 5 Style C Specifications Electromagnetic Interference 1 Emissions EN50081 1 Radiated Emissions 30 MHz 1 GHz EN55022 Class B CISPR 22B Conducted Emissions 150 kHz 30 MHz EN55022 Class B CISPR 22B Conducted Emissions Power Line Harmonics 0 2 KHZ IEC 555 2 3 Immunity EN50082
251. gital display COMM PORT NOT INSTALLED 2715 cannot detect the presence of the communications port COMMAND NOT IMPLEMENTED Feature not installed on this instrument COUNTER FREQUENCY UNSTABLE Perform normalizations again Frequency counter or input to it is unreliable Contact your local Tektronix service center or representative if message persists COUNTER NOT INSTALLED 2715 cannot detect the presence of the counter DATA ERROR IN FILE Firmware hardware error Contact your local Tektronix service center or representative if message persists DBUV M MEASUREMENT MODE IDLE Destination waveform for DBUV M is not being displayed and the correc tion calculation is disabled The mode can be restarted by turning on the destination waveform register DEFAULT DATA LOADED Since a file could not be read to load a data structure the default values were loaded into the file and into the data structure DELETE EDITING BUFFER FIRST The editing buffer must be deleted before the desired function or entry can be accomplished C 3 Appendix System Messages 4 DELETE EXISTING PROGRAM FIRST A user defined program already exists in this register It must be deleted before the new one can be stored DELETE EXISTING TABLE FIRST An attempt was made to store an antenna correction factor table in a file position that is already used You must delete the file with the table deletion menu prior to attempting to store the new file
252. gure 6 13 OCCUPIED BW Mode with MAX HOLD To obtain best frequency accuracy when making occupied BW measurements as with signal bandwidth measurements use small spans division spread the signal over as much of the screen as possible subject to the following limitations The signal spectrum at the edges of the screen should be down at least 40 dB from its peak The signal peak should be at least 40 dB greater than the displayed noise The resolution bandwidth filter must be 1 5 or less of the occupied bandwidth a resolution bandwidth filter that is too wide will artificially broaden the occupied bandwidth remember how the 5 MHz resolution bandwidth filter made the calibrator signal look like it is 5 MHz wide Only vertical scales of 5 or 10 dB div can be used 6 53 Spectrum Analyzer Menus Viewing Instantaneous Frequency Deviation 6 54 m There should be no signal on screen except the desired signal other signals including the zero hertz spur will contribute some inaccuracy For optimum amplitude accuracy keep the signal peak near the reference level 9 Press APPL 4 to turn off OCCUPIED BW turn off all display registers 10 Turn off MAX HOLD A amp B and register B 11 Turn register D back on 100 0MHz AUTO SWEEP ATTN 18 8DBMV VF 300KHz 1 0MHz 10 DB 300KHz RBW AUTO Normally the display you see on the 2715 represents the input signal after it has been AM detected The result
253. hannel Subsequent increments then default to the channel allocation width The up arrow selects the next channel and the down arrow selects the previous channel This means that even though the 2715 is in the CATV mode you can increase and lower the center frequency by the channel allocation width using the up and down arrows You can then fine tune the center frequency using the FREQ MKRS knob The keys remain active whenever the 2715 is in the spectral display mode 2 In MAX SPAN the indicated frequency changes alternately by 3 or 4 MHz and as a percent of the Resolution BW in ZERO SPAN See Selecting the Tuning Increment on page 6 21 for a description of how you can change the tuning rate 2715 User Manual Dedicated Controls Frequency Entry NonCATV Mode 2715 User Manual Keypad Entry For very large frequency changes or to preset a known center or start frequency the direct entry mode is faster To set the center or start frequency to a predetermined value do the following steps 11 Press CHAN FREQ to place the center or start frequency in the immediate entry mode Even though the word CHAN appears at left center of the 2715 screen you can enter the center frequency directly from the keypad immediate entry mode by keying in a permissible value followed by an appropriate terminator key X Y or Z You can enter any value from 0 Hz to 1800 MHz even though the 2715 low frequency specification is 9 KHz Your
254. has passed by a greater margin than indicated by the measurement result Note that whenever the Ist mixer input level has to be increased the test result is flagged by adding 2000 to its magnitude see individual test descriptions for more details If a measurement is flagged by adding 2000 to its magnitude you must decide whether or not to accept the measurement If the numerical result is acceptable no further action is necessary If you want a more accurate measurement you should consider using preselection in front of the 2715 either use a CATV preselector or make the measurement through a set top converter if applicable Alternatively use a nongated measurement which will not need to make the 1st mixer level readjustment 5 19 Measurements The 2715 is designed so that you will always have a choice of whether or not you use gated in service measurement techniques If you follow the In Service menu selections for C N CSO or ICR you will be making a gated measure ment otherwise you will be making a measurement in the conventional way without gating CARRIER LEVEL and AVERAGED POWER Measurement The 2715 can take measurements on negative and positive video modulation scrambled video channels dual aural carrier video channels AM or FM aural modulation and digital channels Aural measurements are only made on analog video channels 2715 signal type Refer to Table 5 2 on page 5 5 The CARRIER LEVELS
255. he t icon below the D key This waterfall display is more effective in peak acquisition mode discussed under DSPL on page 6 27 100 0MHz AUTO SWEEP ATTN 40DB 58 8DBM VF 300KHz 5 0MHz 10 DB 300KHz RBW AUTO CALIBRATOR 22 Press DSPL 4 to enter the peak acquisition mode 23 Press SAVE ENABLE D to enter the waterfall mode All eight of the register status LEDs light and four traces appear Registers A B and C must be cleared before the 2715 allows you to enter the waterfall mode because the waterfall mode uses all four registers This is a safeguard to prevent accidental overwriting of previously saved data If you attempt to enter this mode without first clearing the registers you receive an error message Look at Figure 4 1 D is the bottom waveform and A the top Each waveform is displaced upwards one division from the preceding waveform and shifted 1 2 division to the right The current sweep is in the D register the previous sweep in C the next previous in B and so on At the end of each sweep the waveforms are all shifted up one register This display can be used to watch slowly varying spectra evolve or to obtain a feel for the variability of signals Waterfall can also be useful for catching an event that occurs quickly In the present case of the calibration signal you will observe that there is virtually no variation 24 Create a small signal shift by slightly changing the center frequency Notice h
256. he YIG oscillator settling delay time if desired Settings less than 5000 ms may affect instrument compliance with published specifications SIGNAL CANNOT BE SET PROPERLY Perform normalizations again Contact your local Tektronix service center or representative if message persists SIGNAL OUT OF IF PASSBAND Frequency to be counted is not within one resolution bandwidth of the center frequency Repeat CTR MEAS or use a wider resolution bandwidth filter Performing a frequency normalization may also facilitate a count Because of span and display storage inaccuracies the signal may not be exactly centered in the digital display 2715 User Manual Appendix System Messages 2715 User Manual The message may also be displayed in Signal Track mode with the Frequen cy Counter enabled when tracking a rapidly moving signal Disabling the Frequency Counter may correct the problem The instrument may also try to count random noise on the filter skirts resulting in this error message Turning on the Video Filter or raising the Signal Threshold corrects the problem SIGNAL OVER RANGE The signal peak is above the top of the CRT display Lower the reference level SINGLE SWEEP ARMED Instrument armed for single sweep SINGLE SWEEP MODE Instrument in single sweep mode SINGLE SWEEP TRIGGER Single sweep has been triggered SIGNAL SEARCH COMPLETE Firmware routine finished SIGNAL SEARCH IN PROCESS Firmware routine running
257. he calibration signal third harmonic is almost lost in the noise 39 Now ensemble average the spectrum MEAN values and store the result in A The mean spectrum leaves little doubt as to the presence or location of the signal peak Sometimes you can achieve even better results using the average minimum 40 Experiment if you like before proceeding then clear the A B and C registers and leave only the D register active 2715 User Manual 6 31 Spectrum Analyzer Menus Subtracting Stored 400 0MHz AUTO SWEEP ATTN 12DB Signals VF WIDE 100MHz 10 DB 5MHz RBW AUTO CALIBRATOR The B C MINUS A feature of the Display menu enables you to subtract a sweep stored in register A from an active sweep in registers B or C You can use it to flatten a noise spectrum get rid of unwanted signals easily detect signal changes and so forth Observe the current sweep especially the zero frequency and calibration signal peaks In your instrument the noise floor may rise slightly with increasing frequency 1 Perform a 24 sweep MAX MIN ensemble average and store the result in A The average indicator is displayed only when the 2715 is in the non CATV mode 2 Wait until the ensemble average is complete 3 Ensure item 3 of the Display menu reads B C MINUS A OFFSET TO CENTER If it does not select item 3 once 4 Press DSPL 2 to activate the B C MINUS A mode 5 Turn on the B register and turn off A and D Th
258. he features of the 2715 Cable TV Spectrum Analyzer What is a Spectrum Analyzer 2715 User Manual There are several types of spectrum analyzers but we will describe only the heterodyne or scanning spectrum analyzer A scanning RF spectrum analyzer is essentially a radio receiver Tune a conventional FM broadcast receiver from one end of the band to the other As you tune plot the reading of the signal level meter versus frequency The graph you produce is a frequency domain representation or spectrum of the FM broadcast band The graph tells you at which frequencies the signals occur and how strong they are If stations are too close together you will not be able to get an independent meter reading for each individual station and you will hear them simultaneously This is because the intermediate frequency IF filter of the receiver has a bandwidth that is too wide to separate resolve the stations What you have just done is tune or scan the FM broadcast band with a resolution bandwidth equal to the bandwidth of the IF filter in your receiver If you plot your measurements on graph paper with one centimeter divisions making each division equal 1 MHz the span division of the resulting plot is 1 MHz division If you stop tuning the receiver no longer spans a range of frequencies but is fixed at the currently selected frequency it is in zero span mode The output of the receiver depends on the signal coming through the IF filter a
259. he on screen readouts are saved along with the sweep A saved sweep cannot be erased modified or updated without operator interaction When the D green LED is lighted the 2715 is in the waterfall mode A and D are toggle action keys that activate and deactivate the display registers A register s contents are displayed only when it is active red LED lighted although it still contains saved data as long as its green LED is lighted 1 Press C to turn on the C register The only change that might be apparent is an increase in intensity since the 2715 is now displaying the C trace on top of the D trace 2 Press A and B to turn on the A and B registers There may be an increase in intensity but the shape of the spectral display should not change because each register contains exactly the same informa tion 3 Press B and D to deactivate the B C and D registers This display is no different than the D register waveform Verify this by turning on the D register and turning off A press D and then A D Verify that this is true of the other registers by alternately switching a new one on and the previous one off Deactivate all registers to display the analog output of the 2715 Note its similarity to the MAX MIN display Any time all four red LEDs are extinguished the analog output of the 2715 s detector is displayed The digitizer is still working you have just disabled all the d
260. he signal peaks are no 4 longer folded FRE E CALIBRATOR F I 8 18 es IE Figure 6 8 B C Minus A Offset to Top 6 35 Spectrum Analyzer Menus Changing Acquisition Mode Adding Titles and Labels 6 36 100 0MHz AUTO SWEEP ATTN 20DB 18 8DBMV VF WIDE 20 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR Item 4 on the Display menu toggles between MAX MIN and PEAK signal acquisition modes 1 Press DSPL 4 to change acquisition modes 2 Toggle back and forth between MAX MIN and PEAK several times Notice that the display PEAK is essentially the top of the MAX MIN display The 2715 produces an analog spectrum In the MAX MIN acquisition mode the maximum and minimum amplitudes of this spectrum are alternately sampled at 512 successive points Plotting the two interleaved sets of 256 points each produces the analog like MAX MIN spectrum that you see In the PEAK acquisition mode the maximum amplitude only is sampled and displayed at all 512 points The Max Min mode has the advantage of bearing some semblance to the analog signal and readily revealing pulsed versus constant carrier signals Pulsed signals cause the signal peaks to be filled in 3 Leave the display in the MAX MIN mode 175 0MHz AUTO SWEEP ATTN 2DB 18 8DBMV VF WIDE 20 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR If you want to permanently store a spectral display either by photographing the screen or
261. hen measuring digital channels Note the following limitations that apply when using gated measurements m Gated measurements are not generally available on scrambled channels since the gate timing hardware depends on normal horizontal and vertical sync pulse structure for its operation W Measurement speed is reduced in some cases since it takes longer to obtain trace filling and or averaging when the gate is open so little of the time typically less than 1 W Selection of beat frequencies is more difficult in interactive CSO mode because the gating is not compatible with ordinary video filtering Visually the dominant feature of the resulting screen display is the collection of noise peaks as opposed to the average noise level viewed with appropriate video filtering A technique for minimizing the impact of this effect is suggested in the section on CSO measurement details however there will always be some loss in the ability to see weak CSO components This does NOT impact the accuracy or dynamic range of the earnest CSO measurement taken once you have defined the frequencies to be checked m Since the channel is active during in service measurements it is possible for the measurement accuracy to be affected adversely by residual or inaccurate video content in the line s being measured For example if a noisy video signal is applied to the modulator at the head end the resulting noise sideband power will be indistinguishable
262. hird press turns off both markers Each key respectively jumps the moveable marker from its current position to the next on screen signal peak to the left or right Signals must be above the detection threshold see Setting the Signal Threshold on page 6 22 em B Ces 1 D Ces D fm SPAN REF LVL ZERO MAX STEP Figure 3 4 Fundamental Analyzer Controls Selects the channel number immediate entry mode when CATV mode is active CHAN appears on the screen at left center Enter the desired channel from the keypad terminate with W In nonCATV mode it selects the center or start frequency for immediate entry mode FREQ appears on the screen at left center Enter the desired frequency from the keypad terminate with Hz KHz MHz or GHz key Range 0 Hz to 1 8 GHz Selects the span per division for the immediate entry mode SPAN appears on the screen at left center Enter the desired span div from the keypad terminate with Hz KHz MHz or GHz key Range 1 kHz to 180 MHz 2715 User Manual Operating Basics REF LEVEL Selects the reference level for the immediate entry mode REFL appears on the screen at left center Enter the desired reference level from the keypad terminate with dBx or dBx key Range 68 8 to 21 2 dBmV or equivalent in other units REF LEVEL The arrow buttons increase or decrease the FREQUENCY SPAN DIV and Keys R
263. hreshold established by the setting of the LEVEL control providing the previous sweep is completed and item 2 EXTERNAL is selected from the Sweep Trigger menu A typical external trigger signal might be a 5 V pulse signifying that a transmitter has been keyed on or that a receiver has detected a signal that rises above its squelch setting For instance to determine the spectrum of a gated CW signal you could apply the gated CW to the 2715 input while triggering externally with the gating signal The 2715 would then perform a spectral sweep only when the CW signal was present at its input To trigger the 2715 externally connect the external trigger signal to the EXT TRIG connector and select item 2 EXTERNAL from the Sweep Trigger menu Turn the LEVEL control fully counter clockwise and then rotate it slowly clockwise until a sweep occurs If the external trigger is pulsing the 2715 sweep should now remain in sync with it 1f not you may have to adjust the LEVEL control a bit more When you are finished reselect the FREE RUN trigger mode J103 Accessory Connector E 2 The accessory connector J103 is a 15 pin D connector not RS 232 compat ible The connector provides an interface for video I O the 2715 s sweep gate and the sweep ramp signals The connector also provides signals used by the Tektronix 2707 External Tracking Generator Terminations are shown in Figure E 1 The following signals are discussed in detail m
264. ic its performance requirement or to describe characteristic performance that is impractical to verify Supplemental Information is not guaranteed and may not be supported by a performance check procedure Changes to a characteristic because of the addition of an option are included in Table A 7 Specifications Table 1 CATV Characteristics Characteristic Input Configuration All except Option 50 Option 50 Channel Selection Tune Configuration Channel Range Description 75 O Female F connector 50 Type N connector The visual and aural carriers are displayed when the channel number is entered or either or next to CHAN FREQ is pressed STD 73 603 HRC 73 605 IRC 73 612 and Custom 0 to 9991 Frequency Range except Opt 50 and Opt 75 1 MHz to 1 8 GHz2 Preamp limited to 600 MHz Frequency Range Opt50 and Opt 75 1 MHz to 2 15 GHz2 Preamp limited to 600 MHz Visual Carrier Frequency Measurement Method Resolution Accuracy Visual to Aural Carrier Frequency Measurement Method Difference Range Resolution Accuracy Visual Carrier Peak Level Measurement Accurate Frequency and Amplitude Accurate Amplitude Only FastAmplitude Only Amplitude Range Accuracy is dependent on the accuracy ofthe spectrum analyzer see Frequency Accuracy in Table A 2 Internal Counter 1Hz 5 x 1077 x Carrier Frequency 10 Hz 1 Least Significant Digit 55 25 MHz Ch 2 worst
265. ications menu 18 Press 9 to select the Setup Table 19 Press 1 to select NORM BW FOR C N 6 47 Spectrum Analyzer Menus 6 48 Searching for Signals 20 Press 4 X to reset the noise bandwidth to 4 MHz for the carrier to noise C N measurement 21 Press BKSP to return to the Applications menu 22 Press 2 to turn on the NOISE NORM D feature Notice the measured noise is approximately 42 dBmV If we connected the 2715 to a cable television tap with a 0 dBmV video signal and a 43 dB C N we would be unable to measure the noise or C N because the cable noise 43 dBmV in this example is below the normal 2715 noise floor 23 Press INPUT 9 to turn off the calibrator 24 Press INPUT 1 to turn on the preamplifier 25 Press INPUT 5 0 y to set the RF attenuation to zero Notice that the 2715 noise floor has been reduced by over 12 dB to approximately 55 dBmV making it possible to measure both noise and C N on our hypothetical cable 26 Turn off the preamp and noise measurement mode 27 Press UTIL 1 1 to reinitialize the 2715 to the factory default power up settings NOTE If the 2715 is in the PEAK acquisition mode it reverts to MAX MIN mode whenever the normalized noise or carrier to noise features are activated You can return it to PEAK mode by pressing DSPL 4 900 0MHz AUTO SWEEP ATTN 50DB 68 8DBMV VF WIDE 180MHz 10 DB 5MHz RBW AUTO The 2715 pro
266. idth filter brackets the designated center frequency Because the display screen is still swept the span readout indicates sweep speed time per division rather than frequency per division The word ZSPAN follows the sweep speed to denote Zero span operation In a sense you have turned your spectrum analyzer into an oscilloscope 16 Press ZERO to return to 20 MHz div span The following procedures demonstrate two methods of entering a channel selection Arrow Keys This procedure uses the arrow keys to select a channel from a selected channel table 1 Press UTIL 1 1 to restore the factory defaults 2 Press adjacent to CHAN FREQ The channel selection steps to the next channel in the selected channel table 2715 User Manual Dedicated Controls Frequency Entry Normal Mode 2715 User Manual 3 Press adjacent to CHAN FREQ The channel selection steps to the previous channel The up arrow selects the next higher channel in the channel table whereas the down arrow selects the previous channel If you step past the end of the channel table the display wraps to the start of the table and vice versa The keys remain active whenever the 2715 is in the spectral display mode Keypad Entry CHAN FREQ defaults to CHAN whenever the CATV mode is active The abbreviation CHAN appears at left center of the 2715 screen CHAN indicates that you can enter the channel number directly from the keypad This is
267. ier to Noise Ratios 6 46 Measuring Occupied Bandwidths OBW 6 50 Measuring Signal Bandwidths 6 44 Menu Display Mode 3 1 Menu Display Mode Test Screen 3 2 Menu Items Are Not Present 3 3 Menu Status Change 6 2 Menu Structure CATV APPL Applications 3 19 CATV APPL CATV Measurements 3 14 DEMOD 3 19 DSPL 3 20 INPUT 3 21 MRK FREQ 3 13 SWP TRG 3 11 USER DEF 3 20 UTIL 3 12 Menu Entered Control Settings 6 60 2715 User Manual Index Menus 3 2 APPL 6 43 Change Status 6 2 DEMOD Menu 6 56 DSPL 6 27 Enter Parameter Value 6 3 Exit From a Menu 6 3 INPUT 6 4 MKR FREQ 6 17 SWP TRIG 6 83 USER DFF 6 89 Using 6 1 UTIL 6 60 Minimum Hold Activating 6 42 Minimum Signal Size Setting 6 72 MKR Delta OFF 3 4 MKR FREQ Menu 6 17 Center or Start Frequency 6 22 Changing the Knob Function 6 19 Counter Resolution 6 23 Frequency Offsets 6 26 Marker to the Reference Level 6 21 Moving the Marker to the Next Higher or Lower Peak 6 20 Programmed Tuning 6 24 Selecting the Tuning Increment 6 21 Setting Start and Stop Frequencies 6 17 Setting the Signal Threshold 6 22 Transposing Markers 6 18 Using Markers to Set Start and Stop Frequencies 6 17 Mode 1 Frequency Response Measurement Test 5 43 Mode 2 Frequency Response Measurement Test 5 43 5 44 MODULATION DEPTH Measurement 5 28 ADJUSTMENT MODE 5 30 Enable MODULATION DEPTH Measurement 5 29 N Noise Averaging Filter
268. iet lines measured are still quiet Turns preamp on or off as needed Stores measured waveform in Display Register NOTE The Carrier to Noise test result may be marked with an asterisk This indicates that the measured noise level is within 2 dB of the 2715 5 calculated noise level Under these conditions the inaccuracy is always on the conservative side the actual Carrier To Noise ratio will be better than the measured value The gated Carrier to Noise test result may also have 1000 2000 or 3000 added to it This indicates that events occurred during the measurement which may cause an inaccurate result If so the inaccuracy is always on the conservative side the actual Carrier To Noise ratio will be better than the measured value If 1000 is added to the result the instrument detected that one or more of the quiet lines found at the start of the test were not quiet at the end of the test If 2000 is added to the result the instrument increased the signal level at the Ist mixer input above optimum to ensure adequate signal level for accurately timed gating control For Carrier to Noise measurements this should occur only on channels that are substantially weaker than the general system level If 3000 is added to the result both of the above events occurred When performing in service tests the instrument checks for quiet lines at lines 10 through 20 and 272 through 282 on NTSC systems or at lines 6 through 20 and 318 thro
269. ieved by reducing attenuation However the noise floor is generated after the RF attenuator so it is not affected Reset the reference level to 48 8 dBmV and select the INPUT menu Item 5 indicates that the RF attenuation is 30 dB and that it is selected automati cally by the 2715 We can control the RF attenuation so that it remains at a fixed value 9 10 11 12 Press 5 and this prompt appears ENTER NEW VALUE __ 0 TO 50 IN 2 DB STEPS W AUTO Press 3 0 Y to enter a fixed value of 30 dB The display returns unchanged Press twice Now the signal peak and the noise floor both rise This is because pressing 9 twice increased the 2715 IF gain by 20 dB to lower the reference level but the RF attenuation is unchanged Press INPUT 5 W to place the RF attenuation back in the automatic mode The following steps show how to change reference level units 13 14 15 Press CATV APPL to select the APPL menu Press 8 to select CATV MEASUREMENTS SETUP Press 6 to select REF LEVEL UNIT Item 6 toggles between DBUV and as indicated on the right side of the screen There is an alternate method to change reference level units from the INPUT menu 16 Press INPUT to select the Input menu 6 5 Spectrum Analyzer Menus Accommodating External Amplification Attenuation 6 6 17 Press 3 to select REF LEVEL UNIT Six selections are shown I
270. indicates 5 MHz The calibration signal now appears to be 5 MHz wide Theoretically the calibration signal should be infinitely narrow a spike at 100 MHz To understand what has happened you must recall the process going on within the 2715 It is sweeping a narrow band signal the calibration signal past a broadband filter the 5 MHz resolution filter As the signal is moved past the filter it maps the shape of the resolution filter What you see is the spectral shape of the filter rather than that of the calibration signal This means that on unmodulated signals a resolution bandwidth filter that is too wide can artificially broaden the displayed spectrum although the signal peak remains accurate 10 Repeatedly press in the RES BW function block to narrow the resolution bandwidth until the on screen readout indicates 3 kHz There is a high level beep and the message UNCAL if there is no beep check that the audio alert is set to ERROR ONLY or BOTH see The Audio Alert on page 6 71 The 2715 is now sweeping the calibration signal past the resolution filter too quickly for the filter output to rise to its steady state value before the signal is no longer present at the filter input This can result in low amplitude and skewed frequency readings This means that a resolution bandwidth that is too narrow can result in incorrect amplitude and skewed frequency measurements Measure ment accuracy is compromised when the UNCAL m
271. ing VITS Visible When knob selectable TV line triggering is active pressing MKR FREQ 2 allows the knob function to be changed from frequency control to marker control or video line selection This is a great convenience if you want to change TV channels See Changing the Knob Function on page 6 19 for more information 6 87 Spectrum Analyzer Menus SWP TRTV Video Field Triggering Setting the Sweep Rate 6 88 12 Call up the SETUP TABLE from the SWEEP TRIGGER menu If you select item 2 KEYPAD ENTERED LINE the sync pulse indicated at the end of the line will be used as the trigger 13 Select item 3 KEYPAD ENTRY and enter number 279 from the numeric keypad The number you enter appears at the end of the KEYPAD ENTERED LINE This number also changes when you operate in the knob selectable mode it shows the number of the sync pulse last used as the trigger 14 Press 2 and return to the waveform display On most U S NTSC stations you now see the VITS for the second picture field When using the keypad entered lines the tuning knob controls frequency instead of the line number Item 5 TV FIELD of the Sweep Trigger menu is the second of two internal triggering modes that are particularly useful for time domain analysis of television signals Call up the Sweep Trigger menu and choose item 5 The display is now being triggered by the TV vertical sync pulse that occurs near the beginning of each field Using
272. ing TV channel signals Automating measurements m Controlling 2715 operational modes Changing control increments and settings m Storing and recalling control settings m Normalizing the 2715 m Executing diagnostic routines Each menu is a list of numbered items Choosing an item often results in a submenu being displayed Some infrequently used items from the sub menu may call up a secondary sub menu A few items from the menus are neither listed nor explained in the following discussions these represent factory troubleshooting and calibration aids not intended for general operator use Some items discussed may not appear in your instrument because of the installed options An overview of the menus is included in Operating Basics The overview should provide all the information you need to use the menus once you become familiar with the menu features From the spectral display mode first press the appropriate menu key in the MENUS function block then press the number key on the keypad corresponding to the desired selection If you are in a menu a menu key just takes you back to the spectral display mode A feature status indicator on the right side of the menu item shows the present value or condition of that parameter or feature See Figure 6 1 as an example The status indicator is updated as you make selections or alter parameters Spectrum Analyzer Menus 6 2 INPUT MENU 1 PREAMP OFF 3 REF LEVEL UNIT DBM 4 1ST M
273. ing the Spectrum Analyzer including reference normalization File Names Curves Settings User Defined Programs Antenna Tables n A B C n A B C D nWFMO00 nWFM39 nSET00 nSET39 UDPO UDP8 ACF1 ACF5 Channel Tables CATV Measurement Results Flatness Corrections Normalizations CHTBLO CHTBL9 RSLTX FCOR NORM 6 76 Table 6 4 Additional File System Name Description 12 88 Version SEARCH Signal search configuration SETUP Instrument configuration S CATV CATV configuration S GPIB GPIB configuration S PLOT Plotter configuration S RTC Real time clock configuration S TTYx RS 232 configuration 2715 User Manual Spectrum Analyzer Menus Protecting Files Confirming Installed 2715 User Manual Options DSETO0 and SETOBU are special files They are created automatically by the 2715 and contain the D register settings used when the 2715 was last turned off SETOBU is a backup in case DSETOO is corrupted during a power down or power up cycle Other temporary files may also be created by the 2715 for internal purposes Files you wish to preserve such as waveform settings or UDP files can be protected from accidental erasure in several ways UDP files can be selectively protected from the USERDEF menu while all settings files can be protected by pressing UTIL 4 5 However to protect an individual file in the file system first determine its file number by viewing the file directory by p
274. ing the ambient light or shielding the display If the 2715 is used in direct sunlight a contrast enhancing light filter is recommended part of the Travel Line Package Option 33 Rear Panel Trace Adjustments There are three controls TRACE ROTation VERTical POSition and HORIZontal POSition at the upper right of the 2715 rear panel that are used with a built in test display to adjust trace alignment The control shafts are recessed within hexagonal nuts that attach the controls to the 2715 chassis Do not attempt to turn the hexagonal nuts and do not use excessive force when turning the control shafts A plastic adjustment tool is recommended instead of a screwdriver 4 35 Dedicated Controls 4 36 2715 User Manual Oe ooo CATV Measurements CATV Measurements Firmware based CATV measurement routines allow technicians to easily make frequency domain and baseband measurements Without these automated routines making these measurements would require a high degree of technical expertise require a long setup time and be subject to error CATV Preliminary Information 2715 User Manual This section provides information on input power limitations for CATV operation an overview of preparatory information and specific 2715 applications CATV measurements and capabilities include the following W Carrier level and frequency measurement m Averaged power measurement m Survey of
275. injury or loss of life CAUTION Caution statements identify conditions or practices that could result in damage to this product or other property Terms on the Product These terms may appear on the product DANGER indicates an injury hazard immediately accessible as you read the marking WARNING indicates an injury hazard not immediately accessible as you read the marking CAUTION indicates a hazard to property including the product Symbols on the Product The following symbols may appear on the product A AN m WARNING Protective Ground CAUTION Double High Voltage Earth Terminal Refer to Manual Insulated 2715 User Manual Cc l Preface This manual contains operating information for the Tektronix 2715 Spectrum Analyzer and includes menus and operating features The following manuals also support the Tektronix 2715 Spectrum Analyzer m 2714 amp 2715 Spectrum Analyzer Programmer Wm 2714 amp 2715 Spectrum Analyzer Reference m 2715 Spectrum Analyzer Service m Cable TV RF Measurements Software User For manual ordering information refer to Appendix F Accessories amp Options or contact your local Tektronix Field Office or representative Who Should Use This Manual This manual is intended for electronic technicians with experience in making cable television related measurements Standards and Conventions Used Most terminology is consistent with standards adapted
276. instrument to dissipate body static charge before touching the antenna B 1 Appendix Broadcast AM FM and TV Signal Sources B 2 2715 User Manual P pU d Appendix C System Messages 2715 User Manual The 2715 will display messages under the following conditions m Self check routines detect abnormalities m Incorrect information is entered m An improper operation is attempted 15 necessary to alert you to an operation in progress The messages that may be displayed are contained in the following list Their causes and corrections are indicated immediately below the message If you are unable to correct an abnormal situation contact your local Tektronix Service Center and report the message IST MEASUREMENT COMPLETE Go to the next step in the procedure 2ND MUST BE W IN CHAN BW The second aural carrier must be within the channel bandwidth 2ND MUST BE W IN RANGE OF IST The second aural carrier must be 200 kHz to 2 550 MHz greater than the first aural carrier 300HZ FILTER NOT INSTALLED 2715 cannot detect presence of 300 Hz filter ADDITIONAL NVRAM NOT INSTALLED Occurs when accessing a file located in extended NVRAM if the 2715 cannot detect the presence of the extended NVRAM AMPL NORM SUGGESTED VR PIN DAC Perform amplitude normalization Contact your local Tektronix service center or representative if message persists AMPL OUT OF RANGE NORMALIZATIONS Perform amplitude normalization
277. ion of the input signal power Logarithmic A display in which the scale divisions are a logarithmic function of the input signal voltage Display Reference Level A designated vertical position representing a specified input level The level may be expressed in dBm volts or any other units Distortion Degradation of a signal often a result of nonlinear operations resulting in unwanted signal components Harmonic and intermodulation distortion are common types Dynamic Range The maximum ratio of the levels of two signals simultaneously present at the input which can be measured to a specified accuracy Effective Frequency Range That range of frequency over which the instrument performance is specified The lower and upper limits are expressed in hertz Envelope The limits of an electrical signal or its parameters For instance the modulation envelope limits the amplitude of an AM carrier Envelope Display The display produced on a spectrum analyzer when the resolution bandwidth is greater than the spacing of the individual frequency components Glossary 3 Glossary Glossary 4 Filter A circuit which separates electrical signals or signal components based on their frequencies Frequency The rate at which a signal oscillates or changes polarity expressed as hertz or number of cycles per second Frequency Band The continuous range of frequencies extending between two limiting frequencies expressed in hertz F
278. irectly subtract a stored trace from an active trace m Switch between MAX MIN and PEAK signal acquisition modes m Title and label displays and plots m Turn the graticule lights on and off m Change the source of the display from an internal to an external signal Control an on screen reference line to simplify amplitude measurements and establish alarm thresholds W Enable and disable the Min Hold feature 6 27 Spectrum Analyzer Menus Changing the Display Mode Ensemble Averaging 6 28 You can place the 2715 in the analog display mode by turning off all the display registers using A B C and D see Display Storage on page 4 20 However a more convenient method when two or more registers are active is to use item 0 on the Display menu Item 0 is a toggle that switches the 2715 between analog and digital display modes If the 2715 is in the digital display mode pressing item 0 turns off all display registers enters analog display mode When in the analog mode pressing item 0 performs one of two actions m If analog mode was entered using item 0 the register configuration prior to entering analog mode is restored m If analog mode was entered by manually turning off all registers with A B C and D the last register turned off is reactivated 13 Ensure the C and D display registers are active Save the C register and change the center frequency to 280 MHz so you can distinguish the two active tra
279. is error occurs if WAIT is requested while in single sweep mode with the sweep not armed WARNING USING EMPTY ANT TABLE The table called for is empty The function is still being performed but with values of zero for each increment of the table ZERO SPAN ENTERED Instrument is now in zero span 2715 User Manual C 15 Appendix System Messages C 16 2715 User Manual ee ry Appendix D Global Resets Definitions Settings on the 2715 can be reset in many ways Some instrument settings are always reset while others are never reset and still others are reset during certain reset cycles only This appendix includes a description of which settings are in each category and when each category of settings is reset These definitions are included to make the following explanations more clear Reset To restore a setting to a previous state This is what happens to the center frequency for example when power is removed and re applied The center frequency setting is RESET Reset Category Each setting belongs to one RESET CATEGORY such as center frequency belongs to the fragile reset category The categories are described later in this appendix Reset Cycle An operation that causes one of the RESET CATEGORIES to be operated on Retain The opposite of RESET A setting is RETAINED for a particular RESET CYCLE if its value can be set to any allowable value and remains at that value after the RESET CYCLE completes Reset Cyc
280. is that there is no difference in the time bases used by the 2715 and the oscilloscope The disadvantage is that you cannot control the oscilloscope time base independently of the 2715 2715 User Manual Appendix E External Input and Output J104 Digital Communications Port 2715 User Manual GPIB The 2715 is equipped with a digital communications connector labeled J104 The type of connector on your instrument depends on the communications option selected when the 2715 was purchased If Option 03 GPIB is installed J104 is a 24 pin IEEE Standard 488 GPIB connector The pin outs for the GPIB connector are shown in Figure E 3 Signal levels handshaking protocols and other matters of importance to digital communications are detailed in the 2714 amp 2715 Programmer Manual and the pertinent standards NRFD NDAC IFC Logic Gnd Gnd 011 Gnd 010 Gnd 09 Gnd 08 Gnd 07 Figure E 3 IEEE Standard 488 GPIB Connector Pin Assignments GPIB Cable GPIB cable connectors are consistent The following two intercon nect cables are available from Tektronix see Appendix F Accessories and Options for more information m GPIB cable 1 meter long m GPIB cable 2 meters long E 7 Appendix E External Input and Output E 8 RS 232 If Option 08 RS 232 is installed J104 is a 9 pin male D connector The pin outs
281. ischarge Immunity IEC 801 3 RF Electromagnetic Field Immunity IEC 801 4 Electrical Fast Transient Burst Immunity IEC 801 5 Power Line S urge Immunity EC Declaration of Conformity Low Voltage Compliance was demonstrated to the following specification as listed in the Official J ournal of the European Communities Low Voltage Directive 73 23 EEC EN 61010 1 1993 Safety requirements for electrical equipment for measurement control and laboratory use Approvals Installation Category Descriptions 2715 User Manual UL1244 Standard for Electrical and Electronic Measuring and Testing Equipment CAN CSA C22 2 No 231 Safety Requirements for Electrical and Electronic Measuring and Testing Equipment Terminals on this product may have different installation category designations The installation categories are CAT III Distribution level mains usually permanently connected Equipment at this level is typically in a fixed industrial location CAT II Local level mains wall sockets Equipment at this level includes appliances portable tools and similar products Equipmentis usually cord connected CATI Secondary signal level or battery operated circuits of electronic equipment A 23 Specifications Table A 12 Safety Certification Compliance Category Description Temperature operating 5 C to 450 C Altitude maximum operating 2000 meters 6562 ft Relative Humidity maximum op 80 for temperatures
282. isplay registers The analog display can be very useful for viewing time varying modulation such as television video signals 4 21 Dedicated Controls 4 22 It is also useful if you are used to a spectrum analyzer that may not have digital display capabilities since it provides a display you are familiar with and allows you to see the similarity between the MAX MIN display and the analog signal You can usually obtain a sharper analog display especially at higher sweep speeds by varying the intensity see INTENSITY on page 4 35 and or turning off the on screen readouts 4 Activate the D register SAVE ENABLE A B C Registers The SAVE ENABLE key modifies the function of the A B C and D keys When used with A B or C key it enables you to save the current digitizer output in the corresponding register NOTE The CATV mode assumes full control of the waveform storage registers Therefore waveforms stored manually will be erased when CATV mode is activated at power up during a reboot cycle UTIL 5 0 9 or when it is reactivated after having been disabled 5 Press SAVE ENABLE to manually save a waveform The red LED below SAVE ENABLE lights This indicates that the SAVE function is armed 6 Press A to save into the A register what is presently being displayed The green LED below A lights but observe that the A register was turned off and remains turned off 7 Press D to turn
283. isplay the CATV MEASUREMENTS menu 2 Press 1 to select the CARRIER LEVEL AVG POWER measurement menu 3 This gives you the following options 0 RUN LEVELS POWER FREQ AMPL 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 SET UP CARRIER LEVELS 6 EXTERNAL ATTEN AMPL 9 LEAVE CARRIER LEVEL AVG PWR In this example the accurate amplitude measurement mode ACCUR AMPL is selected see menu item 0 4 Press 5 to select a different measurement mode This displays the SET UP CARRIER LEVELS submenu with the following menu choices 0 ACCURATE FREQUENCY AND AMPL 1 ACCURATE AMPLITUDE ONLY 2 FAST AMPLITUDE ONLY 5 Press 0 to select ACCURATE FREQUENCY AND AMPL Note that the asterisk moves to that selection in the menu indicating that it 1s the current selection 6 Press BKSP to return to the CARRIER LEVEL AVG POWER measurement menu 7 Press 0 to run the Carrier Levels measurement using the accurate frequency and amplitude mode After completing the measurement the instrument displays the current results superimposed on the spectral display 8 Press CATV APPL to again display the CARRIER LEVEL AVG POWER menu 5 23 Measurements 5 24 9 Press 1 to store the results of the last measurement along with the channel table channel number time date site and operator information After a short peri
284. ist between signal peaks for them to be recognized as separate peaks during Next Higher and Next Lower or Marker arrow operations It is expressed in bits full scale being 255 bits The minimum value is 2 bits factory default is 20 bits or approximately 846 of full scale three minor divisions 1 Press 1 to select MINIMUM SIGNAL SIZE from the Instrument Configu ration menu 2 anew value and enter it by pressing W The new value appears at the end of item 1 3 Experiment if you want then restore the factory default value NOTE This feature is used primarily for certain procedures at the factory we recommend that you leave WAVEFORM TO PRINTER turned off Item 2 of the INSTRUMENT CONFIGURATION menu WAVEFORM TO PRINTER UTIL 4 3 2 sends a binary or ASCII representation of the displayed waveform to the serial port following each sweep The 2715 must have the RS 232 port installed and PRINTER CONFIGURATION must be set to TTYO0O 4 2 0 Item 2 toggles data transmission ON and OFF and item 3 toggles the data format between ASCII and binary 100 0000MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF 3KHz 20 0KHz 10 DB 3KHz RBW AUTO CALIBRATOR The 2715 uses internal reference oscillators to analyze the input signal At wide spans a slight amount of drift in an internal oscillator is not noticeable However as the span is reduced to a few kHz div or less any internal oscillator jitter become
285. itive for example the French L system When the HUM LFD measurement is initiated the firmware configures the 2715 as follows W Sweep triggering Free run single sweep m Center Frequency Visual carrier of the currently selected channel m Span div 600 kHz div 5 40 2715 User Manual Measurements m Resolution bandwidth 300 kHz m Video filter Off W Acquisition mode Peak m Reference level Signal peak is at top of screen m Vertical mode Linear W Span Zero Span W Sweep speed 20 ms div A time domain ZERO SPAN waveform is acquired This waveform is converted to the frequency domain using a Fast Fourier Transform FFT calculation so that the percent hum for the power line fundamental and 1 harmonic can be measured The hum values are calculated from the FFT result as follows 4 x 100 x Power Line Frequency Component Visual Carrier Component The factor of four 4 comes from the following two sources m The two sided nature of the FFT requires that the apparent levels of each harmonic be doubled The result must be doubled again to obtain the peak to peak harmonic levels since the FFT finds only the peak value of each harmonic component The hum data values are shown in the two readout lines as follows ZZ Z TOTAL HUM XX X Fo YY Y F1 where Fo is the power line fundamental 50 Hz or 60 Hz and F is the power line 1 harmonic 100 Hz or 120 Hz The time domain data is displayed in
286. itivity by a further 20 dB over the 300 kHz filter 2715 User Manual Spectrum Analyzer Menus MKR FREQ Setting Start and Stop Frequencies Using Markers to Set Start and Stop Frequencies 2715 User Manual 100 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF WIDE 20 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR With the Marker Frequency menu you can directly affect the frequency characteristics of the spectral display and control the markers in ways not available from the front panel Perhaps you would prefer to directly specify the beginning and ending frequen cies of the display rather than its center frequency and span The 2715 enables you to do so as follows 1 Press MKR FREQ 7 to call up the Marker Frequency menu 2 Press 7 to select FREQUENCY START STOP A submenu appears enabling you to specify start and stop frequencies for the spectral display 3 Press 0 4 Press 1 7 5 X to specify a start frequency of 175 MHz Note that the indicated start frequency has changed 5 Press 1 6 Press 4 2 5 X to enter a value of 425 MHz for the stop frequency 7 Press any menu button to return to the spectral display The span is 25 MHz division making the start and stop frequencies 175 MHz and 425 MHz respectively If you make the start frequency greater than the stop frequency the 2715 enters ZERO SPAN mode tuned to the start frequency You can also set the start and stop frequencies with the markers
287. itivity decreases linearly approxi mately 8 dB from 9 KHz to 1 8 GHz Above 1 8 GHz sensitivity decreases linearly approximately 10 dB NOTE Sensitivity degrades as the FREQUENCY setting is decreased from approximately 10 MHz to 9 kHz Maximum loss in sensitivity is approxi NOTE Sensitivity with the Preamp enabled is not specified above 2715 User Manual Specifications Table A 4 Amplitude Related Characteristics Cont Characteristic Spurious Responses Residual no input signal Performance Requirement Supplemental Information All except Option 50 and Option 75 With 0 dB RF attenuation lt 51 dBmV lt 100 dBm exceptat 1780 MHz where the spurious response is lt 41 dBmV lt 90 dBm Option 50 and Option 75 lt 26 dBmV lt 75 dBm at 2 0 GHz 3 Order IM Intermodulation Products All except Option 50 and Option 75 70 dBc up to 1 8 GHz From any two on screen signals within any frequency span Option 50 and Option 75 Typically lt 65 dBc at 2 15 GHz Zero Frequency Spur 439 dBmV x 10 dBm Referenced to input with 0 dB RF attenuation 2nd Harmonic Distortion LO Local Oscillator Emission 66 dBc Measured with 15 mixer input level of 49 dBmV With 0 dB RF attenuation and preamp All except Option 50 and Option 75 lt 21 dBmV lt 70 dBm off Option 50 and Option 75 When frequency is below 90 MHz Typically 429 dBmV 20 dBm When frequency is a
288. its power up self test When power is applied to the 2715 it initializes its front panel controls to settings stored in memory If the instrument has been used before those settings may be user defined see User Defined Power Up Settings on page 6 62 If no user defined settings exist the 2715 defaults to the factory power up settings that are permanently stored in initialized RAM random access memory The only exception is that the default channel table and channel are replaced by the last selected channel table and channel before power down A display appears on screen almost immediately You may see the following message WARMUP TIME 15 MIN When the factory default power up settings are being used it is possible to make general observations immediately after the power is turned on If user defined power up settings are implemented the message WAITING FOR USER DEFINED POWERUP appears briefly The 2715 front panel is locked out while the message is displayed After the message disappears the factory default settings are replaced by the user defined settings and you can proceed with your observations 2715 User Manual Getting Started Initial Normalization 2715 User Manual Whichever settings are used the WARMUP message is displayed It disappears after a few seconds Remember however that the spectrum analyzer may require a full 15 minutes to be operating within specification Consequently measure ment errors and s
289. ixed marker on top of the 100 MHz signal peak the 2715 places the fixed marker on the signal peak nearest the center of the screen in the C N mode The moveable marker appears 1 division from the left screen edge 16 Reposition the moveable marker 50 MHz above the signal NOTE The moveable marker is initially positioned only to clearly separate it from the fixed marker You must place the noise marker at the frequency where you want the noise measured The first two items in the right on screen column read approximately as follows C N 63 0DB 5 0MHZ The reading may vary slightly You will also receive the NOISE LEVEL LESS THAN 2DB warning The C N reading is the ratio of the signal power at the fixed marker s position to the average noise power at the movable marker position The noise reading is corrected as indicated in the normalized noise measurement section Since the noise level measured earlier was approximately 44 2 dBmV and the signal peak is 18 8 dBmV the ratio should be approximately 63 dB The preamplifier discussed with the INPUT menu in this section can be very important when making noise or C N measurements in broadband networks For instance in the U S good cable television operating practice requires that the video signal be at least 0 dBmV while picture quality requires the noise to be approximately 43 dB lower or approximately 43 dBmV in a 4 MHz band 17 Press CATV APPL to call up the Appl
290. k of the knob moves the marker to the next bit in the digital waveform memory thus tracking the stored max and min values 4 Turn the FREQ MKRS knob counterclockwise and the marker moves left Again the readout tracks the signal amplitude and frequency at the marker position Be aware that the marker frequency accuracy is not as good as the center frequency accuracy because it includes a span nonlinearity component see CTR MEAS TRKG on page 4 29 for a discussion of frequency measurement accuracies 4 27 Dedicated Controls 4 28 If you attempt to move the marker past either edge of the display the spectrum will move towards the opposite edge while the marker remains stationary If you move the marker past the right edge the signal peak moves to the left 5 Turn the FREQ MKRS knob a few clicks counterclockwise The marker moves to the left but the spectrum will not move back towards its original position until you attempt to move the marker past the other edge of the display 6 Recenter the calibration signal peak by trying to move the marker past the left edge of the display 7 Ensure the marker and the calibration signal peak are centered and press MKR A OFF again The spectral display did not change but the marker frequency and amplitude readouts now read something like the following D 0KHZ D 0 0DB The delta marker mode is turned on 8 Turn the tuning knob clockwise Now you can see both markers
291. ktronix service center replaces your battery it also renormalizes the references ensuring that your instrument will operate within its specifications 6 81 Spectrum Analyzer Menus Generating a Service Request Printing the On Screen 6 82 Readouts If NVRAM is ever lost in the field you may have to renormalize the 2715 1 Press UTIL 3 1 to carry out a frequency normalization The 2715 will use default reference values from internal EPROM s or DIP switches The default values will not result in optimum accuracy but they will enable you to make approximate measurements More importantly they will enable you to carry out the reference normalizations required to ensure that the 2715 is fully within its specification and operating at maximum accuracy 2 Follow the instructions in Service Normalizations on page 6 80 and the resulting on screen prompts to perform the service reference normalizations 3 After the reference normalizations are complete press UTIL 3 0 to complete the frequency and amplitude normalizations If external reference sources are not available simply perform the frequency and amplitude normalizations with UTIL 3 0 The 2715 will be useable but the references should be renormalized at the earliest opportunity If the battery is worn out you will have to renormalize the 2715 each time it is used until the battery can be replaced NOTE Any control settings can be used
292. l Information DC output to Option 05 External Tracking Generator typically 9 5 V with TG level set to ON Negative going ramp output to Option 05 External Tracking Generator typically 5 V with analyzer set to max span Pins 13 through 15 Notused Digital Communications P ort J 104 RS 232 or GPIB connector Table A 6 Power Requirements Characteristic Performance Requirement Input Voltage Line Voltage Range 90 VAC to 250 VAC Line Frequency Range 48 Hz to 63 Hz Line Voltage Range 90 VAC to 132 VAC Line Frequency Range 48 Hz to 440 Hz Line Fuse 2 A Slow Blow Input Power 90 W 1 2 A for standard instrument 105 W 1 4 A maximum with options 115 W maximum at 90 V and 440 Hz Leakage Current Table A 7 Supplementary Characteristics Due to Options Supplemental Information At 115 V and 60 Hz 3 5 mARMs maximum or 5 mApeak maximum Characteristic Performance Requirement Supplemental Information Option 03 Provides a GPIB interface port at 104 to replace RS 232 Option 08 Provides a RS 232 serial interface port at 104 to replace GPIB Option 15 Add a 1510 output 1510 Output Level 2448 8 dBmV 20 0 dBm Atspectrum analyzer frequencies 2100 kHz 2715 User Manual A 19 Specifications Table A 8 General Characteristics Characteristic Performance Requirement Sweep Sweep Rate 1 us div to 2 s div in a 1 2 5 sequence Accuracy 10 over the center 8 divisions Tri
293. l oscilloscope It also controls the horizontal sweep position in the manual scan mode It has no effect in the other trigger modes The outer knob controls the volume of the AM and FM demodulators and picture framing in video monitor mode Alternate uses of the LEVEL control are discussed under DEMOD on page 6 56 and Manually Scanning on page 6 89 The 2715 can display an analog spectrum of up to four sampled and stored digital spectra A major advantage of display storage is that it results in a flicker free sweep 100 0MHz AUTO SWEEP ATTN 20DB 38 8DBM VF 300KHz 5 0MHz 10 DB 300KHz RBW AUTO CALIBRATOR 2715 User Manual Dedicated Controls 2715 User Manual Display Registers The digital display storage registers are named A B C and D Their status is controlled by the A B C and D keys the red and green LEDs below each key indicate the status of the corresponding register When a red LED is illuminated the contents of the corresponding register are displayed The contents of a register can be either the measurement currently being carried out or previously saved data When only a red LED is illuminated the register contents are the result of the 2715 s current activity Current results are updated from the signal at the 2715 input during each sweep The present control settings are used for the update When an A B or C green LED is illuminated the corresponding register contains a saved sweep t
294. le Description 2715 User Manual Following is a list of all the possible reset cycles POWER DOWN UP CYCLE Invoked by powering the instrument down and back up again INITIALIZE INSTRUMENT SETTINGS CYCLE Invoked with UTIL 0 RECALL LAST POWER DOWN CYCLE Invoked with UTIL 1 0 RECALL FACTORY DEFAULT POWER UP CYCLE Invoked with UTIL 1 1 Appendix D Global Resets Reset Categories D 2 Precious Settings Mode related Settings RECALL USER DEFINED POWER UP CYCLE Invoked with UTIL 1 2 W RECALL NUMBERED SETTINGS CYCLE Invoked with UTIL 1 xx W xx is one of a selection of stored settings designated by numerals 0 9 on 4 successive screens POWER UP DIAG AND REBOOT CYCLE Invoked with UTIL 5 0 9 The 2715 has several distinct settings categories Precious settings are not reset by any reset cycle The settings in this class can only be changed by manually setting each to its desired value The following are precious settings W Measurement Channel m Saved Waveforms m Plot Configuration including Comm Port Plot Language and Plot Speed GPIB or RS 232 configuration m Real Time Clock Configuration m Audio Alert Setting W Settings Protect Mode m Signal Search Parameters These are settings that are reset during some cycles and retained during others The settings are reset as follows m During an INITIALIZE INSTRUMENT SETTINGS cycle settings are reset to the values
295. lower bound on the real time signal in D As time passes you will notice that the upper and lower bounds no longer change because the probability of new random spectral peaks exceeding those already observed becomes very small Press DSPL 9 to turn off the minimum hold feature Reselecting MIN HOLD when it is already on toggles the feature off Press MAX HOLD to turn maximum hold feature off Clear and turn off the A and B registers 100 0MHz AUTO SWEEP ATTN 18 8DBMV VF 30 KHz 100 0KHz 10 DB 30KHz RBW AUTO CALIBRATOR This menu is not accessible when the 2715 is in the CATV mode When the 2715 is in the CATV mode and CATV APPL is pressed the CATV Measure ments pages come up on the screen Disable the CATV mode by pressing CATV APPL 8 0 6 43 Spectrum Analyzer Menus 6 44 Measuring Signal Bandwidths The Applications menu automates some routine but time consuming spectral measurements It enables you to quickly determine the following m Signal bandwidths m Normalized noise amplitudes Carrier to noise ratios W Occupied bandwidth m deviation W Search for signals in a specified frequency range Most of the items in this menu are toggles that turn the indicated measurement mode on and off However you can specify certain measurement parameters using item 9 SETUP TABLE Because several of the measurement modes make use of the markers you can also exit from those modes by tur
296. ls 4 30 17 Use the FREQ MKRS knob to place the marker near the calibration signal In general place the marker near the signal of interest If you do not turn on the marker the signal nearest center screen is measured 18 Set the reference level so the signal peak is within one division of the top graticule line 19 Press CTR MEAS TRKG The calibration signal is recentered and the amplitude and frequency of the centered signal are read out at the upper right of the screen preceded by a C counter The counter readout provides the most accurate frequency determination available on the 2715 and its resolution can be set to 1 Hz if desired The counter readings disappear when a control setting is altered The marker and counter amplitude readouts are equally accurate However the signal amplitude indicated by the position of the marker relative to the graticule may differ slightly from the readout The readout is more accurate because it contains no display nonlinearities The center frequency and counter measurements are also equally accurate but in general the counter readout is more precise 20 To look closely at the calibration signal third harmonic place the marker near the third harmonic approximately 280 MHz 21 Press CTR MEAS TRKG The calibration signal third harmonic is now the new center frequency and its frequency and amplitude are displayed at the top of the right hand readouts 22 Press MKR
297. lues Test results can be displayed and stored Stored or current results can be printed if you have an RS 232 interface installed in the 2715 NOTE This measurement has no meaning for channels in which the aural carrier uses AM modulation You make selections and run tests using the CATV MEASUREMENTS submenu AURAL FM DEVIATION which provides the following choices 0 RUN FM DEVIATION INTERACTIVE 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 SET UP AURAL FM DEVIATION 6 ENTER ADJUSTMENT MODE 9 LEAVE AURAL FM DEVIATION Note that the RUN FM DEVIATION selection indicates the measurement mode in this example interactive is selected You use the SET UP AURAL FM DEVIATION selection in the above menu to do the following W Change measurement modes m View or change the selected measurement time The SET UP AURAL FM DEVIATION submenu provides the following choices 0 INTERACTIVE RESUME ACCEPT 1 AUTO 5 MEASUREMENT TIME 0 17MIN When you select MEASUREMENT TIME you are prompted to enter a new value for the measurement time Use the keypad to enter the new time in minutes 0 17 minutes to 1440 minutes If the value you enter is outside the range an OUT OF RANGE message displays and the measurement time is set to the closest limit 2715 User Manual Measurements Auto Mode Interactive Mode 2715 User Manual Auto
298. lution bandwidth filter and any video filter that is active and the FM discriminator when FM detection is selected Reset the 2715 controls according to the following settings box 100 0MHz AUTO SWEEP ATTN 10DB 28 8DBM VF WIDE 20 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR The signal track feature of the 2715 continuously repeats the center measure operation On each sweep the signal nearest midscreen is remeasured and recentered This is useful for keeping a slowly varying or jittering signal centered for close observation 26 Press CTR MEAS TRKG twice to activate signal track The term TRKG appears in center screen indicating that the 2715 is in the signal track mode If you turn the tuning knob while a sweep is underway the signal will be displaced a bit during the next sweep On the following sweep the signal is recentered The frequency readouts change because the tracking mode continu ously repeats the center measure feature If the signal being tracked falls below a preset threshold see Setting the Signal Threshold on page 6 22 tracking halts and the message NO SIGNAL FOUND ABOVE THRESHOLD is displayed The message is accompanied by a beep When the signal rises back above threshold signal track automatically resumes 27 Simulate signal loss and recovery by turning the calibrator off and then back on again The audible beep makes this signal track mode useful as an amplitude threshold detector You can also
299. ly m If the signal amplitudes are less than 3 dB different they are resolved when their frequency separation equals the resolution bandwidth m For signals more widely separated in amplitude and frequency let A be the amplitude difference Then 1 24 x resolution BW where F is the required frequency separation This rule is based on the fact that the 2715 s 60 dB filter bandwidths tend to be approximately 7 times the 6 dB bandwidth and assumes the filter roll off is approximately linear in dB Using this condition if the signals are 30 dB different in amplitude A then they have to be separated by approximately 2 4 x resolution BW 2715 User Manual Dedicated Controls 2715 User Manual 8 Set the span to 2 0 MHz div The resolution bandwidth readout indicates 300 KHz 9 Press in the RES BW function block to change the resolution bandwidth Notice that the noise floor increases approximately 12 dB as you switch from 300 KHz resolution bandwidth to 5 MHz The reason for this rise in the noise floor is that the noise coming through a filter is proportional to the filter bandwidth A wide filter passes more white noise components frequencies than a narrow filter Consequently more noise comes through a 5 MHz filter than through a 300 KHz filter The LED below the RES BW AUTO key went out indicating that the resolution bandwidth is no longer being automatically selected and the resolution bandwidth readout
300. ly being automatically selected by the 2715 In AUTO mode the tuning increment is as shown in Table 6 2 6 21 Spectrum Analyzer Menus Center or Start Frequency 6 22 Setting the Signal Threshold Table 6 2 AUTO Tuning Increment Span div Resolution Bandwidth Filter Tuning Increment Zero span 300 Hz 3 kHz and 30 kHz 0 033 of RBW 1 kHz 10 kHz 100 kHz and 1 MHz 0 05 of RBW 300 kHz 20 kHz 1 Because of the readout resolution this appears as 3 and 4 MHz on alternate clicks of the knob in MAX SPAN 2 Slowly press 8 twice The tuning increment progresses from AUTO to PROGRMD programmed and back to AUTO again If programmed tuning is selected see Pro grammed Tuning on page 6 24 you can specify whether the center frequency marker frequency or keypad entered frequency increment will be used as the tuning increment The following steps show how to toggle between Center or Start Frequency 3 Choose item 9 from the Marker Frequency menu to bring up the setup table The first item toggles frequency control between center and start frequency When start frequency is selected the FREQ MKRS knob controls the frequency at the left edge of the display rather than the frequency at the center 4 Choose item 0 from the setup table The spectral display reappears but the center frequency bright spot is now moved to the left edge of the screen and the frequency readout is preceded by the letters SF as in SF
301. m the SWP TRIG menu 10 If the screen goes blank readjust the LEVEL control The sweep is triggering on a sample of the AC power line voltage The display may be slowly drifting or stationary TV sweep rates are nearly harmonically related to line frequency but small fractional hertz differences create the slow drift 11 Turn on the readouts 100 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF 300KHz 1 0MHz 10 DB 300KHz RBW AUTO Item 4 TV LINE of the Sweep Trigger menu is one of two internal triggering modes that are particularly useful for time domain analysis of television signals A horizontal sync pulse begins each TV line You can designate the TV line standard in use NTSC PAL SECAM or OPEN and how the line is selected using item 9 SETUP TABLE When CONTINUOUS line triggering is selected any sync pulse will trigger the sweep KNOB SELECTABLE and KEYPAD ENTRY modes enable you to select a particular horizontal sync pulse as the trigger signal The selected line is displayed at the bottom of the right on screen readout column Choosing any HORIZONTAL LINE TRIGGERING mode from the SETUP TABLE also selects the TV LINE trigger mode The following steps show how TV line triggering works 1 Connecta short antenna or CATV tap to the 2715 input as outlined in Appendix B Broadcast AM FM and TV Signal Sources 6 85 Spectrum Analyzer Menus 6 86 Change the resolution BW to 5 MHz Tune to a strong TV video carri
302. m which each test is run equivalent to selecting 0 RECENTER CHANNEL xx from the CATV Measurements menu page one Sets sweep to single sweep mode acquisition mode to peak detect and selects 5 MHz video filter bandwidth Sets span div so that the screen covers one channel width or 50 KHz div for FM channels Sets the resolution bandwidth to 100 KHz for FM channels otherwise sets it to 300 KHz Sets the time div based on measurement mode video modulation polarity channel scrambled status and span div Tunes to the center of the channel takes a sweep and adjusts the reference level up in 10 dB steps if max signal is off the top of the screen If the channel is not a dual aural carrier TV channel identifies and measures all carriers in 10 dB div if the channel is a dual aural carrier TV channel sets span to 50 kHz div If you select FAST AMPL measurement mode the 2715 executes the preceding common steps followed by these steps for each carrier in turn If a dual aural carrier TV channel tunes to the carrier in 50 KHz div and 100 KHz resolution bandwidth Identifies the carrier and measures amplitude in 10dB div Adds flatness correction to the amplitude or amplitude relative to visual carrier values measured in 10 dB div and stores results If you select ACCUR AMPL measurement mode the 2715 executes the common steps listed earlier followed by these steps for each carrier in turn If a dual aural carrier TV channel tune
303. main representation of CW and noise like signals Just as on a conventional oscilloscope you can choose the input signal an external signal applied at the back panel of the 2715 or the AC power line as the trigger source You do this by selecting INTERNAL EXTERNAL or LINE trigger from the SWP TRIG menu 6 83 Spectrum Analyzer Menus The INTERNAL EXTERNAL and LINE trigger modes cause the sweep generator to start a new sweep when the trigger signal amplitude crosses a threshold determined by the setting of the LEVEL control inner knob to the left of SWP TRIG If the 2715 is placed in zero span and linear amplitude mode the resulting waveforms resemble those that you would see on an oscilloscope detected signal amplitude vs time Internal triggering requires the signal to be at least one division in amplitude and is most often used for time domain analysis If internal triggering is used for spectral analysis the triggering signal must be tuned to the left edge of the spectral display The LEVEL control adjusts a threshold so that the sweep begins when the amplitude of the input signal crosses that threshold 1 Connect a short antenna or tap to the 2715 input as outlined in Appendix B Broadcast AM FM and TV Signal Sources 2 Tune to a strong television video carrier and adjust the signal height to near the reference level 3 Setthe 2715 to LIN mode zero span and 5 MHz resolution bandwidth 4 Setthe sweep
304. marker on the 500 MHz peak The difference is 200 MHz 14 Select item 5 TRANSPOSE MARKERS from the Marker Frequency menu 15 Turn the FREQ MKRS knob The movable marker has become the reference and the old reference is now the movable marker 16 Move the marker to the 200 MHz peak and note the frequency difference 17 Exit from delta marker mode 6 18 2715 User Manual Spectrum Analyzer Menus Changing the Knob 2715 User Manual Function 100 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF WIDE 20 0MHz 10 DB 5MHZ RBW AUTO CALIBRATOR The knob is normally used to vary the center start frequency marker position or the video line selection The following procedure describes how to measure the frequency difference between the calibrator signal and each of its harmonics but you could use the same procedure to measure any series of signals across the whole range of the 2715 1 Enter the delta marker mode with both markers at the calibrator signal peak 2 Callup the Marker Frequency menu 3 Select item 2 KNOB FUNCTION The Knob Function menu appears Currently the knob is controlling the markers as you would expect in delta marker mode 4 Select item 0 from the Knob Function menu to change to frequency control 5 Press MKR FREQ The spectral display reappears 6 Rotate the FREQ MKRS knob several clicks clockwise Notice how the center frequency increases and the spectrum slides to the left One mark
305. mble Figure 6 12 100 lI REF 100 38MHZ ATTN ME T VE 10 1 0MHZ l 10 DB 5300 2 RBW 20 i 30 i 40 Du 5 25 60 HH to T 1 I N I M gt dB Figure 6 12 Portion of U S Broadcast FM Band 6 52 Press CATV APPL to return to the Applications menu Press 4 to select OCCUPIED BW The spectral display reappears with both markers active Set the span to 25 kHz div and recenter the signal if necessary The right hand data column will display something similar to the following OBW 57 36KHZ 90 2715 User Manual Spectrum Analyzer Menus 2715 User Manual Because the signal varies considerably from sweep to sweep the markers jump around the screen and you will not get a consistent occupied BW reading 8 Activate MAX HOLD in register B and turn off register D Remember that the markers are present only on the highest priority waveform In a short time a broad spectral peak develops and the OBW reading begins to settle to a constant value Figure 6 13 shows a typical MAX HOLD waveform from an FM stereo broadcast The relatively sharp skirts near 70 kHz denote the upper and lower limits of frequency deviation Markers Denote Occupied Bandwidth 100 100 38MHZ 118 8DBMV 50 0KHZ 7 300 KHZ RBW RZ Fi
306. measurement is also reported but not stored The following procedure shows how to make a CARRIER TO NOISE or DESIRED to UNDESIRED measurement 1 3 Press CATV APPL to call up the CATV MEASUREMENTS menu See Figure 5 1 Press 5 to select the CARR NOISE DESIRED UNDESIRED measure ment menu This displays the following options 0 RUN C N D U 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 SET UP CARRIER NOISE 7 IN SERVICE 9 LEAVE CIN D U Press 7 to toggle between normal or in service basis 2715 User Manual Measurements 2715 User Manual 4 Press 5 to call up the CARRIER NOISE setup menu test modes This gives you the following options 0 INTERACTIVE 1 AUTO 2 AUTO with PAUSE FOR CARRIER OFF 5 NOISE NORM D BW NOTE Option 2 is not available if IN SERVICE is selected in the CARRIER TO NOISE menu If the channel to be measured is digital the measurement is made with option 2 no matter which mode you selected In Interactive Test Mode you will be prompted to place the marker on the noise floor at some time during the measurement NOTE When measuring Carrier to Noise on an in service basis in interactive mode the apparent noise level displayed will be higher than the true noise level This is because the gating is not compatible with video filtering and visually the dominant feature of
307. ment 5 40 Initial Setup 5 3 Input Power Limitations 5 2 MODULATION DEPTH Measurement 5 28 Preliminary Information 5 1 Typical 2 12 Center Measure 4 29 Center or Start Frequency Selection 6 22 CHAN FREQ 3 4 Change Menu Status 6 2 Changing Acquisition Mode 6 36 Changing Reference Level Units 6 5 Channel Entry 4 4 Arrow Keys 4 4 Keypad Entry 4 5 Channel Skip Procedure 5 26 Index 1 Index Channel Table Editing 5 7 Channel Table Files 6 76 Channel Table Selection 2 11 5 6 5 7 Communication Ports Configuring GPIB Configura tion 6 69 Communications Ports Configuring 6 67 RS 232 Configuration 6 68 Connectors 3 2 Control Panel Arrow Keys 2 8 Dedicated Controls 2 8 Function Blocks 2 8 Control Panel Basics 2 8 Controls 3 2 FREQ MKRS 3 3 MKR Arrow Keys 3 4 Three Fundamental 2 8 Cooling 2 2 Counter Resolution 6 23 Create an Antenna Table 6 13 CROSS MODULATION Measurement 5 60 CTB CSO Measurement 5 49 Automatic Mode 5 50 5 54 Automatic With Pause Mode 5 50 5 56 Interactive Mode 5 50 5 53 Single sweep Mode 5 51 5 57 5 58 Typical CTB CSO Measurement Results Display 5 54 5 59 CTR MEAS TRKG 4 29 4 32 CTR MEAS TRKG 3 3 Curve Files 6 76 D D Register 4 24 Damage to Spectrum Analyzer See spectrum analyzer Damage Precautions to Prevent 2 2 Date and Time Setting 6 75 DBUV M Antenna Factors 6 15 Create an Antenna T
308. meters as follows Item 3 REF LEVEL UNIT DBM Item 6 EXTERNAL ATTEN AMPL 4 6 7 Spectrum Analyzer Menus 6 8 Setting the First Mixer Input Level In this case you select the dBm unit via INPUT 3 0 and the 50 source because the 2715 is matched to the 75 Q side of the minimum loss pad and the signal really is being terminated in a 50 Q impedance Further it is the attenua tion of the pad that is entered under item 6 and not its insertion loss The 7 5 dB accounts for both the insertion loss and the fact that the signal at the input to the minimum loss pad is 1 9 dB less than it would be if the 50 source were connected directly to the 2715 2715 Source Minimum Loss Pad Input 50 Q 43 3 Q gt 2 49 86 7 Q 50 77 Figure 6 3 75 50 Matching Minimum Loss Pad If in doubt whether the pad is needed compare a measurement with the pad to the same measurement without the pad If there is no significant difference omit the pad In some cases such as carrier to noise measurements the use of a pad may drop your system noise level below the 2715 noise floor In such cases the pad cannot be used Removing the pad typically does not distort carrier to noise measurements When a 50 Q source is frequently used you can store the settings above in one of the STORED SETTINGS registers see the UTIL menu discussion on page 6 60 then you merely have to recall the settings each time a 50 Q
309. mode runs until the user selected measurement time elapses or you terminate or abort it and then terminates with the measurement results dis played This mode can be used in System Test Programs since it does not require user interaction When you initiate an auto FM deviation measurement the 2715 does the following 1 Checks if the channel table specifies this channel as TV or FM If the channel is specified other than TV or FM the measurement is aborted 2 Tunes to the aural carrier of the current channel as specified in the channel table and places a marker at the aural carrier location 3 Sets the RBW and VF to 100 kHz 4 Performs a center measure to count and recenter the aural carrier 5 Enables ZERO SPAN selects FM Deviation sets sweep time to 100 ms div enables waveform C as the MIN HOLD destination and turns on min hold 6 Continues to sweep while waveform C accumulates peak deviation until one of the following occurs W You press W terminates test and saves results W You press Z aborts test and does not save results A GPIB Device Clear Command DCL is received aborts test and does not save the results W The user selected time limit is reached 7 Computes the result as a mean peak deviation after rejecting widely deviating readings It computes the mean and standard deviations of all the data in waveform C discards the data more than two standard deviations from the mean and computes a new me
310. modulation for any channel that uses positive video polarity Frequencies above 1 8 GHz are not supported by the Cable TV RF Measurements Software The 2715 Spectrum Analyzer with either Option 50 or Option 75 installed is capable of frequencies up to 2 15 GHz For frequencies above 1 8 GHz you are limited to the 2715 front panel to create and edit the channel tables 2715 User Manual Measurements Selecting a Channel Table Editing a Channel Table Opt 50 and Opt 75 Only 2715 User Manual There are two sources of channel tables one source is the three default tables STD HRC and IRC and the other source is the unlimited user defined tables Up to seven of these user defined tables can be stored in NVRAM in the 2715 Press CAT V APPL 8 1 to call up the channel table menu then press number corresponding to the desired channel table to select the table Press any menu button to return to the spectral display Press CAT V APPL 8 7 or shortcut UTIL 9 8 to call up the channel table edit function Press the number s corresponding to the desired channel table to select a table for edit Figure 5 2 shows the STD table with SCRAMBLED element selected Select the element to be edited by turning the FREQ MKRS knob and incrementing through each field until the desired element is highlighted reverse video NOTE If you assign a channel frequency above 1 8 GHz the channel table will be unusable by the
311. mpted to enter a new mixer input level You can enter values from 50 dBm to 20 dBm in 2 dB steps Try 20 dBm and 40 dBm while observing the level of the noise Because the RF attenuation is increased by the same amount the first mixer input is decreased and the noise floor rises as the mixer level is reduced When you are done experimenting set the mixer input level back to 30 dBm 100 0MHz AUTO SWEEP ATTN 0 0DBMV VF 300KHz 5MHz 10 DB 300KHz RBW AUTO The 2715 is equipped with an internal preamplifier The preamplifier can be very useful when measuring cable TV noise see Measuring Carrier to Noise Ratios on page 6 46 or other signals near or below the normal 2715 noise floor It is also useful for increasing the sensitivity of radiated RF energy measurements leakage etc The nominal gain in sensitivity using the preamplifier is 12 dB Above 600 MHz the preamplifier remains usable and useful but its flatness rolls off somewhat and is not specified To be effective the preamplifier must be used with no RF attenuation The preamplifier is not normally turned on because it can easily result in overdriving the first mixer The signal amplitude at the first mixer with the preamplifier on and no RF attenuation is equal to the input signal level plus approximately 18 dB that is a 10 dBmV signal would probably overdrive the first mixer Total signal amplitude greater than 0 dBmV at the input to the 2715 with the pre
312. n off the line The following steps show another way to set the level of the line 4 5 6 Turn on the marker and set it at the peak of the calibration signal third harmonic Press DSPL 8 Press 3 to select DISPLAY LINE TO MARKER The spectral display reappears with a horizontal line at the marker position This provides a convenient way to identify all signals greater or less than another signal If the marker is not turned on when item 3 is selected you receive an error message 7 8 10 11 12 13 Press DSPL 8 Press 4 to select LIMIT DETECTOR The end of line status indicator changes to OVER the display line has been made an upper limit If an on screen signal goes over the limit the audio alarm sounds Press DSPL to return to the spectral display The alarm should be sounding When the limit detector and the display line are both selected the marker automatically turns on and moves to the highest signal peak on screen This feature enables you to quickly read the amplitude of the largest signal after the alarm alerts you that the limit has been exceeded Press DSPL 8 Press 2 and enter a new value of 23 8 dBmV for the display line The alarm should stop because all signals are now below the limit Press DSPL 8 4 The status indicator changes to UNDER The display line has now changed to a lower limit the alarm will sound when all signals on screen are under the limit
313. n use spectrum analyzers to detect spurious signals align transmitters and receivers and check specifications The Tektronix 2715 Cable TV Spectrum Analyzer is a portable cable TV radio frequency RF scanning spectrum analyzer for use in the field or in the shop It weighs less than 22 165 9 5 kg and can be equipped with a battery and inverter for use in locations without AC power The user interface is simple enough for the beginner but versatile enough to satisfy an expert Fundamental cable TV CATV measurement parameters such as center frequency span division and reference level are automatically set when you select a channel table and channel In nonCATV mode measurement parameters can be controlled directly with dedicated keys You can display a spectrum by using only three controls Call up menus enable you to automate operations such as bandwidth or carrier to noise ratio measurements and to directly enter front panel control settings Measurement parameters and results are displayed on screen To increase measurement flexibility the 2715 Cable TV Spectrum Analyzer has the following standard features m Automated CATV measurements including in service measurements of carrier to noise C N composite second order CSO and in channel response ICR m Frequency corrected YIG oscillator for high frequency accuracy you can change the default oscillator settling delay time to optimize settling time for your particular us
314. nal which varies or regulates some characteristic of another signal Modulation The process of varying some characteristic of a signal with a second signal Modulation Envelope The curve limiting the carrier amplitude of an AM signal Multiple Display Memory A digitally stored display having multiple memory sections which can be displayed separately or simultaneously Noise Unwanted random disturbances superimposed on a signal which tend to obscure it Noise Floor The self noise of an instrument or system that represents the minimum limit at which input signals can be observed The spectrum analyzer noise floor appears as a grassy baseline in the display even when no signal is present Noise Sidebands Undesired response caused by noise internal to the spectrum analyzer appearing on the display around a desired response Nonvolatile RAM NVRAM A type of random access memory RAM which does not lose its contents when power is switched off Oscilloscope An instrument for displaying a time domain representation of an electrical signal displays the amplitude of an input signal as a function of time Peak Detection A detection scheme wherein the peak amplitude of a signal is measured and displayed In spectrum analysis 20 log peak is often displayed Glossary 7 Glossary Glossary 8 Phase Lock The control of an oscillator or signal generator so as to operate at a constant phase angle relative to a stable re
315. nation Waveform D 3 Appendix D Global Resets D 4 Fragile Settings Normalization Values m Ensemble Averaging Mode m Ensemble Averaging Number of Sweeps m B C Minus A Offset Mode Display Acquisition Mode PEAK MAX MIN m Display Line Value CATV Applications Menu Items m Bandwidth Display dBc Value W Occupied BW percent m Carrier to Noise Reference Bandwidth m Normalized Noise Reference Bandwidth Demod Menu Items m Video Monitor Mode BROADCAST SATELLITE Sync Polarity Video Polarity Fragile settings are those that are reset during any reset cycle Any settings not covered by the previous categories are fragile Resets occur as follows During POWER DOWN UP INITIALIZE INSTRUMENT SETTINGS and POWER UP DIAG AND REBOOT cycles settings are reset to user defined power up if it exists otherwise settings are reset to default values During RECALL LAST POWER DOWN cycle settings are reset to last power down settings During RECALL FACTORY DEFAULT POWER UP settings are reset to the factory default settings During RECALL USER DEFINED POWER UP and RECALL NUM BERED SETTINGS cycles settings are reset to the specified settings storage register The normalization values are modified by executing some or all of the normal izations These values are only lost in the case of certain NVRAM failures The values being used by the instrument may be set to default values with the service menus Normalization valu
316. nd press the arrow keys The movable marker jumps in the direction of the arrows just as the single marker did and the readouts behave as if you had manually moved the marker 2715 User Manual Dedicated Controls Miscellaneous Controls 2715 User Manual PEAK FIND You can use PEAK FIND to automatically position a marker on the highest signal on screen 42 Ensure that the markers are turned off 43 Set the center frequency to 275 MHz 44 Press PEAK FIND The marker is automatically turned on and jumped to the peak of the calibration signal at 100 MHz The 2715 detected the highest signal on screen and automatically moved the marker to it After the move the 2715 behaves exactly as if you had moved the marker there manually 45 Press MKR 9 to move the marker to the peak of the third harmonic 46 Press PEAK FIND again The marker moves back to the fundamental the marker peak find feature always locates the highest peak on screen We have discussed and experimented with all the 2715 functions except the menu keys and a few miscellaneous controls The menu keys are covered thoroughly in Operating Basics section and the remaining miscellaneous controls will be covered briefly here NOTE Any control settings can be used PLOT Immediately below the VERT SCALE function block is a PLOT button that causes an optional printer or plotter to draw an image of the screen The on screen readouts are plotted on
317. nds between measurements Press CAT V APPL to display the CSO menu Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed Press 2 to display information concerning the tests performed A display resembling Figure 5 9 comes up To view other previously stored results press W or to stop viewing press Z eso STORED CHAN 71 09 AUG 93 12 00 00 20 30 4 BEATS MEASURED 56 TIMES AT 15 SECOND INTERVALS b VIEN RESULTS VIA EXTERNAL PORT 50 60 in L PRESS W TO 72 oor Figure 5 9 Typical Continuous Mode Results Display 17 Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 18 19 Press 4 to print all stored results of the measurement A printer must be connected to the 2715 Press 9 to exit this mode or continue to the next measurement mode 5 59 Measurements CROSS MODULATION Measurement 5 60 The spectrum analyzer has tw
318. ng decibels that yields an incorrect answer The display does not change but you may notice a pause while the 2715 carries out the noise measuring algorithm First the 2715 measures the average noise power in ZERO SPAN using a narrow bandwidth video filter see a better approximation of the average noise by pressing VID FLTR It then corrects the measured value for the difference between average and RMS amplitudes More corrections are added for the effects of log amplification and to account for the equivalent noise bandwidth of the resolution bandwidth filter not being exactly 5 MHz The resulting noise is then normalized to the specified bandwidth 8 Turn off the markers and the video filter To demonstrate the carrier to noise C N ratio feature of the 2715 we will measure the calibrator to 2715 noise floor ratio in a 5 MHz bandwidth However you are more likely to measure a carrier peak to system noise ratio but the technique is the same 9 Press INPUT 9 to turn on the calibrator 10 Press CATV APPL to call up the Applications menu 2715 User Manual Spectrum Analyzer Menus 2715 User Manual 11 Press 9 to select the Setup Table 12 Press 1 to select NORM BW FOR C N 13 Press 5 X to enter 5 MHz for the noise bandwidth for the carrier to noise C N measurement 14 Press BKSP to return to the Applications menu 15 Press 1 to turn on the C N feature The spectral display reappears with the f
319. ng menu 22 Press 2 4 IW Item 7 will update as you press W You are now ready to compile a parameter average There are four choices Begin with the max min display 23 Press 6 MAX MIN from the Ensemble Averaging menu The asterisk moves down to indicate MAX MIN is selected 24 Press 1 to start averaging The spectral display reappears and both status indicators for register A light At the bottom of the right hand readout column the number of sweeps averaged is displayed displayed only when the 2715 is in the non CATV mode When all 24 sweeps have been included in the average the readout stops indicating the number unless the A register is the only one turned on 25 Turn the D register on and off several times and note the difference Most of the sweep to sweep variations in the noise have disappeared Now we will repeat the experiment this time storing the MAX average in register B In this case only the 256 maximum values of each max min sweep are averaged and stored 26 Press DSPL 1 3 to select MAX 27 Press 8 repeatedly to select register B 28 Press 1 to start the averaging process Both status indicators for register B light the average peak value almost coincides with the upper edge of the MAX MIN average 29 Turn off the A register to see the average maximum by itself 30 Turn the A register back on 31 To store the MIN average in register C press DSPL 1 5 8 32 Press 1 f
320. ng options 0 RUN MODULATION DEPTH 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 SET UP ADJUSTMENT MODE 6 ENTER ADJUSTMENT MODE 9 LEAVE MODULATION DEPTH 4 Press 0 to run the Modulation Depth measurement After the measurement is complete the instrument displays the current results superimposed on the spectral display 5 Press CATV APPL to display the MODULATION DEPTH menu 6 Press 1 to store the results of the last measurement After a short period the RESULTS STORAGE COMPLETE is displayed 7 Press 2 to display results of the last measurement performed A display resembling Figure 5 4 on page 5 24 shows the percent modula tion Now you can choose to either view other previously stored results for this measurement by pressing W or stop viewing the results by pressing Z 8 Press Z to return to the MODULATION DEPTH menu 5 29 Measurements 5 30 ADJUSTMENT MODE 9 Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 10 Press 4 to print all stored results of the m
321. ngle Sweep 3 9 4 19 Skip Channels Procedure 5 26 Sounds 2 9 SPAN DIV 3 4 Span Div Operation 4 2 Arrow Keys 4 2 Keypad Entry 4 3 Max Span 4 3 Zero Span 4 4 Spectral Display In Menus 6 74 Spectral Display Mode 3 1 Spectral Display Mode Test Screen 3 1 Spectrum Analyzer Cooling 2 2 Damage or Defects 2 1 Installation 2 2 Missing Components 2 1 Returning 2 1 Storing 2 1 Start and Stop Frequencies Setting 6 17 Stored Settings Protecting 6 75 Stored Signals Subtracting 6 32 Storing 2 1 SWEEP 4 17 Arrow Keys 4 17 AUTO 4 18 SINGLE SWEEP 4 19 Sweep Generator Free Running 6 83 Sweep Holdoff Changing 6 74 Sweep Rate Setting 6 88 SWP TRIG Menu 6 83 Free Running the Sweep Generator 6 83 Manually Scanning 6 89 Oscilloscope Trigger Modes 6 83 Setting the Sweep Rate 6 88 TV Line Trigger 6 85 TV Video Field Triggering 6 88 2715 User Manual Index System Checkout Factory Default Settings 2 4 Initial Normalization 2 5 Turning On the Spectrum Analyzer 2 4 User Defined Power Up Settings 2 4 Warmup Time 2 4 System Configuration 6 67 Configuring the Communications Port 6 67 Confirming Installed Options 6 77 File System 6 75 Protecting Files 6 77 Protecting Stored Settings 6 75 Selecting the Screen Plotter Configuration 6 70 Setting the Date and Time 6 75 T Terminator Keys 3 6 Terminators 2 9 Test Channel Selection 5 10 Test
322. ngs a To delete old settings press Y and then W to confirm the deletion Then store the current settings Turn the instrument power off and back on During the standby period the factory default power up settings are displayed but immediately afterwards the settings you just stored are automatically implemented At power up the 2715 restores the user defined power up settings if they exist following the standby period If they do not exist it uses the factory default settings If the user defined power up settings include a narrow span the NORMALIZATION SUGGESTED message may appear The message should disappear following warmup as soon as you use a control The remaining items on the Stored Settings Displays menu can be used exactly as you used USER DEFINED POWER UP SETTINGS The difference is that they are not automatically implemented at power up time or by the initialization selection they must be recalled from the Stored Settings Displays menu 6 7 8 9 10 12 13 14 15 16 17 18 Press INPUT 9 to turn on the calibrator Press CHAN FREQ 9 0 X to change the frequency to 90 MHz Press REF LEVEL 3 8 8 Y to set the reference level to 38 8 dBmV Press DSPL 1 to select ENSEMBLE AVERAGING Press 4 to select MEAN If the number of averages is not set to 16 press 7 and set number to 16 Press 8 repeatedly until A register is selected Press 1 to save a 16 sweep
323. ning off the markers One of the items SIGNAL SEARCH enables the 2715 to automatically detect and catalog any signals within a specified frequency range and above a desig nated threshold The signal amplitudes and frequencies are measured and the results can be displayed on screen or if you have a RS 232 port sent to a printer The 2715 measures signal bandwidth by detecting the signal peak and then finding the frequency points on the signal spectrum that are a designated number of dB down from the peak You specify the number of dB using the Application menu Setup Table The difference between the frequency points is the bandwidth Optimum resolution is obtained by spreading the signal across as large a portion of the screen as possible resolution is essentially plus or minus one frequency cell or 1 512 of the total span in PEAK acquisition mode For the following example on how to measure signal bandwidths you need to first change the resolution BW to 300 kHz This provides a simulated signal several divisions wide and equal to the width of the resolution BW filter 1 Press RES BW until RBW readout is 300 kHz 2 Press CATV APPI Item 0 indicates BANDWIDTH MODE 3 DB which means that by selecting this item the 2715 will measure the bandwidth of a displayed signal at points 3 dB down from its peak amplitude To measure the bandwidth at a point other than 3 dB down do the following steps 3 Press 9 to select SE
324. nnn Sess rU ee 5 12 Table 5 6 IRG 3 56046 retexefterr ate uere ae e ees 5 15 Table 5 7 Examples of Cycle Delay Target Line Duration Interaction ool gy Rutrum RR RE 5 31 Table 5 8 Locations of Noise Measurement 5 37 Table 6 1 Equivalent Decibel Voltage Values 6 12 Table 6 2 AUTO Tuning Increment 6 22 Table 6 3 The File System 6 76 Table 6 4 Additional File System eee 6 76 Table A 1 CATV Characteristics _ A 2 Table 2 Frequency Related Characteristics A 11 Table 3 Frequency Amplitude Related Characteristics A 13 Table A 4 Amplitude Related Characteristics A 14 Table A 5 Input Output Signal Characteristics A 17 Table 6 Power Requirements A 19 Table A 7 Supplementary Characteristics Due to Options A 19 Table A 8 General Characteristics A 20 Table A 9 Environmental Characteristics A 21 Table A 10 Physical Characteristics A 22 Table A 11 Certifications and Compliances A 23 Table A 12 Safety Certification Compliance A 24 Table A 13 Safety Standards A 24 Table E 1 9 Pin Female to 9 Pin Female Null Modem Cable E
325. nt channel leakage ACL measures the average power in the channel under test and then measures the average power in the adjacent channels The results is a ratio of these two numbers The adjacent channels must not be active during the measurement The adjacent channel leakage measurements only run on digital channels The measurements should be made at the output of the modulator at the head end At this location the adjacent channels cannot be seen so the ACL can run without requiring that you the turn adjacent channels off ACL measurements may be made beyond the combiner but four channels the two adjacent channels on each side of the channel under test must be turned off before the measurement is made ACL measurements may be selected in the menu to occur on either the lower side upper side or both sides of the channel under test Only the worst ACL encountered is reported If any coherent spurious signals are found in the adjacent channels the largest is reported to the instrument screen but is not stored as part of the results The 2715 assumes that the adjacent channel is of the same type as the channel under test Both the measurements of the average power level of the channel under test desired and the average power level of the adjacent channel undesired are performed as described in DESIRED to UNDESIRED on page 5 38 The following procedure shows how to make an adjacent channel leakage measurement 1 Press CATV AP
326. ntents of memory B Visual Carrier Level The rms voltage of a channel s visual picture carrier considered as a sine wave at the peak of the modulation envelope measured across a termination impedance which matches the internal impedance of the system Volatile Nonvolatile Storage A volatile storage system is one where any total loss of power to the system will result in a loss of stored information Nonvolatile memory is not subject to the instrument power supply for its storage Waveform Subtraction A process wherein a saved waveform can be subtracted from a second active waveform Zero Pit Response An output indication which corresponds to zero input frequency Zero Span An operating mode in which the frequency span is reduced to zero 2715 User Manual Index Numbers 10 5 1 Vertical Scale 4 16 50 Ohm Source 6 7 A A amp B MAX HOLD 4 26 A B C Registers 4 22 Acquisition Mode Changing 6 36 Adding Titles and Labels Edit a Title 6 37 Adjacent Channel Leakage Measurement 5 47 Adjustments and Diagnostics 6 78 Aligning the Display 6 78 AM Transmissions Listening to 6 57 AM VOL 3 8 Amplification Attenuation External 6 6 Amplitude Measurement Process 2 13 Analog Display 4 21 Antenna Factors 6 15 Antenna Table Create 6 13 Antenna Table Files 6 76 APPL Menu 6 43 Measuring Average Noise 6 45 Measuring Carrier to Noise Ratios 6 46 Measuring Occupied Bandwidths OBW
327. number of signals detected is displayed at the end of item 3 DISPLAY RESULTS 14 Press 3 The SIGNAL SEARCH RESULTS table appears Five signals are listed the calibration signal fundamental and its first four harmonics The amplitude and frequency of each are indicated 15 Press CATV APPL twice to return to the spectral display 900 0MHz AUTO SWEEP ATTN 50DB 68 8DBMV VF WIDE 180MHz MAX 10 DB 5MHz RBW AUTO Measuring occupied bandwidths is similar to measuring signal bandwidths except that the 2715 determines the bandwidth that contains n of the signal s energy rather than the bandwidth enclosed by the x dB down points 2715 User Manual Spectrum Analyzer Menus 2715 User Manual To determine the occupied bandwidth the 2715 first sums the signal power in all 512 frequency cells of the displayed spectrum ignoring any contributions more than 40 dB below the signal peak This is the total displayed signal power P It then sums the power in the cells starting at the left hand edge of the screen until the accumulated power equals or exceeds the following lg 2 Ft Uc TOO Pt total signal power n percentage of signal power within the occupied BW It then performs a similar calculation starting at the right hand screen edge That is it finds the frequency cells both above and below the signal beyond which half the power not in the occupied bandwidth resides The frequency difference between the uppe
328. o methods for measuring cross modulation Time Domain NCTA National Cable Television Association and Frequency Domain You can select the method from the CROSS MODULATION measurement menu refer to Enable CROSS MODULATION Measurement on page 5 61 Both methods measure and record the cross modulation in the current channel For meaningful calibration both methods require using the system stimulation recommended by the NCTA This stimulation requires the following carriers except the channel under test must be synchronously modulated 100 with a horizontal rate square wave m The channel under test must carry an unmodulated CW carrier The two methods measure cross modulation effects on the CW carrier in fundamentally different ways The Time Domain NCTA method tunes the spectrum analyzer to the visual carrier frequency sets ZERO SPAN and then detects any modulation with an envelope detector A Fourier analysis is performed on the output of the detector to assess the amplitude of the modulation at the horizontal rate The result is scaled and reported in units of dBc The Time Domain NCTA method closely conforms to the recommended NCTA procedure This method is often thought to most accurately reflect the level of visible picture impairment However this may not be the best method for measuring sideband amplitudes since cross modulation can also occur as phase modulation which the envelope detector used by this method doe
329. o the C register for display on the screen This process continues until the user terminates the test by pressing W or Z At termination the last difference waveform is left saved in the C display 5 43 Measurements Running The Mode 2 Test 5 44 Enable FREQUENCY RESPONSE If mode 2 NO REF is selected the instrument is set up to sweep between the specified frequency limits The 5 MHz RBW is selected and the peak acquisi tion mode is installed The start and stop frequencies of the sweep are taken from the start and stop frequencies currently defined for the reference These default to the lowest and highest frequencies found in the channel table but can be changed by the user in the FREQ RESP SETUP menu The instrument then simply displays the raw sweep as it sweeps between those limits The following procedure shows how to make a frequency response measurement 1 Press CATV APPL to call up the CATV MEASUREMENTS menu See Figure 5 1 2 Press 7 to select the FREQUENCY RESPONSE measurement menu This gives you the following three options and displays the current frequency response reference if one exists 0 RUN FREQUENCY RESPONSE CURRENT REFERENCE Site Name Date Start Frequency Stop Frequency user defined name or lt NONE gt The reference name appears only if the test mode WITH REF is selected The string lt SITE NAME gt DATE START STOP is the default reference name assign
330. od the message RESULTS STORAGE COMPLETE is displayed 10 Press 2 to display the results of the last measurement performed A display resembling Figure 5 4 is displayed CARR LEVEL CURRENT CHAN 8 05 JAN 94 12 00 00 STD VISUAL 13 2 DBMV 181 239780MHZ AURAL 16 8DBC 4 500001MHZ PRESS W TO CONT Z TO ABORT Figure 5 4 Carrier Level Averaged Power Measurement Results The word CURRENT appearing at the upper right corner of the display means that you are looking at the result of the most recent measurement performed The word STORED appearing at the upper right corner of the display means that you are looking at a stored result for the particular measurement Stored results are displayed in sequence starting with the most recently stored result At this point you can choose to either go ahead and view other previously stored results by pressing W or stop viewing the results by pressing Z 11 If you have not already done so press Z to return to the CARRIER LEVELS menu NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 2715 User Manual Measurements 12 Press 3 to print the results of the last measurement performed A printer must be connected to the
331. of volts rms per division decibels per division watts per division or any other specified factor Depth of Modulation The difference between the maximum and the minimum of the RF envelope amplitude expressed as a percentage of the maximum RF envelope level Digitally Averaged Display A display of the average value of digitized data computed by combining serial samples Digitally Stored Display A display method whereby the displayed function is held in a digital memory The display is generated by reading the data out of memory Display Frequency The input frequency as indicated by the spectrum analyzer and expressed in hertz Display Dynamic Range The maximum ratio of the levels of two nonharmonically related sinusoidal signals each of which can be simultaneously measured on the screen to a specified accuracy 2715 User Manual Glossary 2715 User Manual Display Flatness The unwanted variation of the displayed amplitude over a specified frequency span expressed in decibels NOTE Display flatness is closely related to frequency response The main difference is that the spectrum display is not moved to center screen Display Law The mathematical law that defines the input output function of the instru ment The following cases apply Linear A display in which the scale divisions are a linear function of the input signal voltage Square Law Power A display in which the scale divisions are a linear funct
332. on bandwidth is set to 5 MHz and the readouts are turned off If a VITS line is specified in the channel table you should see that VITS line If a VITS line is not specified then you should see line 17 of the video signal If you wish to change the displayed line press READOUT and turn the FREQ MKRS knob to select the desired line then turn off the readouts View Picture provides demodulation of the video carrier on the current channel The instrument sets up for the video demodulation mode on the current channel with the following settings Frequency 1 5 MHz above Visual Carrier Reference Level Set for viewable picture Span Div Zero Span Sweep Time 5 us Div Resolution Bandwidth 5 MHz Both NTSC and PAL video channels are supported The instrument stays in this mode until the mode is deselected the channel is changed or another test is run Item 3 in the DEMOD menu BROADCAST AM VIDEO is displayed as ON any time VIEW PICTURE is enabled 5 69 Measurements 5 70 Listen To view the video picture press CATV APPL 3 Video monitor mode is automatically enabled Turn the outer LEVEL knob to obtain a full size and locked picture Also you can change the reference level to obtain the best contrast To disable the VIEW PICTURE mode press CATV APPL 3 again or DEMOD 3 This operation turns on either the FM or the AM demodulator according to the type of modulation on the channel If the
333. ontains related controls The central gray colored block contains the fundamental channel center or start frequency span and reference level controls For convenience one function block is dedicated exclusively to menu display The control panel and its major functional areas are shown in Figures 3 3 through 3 8 The Dedicated Controls section contains detailed discussions of the controls 2715 User Manual Operating Basics FREQ MKRS CTR MEAS TRKG 2715 User Manual Trace alignment controls and various input output connectors are located at the rear panel Figure 3 9 on page 3 10 shows the spectrum analyzer back panel and its connectors The alignment controls are discussed in Miscellaneous Controls on page 4 33 and the connector terminations are described in Appendix E External Input and Output The menu structures are shown starting on page 3 11 Some menu items are not present because they either are not available at the current menu level are intended primarily for factory calibration and troubleshooting or they apply to instrument options not currently installed A brief description of the function of each of the listed menu selections is given The functions of the menu selections are discussed in greater detail in the CATV Measurements and Spectrum Analyzer Menus sections FREQ MKRS PEAK CTR MEAS FIND TRKG Figure 3 3 The Frequency Marker Function Block In the n
334. or confugurations The menu shows the following 0 GPIB OFFLINE ADDR 2 RS 232 OFFLINE BAUD RATE If the GPIB port is currently active its GPIB address 0 through 30 is displayed at the end of the line Otherwise the line ends with OFFLINE If the RS 232 port is currently active its baud rate is displayed at the end of the line for example 9600 Otherwise the line ends with OFFLINE 6 67 Spectrum Analyzer Menus 6 68 RS 232 Configuration 4 Press 2 to select RS 232 from the COMMUNICATION PORT CONFIG menu Several choices are offered in all cases the 2715 settings must match those used by the controller or printer plotter Item 0 STATUS enables you to toggle the RS 232 port on and off line The port must be on line to communicate with any other device Item 1 BAUD RATE cycles through the baud rate of the port Possible baud rates are 110 600 4800 150 1200 9600 300 2400 Normally you set this parameter to as large a value as possible to speed up data transfer However the controller or the printer plotter must support data transfers at the same rate When 110 is chosen two stop bits are automatically selected for any other value 1 stop bit is automatically selected The default value is 9600 Item 2 DATA BITS determines the number of data bits per word The default is 8 bits and is required for binary data transfers Seven bits can be used for ASCII character transfers Item 3 PARITY
335. ormal spectral display mode the knob changes the center or start frequency by 0 02 of the span div per click In programmed or tabular tuning modes frequency is changed by the designated tuning increment per click In ZERO SPAN frequency is changed by a percent of the resolution BW per click see Selecting the Tuning Increment on page 6 21 In other modes the knob may control marker horizontal position or video line number One press initiates a center measure The frequency of the signal nearest center screen or nearest the marker if active is measured and made the new center frequency Signal frequency and amplitude are displayed at the upper right of the screen Two quick presses enter the signal track mode continuously repeated center measures enabling a drifting signal to be tracked signal frequency readout is optional in this mode and is enabled by pressing MKR FREQ 9 1 A third press returns to normal operation 3 3 Operating Basics PEAK FIND MKR A OFF MKR 4 Keys CHAN FREQ SPAN DIV 3 4 The marker is moved to the highest on screen signal peak turns the marker on if it is not active independent of the detection threshold The first press turns on a single marker at center screen its position is control lable with the FREQ MKRS knob A second press fixes the position of the first marker and turns on a second marker delta marker mode its position is controllable with the FREQ MKRS knob A t
336. orner of the display If the sync tip voltage varies during the adjustment process the 2715 automatically adjusts the reference level to keep the sync tips at the top of the screen and displays the new sync tip voltage value m User Prompt instructions on how to quit the adjustment mode W Z To Quit appear in the lower left hand corner of the screen W Error Message Out Of Range appears in the center of the screen if the input voltage is outside the reference level ranges for the 2715 To use the adjustment mode adjust the modulator so that the peak white level extends down into the displayed target line Some differences may occur in the measured modulation depth values depend ing upon the exact point to which you adjust the peak white level If you adjust the peak white level to the top or bottom edge of the target line you may find a 0 4 to 0 8 difference in the measured value It is best to adjust the peak white level to the center of the target line 5 31 Measurements AURAL FM DEVIATION Measurement 5 32 The aural FM deviation measurement records and displays the peak frequency deviation of the aural carrier on the current channel There are two user select able measurement modes interactive and auto Both modes require that you select a measurement time from 10 seconds to 24 hours in minutes The mode and the measurement time defaults to the last values used if you do not select new va
337. orrect value Pressing a terminator key only Y or Z in this case determines the units The Y key can represent units of KHz uSEC uV or dBx Because the reference level immediate entry mode requires decibels and because the reference level unit is dBmV the 2715 correctly interprets the currently displayed value as 21 3 dBmV when you press Y If a frequency unit had been required the 2715 would have interpreted your entry as 21 3 kHz when you pressed Y On the other hand had you wanted to enter a negative reference level you would have pressed Z for dBx The 2715 ignores the W or X terminator keys because they do not represent acceptable reference level units REF LVL STEP The calibration signal peak is now less than one division below the reference level 5 Press REF LVL STEP Nothing happened on screen but the red LED next to the key is illuminated This indicates that the rate at which the reference level arrow keys change the on screen signal height and reference level is now 1 dB per press rather than 10 dB 2715 User Manual Dedicated Controls Enhanced Versatility Res BW 2715 User Manual 6 Press three times The signal peak rises until it is just above the reference level and the readout indicates 18 3 dBmV You cannot get the signal peak closer to the reference level without entering a new reference level in the immediate entry mode 7 Press 4 ten times The signal
338. osition Channel Band Channel limits defined in the current channel table If the last selected channel does not exist such as when NVRAM has been erased the default channel becomes Channel T 7 labeled 907 on the display the first channel in the first channel table Measurements The CATV MEASUREMENT will remain active until it is explicitly disabled by pressing CATV APPL 8 0 General CATV 2715 Mode If the 2715 is in the CATV mode press CATV APPL and the CATV mode comes up on the screen If the 2715 is not already in the CATV mode press CAT V APPL 8 0 from the spectral display The firmware centers the channel on the screen then displays the top level PG 1 of the CATV MEASUREMENTS menu The menu resides on two pages You can toggle between the menu pages by pressing 9 from either page See Figure 5 1 CATV MEASUREMENTS PG1 gt 0 RECENTER CHANNEL 1 CARRIER LEVEL AVG POWER 2 CARRIER SURVEY 3 MODULATION DEPTH 4 AURAL FM DEVIATION 5 CARR NOISE DESIRED UNDESIRED 6 HUM LFD 7 FREQUENCY RESPONSE 8 CATV MEASUREMENTS SETUP 9 MORE gt CATV MEASUREMENTS PG2 0 ADJACENT CHANNEL LEAKAGE 1 VIEW MODULATION FIELD 2 VIEW MODULATION LINE 3 VIEW PICTURE 4 LISTEN 5 CTB 6 CSO 7 CROSS MODULATION 8 IN CHANNEL RESPONSE 9 MORE Figure 5 1 CATV MEASUREMENTS Menu Signal Types The 2715 is capable of making certain measurements on TV
339. ou selected an entry mode that requires a channel the 2715 correctly interprets the currently displayed entry as STD CH 8 Direct frequency entry capability is available from the front panel However the 1 GHz terminator is not available in the normal mode because it is reserved for channel selection You are now ready to perform a CATV measurement 2715 User Manual Getting Started 2 12 Typical CATV Measurement This example is one of several CATV measurements and allows you to measure the visual and aural carrier levels over the selected channel Note that the following are the only actions needed to make a measurement Select a channel table Select a measurement channel Select a measurement m Runthe measurement The channel table and measurement channel selected at power down will be remembered when power is reapplied to the 2715 Therefore the only thing that needs to be selected after that is the type of measurement Items 1 through 4 on the second page of the CATV MEASUREMENTS menu are toggle type functions For example if you select VIEW MODULATION LINE with CATV APPL 9 2 you get a preselected VITS line You must make the same selection or select another measurement to disable the line display 7 Press CATV APPL 1 to call up the CARRIER LEVELS menu 8 Press 0 to select run the Carrier Levels The 2715 starts the measurement routine much like performing a center measure on the visual
340. ow the waterfall mode records the shift 2715 User Manual Dedicated Controls 2715 User Manual 1 2 Division Displacement Gos 100 A REF 1 ATTN 40DB 10 0DBM i VF 300KHZ 5 0MHZ i 10 DB z 300KHZ RBW i 2 30 Registers A gs Oldest l Sweep CHAN i 50 5 4 tH TE CETTE TT TTT TTT TTT TTT 25 JE 60 c TT D HIERHER HE HEEL Newest Sweep Figure 4 1 Example of a Waterfall Display 25 Press SINGLE in the SWEEP function block to halt the waterfall action Thereafter each time you press SINGLE the waterfall will advance one trace 26 Press AUTO in the Sweep function block to exit from the single sweep mode and continue the waterfall display You do not have to view all the traces 27 Turn off the A and C registers 28 Turn off B and D registers 29 Turn A and C registers back on You can view any all or none of the registers Turn them all off and the analog display reappears However the 2715 is still in waterfall mode You cannot selectively erase a register or store new data in it without first exiting from the waterfall mode 30 Turn on all registers 31 Press SAVE ENABLE D to exit from the waterfall display mode All LEDs except the red D turn off and the waterfall display collapses to a single D register trace 32 Reset
341. ower directly to the RF INPUT The 1 mixer can be overloaded making accurate measurements impossible Also a power surge might raise the peak AC voltage above the maximum safe input level CAUTION The maximum safe RF and DC input levels are clearly printed near the signal input jack RF INPUT m Do not apply incorrect AC input power The 2715 will accept mains power up to 250 VACrms refer to Appendix Specifications for additional information It is unlikely that you will apply incorrect power while using standard plugs and receptacles in the normal working environment However in the field or during abnormal conditions you might have to connect temporary power Be certain that any power source connected to the 2715 applies less than 250 VACrms between conductors or between either conductor and ground To avoid damage to the source ensure that it is rated for at least 120 W operation m Do not allow moisture dust or other contaminants inside the case Electronic circuits do not mix well with water chemicals dust or grit The case is not water tight or air tight so avoid exposing your instrument to these or other contaminants Do not place liquid containers on or near the spectrum analyzer where they can be spilled into it Use the Travel Line rain cover Option 33 or other suitable covering when transporting the spectrum analyzer outside in inclement weather m Do not handle the spectrum analyzer with undue roughness
342. oximately two divisions down from the reference level but some of the calibration signal peaks fold over and point downward See Figure 6 7 15 Press DSPL 3 The waveform is now nearer the bottom of the screen where you can see it more clearly 2715 User Manual Spectrum Analyzer Menus 2715 User Manual B I Note folded over 50 30 signal peaks at i 100 MHz 200 MHz FRE 50 and 300 MHz CALIBRATOR o Figure 6 7 B C Minus A Offset to Center You have offset the difference between the B and A register waveforms which is always greater than zero to the top of the screen zero difference is at the reference level However values above the reference level appear at the bottom of the screen See Figure 6 8 The points labeled A and B in Figures 6 7 and 6 8 have exactly the same value in each figure Imagine that the screen curves backwards at the top and bottom until it joins itself forming a cylinder points of zero difference lie along the joint Now cut the joint and uncurl the cylinder allowing it to become a flat screen again Both the top and bottom of the screen represent zero difference with negative signal peaks descending from the top of the screen and positive peaks rising from the bottom 100 REF 400MHZ I ATTN F VF WIDE 100 OMHZ T 10 DB 75 R T 20 A 30 Note t
343. p menu This measure ment is the reference level that all subsequent measurements are referred to Up to 5 beats are measured The results are presented in terms of dBc relative to the carrier level measured at the beginning When the CTB and CSO measurement is done on a digital channel the average channel power is measured The Interactive mode and Automatic with Pause modes are used to perform the measurement This measurement is not available in the in service mode NOTE The or CSO test result may be marked with an asterisk This indicates when a beat signal is within 2 dB of the 2715 s noise level Under these conditions the displayed dBc value may be lower than the actual value that is the beats may have a smaller amplitude than the displayed value The gated CSO test result may also have 1000 2000 or 3000 added to its magnitude This indicates that certain events occurred during the measurement which may cause an inaccurate result If so the inaccuracy is on the conserva tive side the actual CSO will be weaker than the measured value If 1000 is added to the result the instrument detected that one or more of the quiet lines found at the start of the test were no longer quiet at the end of the test This can occur only on gated measurements If 2000 is added to the result the instrument increased the signal level at the Ist mixer input above optimum to ensure adequate signal level for accurately timed gating cont
344. point in the response and taking another measurement The 2715 then divides the difference between these measurements by two and presents the quotient as the measure ment result For this mode the IN CCHANNEL RESPONSE is usually measured at six frequencies which commonly correspond to burst frequencies of a test genera tor The default test locations are 0 5 MHz 0 5 MHz 1 MHz 2 MHz 3 MHz and 3 75 MHz all relative to the visual carrier NOTE Statutory proof of performance tests may require test frequencies other than the default values Frequencies entered into the 2715 s IN CHANNEL RESP SETUP menu items 2 through 7 must match the frequencies actually produced by your test generator If a sweep generator is used you may enter any frequency that is within the generator s range However do not enter frequencies that are closer than 500 kHz to the visual carrier When using a multiburst generator you must enter the frequencies that it actually produces If you are not sure which frequencies your generator produces consult your generator manual or use the 2715 to measure them Do not use the 2715 count function to measure the multiburst frequencies It may not produce accurate results on burst and pulsed signals NOTE The Out Of Range message may appear after running an In Channel Response measurement This message indicates one of these conditions m IN CHANNEL RESP SETUP menu test locations do not mat
345. power has been turned on before continuing your test For those cases you can toggle the POWER ON SRQ to ON by pressing 2 2715 User Manual 6 69 Spectrum Analyzer Menus 6 70 Selecting the Screen Plotter Configuration Item 3 EOI LF MODE sets the end of message designator When a message is transmitted over the GPIB the instrument sending the message signifies to other instruments on the bus including the system controller that the message has been completed This can be done in two ways The interface management line named End Or Identify EOD is asserted brought to its low state simultaneously with the last data byte that is transmitted The ASCII codes for carriage return CR and line feed LF are appended to the message EOI is still asserted simultaneously with the transmission of LF All Tektronix instruments and controllers use EOI to terminate messages You should therefore toggle item 3 until the end of the line indicates EOI The EOI LF MODE option is included for controllers that do not use the EOI signal line Item 4 TALK ONLY MODE must be set to OFF when the 2715 is used with a controller because the controller determines whether the 2715 is talking or listening If you normally use the 2715 with a controller set the TALK ONLY MODE to OFF However to send screen plot data directly to a GPIB plotter without a controller set the TALK ONLY MODE to ON and disconnect all instru ments except the 271
346. present units of MHz ms or mV Had you wanted to set the frequency to 101 kHz you would have pressed Y This method of changing center or start frequency is most useful when large changes are required or if you know ahead of time exactly what frequency is required The span is now set to 6 MHz and the fundamental of the calibrator signal is not quite centered on screen Center the calibrator signal with the FREQ MKRS knob 16 Turn the FREQ MKRS knob several clicks counterclockwise to reduce the center or start frequency Each click reduces the frequency by the currently selected tuning increment 0 02 times the span div or 0 12 MHz in this case The control functions as the fine frequency adjustment Rotating the knob clockwise increases the frequency at the same rate 17 Continue turning the knob in either direction until the signal is centered Your screen should now resemble Figure 2 6 2715 User Manual Getting Started 2715 User Manual Signal Frequency Center Frequency 100 MHz wo T Signal Amplitude 100 0MHZ 1 ATTN 2DB 18 8 dBmV 20 8DBMV VF 300KHZ 5 6 0MHZ J 10 DB 73 300KHZ 1 20 RBW 30 50 40 FREQ 25 60 Figure 2 6 Calibrator Signal Fundamental The signal frequency is 100 MHz and the signal peak is 0 2 division below the reference level so its amplitude is 18 8 dBmV as shown in the following equation 20
347. presents the most accurate method for determining signal amplitude with the 2715 unless a separate extremely precise signal is used for direct comparison In general amplitude accuracy is further enhanced if the signal being measured is first moved to within one division of the top graticule line using the REF LEVEL controls In delta A marker mode two markers designate the points on the waveform between which the differences in signal amplitudes and frequencies are measured and displayed It is not possible to display one marker on a particular trace while displaying the second marker on another trace More than one register can be displayed but the markers appear only on the highest priority waveform 1 Press MKR A OFF to activate the marker The sweep does not change but the RF attenuation and video filter readouts have been replaced by approximate marker frequency and amplitude readouts such as the following M 100 0MHZ M 18 8DBMV The M preceding the readouts represent the amplitude and frequency of the signal at the marker position 2 Turn the FREQ MKRS knob several clicks clockwise The marker moves to the right and the readout tracks it The knob now controls the marker position rather than the center frequency 3 Turn the FREQ MKRS knob to move the marker into the noise Notice that the marker actually moves up and down between the max and min noise values on alternate clicks of the knob This is because each clic
348. r Defined Power Up Settings 6 62 Ventilation 2 3 VERT SCALE 3 7 4 16 10 5 1 4 16 LIN 4 16 Vertical Position Adjustment 4 35 VID FILTER 3 8 Video Demodulation 6 58 Video Filter 4 14 Video Modulation Negative 5 6 Positive 5 6 View Modulation Field Operation 5 68 View Picture Operation 5 69 Viewing Instantaneous Frequency Deviation 6 54 W Waiting For User Defined Power Up 2 4 Warmup Time 2 4 Waterfall Mode 4 24 Index 7 Index YIG Oscillator ZERO Key 3 5 Changing Settling Delay Time 6 79 Zero Span 4 4 Minimum Acceptable Settling Time 6 79 Settling Delay Time Default 6 78 Index 8 2715 User Manual
349. r and lower cells is the occupied bandwidth For instance if you specify the 9096 occupied bandwidth the 2715 first computes the total signal power Next it sums the signal power in the cells starting at the left hand edge until it accumulates 5 of the total The percent signal power not in the occupied bandwidth is 10096 90 10 and half of it is below and half above the occupied BW See Figure 6 11 5 Power 90 Power 5 Power gt h f fi f 90 Occupied BW Figure 6 11 Illustration of Occupied BW Measurement If the accumulated power does not precisely equal half the power not in the oc cupied bandwidth the usual case the 2715 linearly interpolates between frequency cells to arrive at better frequency estimates 6 51 Spectrum Analyzer Menus NOTE The occupied bandwidth mode always works on the digitally sampled signal Therefore different results can be obtained in PEAK and MAX MIN modes unless video filtering is used to minimize post detection noise You can demonstrate occupied bandwidth mode using a broadcast signal 1 Connect a short antenna or CATV tap to the 2715 input as outlined in Appendix B Broadcast AM FM and TV Signal Sources Ensure that the calibrator is turned off Adjust the reference level until you can see individual FM broadcast or TV sound carrier signal peaks Tune the 2715 until a strong signal is centered Your display might rese
350. r item 1 Repeatedly select item 2 PLOT SPEED to cycle through the available speeds of FAST FASTER FASTEST SLOW and NORMAL the default Try the various speeds with your plotter to see which produces the most satisfactory results Printers do not support these options m Item 3 PLOTS PER PAGE only appears if a plotter is selected for item 1 Repeatedly select item 3 to cycle through the available plots per page m tem 4 PLOT POSITION only appears if 4 PLOTS PER PAGE is selected for item 3 This option enables you to select the quadrant of the paper on which the current plot will be placed Repeatedly select item 4 PLOT POSITION to cycle through the available positions m tem 5 on the SCREEN PLOT CONFIGURATION menu determines whether or not graticule lines are printed on the hard copy output Status of the plotted graticule lines is independent of whether the on screen graticule illumination is on or off Press 5 to toggle the GRATICULE LINES ON PLOT between ON and OFF Selecting the Printer All CATV measurements enable you to send ASCII character strings to the CRT Configuration or to the optional RS 232 port if it is installed You cannot send these strings to a GPIB device 1 Press UTIL 4 to return to the SYSTEM CONFIGURATION menu 2 Press 2 to select PRINTER CONFIGURATION 3 Press 0 to select PRINTER DEVICE The PRINTER DEVICE will toggle between TTY00 and CRT TTYOO is functional only if an RS 232 interface i
351. r the fifth beat frequency Press 5 to use the default frequencies Press BKSP BKSP 0 to run the measurement The instrument measures the visual carrier peak for a reference then sets the span div setting such that the measurements are made over a 100 KHz span on either side of the frequency position The instrument measures the first second third fourth and fifth beats After the measurement is complete or after the routine is aborted the worst case result is displayed in the spectral display Press CATV APPL to display the or CSO menu Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed Press 2 to display results of the last measurement performed A display resembling Figure 5 8 comes up You can either view other stored results by pressing W or stop viewing the results by pressing Z Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 14 Press 4 to print all stored results of the measurement A printer must be connected to the 2715 5 55 Measurements
352. re saved along with the settings Press 3 W The control settings and the saved waveforms are both restored Whenever you save settings including LAST POWER DOWN and USER DEFINED POWER UP you also store the contents of digital storage registers A B and C You can store up to 108 waveforms as well as 36 groups of settings actual numbers depend on what else such as user defined programs is being stored Furthermore this information is saved even after the power is turned off You can do things like record waveforms in the field and bring them back to the lab with you for further analysis or permanent recording or store reference waveforms in the lab for comparison in the field If your instrument has been used previously you may find that some or all of the items already contain saved settings and displays 2715 User Manual Spectrum Analyzer Menus Normalizing the 2715 2715 User Manual You can also store settings and waveforms by title as follows 1 Using the Display menu create a title for the current display see Adding Titles and Labels on page 6 36 Call it MY SETTINGS Turn on title mode and return to the spectral display 2 Press UTIL 1 4 X This saves the settings under item 4 of the Stored Settings Displays menu 3 Press UTIL 1 Item 4 on the menu is now MY SETTINGS The settings are recalled like any other but the title often helps remind you what the settings are used for N
353. rement 1 Press CATV APPL to call up the CATV MEASUREMENTS menu See Figure 5 1 2 Press 7 to display the CROSS MODULATION measurement menu shown below 0 RUN CROSS MODULATION 1 STORE CURRENT RESULTS 2 DISPLAY RESULTS 3 PRINT CURRENT RESULTS RS 232 Only 4 PRINT STORED RESULTS RS 232 Only 5 METHOD FREQUENCY DOMAIN or TIME DOMAIN NCTA 9 LEAVE CROSS MODULATION 3 Press 5 to select the method for measuring the cross modulation Refer to CROSS MODULATION Measurement on page 5 60 for information about the measurement methods 5 61 Measurements 4 Press 0 to run the Cross Modulation measurement The instrument prompts you to turn off the modulation 5 Turn off the modulation and press W to continue or Z to abort the measurement The instrument measures the Cross Modulation and displays the result 6 Press CATV APPL to display the CROSS MODULATION menu 7 Press 1 to store the results of the last measurement The message RESULTS STORAGE COMPLETE is displayed 8 Press 2 to display results of the last measurement performed You can either view other previously stored results for this measurement by pressing W or stop viewing the results by pressing Z 9 Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB int
354. rements this is one way to look at positions where harmonics should be present In fact any time your measurements require you to look at multiples of a frequency difference but you do not want to be bothered with actually entering the frequency the delta marker tuning increment mode provides a quick convenient way of doing it 16 Return to the Programmed Tuning Increment menu to specify a particular tuning increment 17 Choose item 3 KEYPAD ENTRY and enter a value of 7 MHz The spectral display reappears 18 Turn the FREQ MKRS knob The frequency changes by 7 MHz per click a value not otherwise available Entering a keypad tuning increment automatically places the 2715 in programmed tuning mode 19 There are two ways to turn off any programmed increment including the keypad entered increment a First toggle item 8 on the Marker Frequency menu to read AUTO This turns off the keypad value and restores automatic selection of the tuning increment b Second select the programmed tuning increment from the MKR FREQ menu and choose item 4 RETURN TO AUTO from the Programmed Tuning Increment menu This also turns off the keypad value and restores automatic selection of the tuning increment 20 Turn the keypad increment back on by reselecting PROGRMD TUNING INC from the MKR FREQ menu and choosing item 2 KEYPAD ENTRD INC 21 Now turn off the keypad selected increment 2715 User Manual 6 25 Spectrum Analyzer Men
355. requency Domain Representation The portrayal of a signal in the frequency domain representing a signal by displaying its sine wave components the signal spectrum Frequency Drift Gradual shift or change in displayed frequency over the specified time due to internal changes in the spectrum analyzer where other conditions remain constant Expressed in hertz per second Frequency Linearity Error The error of the relationship between the frequency of the input signal and the frequency displayed expressed as a ratio Frequency Marker An intensified or otherwise distinguished spot on a spectrum analyzer display indicating a specified frequency point Frequency Modulation FM The process or result of a process in which the frequency of an electrical signal the carrier is varied in accordance with some characteristic of a second electrical signal the modulating signal or modulation Frequency Range That range of frequencies over which the performance of the instrument is specified Frequency Response The unwanted variation in the displayed amplitude over a specified center frequency range measured at the center frequency expressed in decibels Frequency Response Cable TV System Related The overall gain variation of a system as a function of frequency Normally measured in dB p p sometimes called peak to valley or as dB half the peak to peak value Frequency Span Dispersion The magnitude of the frequency band displayed
356. ressing UTIL 4 6 The number is listed under the FID column in the directory Return to the System Configuration menu and select item 7 PROTECT FILE Following the on screen prompt enter the number of the file you want to protect Confirm your selection by pressing W It is now impossible to delete the file without first unprotecting it Repeat the foregoing process to unprotect a previously protected file The process constitutes a toggle that alternately protects and unprotects the desig nated file NOTE Unless you have specific reasons for doing otherwise do not protect system parameter and normalization files see Table 5 6 on page 5 15 Doing so may prevent the 2715 from carrying out its normal functions or updating data If you are in doubt as to which options are installed in your instrument press UTIL 4 9 The resulting display begins by listing the instrument s firmware version and the Tektronix copyright Below that two columns list the options installed in your 2715 You will see a readout similar to the following NVM 1 12 88 NVM 2 12 88 GPIB RS 232 The number following NVM nonvolatile memory is for internal Tektronix use only and of no value to the user The list will vary according to the options actually installed in your instrument GPIB and RS 232 both appear regardless of which is physically installed in the 2715 See Configuring the Communications Port on page 6 67 for additional in
357. retained at the last physical power down m During a POWER DOWN UP cycle settings are reset to the values retained at the last physical power down unless a User Defined Power up exists in that case settings are reset to those stored in the User Defined Power up setting m During a POWER UP DIAG AND REBOOT cycle settings are reset the same as during a POWER DOWN UP cycle but instead of the values resetting to those retained at the last physical power down they reset as if a physical power down had just occurred 2715 User Manual Appendix D Global Resets 2715 User Manual m During all other cycles settings are not reset The following are mode related settings m Utility Menu Items Spectral Display in Menus m Marker Freq Menu Items Frequency Reference Mode CENTER START Counter Resolution Frequency Tuning Mode AUTO and TABULAR only others revert to AUTO Entered Frequency Tuning Increment Tabular Tuning Table Frequency Offset Frequency Offset Mode ON OFF Input Menu Items Input Impedance Reference Level Units External Gain Attenuation External Gain Attenuation Mode ON OFF dBuV M Measurement Distance dBuV M Antenna Table dBu V M Target Waveform m Sweep Trigger Menu Items Video Sync Polarity Video Line Triggering Mode CONTINUOUS KNOB ENTERED Video Line Triggering Standard NTSC SECAM PAL OPEN m Display Menu Items Ensemble Averaging Destination Waveform MIN HOLD Desti
358. rol For CSO measurements this normally occurs on channels that are only a few dB weaker than the general system level If 3000 is added to the result both of the above events occurred 5 49 Measurements Interactive Mode First the instrument measures the peak of the video carrier on the current channel You are prompted to move the marker to the first beat to be measured You may make any required changes to the instrument setup to help locate beats For example you can use menu choice 6 to select the analog display If you are using the in service basis the instrument first finds quiet lines if none were specified in the channel table Then the algorithm that performs the earnest beat amplitude measurements will reset the RF attenuator preamp combination to appropriate settings The algorithm has its own means of adequate averaging for the measurement To measure the beat the instrument returns to the specified frequency sets the instrument to NCTA recommended settings span at 50 kHz div RBW to 30 kHz and video filter to 10 Hz The 2715 may adjust the reference level so that the reading is at least one division from the bottom of the screen to minimize logging errors It then searches for the maximum value within two divisions 100 kHz of the specified frequency and returns this as the measure ment normal basis When earnestly measuring each CSO product on an in service basis the instrument moves to
359. rom the ENSEMBLE AVERAGING submenu to start averaging Both status indicators for register C light Here too we see that the average minimum coincides closely with the lower edge of the MAX MIN average In computing the average MIN the 256 minimum points from each max min sweep are used 2715 User Manual Spectrum Analyzer Menus 33 To store the MEAN value of the spectrum in register A press DSPL 1 4 8 34 Press 1 from the ENSEMBLE AVERAGING submenu to start averaging 35 At the prompt press W to overwrite the previously stored max min average Again the mean value of the noise appears to be halfway between the max and min values The average MEAN is what you get if you add successive maximum and minimum values in dB from the MAX MIN display divide by two and average the results The MEAN average is a visual mean not a true mean that can be very useful in making weak signals visible 36 Turn on the D register to see the current sweep with its visual mean and average maximum and minimum values superimposed The mean along with the max and min values provide an estimate of the variability of the signal The signal peak does not appear to have changed because the calibration signal is essentially constant little or no variability so its min max and mean amplitude are all about the same This can be used to advantage 37 Turn off the A B and C registers 38 Set the reference level to 58 8 dBmV T
360. rom the desired response by the fundamental or harmonic of the power line frequency Impulse Bandwidth The displayed spectral level of an applied pulse divided by its spectral voltage density level assumed to be flat within the pass band Inactive Trace SAVE A trace or a trace recalled into the B display before the sweep is started Input Impedance The impedance at the desired input terminal Usually expressed in terms of VSWR return loss or other related terms for low impedance devices and resistance capacitance parameters for high impedance devices Glossary 5 Glossary Glossary 6 Intermediate Frequency IF In a heterodyne process the sum or difference frequency at the output of a mixer stage which will be used for further signal processing Intermodulation Spurious Response Intermodulation Distortion IMD An unwanted spectrum analyzer response resulting from the mixing of the order frequencies due to nonlinear elements of the spectrum analyzer The resultant unwanted response is displayed Line Display The display produced on a spectrum analyzer when the resolution bandwidth is less than the spacing of the signal amplitudes of the individual frequency components Line Spectrum A spectrum composed of signal amplitudes of the discrete frequency components Live Trace Any combination of the A trace and or the B trace when SAVE A is off Local Oscillator LO An oscillator which produces the internal signal
361. s 0 through 5 to update the clock Terminate each entry by pressing W 4 Press 6 to toggle the clock display on or off in the menu the spectral display and printer plotter outputs 5 Press UTIL to return to the spectral display You can protect your stored settings so that they are not accidentally deleted 1 Press UTIL 4 to call up the SYSTEM CONFIGURATION menu 2 Press 5 to toggle item STORED SETTINGS PROTECT to ON 3 Press BKSP to return to the UTILITY menu 4 Press 1 to select STORED SETTINGS DISPLAYS 5 Attempt to delete any stored setting The message ONLY WAVEFORMS DELETED appears When STORED SETTINGS PROTECT is turned on you cannot delete the stored settings but waveforms stored along with them will be deleted 6 Press BKSP 4 to return to the SYSTEM CONFIGURATION menu 7 Press 5 to turn off STORED SETTINGS PROTECT 8 Press UTIL to return to the spectral display The 2715 stores settings waveforms and other data in a system of files in NVRAM Normally you will not alter those files Press UTIL 4 6 to view a directory of existing file names File names are established by the firmware Table 6 3 and Table 6 4 list the file names and describe their contents Files are created only as required That is you will not find a BSETO3 settings file unless you have previously saved the B register settings in the third storage location Several other files representing system parameter
362. s apparent The on screen indication is phase noise close to the base 2715 User Manual Spectrum Analyzer Menus Frequency Corrections On 2715 User Manual and Off of a signal and or an apparently drifting signal Therefore the oscillators in the 2715 are typically phaselocked to a stable reference when operating at narrow spans This happens automatically when the span is 20 kHz div or less Phaselock minimizes the amplitude of the noise pedestal close to a signal but may actually increase it slightly at frequencies farther away Therefore phase lock may be turned off when desired Toggle phaselock between AUTO and OFF using item 4 PHASELOCK from the Instrument Configuration menu Return to the spectral display to see the effects Leave PHASELOCK in AUTO when you are done 300 0MHz AUTO SWEEP ATTN 10DB 28 8DBMV VF WIDE 50 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR During normal operation the 2715 periodically computes frequency corrections to compensate for short term drift within the 2715 itself and applies them to the displayed trace It does this between sweeps You can shorten the intersweep interval by disabling the frequency corrections although some high frequency accuracy may be sacrificed and the signal may drift off screen at small spans div NOTE Short Holdoff mode reduces the intersweep interval even further but also disables most marker measurement modes 1 Observe the spectral display for
363. s automatically upon completion of normalization In case of repeated failures contact your local Tektronix Service Center or representative All configuration settings selected in the UTIL menu are retained in NVRAM until you change them The System Configuration menu offers nine choices 1 Press UTIL to call up the Utility menu 2 Press 4 to select SYSTEM CONFIGURATION The 2715 is provided with a digital communications port to exchange data and commands with an external instrument controller or a printer plotter Either an RS 232 Interface Option 08 or an IEEE 488 General Purpose Interface Bus GPIB port Option 03 is available The RS 232 port is modem compatible and makes possible remote operation via a telephone line Port connectors are located on the rear panel See Appendix E External Input and Output The accompanying Programmer Manual contains additional information about setting up and configuring the 2715 for remote or automated operations and complete explanations of the commands that are used See the Programmer Manual for additional information 3 Press 0 to select COMMUNICATION PORT CONFIG COMMUNICATION PORT CONFIG displays both GPIB and RS 232 selections regardles of which is installed You must select whichever one is currently installed in your instrument check the physical configuration of J104 at the rear panel See Figures E 3 and E 4 in Appendix E External Input and Output for GPIB and RS 232 connect
364. s indicator at the end of the menu line change However the change is also reflected in the on screen readouts in many cases or by the nature of the spectral display itself The following prompt is displayed at the bottom of all menus prior to making a selection PRESS ANY MENU KEY TO EXIT PRESS BKSP FOR PREVIOUS DISPLAY m Simply pressing a menu key returns instantly to the spectral display You can use this technique if you decide not to make a selection W Pressing the backspace key BKSP returns to the previous menu If there is no previous menu you return to the spectral display The backspace key can therefore be used to return to a previous menu to alter a selection or to back entirely out of a menu and return to the spectral display In general menus are not reproduced here It is intended that you call up menus on the 2715 and follow along with the examples in this section as they are described For a handy reference consult Operating Basics 6 3 Spectrum Analyzer Menus Input Turning the Calibrator On 6 4 and Off Setting RF Attenuation To view the attenuation and video filter screen readouts turn the markers off during these menu descriptions menus are turned on by default 100 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF WIDE 600MHz 10 DB 300KHz RBW AUTO The Input menu see Figure 6 1 controls parameters that alter signal sensitivity change measurement amplitude units and turn the c
365. s installed in your instrument If the GPIB option is installed CRT is always displayed Select CRT if you want results that would normally be sent to a printer to be displayed on the 2715 screen instead On screen display is sometimes not satisfactory if there is more than one screen of data because only the last screen remains visible Instrument Configuration Item 3 INSTRUMENT CONFIGURATION of the System Configuration menu enables you to reset internal parameters and conditions Some of the more useful ones are described in the following subsections The Audio Alert 0 AUDIO ALERT of the Instrument Configuration menu is a four step sequencer whose status is indicated at the end of the line You can choose one of the following features m OFF The 2715 creates no audible beeps m KEYCLICK ONLY The 2715 emits a short beep when a key is pressed 2715 User Manual 6 71 Spectrum Analyzer Menus Setting the Minimum Signal Size Sending Waveforms to a 6 72 Computer Turning Phaselock On and Off m ERROR ONLY This is the factory default A beep occurs only when the 2715 issues an alarm error or warning message The alert sounds only once even if the condition repeats and a displayed message is repeated m KEYCLICK amp ERROR Combination of KEYCLICK ONLY and ERROR ONLY modes Switch the audio alert to the setting of your choice Minimum signal size is the smallest amplitude difference that must ex
366. s may also be present including the following 6 75 Spectrum Analyzer Menus Table 6 3 The File System Settings Files Curve Files User Defined Program UDP Files Each file saves the control settings for a particular register A B C D in a designated location 00 39 saves B register settings in the number 3 location Each file saves curve data from register A B or C in a designated location 00 39 D register curves are never saved AWFM04 saves the A register curve in location 4 Each file saves a keystroke sequence representing a particular UDP in a designated location 0 8 UDP 1 is the second user defined program Channel Table Files Each file saves the channel table in a designated location 0 9 representing channel table data for a particular table CHTBL3 saves the channel table information in location 3 CATV Measurement Results Files Each file saves the CATV measurement results in a designated location 1 4 RSLT3 saves the CATV measurement results in the number 3 location Flatness Correction Data Files Flatness files save the data generated by running the flatness correction procedure Antenna Table Files Each file saves the antenna table in a designated location 1 5 representing antenna data for a particular antenna ACF3 saves the antenna information in location 3 Normalization Files Normalization files save the data generated by normaliz
367. s not detect Therefore the cross modulation sidebands can have significantly higher amplitudes than indicated by the Time Domain measurement result This may result in picture impairment arising from phase modulation to amplitude modulation conversion in the asymmetric IF filter of the TV receiver and may lead to failure to detect coherent disturbances in excess of legal limits NOTE The Frequency Domain method is sensitive to the accuracy of the frequency of the visual carrier when the frequency is defined in the channel table refer to Channel Tables on page 5 6 If the channel under test has an aeronautical offset of 12 5 kHz and the offset is not accounted for in the channel table then the cross modulation measurement may not find the 15 73 kHz sidebands If the sidebands are not found the measurement will abort The Frequency Domain method reliably detects sidebands arising from either amplitude modulation or phase modulation or a combination of both Also the useful measurement range of the Frequency Domain method is significantly greater than that of the Time Domain method 2715 User Manual Measurements Enable CROSS MODULATION Measurement 2715 User Manual The Frequency Domain method measures the carrier peak with a wide resolution filter and then directly measures sideband amplitudes using a narrow resolution filter However the result is scaled to produce readings conforming to the NCTA method for
368. s of a front panel mask and rack mounting cradle which adapts the 2715 to a standard 19 in 482 6 mm rack The adapter requires 7 in 177 8 mm vertical rack space This option preserves the portability of the 2715 Slide assemblies are provided for front access to and easy removal of the 2715 This option provides a 50Q input frequency range of 9 KHz to 2 15 GHz and channel table editing from the front panel of the 2715 This option provides 750 input frequency range of 9 KHz to 2 15 GHz and channel table editing from the front panel of the 2715 2715 User Manual eee Glossary and Index Glossary 2715 User Manual Active Trace Live trace or the B SAVE A trace a trace recalled into B is not an active trace Amplitude The magnitude of an electrical signal Amplitude Modulation AM The process or result of a process in which the amplitude of a sine wave the carrier is varied in accordance with the instantaneous voltage of a second electrical signal the modulating signal Aural Carrier Level The RMS voltage of a channel s aural sound carrier measured across a termination impedance which matches the internal impedance of the system Baseline Clipper Intensifier A means of increasing the brightness of the signal relative to the baseline portion of the display Calibrator A signal generator producing a specified output used for calibration purposes Carrier Carrier Signal The electrical signal typi
369. s the procedure you should follow when your new 2715 arrives from the factory Observe the indicated precautions to prevent damage to the instrument during initial checkout and subsequent use Receiving and Unpacking Packaging and Storing 2715 User Manual The spectrum analyzer and its standard accessories are carefully packed at the factory using a specially designed shipping container to prevent damage during transit If upon receipt damage to the shipping container is evident notify the shipper Tektronix Inc is not responsible for damage caused during shipping If you have not already done so carefully remove the spectrum analyzer and its accessories from the shipping container and inspect them for damage Do not destroy the shipping container Test spectrum analyzer operation using the System Checkout procedure on page 2 4 If damage or defects are discovered or if components are missing notify your local Tektronix field office or representative In the event that the equipment must be returned to a Tektronix Service Center carefully package it in the original shipping container Use the vinyl vapor barrier and insert the original foam blocks in the same fashion they were received If the original shipping materials are not available use a container of equivalent strength and dimensions Wrap the instrument in a vinyl vapor barrier and cushion the instrument on all sides with foam or other suitable packing material At
370. s to the carrier in 50 KHz div and 100 KHz resolution bandwidth Identifies the carrier and measures amplitude in 10dB div If the carrier was identified in 10 dB div measures amplitude more accurately as follows Sets the reference level to 1 dB above the carrier level measured in 10 dB div sets to 1dB div takes a sweep and adjusts the reference level up in 1 dB steps if carrier peak is off the top of the screen 5 21 Measurements 5 22 AVERAGED POWER Ifthe aural carrier has AM modulation increments the reference level 2 dB switches to LIN vertical display mode and averages 25 sweeps Adds flatness correction and stores the resulting amplitude from 1 dB or the averaged LIN waveform as a visual or FM carrier amplitude or stores the amplitude relative to visual carrier if this 1s an aural carrier If you select FREQ AMPL measurement mode the 2715 executes the common steps listed earlier followed by these steps for each carrier Tunes to the carrier 1f in 50 KHz div If carrier is one from a dual aural carrier TV channel attempts to identify the carrier in 10 dB div If the carrier is identified counts the carrier and sets span to 50 KHz div Then measures amplitude more accurately as described earlier in second bullet item under ACCUR AMPL measurement mode Stores the resulting frequency as a visual or FM carrier frequency or if an aural carrier stores the frequency relative to the visual carrier If
371. s to the right of the frequencies are the antenna factors or K factors When creating antenna tables the 2715 supplies default values of zero for the K factors To begin changing the antenna factors press W and enter the appropriate factor The asterisk indicates which factor is to be edited 2715 User Manual Spectrum Analyzer Menus 2715 User Manual After you enter a value for a factor the asterisk moves to the next frequency If you do not want to change the antenna factor at the indicated frequency turn the FREQ MKRS knob to move the asterisk to the desired frequency For instance suppose an antenna manufacturer specifies the antenna factors for his antenna as follows f k f k f k 55 0 2 7 60 0 3 5 51 0 2 1 56 0 2 9 61 0 3 6 52 0 2 3 57 0 3 0 62 0 3 8 53 0 24 58 0 3 2 63 0 3 9 54 0 2 5 59 0 3 3 Then to make measurements from 55 to 60 MHz the entries in the antenna table should look like this 1 55 000000 2 7 2 gt 56 000000 2 9 3 gt 57 000000 3 0 4 gt 58 000000 3 2 5 59 000000 3 3 6 60 000000 3 5 10 If you are creating a new antenna table press Z to exit return to EDIT ANTENNA TABLE after the last entry has been completed If you are editing an existing table press W after your last entry Then press Z to return to EDIT ANTENNA TABLE Naming antennas is not required but names can provide quick reminders of the purpose of each antenna The following steps show
372. same as the size of the existing file The most probable cause is that there is a version mismatch between the file system and the current firmware FILE SYSTEM DIRECTORY FULL Occurs when attempting to store a file in the NVRAM and there are no more directory entries available FILE SYSTEM FULL Occurs when attempting to store a file in the NVRAM and there is no more room to store the file FIRST STEP MUST BE DONE FIRST Preceding step must be performed prior to selected one Part of the reference normalizations are order dependent FLATNESS CORRECTION NOT AVAIL An attempt to access the measurement specific flatness correction failed A value of 0 0 is used on failure to access correction data This failure is usually due to a corrupted or missing flatness correction data file FORMATTING PLOT Downloading plot file to hardcopy device FREQ OUT OF RANGE NORMALIZATIONS Perform frequency normalization again Contact your local Tektronix service center or representative if message persists FREQ NORM SUGGESTED 1ST LO Perform frequency normalization Contact your local Tektronix service center or representative if message persists FREQ NORM SUGGESTED FIND SIDE Perform frequency normalization Contact your local Tektronix service center or representative if message persists FREQ NORM SUGGESTED INNER PLL Perform frequency normalization Contact your local Tektronix service center or representative if message persists FREQ NO
373. se but does not significantly alter the displayed amplitude of narrow band signals However if you must measure very wideband or pulse like signals you may wish to use a filter somewhat wider than that automatically selected by the 2715 See Menu Entered Control Settings on page 6 60 The video filter width is indicated in the on screen readouts by VF bandwidth where bandwidth is equal to the bandwidth of the video filter being used This is true except in the case of the 5 MHz or the 1 MHz filter where the WIDE video filter is automatically selected You can select WIDE video filter for any resolution bandwidth 2715 User Manual Dedicated Controls When you press VID FLTR the 2715 automatically selects a narrower video filter bandwidth approximately 1 100 of the resolution BW specifying particular filter bandwidth using the UTIL menu is described later in this section The narrow video filter dramatically reduces the noise and enhances the visibility of narrow band signals Care must be taken though because it will also reduce the indicated amplitudes of wideband signals such as video modulation and short duration pulses The following steps demonstrate the effects of the video filter 1 Ensure that the 2715 is set as in the settings box on page 4 14 and note if the signal peaks at 700 MHz 800 MHz and 900 MHz are visible 2 Press VID The red LED below the key lights indicating that a narrow video filter
374. se that you perform a marker peak find function during the UDP The frequency and amplitude of the signal are displayed at the upper right of the screen the normal marker readouts To have the 2715 print the readouts through the RS 232 port ensure your printer is powered up on line and ready 1 Press UTIL 4 0 2 0 to place the RS 232 port on line Press BKSP three times to return to the UTILITY menu Press 9 to select MORE O XO Press 0 to select the PRINT READOUTS option Printing begins immediately 100 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF 300KHz 1 0MHz 10 DB 300KHz RBW AUTO The Sweep Trigger menu enables you to select the 2715 trigger mode During normal operation of the 2715 the sweep generator is free running new sweep begins as soon as possible after the end of the previous sweep However when dealing with time domain analysis or pulsed signals it may be advantageous to trigger the sweep from some characteristic of the input signal or from another signal related in a fixed way to the input signal The Sweep Trigger menu also enables you to specify the sweep rate and enter the manual scan mode Press SWP TRIG to call up the Sweep Trigger menu Press 0 to select FREE RUN to place the 2715 sweep generator in the free running or continuous mode This is the default setting and is usually satisfactory for analyzing continuous signals It is also a good mode for examining the time do
375. ser Manual General Safety Summary Preface eR rri mpeg vin age a eae ae Introduction eae EG Sele A eer wie Re What is a Spectrum Analyzer What Can You Do With a Spectrum Analyzer About the 2715 Getting Started ree erm S Receiving and Unpacking Packaging and Storing Installation 21e A ek DR Precautions sss Ge wa epee ee as System Checkout Making Your First Measurement Operating Basics RE rA wie ee ERA RETE RSS Display Screen Connectors Controls and Menus SWP TRG Menu Structure UTIL Menu Structure QI OE ETE cos tte Ure vtr UTIL Menu Structure 2 66 2 te eg eee EESTI MRK FREQ Menu Structure CATV APPL CATV Measurements Page 1 Menu Structure 1 of 3 CATV APPL CATV Measurements Page 1 Menu Structure 2 of 3 CATV APPL CATV Measurements Page 1 Menu Structure 3 of 3 CATV APPL CATV Measurements Page 2 Menu Structure 1 of 2 CATV APPL CATV Measurements Page 2 Menu Structure 2 of 2 CATV APPL Applications Menu Structure DEMOD Menu Structure DSPL Menu Structure USER DEF Menu Structure
376. signal height 2715 User Manual 4 9 Dedicated Controls 4 10 Keypad Entry As with frequency and span div you can directly enter the reference level from the keypad This feature is especially handy when you have a good estimate ahead of time of what the signal amplitude is or when you are simply interested in how much below a given amplitude a particular signal is For instance you might want to preset the reference level to 15 dBmV to examine cable TV signals at a customer drop The following procedure shows you how to set the reference level to a predeter mined value 3 Press REF LEVEL to place the reference level in the immediate entry mode Notice that the abbreviation REFL has appeared at left center of the 2715 screen The REFL notation indicates that you can enter the reference level directly from the keypad This is done by keying in a permissible value followed by an appropriate terminator key You can enter any value from 21 2 to 68 8 dBmV or the equivalent in other units You can enter up to 25 characters but regardless of how many you enter the 2715 rounds and displays the reference level to a tenth of a dB 4 Press 2 1 e 3 Y to set the reference level to 21 3 dBmV The numbers you type appear on screen to the right of REFL If you make a mistake you can correct it any time prior to pressing Y by repeatedly pressing BKSP until the incorrect number disappears and then typing the c
377. sing Z 13 Press Z to return to the AURAL FM DEVIATION menu 14 Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 15 Press 4 to print all stored results of the measurement A printer must be connected to the 2715 16 Press 9 to leave the AURAL FM DEVIATION measurement and return to the CATV MEASUREMENTS menu CARRIER TO NOISE DESIRED to UNDESIRED Measurement 2715 User Manual The CARRIER TO NOISE DESIRED to UNDESIRED measurement records and displays the visual carrier to noise ratio for the current analog channel or the desired to undesired ratio for digital channels The desired to undesired ratio is the measurement of averaged power in the selected channel with the desired signal applied compared to the measurement of averaged power in the selected channel without the desired signal If the in service basis is selected not available in positive modulation systems or when measuring a digital channel this measurement is made during gated slices in the vertical retrace interval This permits the carrier to noise measurement to be performed within the normal video frequency
378. sions down from the reference level 19 Enter the characters 2ND HARMONIC 20 Move the cursor to the peak at the left of the screen label it FUNDAMEN TAL The labels denote the calibrator signal and its second harmonic 21 Press X to store the label s Pressing Z exits from the procedure without any changes 22 Press 3 from the Title Mode menu to make labels appear on your plot Item 3 is a toggle which turns the labels on and off 23 Press DSPL to return to the spectral display NOTE Labels only appear on the hard copy device not on the screen See Figure 6 9 for an example of what the plot should look like 24 Turn off the title and plot labels Turning Graticule Item 6 on the Display menu is a simple toggle that turns the graticule illumina Illumination On and Off tion on and off Press DSPL 6 several times to see the graticule illumination change states 2715 User Manual 6 39 Spectrum Analyzer Menus Displaying an External Source The Display Line and Limit 6 40 Detector Tek C TEST123 271 5 FUNDAMENTAL i 175MHz HARMONIC ATTN 1008 10 dB STD CH7 TIME 50 ms DIV Note Readouts 175 0MHz 275 0MHz 0 Figure 6 9 2715 Plot with Title and Plot Labels Item 7 DISPLAY SOURCE in the Display menu enables you to substitute an external low pass signal for the normally di
379. solution Accuracy Composite second order CS O is measured relative to the visual carrier peak according to the NCTA recommended spectrum analyzer settings SINGLE SWEEP and CONTINUOUS modes do not use all the NCTA recommended settings See Figure A 3 on page A 8 See Figure A 3 on page A 8 0 3 dB See Figure A 3 on page A 8 CSO products are measured per NCTA recommendations during quiet lines in the vertical interval then expressed as dBc See Figure A 4 on page A 8 See Figure A 4 on page A 8 0 3 dB See Figure A 4 on page A 8 Measured relative to the averaged power of the test channel 0 3 dB 2 0 dB within the limits shown in Figure 7 on page A 10 Frequency Response Measurement Typical For fixed amplitude scrambling or no scrambling system amplitude variations flatness are measured relative to a reference trace stored during the frequency response reference setup Reference Trace Storage Nonvolatile Up to 10 traces with spectrum analyzer states Range 5 dB div fixed Resolution 0 2 dB Trace Flatness Accuracy 0 75 dB A 4 2715 User Manual Specifications Table A 1 CATV Characteristics Cont Characteristic Carrier Survey Description Absolute peak amplitude of each visual carrier measured and each associated aural carrier level measured relative to the measured visual carrier for the selected channels characteristics are identical to the frequency visual and aural
380. source is used with the 2715 Overdriving the 2715 s first mixer circuit can generate spurious signals and cause inaccurate measurements As the signal amplitude increases past the maximum linear range of the circuit its output amplitude becomes less than it should be This creates lower than actual amplitude measurements On the other hand if the signal amplitude at the mixer is too low signals may become lost in the 2715 s internal noise An optimum compromise is achieved within the 2715 by making the top graticule line represent a 30 dBm level at the input to the first mixer However in cases where total signal energy is large it may be beneficial to restrict the input to the mixer to a smaller value By resetting the first mixer input level to say 40 dBm you increase the RF attenuation by 10 dB while simultaneously increasing the IF gain 10 dB This provides additional protection to the first mixer In other cases you may want to examine a low level signal adjacent to a high level signal A 20 dBm level at the first mixer input allows 2715 User Manual Spectrum Analyzer Menus Turning the Preamplifier 2715 User Manual ON OFF you to get an additional 10 dB of sensitivity by reducing the RF attenuation 10 dB and decreasing the IF gain 10 dB to compensate The danger is that internally generated distortion products may become more noticeable To change the signal level at the mixer press INPUT 4 You are pro
381. splayed spectrum The signal must be input to the 2715 on pin 1 of the rear panel Accessory Connector J103 and must be in the range of 0 to 1 4 V with a 3 dB bandwidth of 50 kHz or less DISPLAY STORAGE VERT SCALE 10 5 SWEEP RATE and some VID FLTR selections 10 Hz 1 kHz 10 kHz 100 kHz remain active and can be used to process the external signal Refer to J103 Accessory Connector on page E 2 in Appendix E External Input and Output for additional details 100 0MHz AUTO SWEEP ATTN 18 8DBMV VF WIDE 50 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR The 2715 provides a convenient method to determine whether a signal peak is higher or lower than some particular level or whether it falls within a specified range The DISPLAY LINE feature displays a horizontal line at the level you specify You can visually compare signal amplitudes to the line or set the 2715 to sound an alarm if a signal crosses the line 1 Press DSPL 8 to select the DISPLAY LINE feature 2 Press 2 to select VALUE ENTRY 2715 User Manual Spectrum Analyzer Menus 2715 User Manual Press 2 el 2 Z to enter 2 2 dBmV The 2715 reverts automatically to the spectral display that now contains a horizontal line two divisions down 2 2 dBmV You will notice the A register red LED is lit When you display the line you cannot display the contents of the A register Data stored in A is not destroyed but you cannot see it until you tur
382. ss 5 to acquire a reference When the reference acquisition is complete the instrument reverts to the spectral display and displays the message REFERENCE ACQUIRED If you want to rename the new reference press CATV APPL 5 7 W and follow the on screen instructions After renaming the new reference press 6 n X where n is a number from 0 to 9 representing a storage register to save it Press CATV APPL 0 to run the frequency response measurement If you want to save the new reference without renaming it press CATV APPL 5 6 n X where n is a number from to 9 Press CATV APPL 0 to run the frequency response measurement The measurement runs continuously while the instrument shows a display similar to that shown in Figure 5 7 7133 8MHZ i 108 6MHZ Soor 3 Figure 5 7 Typical Frequency Response Display With Reference 5 46 2715 User Manual Measurements The top trace in Figure 5 7 is the raw trace That portion of the reference where it breaks up might be a group of scrambled channels In this case it is the FM band The reference was taken with the start frequency set at 55 25 MHz and the stop frequency set at 211 25 MHz CH 2 to CH 13 The trace at center screen is the frequency response ADJACENT CHANNEL LEAKAGE Measurements Enable Adjacent Channel Leakage Measurement 2715 User Manual Adjace
383. ss the sequence of number keys representing the numerical value and then press the appropriate terminator key The numbers appear on screen as you type them but they are not entered until you press the terminator key If you make a mistake you can correct it any time prior to pressing a terminator by repeatedly pressing BKSP the backspace key until the incorrect number disappears and then typing the correct value The terminator keys W X Y and Z determine the units and enter the data Each key can represent several units but they are context sensitive and the 2715 will determine the intended unit based on the parameter or setting you are attempting to modify For instance X can represent MHz ms or mV and if you are attempting to enter a sweep rate the 2715 will correctly interpret the units as msec when you press X To enter a value of 20 milliseconds press 2 0 X Whereas to enter 20 microseconds press 2 0 Y Entering a value for the sweep rate also removes the sweep rate parameter from automatic selection To return to automatic selection you press AUTO in the SWEEP function block on the front panel There are three ways to exit from a menu m Many selections cause the 2715 to revert automatically to the measurement mode it was in before calling up the menu In some cases a small delay is provided between making the selection and reverting to the spectral display to enable you to see the statu
384. system analog visual and aural carrier levels and frequencies measure ment plus digital channel averaged power measurement m Depth of modulation measurement Aural carrier deviation measurement Visual carrier to noise ratio measurement m Desired to Undesired signal ratio measurement on digital channels m Hum low frequency disturbance measurement W System frequency response measurement m Adjacent channel leakage measurement on digital channels m Viewing demodulated video and baseband modulation m Viewing picture m Listen mode aural carrier demodulation m Composite triple beat measurements on analog and digital channels m Composite second order beat CSO measurements on analog and digital channels m In Channel response measurement W Cross modulation measurement 5 1 Measurements Input Power Limitations A Be sure that the input power limitation is not exceeded before connecting a cable feed to the RF INPUT Read the information in Input Power Limitations below CAUTION To prevent damage the safe maximum total RF input power for the 2715 is 70 dBmV DC input voltage is limited to 100 VDC maximum Total input power above the rated maximum can cause damage to the instrument and voids the factory warranty For a number of equal amplitude signals the total power is approximately Total Signal Single Signal 10 log Number of Signals Thus the safe maximum amplitude per signal is
385. t available when in service basis is selected The frequency of the reference carrier is selectable either as an absolute frequency or as a frequency relative to the carrier of the channel under test The default is 6 MHz relative The carrier is assumed to be stable in frequency to within 200 kHz The frequencies of the beats may be specified only relative to the carrier of the channel under test At least one beat frequency must be specified for the test to run The beats are assumed to be within 50 kHz of the specified frequencies The interval at which the continuous CSO repeats is selectable from 15 seconds default to 21600 seconds 6 hours in one second increments The 2715 periodically runs a subset of normalizations throughout the test These normalizations take about 3 minutes The interval is selectable from 1 hour default to 24 hours in one hour increments Selecting 24 hours has the effect of turning the periodic normalization off 5 51 Measurements 5 52 Enable or CSO Measurement When the continuous CSO is activated the 2715 runs full normalizations before any CSO measurements are done The initial normalizations take about 12 minutes The 24 hour clock that times the test doesn t start until after the initial normalizations are complete The actual CSO test consists of tuning to the selected reference carrier frequency setting the span to 50 kHz div resolution bandwidth to 300 kHz vi
386. t available when in service basis is selected First the instrument measures the peak of the video carrier on the current channel then pauses and prompts you to turn off the carrier In this mode the instrument scans the signals at frequencies specified in the setup table relative to the carrier frequency Absolute frequencies are ignored If no frequencies are specified the instrument uses the default frequencies From these it creates a single sweep test table It then computes sweep limits that include all the frequencies found in the single sweep table with 250 kHz of oversweep at each end It takes a single sweep using a 30 kHz RBW and no video filter It checks each of the frequencies in the single sweep test table to see that the signals there are neither too near the bottom of the screen nor too near the top for a safe measurement If necessary it adjusts the reference level to ensure that the measurement can be made accurately It then turns on the 100 Hz video filter and sweeps again It now prompts you to turn the carrier back on and proceeds to measure all the beats specified in the single sweep test table using the single sweep data Press CAT V APPL to call up the CATV MEASUREMENTS menu See Figure 5 1 The Continuous mode is designed to run CSO tests repeatedly for 24 hours It assumes that the carrier of the channel under test has been turned off and will remain off for the duration of the test The Continuous mode is no
387. t measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed 9 Press 2 to display results of the last measurement performed A display resembling Figure 5 4 on page 5 24 comes up showing current results and the normalization bandwidth You can either go ahead and view other previously stored results for this measurement by pressing W or stop viewing the results by pressing Z 10 Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 NOTE You can print measurement results only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 11 Press 4 to print all stored results of the measurement A printer must be connected to the 2715 12 Press 9 to leave the CARR NOISE DESIRED UNDESIRED menu and return to the CATV MEASUREMENTS menu HUM LFD Measurement The HUM LFD measurement records and displays the peak to peak HUM LFD parameters for the currently selected channel HUM is measured on an unmodu lated carrier and includes the power line fundamental 2 d harmonic LFD is measured on a modulated carrier and may include some video related energy Measurements on modulated carriers may not give accurate results if the video polarity is pos
388. t the selected frequency If you plot the amplitude of the signal as a function of time or view it on an oscilloscope type display you create a time domain representation signal amplitude versus time A spectrum analyzer performs similarly to the receiver except that the scanning is usually performed automatically and faster than you do it manually and there is a Selection of IF bandwidths or resolution bandwidths to choose from Multiple resolution bandwidths are needed because in some cases you may want to separate closely spaced narrow band signals while in others you may want to examine signals with larger bandwidths There is a maximum speed at which a band can be accurately scanned with a resolution bandwidth of a given width generally the smaller the resolution bandwidth the slower the speed The spectrum analyzer can automatically select the fastest speed for you You can find additional information about basic spectrum analyzer concepts and definitions in Tektronix application note 26W 7037 1 Spectrum Analyzer Fundamentals Introduction What Can You Do With a Spectrum Analyzer About the 2715 Spectrum analyzers measure how the power in an input signal is distributed in frequency You can use spectrum analyzers to determine signal amplitudes and frequencies noise power carrier to noise ratios signal or filter bandwidths distortion harmonic and intermodulation FM deviation and percent modula tion Also you ca
389. tach a tag to the instrument clearly showing W Owner s name and address m Name of the person at your location who may be contacted m Instrument model and serial number Description of the problem and service expected 2 1 Getting Started Installation Precautions The 2715 can be stored up to 90 days in an environment that meets the nonoper ating specifications It is suggested that you provide a dust cover For longer periods the 2715 should be enclosed in a vapor barrier containing appropriate desiccant material and stored in an environment that meets the nonoperating specifications The original shipping material can be used and is also useful for protecting the equipment if it must be moved The 2715 is designed for table top operation in any orientation and requires no special installation However the handle can be positioned at several angles to serve as a convenient tilt stand To position the handle pull out at both pivot points on the sides of the instrument and simultaneously rotate the handle to the desired position Tektronix Inc provides an optional rackmount adapter kit Option 30 that requires 5 25 in 133 4 mm vertical clearance and a cradle mount adapter Option 34 that requires 7 in 177 9 mm Contact your local Tektronix field office or representative for additional information The 2715 is equipped with a plastic front panel cover to protect it from mechani cal damage The cover should always be
390. tail the dedicated controls of the 2715 All of the dedicated controls are on the 2715 front panel except the trace alignment controls which are on the back These dedicated controls are used to carry out the most common and general spectrum analyzer operations without the need to call up the menus The first part of the section covers the controls that initiate frequently performed actions Included in this category are all the operating increment and decrement functions of span channel entry frequency and reference level The second part of the section covers the enhanced versatility controls that increase your ability to make accurate spectral measurements easily and conveniently Fundamental Operations 2715 User Manual Getting Started described the amplitude and frequency measurement of a continuous narrow band signal the calibration signal using only three controls This section will repeat the initial measurement but this time with the CHAN FREQ SPAN DIV REF LEVEL and associated controls contained in the gray colored central function block These controls are fundamental to most spectrum analyzer operations You can perform a majority of spectral measure ments with only these controls First set the 2715 controls to the values shown in the following settings box Frequency AUTO SWEEP ATT 50DB 38 8DBMV VF 300KHZ 600 0KHz MAX 10 DB 300KHz RBW Channel Table Name CH nn CALIBRATOR Frequency Center of default
391. tem 1 DBMV and item 3 DBUV are the only available selections all others are selectable only in the nonCATV mode If items 0 2 4 or 5 are selected error message FUNC NOT AVAILABLE IN CURRENT MODE will appear these items are available only after exiting from the CATV mode which is described below 18 Press CATV APPL 8 0 to disable the CATV mode 19 Press INPUT to call up the Input menu 20 Ensure the reference level is set to 18 8 dBmV and then press 3 A list of six possible units appears Select item 2 dBV The spectral display Is restored but the reference level now reads 41 2 dBV because 1 mV is 60 dB below a 1 V reference Only the units change not the 2715 gain attenuation or input impedance Therefore the displayed spectrum is unchanged 21 Change the units back to dBm and turn off the calibrator Each of the six units except the DBUV M dB relative to a uV m represents simple change of scale Be aware that the 2715 always measures the voltage at its input across its 75 2 input impedance and then scales the result according to the selected units Because the DBUV M is not just a simple unit conversion it is discussed separately in Using the DBUV M on page 6 10 When you want to measure a high amplitude signal it is possible that you will have to attenuate the signal before inputting it to the 2715 Remember the maximum total signal power at the input to the 2715 should not exceed 70 dBmV
392. th at 3 meters then enter 3 meters Press 4 to return to EDIT ANTENNA TABLE Item will continue to indicate EMPTY at the end of the line because there are still no antenna factors in the local buffer To edit an old antenna entry press 3 LOAD from the EDIT ANTENNA TABLE and choose the antenna you want to edit If there is already something in the local buffer you are given the choice W OVERWRITE LOCAL BUFFER Z ABORT If you need the data currently in the local buffer abort the procedure and store it Otherwise press W After the antenna is loaded its name if it has one or number is shown at the end of the first line of EDIT ANTENNA TABLE indicating that the antenna factors for that antenna have been loaded into the local buffer If you attempt to change the frequencies at which you plan to use an antenna whether it is a newly created antenna or an old one you must delete the local buffer and start over as though it is a new antenna To delete the local buffer select item 4 DELETE from EDIT ANTENNA TABLE and then select item 6 EDITING BUFFER Confirm the deletion by pressing Y and proceed as though you are creating a new antenna table 8 After you have loaded an old antenna table or established the frequency range and calibration distance for a new one press 0 from EDIT ANTEN NA TABLE A list of frequencies beginning with the start frequency and ending with the stop frequency appears The number
393. that the product is properly grounded Observe All Terminal Ratings To avoid fire or shock hazard observe all ratings and marking on the product Consult the product manual for further ratings information before making connections to the product The common terminal is at ground potential Do not connect the common terminal to elevated voltages Do not apply a potential to any terminal including the common terminal that exceeds the maximum rating of that terminal Do Not Operate Without Covers Do not operate this product with covers or panels removed Use Proper Fuse Use only the fuse type and rating specified for this product Avoid Exposed Circuitry Do not touch exposed connections and components when power is present Wear Eye Protection Wear eye protection if exposure to high intensity rays or laser radiation exists Do Not Operate With Suspected Failures If you suspect there is damage to this product have it inspected by qualified service personnel Do Not Operate in Wet Damp Conditions Do Not Operate in an Explosive Atmosphere General Safety Summary Symbols and Terms A A Keep Product Surfaces Clean and Dry Provide Proper Ventilation Refer to the manual s installation instructions for details on installing the product so it has proper ventilation Terms in this Manual These terms may appear in this manual WARNING Warning statements identify conditions or practices that could result in
394. the center frequency to 100 MHz 33 Press DSPL 4 to return to the MAX MIN acquisition mode 4 25 Dedicated Controls 4 26 Freq Mkrs MAX HOLD A amp B The A and B registers can be used in the MAX HOLD mode to save the peak values of measured spectra The register must be cleared before you can use it in the MAX HOLD mode The MAX HOLD feature compares the amplitude of the current sweep point for point with the stored maximum value of previous sweeps If the current amplitude is greater the current value becomes the new stored maximum if not the previous value is retained 34 Deactivate the D register 35 Make sure the A register is cleared and activated then press MAX HOLD A amp B The red LED below the MAX HOLD A amp B key lights signifying that you have entered the MAX HOLD mode The spectral display especially the noise is much smoother After several minutes the noise floor appears to drift upwards a couple of dB Because the calibration signal is constant there is no noticeable change in it The upward drift of the noise floor slows and stops as the most likely maximum values are observed and stored Now only an occasional noise peak exceeds the previously stored values 36 Activate the D register Note that the waveform in the D register waveform without MAX HOLD is always less than the A register waveform Recording the peak signal excursions observed during a large number of sweeps using th
395. the deviation in both directions try the MAX HOLD technique outlined in Measuring Occupied Bandwidths on page 6 50 For extremely accurate deviation measurements the Bessel null approach should be used see Tektronix application note 26W 7037 1 Spectrum Analyzer Fundamentals 100 0MHz AUTO SWEEP ATTN 18 8DBMV VF 300KHz 1 0MHz 10 DB 300KHz RBW AUTO The DEMOD menu provides a means of listening to AM or FM modulation on the signals being analyzed and activating the video monitor mode Listening to signals often helps to identify the source A built in speaker is provided but if higher fidelity is needed or if you are using the 2715 in a noisy location headphones can be used A 1 8 inch miniature phone jack is located near the front of the right side of the 2715 1 Connect a short antenna or CATV tap to the 2715 input as outlined in Appendix B Broadcast AM FM and TV Signal Sources 2 Ensure that the calibrator is turned off 3 If necessary adjust the reference level until you can see individual signal peaks in the 88 to 108 MHz FM broadcast band If you do not have broadcast FM in your area you can tune to a TV station audio carrier 4 Tune the 2715 until a strong signal is centered 2715 User Manual Spectrum Analyzer Menus Listening to AM Transmissions 2715 User Manual 5 Press DEMOD The DEMOD TG menu appears 6 Press 2 to select FM DEMODULATOR The LED adjacent to FM VOL on the
396. the drawing in the border area so they do not interfere with the waveform If you wish to have graticule lines on the printout you must turn them on by pressing UTIL 4 1 5 You can also add labels to the plot see Adding Titles and Labels on page 6 36 Before attempting to create a screen plot ensure that the communications port is correctly configured see System Configuration on page 6 67 To make a plot of the screen check that your printer or plotter is powered up on line and that the paper is in correct registry Then with the 2715 displaying the desired trace s press PLOT The printer or plotter quickly begins to draw the trace Because the printer or plotter output data is sent to a temporary buffer the 2715 returns to the spectral display and is ready to accept additional commands before printing or plotting ends A typical plot in shown in Figure 4 2 4 33 Dedicated Controls 4 34 Tek A TEST123 271 5 57 00MHz 22 80BmV 8dBm 6000 0kHz 5300KHz RBW ATTN 4dB VF 300kHz 10 dB M55 27MHz M12 6dBmV STD CH2 TIME 20 ms DIV x MARKER 1 PEAK MODE Note Readouts correspond to 60 00MHz waveform D Figure 4 2 Typical Plotter Output Showing TV Channel Spectrum NOTE Plotting time can be reduced by choosing peak acquisition mode or using the video filter to reduce noise variations Noise variations do not
397. tion procedure 48 dB 0 1 dB Accuracy Listen Typical 2 dB for cross modulation 36 dB 3 dB for cross modulation 48 dB The aural carrier for the selected channel is demodulated Output Speaker or headphones with volume control Demodulation Type FM Sweep Displays instantaneous peak FM deviation 5 Total input power all signals included cannot exceed 70 dBmV 2715 User Manual A 5 Specifications Table A 1 CATV Characteristics Cont Characteristic View Picture Typical Description The visual carrier NTSC or PAL format depending on the selected channel is demodulated View Modulation Field Typical One video field of the selected channel video is displayed View Modulation Line Typical The VITS line is displayed ifno VITS line is specified in the channel table line 17 is displayed TV Line Selection Selectable using the FREQ MKRS knob during View Line Modulation function Line Format NTSC or PAL Line Range 1 to 525 NTSC 1 to 625 PAL Sweep Time 10 us div In Channel Response Range 3 dB the auto testis run in 1 dB div Resolution 0 1 dB Accuracy 10 5 dB Auto mode Adjacent Channel Leakage Typical Resolution Accuracy In Service In Channel Response Typical Resolution Accuracy A 6 0 8 dB Interactive mode Averaged power in adjacent channel s is divided by averaged power for the test channel 0
398. to control which TV line triggers the sweep Selecting FREQUENCY or MARKER continues to let you control the center or marker frequency This feature enables you to conveniently flip between frequency and TV line control This can be very useful when viewing multiple TV channels You can select FREQUENCY for changing channels and then go to VIDEO LINE for choosing the line number For a complete explanation of TV LINE trigger mode see TV Line Trigger on page 6 85 300 0MHz AUTO SWEEP ATTN 10DB 28 8DBMV VF WIDE 50 0MHZ 10 DB 5MHZ RBW AUTO CALIBRATOR The front panel controls enable you to move the marker to the next signal peak to the left or right but the Marker Frequency menu enables you to jump the marker from peak to peak in ascending order of amplitude and then jump down again in descending order 1 Turn on the single marker and place it in the noise it does not matter where 2 Select item 4 from the Marker Frequency menu 3 Press W The marker is now on top of the lowest of the calibration signal harmonics 4 Select item 4 and press W again The marker is now on top of the second lowest peak 5 Repeat this process until the marker reaches the highest peak the fundamental 2715 User Manual Spectrum Analyzer Menus Marker to the Reference Level Selecting the Tuning Increment 2715 User Manual 6 After the marker is on the highest peak select item 4 and press X 7 Repeat this process s
399. to turn on the calibrator Press CATV APPL twice If in CATV MEASUREMENTS mode press 8 0 Press CATV APPL 3 to select the SIGNAL SEARCH menu Press 0 to select BEGIN FREQ Press 5 5 X to enter 55 MHz eS Press 1 to select END FREQ 6 49 Spectrum Analyzer Menus 6 50 Measuring Occupied Bandwidths OBW 8 Press 5 5 0 X to enter 550 MHz The frequency and amplitude of all signals within the specified frequency range that are below the reference level but above the threshold will be stored The threshold is normally set by the 2715 at approximately one division above the lowest signal peaks usually noise but you can reset it manually if desired with MKR FREQ 0 See Setting the Signal Threshold on page 6 22 for details 9 Press 2 to start the test The measurement parameters change and the message SIGNAL SEARCH IN PROCESS is displayed while the search is occurring The center frequency will change as each search range is completed When the search is complete the message disappears and the 2715 is reset to its original measurement parameters 10 Press UTIL 4 2 to select PRINTER CONFIGURATION from the SYSTEM CONFIGURATION menu 11 Press 0 until the status indicator reads CRT this feature is explained in the UTIL discussion on page 6 60 12 Press UTIL 13 Press CATV APPL 3 to reselect the SIGNAL SEARCH MENU from the Application menu Notice that the
400. tronix application note 26W 7037 1 Spectrum Analyzer Fundamentals concerning return loss measurements 6 11 Spectrum Analyzer Menus To use the dBuV m follow this procedure 1 2 3 Press INPUT to call up the INPUT menu Press 3 to select REF LEVEL UNIT from the INPUT menu Press 9 to select DBUV M SETUP from the REFERENCE LEVEL UNIT submenu Press 6 to select MEASUREMENT DISTANCE from the DBUV M SETUP Enter the distance at which the measurement will actually be carried out default distance is 3 0 m You can enter distances in feet meters kilometers or miles but the 2715 converts them to meters or kilometers before displaying them Repeatedly press 7 SAVE RESULTS IN WFMXx until the indicated register A B C is the one in which you want the resulting measurement to appear The waveforms are repeatedly saved deleted saved and so on until you terminate the dBuV m mode At that point the last sweep is retained in the selected register Item 9 MARKER DISPLAY controls whether the on screen marker amplitude reads out in decibels relative to a microvolt per meter DBUV M or directly in volts per meter V m The reference unit does not change only the marker amplitude readout changes 7 Toggle item 9 to select the units you prefer Table 6 1 lists equivalent voltage and decibel values in 4 dB steps Interpolate between values if closer results are required Table 6 1 Equivalent Deci
401. u can print the antenna data if your 2715 is equipped with an optional communications port and appropriate printer 19 To print the antenna data select item 5 PRINT from EDIT ANTENNA TABLE 20 Choose the antenna data you want to print from the resulting list The DISPLAY LINE feature DSPL 8 can be used with the dBuV m for making vehicular surveys of leakage from cable TV installations or in other applications where an audible alert is useful whenever a signal amplitude crosses a preset threshold To sound a high level alert whenever the measured RF field strength exceeds the threshold set the DISPLAY LINE at the desired threshold See The Display Line and Limit Detector on page 6 40 for complete details To look for very low amplitude RF energy turn on the 2715 s preamplifier Actual sensitivity depends on the antenna used and losses in cabling and coupling to the 2715 With minimum cable losses and an antenna that matches the 75 2 2715 impedance you should be able to see signals ranging from approximately 2 dBuV m 1 3 uV m at 55 MHz to 14 dBuV m 5 uV m at 216 MHz If greater sensitivity is required the following three options are possible W Provide an external preamplifier m Use a higher gain antenna sensitivity increases directly as antenna gain m If the signal being measured is narrowband reduce the RBW to the narrowest setting still capable of passing the signal for instance the 3 kHz filter increases sens
402. ugh 332 on PAL systems If the only quiet lines available are beyond this range then you must specify the quiet line in the channel table using the Cable TV RF Measurements Software for Windows In this case the in service test is run on the specified line even though it is outside the normal range but there is no verification that the line is still quiet after the test 5 37 Measurements DESIRED to UNDESIRED Enable CARR NOISE 5 38 DESIRED UNDESIRED Measurement When the DESIRED to UNDESIRED measurement is initiated the 2715 performs the following 1 Average power measurements as is done as described in the CARRIER LEVEL AVG POWER menu on page 5 23 The user is prompted to turn the channel under test off Then the Resolution Bandwidth is set to 30 kHz and the Video Bandwidth to 30 Hz A sweep is initiated Any coherent distortion signals are identified and the value of the most powerful one is recorded The power spectral density of all screen locations is integrated between the edges of the channel and is calculated NOTE A correction for the instrument noise floor is made and the power in any signals found in step 5 is included in this calculation The results of the calculation done in step 6 is stored as a desired to undesired ratio The frequency limits that the power was measured within are stored as the signal bandwidth The largest coherent signal found in the undesired
403. ults only when the RS 232 interface is installed in the 2715 The GPIB interface does not support the print function Be sure to select handshaking UTIL 4 0 2 5 to match that expected by the printer or long jobs may not print completely 10 Press 4 to print all stored results of the measurement Again a printer must be connected to the 2715 11 Press 9 to leave the adjacent channel leakage ACL measurement and return to the CATV MEASUREMENTS menu 2715 User Manual Measurements and CSO Measurements 2715 User Manual The methods to make these measurements are Interactive Automatic Automatic with Pause for Carrier Off Single Sweep and for CSO only Continuous Also some of the CSO measurement methods can be performed on an in service basis Interactive mode helps you search for beats The automatic modes let you measure beats when you already know where they occur For the Automatic Automatic with Pause For Carrier Off and Single Sweep modes CSO is usually measured at offsets of 0 75 MHz and at 1 25 MHz for NTSC National Television Systems Committee systems CTB is measured at zero offset A CTB may also be viewed between channels 4 and 5 for a standard channel plan Regardless of the mode selected the first step is to measure the peak level of the visual carrier in the current channel When operated in Continuous mode the carrier frequency measured is that specified in the Setu
404. up to 31 C decreasing linearly to 50 at 40 C erating Equipment Type Testand Measuring Safety Class Class as defined in IEC 1010 1 Annex grounded product Overvoltage Category Overvoltage Category Il as defined in IEC 1010 1 Annex J Pollution Degree Pollution Degree 2 as defined in IEC 1010 1 Note Rated for indoor use only Table A 13 Safety Standards Category Standards U S Nationally Recognized UL1244 Standard for Electrical and Electronic Measuring and Testing Equipment Testing Laboratory Listing Canadian Certification CAN CSA C22 2 No 231 Safety Requirements for Electrical and Electronic Measuring and Test Equipment European Union Compliance Low Voltage Directive 73 23 EEC as Amended by 93 68 EEC EN61010 1 A1 Safety Requirements for Electrical Equipment for Measurement Control and Laboratory Use Additional Compliance UL3111 1 Standard for Electrical Measuring and Test Equipment IEC1010 1 Safety Requirements for Electrical Equipment for Measurement Control and Laboratory Use A 24 2715 User Manual af ee a eee Appendix B Broadcast AM FM and TV Signal Sources AN 2715 User Manual CAUTION To prevent damage when connecting signal sources to the 2715 be certain the total signal strength is less than 70 dBmV If in doubt check with a broadband RF wattmeter or voltmeter For some of the experiments in this manual you need AM or FM modulated signals The most readily
405. urement At the end of the measurement the instrument displays the results and prompts you to move the marker to the second beat Repeat steps 4 through 7 for the second third fourth and fifth beats or press Z to quit at any prompt NOTE If you decide to quit in the middle of the measurement all measurement results up to that point will be retained in a temporary buffer You can then decide to save those results using the STORE CURRENT RESULTS selection or ignore discard them You can also view those results with the DISPLAY RESULTS selection Each time a measurement is made the instrument displays the worst case result up to that point 10 Press CATV APPL to display CTB or CSO menu 5 53 Measurements 5 54 11 Press 1 to store the results of the last measurement After a short period of time the message RESULTS STORAGE COM PLETE is displayed 12 Press 2 to display the results of the last measurement performed A display resembling Figure 5 8 comes up At this point you can choose to either go ahead and view other previously stored results by pressing W or stop viewing the results by pressing Z 13 Press 3 to print the results of the last measurement performed A printer must be connected to the 2715 iE CURRENT CHAN 8 01 92 12 00 00 10 1 250 2 OFFSET 750 000KHZ OFFSET 750 000KHZ OFFSET
406. us 6 26 Frequency Offsets not available in CATV mode 300 0MHz AUTO SWEEP ATTN 12DB 28 8DBMV VF WIDE 20 0MHz 10 DB 5MHz RBW AUTO CALIBRATOR The Marker Frequency Setup Table also enables you to offset the on screen center frequency readout The center frequency itself is not actually changed and the counter readout still indicates the true frequency rather than the offset value This feature is intended to allow the output frequencies of block down converters LNB s used in video communications and other industries to be correctly indicated However it can be used any time a signal has been shifted in frequency by a known amount and you want to display its frequency prior to shifting For example if the signal to be viewed is the output of a down converter with a 5 15 GHz local oscillator perform the following steps 1 Press MKR FREQ to call up the Marker Frequency menu 2 Press 9 to select SETUP TABLE 3 Press 3 to select FREQ OFFSET 4 Enter an offset of 5 15 GHz ignore the CALIBRATOR DOESN T MATCH READOUT warning Notice that the status of item 4 FREQ OFFSET MODE changed from OFF to ON PLUS 5 Press 4 several times The status of the frequency offset cycles through OFF ON PLUS ON MINUS 6 Leave the offset set to ON PLUS and return to the spectral display The center frequency is now indicated as 5450 0 MHz 300 MHz 5150 MHz offset 7 Press
407. used when transporting the 2715 To remove the cover place the 2715 on its back feet then simultaneously pull out and up slightly on each side of the cover Regardless of where the spectrum analyzer is used or installed always provide at least 50 80 mm 2 in clearance adjacent to the cooling vents at the sides bottom and back of the spectrum analyzer See Appendix A Specifications for input power requirements NOTE See the Getting Started section of your 2715 Cable TV System Software Manual for setup instructions needed to connect the 2715 to a personal computer The spectrum analyzer is tough but not indestructible It can be damaged unless the following cautions are observed m Do not apply too large a signal to the input Never apply signals to the RF INPUT connector if their combined amplitude is greater than 70 dBmV 20 dBm or if there is a DC component greater than 100 V If you exceed these input ratings you can permanently damage the spectrum analyzer 2715 User Manual Getting Started If necessary use an external attenuator first Further to prevent damage by transients use maximum RF attenuation when connecting a signal with a DC component Then remove attenuation as needed to make the measurement Also be aware that the 2715 is optimized for a 30 dBm input to the first mixer A larger input signal may lead to nonlinear operation and inaccurate results DO NOT connect a CATV trunk carrying AC p
408. using either disables automatic resolution BW or sweep rate selection respectively RES BW sequences through the installed filters 300 Hz 1 kHz 3 kHz 10 kHz 30 kHz 100 kHz 300 kHz 1 MHz 5 MHz SWEEP follows 1 2 5 sequence from 2 s div to 1 us div Rates 100 us div are useable only in the analog display mode CAUTION The spectrum analyzer RF signal input is an F type 75 Q connector Observe Maximum Input Ratings Input signal Maximum Amplitude 70 dBmV Maximum DC 100 Volts Frequency Range 9 kHz to 1 8 GHz Operating Basics External Trigger Input BNC Female VERT Trigger Level gt 0 1 V lt 50V Peak TRACE pos HORIZ Ventilation Openings Duration gt 0 1us ROT POS DO NOT BLOCK CU TUN y N N x X Accessory Connector DB 9 Female For Model 1405 TV Ext O Sideband Analyzer or lt 50V J102 J103 2707 External Tracking Generator 5 TEST Communications Connector Depends 90 250VAC 48 63Hz on Interface Selected 90 132VAC 48 440Hz See Programmer 110WATTS MAX Manual C 2A Option 15 FirstLO Output CX A SMA Female 500 00000 J101 Figure 3 9 The 2715 Back Panel 3 10 2715 User Manual Operating Basics The remainder of this section shows structure of the menus and submenus displayed by pressing the following keys in the MENUS block m SWP TRIG m UTIL m MKR F
409. ution bandwidths lt 1 MHz Noise Sidebands for all resolution bandwidths lt 100 kHz lt 70 dBc at 30X Resolution Bandwidth Video Filter Table A 3 Frequency Amplitude Related Characteristics Characteristic Performance Requirement Marker Accuracy Frequency Amplitude Delta Marker When activated a second marker is displayed at the same frequency as the first marker This is the Reference Marker Reduces video bandwidth to about 196 of the selected resolution bandwidth or one of 12 video filters 3 Hz 10 Hz 30 Hz 100 Hz 300 Hz 1 kHz 3 kHz 10 kHz 30 kHz 100 kHz 300 kHz or WIDE can be selected from the UTIL menu Supplemental Information The frequency and amplitude values of the marker position are displayed and are preceded by the letter M MKR MKR 4 position the marker to the next right or left signal peak respectively Same as SPAN DIV function ofthe reference level vertical scale factor and normalizations see Display Dynamic Range on page A 15 Also flatness corrections while in CATV mode for range of 15 MHz to 1 105 GHz The FREQ MARKERS control may be used to position the first marker the frequency and amplitude differences between markers are readouts preceded by the letter D Accuracy Frequency 1 PPM 10 Hz of the higher marker frequency With both signals counted Amplitude Same as Marker 2715 User Manual A 13
410. vides a signal search feature that enables you to detect signal peaks over a wide frequency range while still using a narrow span and or resolution BW The 2715 sequentially implements a series of searches using the marker peak find capability and the span and resolution BW that you specify using the Signal Search menu Each search range is equal to 10 times the specified span div but each search range except the first overlaps the previous range by one division 2715 User Manual Spectrum Analyzer Menus 2715 User Manual The first search starts at the beginning frequency and the last stops at or overlaps the end frequency as indicated in Figure 6 10 Although the last search range may overlap the end frequency no signals are reported above the end frequency A verification process looks at the entire range twice and reports only those signals which are present both times Total Search Range 15 2nd Last 1 Search Search Search Range Range Range begin 10xSPAN 7 DIV E o DIV DIV a 10xSPAN 10xSPAN Last Search Range fend 10xS PAN DIV Note the SPAN DIV overlap of each search range Figure 6 10 The SIGNAL SEARCH Frequency Range To see how SIGNAL SEARCH works reset the following 2715 controls to search the frequency range from 55 to 550 MHz SPAN DIV 5 0MHz RESOLUTION BW 300 0KHz REFERENCE LEVEL 28 8DBMV VIDEO FILTER 300 0KHz 1 Press INPUT 9
411. y IN CHAN RESP SETUP TEST SIGNAL LINE NUMBER IN SERVICE LEAVE IN CHAN RESP HS NOTE If you attempt the in channel response measurement based on VITS or ghost cancelling signals carried on the program video strong periodic signals in the video waveform may corrupt the measurement Choose the in service basis with menu item 7 to resolve this problem If you are not measuring in service it is recommended that you have a test signal generator warmed up and connected to the on line switcher 3 Press 5 0 to select the Interactive mode 4 Press BKSP 0 to run the measurement If you are not running the test in service the instrument pauses and prompts you to enable a full field test signal Multiburst or Line Sweep 5 65 Measurements 5 66 10 11 If not running this test as in service replace the modulating video source with a full field multiburst signal or a full field line sweep signal and press W to continue with the measurement The instrument measures the visual carrier peak then prompts you to move the marker to the first test location Use the FREQ MKRS knob to move the marker to the first test location Press W to continue with the measurement The instrument measures the amplitude of the test signal at the marker location then prompts you to move the marker to the second test location Press W to continue with the measurement Press C
412. y from 1 to 525 Therefore the range of potentially valid line numbers for the test signal will be 10 through 20 for odd numbered fields or 272 through 282 for even numbered fields For systems using the Phase Alternation Line PAL standard the test signal line number is typically line 6 through line 20 and line 318 through line 332 NOTE If the only quiet lines available are beyond the ranges listed above then you must specify the quiet line in the channel table using the Cable TV RF Measurements Software for Windows provided with your instrument In this case the in service test is run on the specified line even though it is outside the normal range but there is no verification that the line is still quiet after the test Select the measurement mode from the IN CHAN RESP SETUP menu before initiating the test The Interactive mode assists you in selecting a pair of measurement points The Automatic mode allows measurement levels at up to five locations that are entered using the IN CHAN RESP SETUP menu If you did not choose the in service basis you will be prompted to replace the modulated signal with a test signal for either interactive or automatic modes NOTE When doing the In Channel Response test in service and if the channel under test has a carrier level of 2 dBmV or less it is necessary to turn on the preamp and select an RF attenuation setting such that a Ist mixer input level of 2 dBmV or greater is maintained
413. y menu and its submenus are used by service personnel to troubleshoot the 2715 Therefore not all selections are discussed here If the instrument is not already initialized to factory settings press UTIL 1 1 900 0MHz AUTO SWEEP ATTN 50DB 68 8DBMV VF WIDE 180MHz MAX 10 DB 5MHz RBW AUTO Although the 2715 controls are most conveniently activated or set using the dedicated front panel controls the Utility menu provides a method of setting all the major control functions from a single submenu This feature is especially useful when you are setting up a new measurement and know ahead of time how the 2715 15 to be configured The following example uses the Utility menu to reset the center frequency reference level and span You could also set the resolution BW video filter vertical scale and sweep rate 1 Press INPUT 9 to turn on the calibrator 2 Press UTIL 2 to select the KEYPAD ENTERED SETTINGS from the Utility menu This item enables you to set instrument controls to specific values from a single menu without having to use the front panel controls 3 Press 0 to select FREQUENCY 4 Press 1 0 0 X to enter a value of 100 000 MHz for the center frequency The Keypad Entered Settings menu shows the frequency to three decimal places whereas the on screen readout displays the specified frequency from Zero to four decimal places depending on the span Both values are truncated figures but th
414. ystem messages can occur within the warm up period particularly if you switch the spectrum analyzer to a narrow span or resolution bandwidth BW filter You may also see the following phrase during warmup NORMALIZATION SUGGESTED Normalization is a process by which the 2715 measures and stores its own calibration parameters using a built in reference When this message appears the instrument is reporting that its self test feature has determined that its perfor mance no longer matches that predicted by the previous normalization It is not unusual for the message to appear during the warm up period especially if a narrow resolution bandwidth filter is called for by user defined power up settings or if the ambient temperature is different than that at which the previous normalization was performed If the message remains or reappears after the warm up period a new normalization should be carried out Normalization ensures the utmost accuracy when making measurements We suggest that whenever maximum accuracy is required you allow your instrument to reach a stable operating temperature in the environment in which the measurements will be carried out and then perform a normalization before making the measure ments Perform a normalization to ensure the calibration of the 2715 and to verify its operational status Additional information about normalization may be found in Normalizing the 2715 on page 6 65 1 To do an initial normaliz
415. zer see the previous discussion of J101 on page E 1 E 3 Appendix E External Input and Output E 4 Pin 3 Chassis and Signal Ground Pin 5 Video Output The video signal can be any signal limited to a 0 50 KHz band and an amplitude range of 0 1 4 V The 2715 preamplifier RF attenuator mixer resolution bandwidth filter and log amplifier circuits are bypassed The sweep rate and vertical scale circuits are utilized Since the digital storage remains active you can use the 2715 to store images of external signals for comparison purposes or compile statistical estimates of their parameters using ensemble averaging To experiment you need a signal meeting the external input amplitude and frequency limits Various signal generators can be used m Connect the signal source to pin 1 of the Accessory Connector and its ground lead to pin 3 Toggle DSPL menu item 7 DISPLAY SOURCE to EXTERNAL The 2715 reverts to the display mode in zero span there is no need to sweep the signal past the resolution bandwidth filter since these circuits are bypassed The top graticule line is 0 V The only information in the left on screen readout that is meaningful is the sweep speed The sweep speed is initially the speed in effect before you switched to EXTERNAL source in this case 50 ms division The only information in the right readout that is meaningful is the bottom line EXT 175MV indicating that the external EXT input is

Tektronix 2715 Spectrum Analyzer user manual

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