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AW8920A Return Loss & Cable Fault Test Set

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1. 16 3 RL Tebt 1 2 5 d MHz Trage 1 fis tha HP Ahalyzer 16 u Ch2 Mke2 50 000 MHz 16 1 dB 2 3 4 5 6 7 p 8 4 9 Compafison pf Coupler W Vector Galibrated HPB714B Start 3 MHz Stop 1 800 088 MHz Start 300 MHz Stop 1 MH 1 Mkr MHz dB 2 Mkr MHz dB iig 40 00 16 27 46 08 15 99 150 00 16 41 22 150 00 16 11 3 4608 08 16 57 3 560 00 16 78 H 800 00 16 87 800 00 17 24 Expanded scale comparison plot of a 16 3 dB test termination Notice the scale of the reading and how closely the coupler red trace matches the vector calibrated blue trace Airwave Inc 32 bliReflection M Log Mag 10 8 dB Ref dB 22 Transmission M Log Meg 10 0 dB Ref 0 00 dB 18 29 Taal 30 48 58 68 78 88 90 Abs Comparison RL Measurement of a Portablg Antenna 888 21 Start 8 300 MHz Stop 1 500 088 MHz 1 Mkr MHz dB 2 Mkr MHz dB 1 258 88 EE 1 258 08 4 80 500 00 6 97 2 500 00 6 65 3 750 80 2 3 750 00 13 95 E 1808 00 5 82 1000 00 morol 1250 00 1 86 5 1250 00 1 93 1500 00 1 45 6 1500 00 37 Comparison plot of a 800 Mhz portable antenna measured in a test fixture Notice that the span width has been i
2. Chi MkrS 1888 00 MHz 18 UCET 20 30 ug 5 60 7 88 9 Abs Compatson Plot of VHF Antenna 12 ft Cable Start 8 308 MHz Stop 1 080 088 MHz 1 Mkr MHz dB 2 Mkr MHz dB 11 ug 00 1 5 l 46 08 68 150 00 13 84 2 150 00 12 96 3 468 08 42 08 3 468 08 820 00 Z 4 u 820 08 6 88 gt 1808 00 5 gt 1000 00 9 69 Comparison plot of a VHF mobile antenna on a mag mount base with 12 ft of cable Airwave Inc 33 Sree Teh ANALYZER BW 300 kHz 501 00000 Lvl 2 ERE 0 78 4 2 PE lt 4 lt 4 lt lt lt 4 Pr m mr PIE Controls Ref Level 1 dBm Cable test standing wave pattern TESTS IBASIC Controller 0 lt 3 37 5 56 25 Distance ft Automated test of fifty foot cable Measurement made on the HP8920 running System Support Tests software Airwave Inc 34 Appendix B Maintenance and Retuning Procedures for Antenna Duplexers By Bill Lieskie of EMR Corporation Phoenix AZ EMR Corp Used by permission EMR Corporation manufactures a broad line of antenna duplexers for fixed repeater station applications The following information is offered for the systems engineer or applications technician Duplexer type descriptions comparisons of duple
3. sy teint eI RR ET Spectrum Analyzer teneo ador c ee e CU OF EROR D PE Ue erre rH rrr d P Qo pedites NIME EE Normalizing Settings Notes Adaptors and Jumpers Testing neon ee eae Network Analyzers es iege re e Y re De n Qe EESTI Seta Lea Re ro Qo a Hava Ce ra Rede 14 MEASUREMENT PROCEDURES sun ee 15 Cables hr bested epe 15 BasesAntennds ess ene pl 15 Mobile Aritenn s 8 ete ea eter ee en eive ete Nee 16 Portable Antennas 17 Preamps and feceivers iid rt e ER 17 Mn PIC te cusses ce i 17 Duplexers Filters od ioi bU 18 Site Noise and Receiver Sensitivity iie eoe XY SERRE 19 IMPROVING ACCURACY DETUR REDE PIDE 21 Reliable MeasuremenbRdflige ssid fects S Rte NEIN RUE potete ER 2l SOUNCES Of ETTOTS d eb ario te eee eb tyre ead ese aod ated 2l Establish a Reference ei niire iie iio 22 Using dn Adapter OF Jumper ad ou eerta ed 23 L9 V 11 BI Oif OLOR MM MEETS 25 FAULT LOCATION estate nte Rn ep D tui eene a itu T 25 Test SCHIP se si ku SER 25 TOSIhg xa iss e t e e e SN RR IR es 26 VELO
4. a 1 LLLI 5 2 woke 2 0 aum med m uu a TIPP D primit D ILI B 5 Pr e D 30 e termi inati i ion with an adapt or in li line Airwave Inc 30 kHz BHz Marker Frea SPECTRUM ANALYZER Normalized 452 72500 f 0 ep p FEE Center Frea IHT E ol Ref Level xc c Transmission characteristics of a band pass filter 30 kHz SPECTRUM RHRLYZER Marker Frea Normalized 452 72500 ca To Screen 27 gt nfi 11111100 4 Z HHL DE
5. 9 Drive the RX port and terminate the TX port 10 Using the same procedures as given in steps 1 through 8 tune the RX branch The skirt response is the rejection of the transmitter carrier and must meet or exceed system requirements according to transmitter power When accomplished go to the next step 11 If equipped for return loss measurement drive the antenna port at a frequency about midway between the transmit and receive channel frequencies Expand analyzer frequency range to permit viewing both frequencies You can now monitor the loss toward the T and R ports by monitoring one of them and terminating the other You can also see the return loss that the antenna port at each frequency It should be at least 26 If either or both are less you must go through each branch procedure again to find the optimum of loss reject and return loss at all ports Airwave Inc 39 It will be found that most bandpass duplexers will tune readily if the frequency change is small If a significant change in either or both frequencies is made and poor performance results loop setting cable lengths may have to be changed We recommend retuming the duplexer to its original manufacturer for this level of retuning The required cable lengths and loop setting procedures vary from one manufacturer to another according to design philosophy making it the least problem for the original manufacturer to affect such changes We also recommend that all expanded b
6. For 125 watt or higher transmitter powers at least 95 dB of noise rejection is needed and up to 120 dB where T R spacings are close under 1 Mhz in VHF 3 Mhz in UHF and 6 Mhz in 800 960 Mhz band 6 If equipment for return loss measurement is available you should see a R L of 26 dB or higher at the transmit frequency Reverse the drive and monitor leads to check the R L at the antenna port at the TX frequency 7 Reverse the leads again Adjust the frequency source and display to the new transmit frequency Now tune all cavity adjustments sequentially until a peak or overall response is achieved If equipped for expanded range measurement check the nose of response to see if it meets rated insertion loss 8 Observe the R L at the new frequency Carefully adjust all cavity tuning for best attainable return loss consistent with lowest branch insertion loss Where two three or more cavities are used in each branch go through the cavities several times to find the optimum Note that it may be possible to secure and excellent return loss but with a higher insertion loss than the duplexer s rating Note also that the pass band geometry should be a smooth skit dropping symmetrically on either side of the peak of response If other bumps in the response pattem or a marked difference in skirt slope exists improper tuning is usually indicated Keep going through the string of cavities over and over until the desired responses are obtained
7. ba Standing Wave Pattern of Unterminated Cable Same Cable Terminated in Short Circuit Preparation Cutting Cutting Cable to a Desired Wavelength Sometimes it is desirable that several cables be trimmed to have a particular electrical length such as when preparing interconnecting cables for a duplexer or isolator Half wavelength cables present a well matched source and load with phase relationships delayed but essentially unchanged A quarterwave stub can be useful for suppressing interference at the tuned frequency and a length of cable can often serve as an impedance transformer to match a mismatched source and load Set up the test set as described in the previous section entitled Cable Tests 1 Using the following equation calculate the approximate length of cable needed for the desired wavelength A of cable at your desired frequency f 571 s f 299 792 Vi Meters A See Appendix G to find the velocity of propagation Vr for many cable types Or Length 2 Measure your cable length from the above equation plus a little extra to account for Vr variations If you are making a jumper and the length of cable you will need is longer than your calculated length cut in multiples of the calculated length plus a small amount to allow trimming 3 Install one connector to the cable and connect to the test setup Set t
8. 29 BW 30 rk 0 kHz Frea i 501 00000 To Screen eel SP ECTRUM RHRLYZER N ormalized EE ES docas showing the appr oximate measur ement range wecece ee 4 4 1111 aT f fee n ter 1011 Test set IS ter minated W ith a precisio minat eee sessvsepen scopone woeqee sese e P oo 22 P A copes coco ssedesese ssvese sactdoces c o eco So im BW 30 m zig Frea 501 00000 To Screen T RUM ANALYZER g r 7 T 1 H Q te age EEE e n e DP A 5 sechecee e gener sree 222 nemen 5 0 a e
9. 406 450 Mhz 450 512 806 896 Mhz 896 960 Mhz bands Standard expanded pass band duplexers are available for the 806 821 851 866 Mhz and 896 901 935 940 Mhz SMR system bands Special model broad band band pass models capable of serving multiple transmitter receiver system in all bands are available where uniform T R channel pairings are present The characteristics of the band pass duplexer are such that sufficient rejection of transmitter wide band noise harmonic and spurious emissions are provided along with narrow pass band responses to protect the receiver not only from its associated transmitter emissions but from all other undesired signals Transmitter spurious and harmonic radiation s are also controlled by the highly selective band pass characteristics Branch losses are generally higher than other duplexer types since each cavity must be set for at least 0 5 dB of coupling factor to secure required branch selectivitys The minimum T to R spacing that can be used is determined by cavity Q More cavity elements are required for a given T R spacing than for the other duplexer types resulting in higher costs to manufacture Band Reject Duplexers This duplexer type employs one or more notch type cavity resonators in each branch depending on T R frequency spacing operating frequency band and transmitter power level In this design a single loop is used to excite each cavity using the resonant response of the cavity to define a rather
10. 800 67 64 48 08 158 00 66 57 158 080 46 29 460 00 67 44 460 98 46 13 808 00 66 57 800 00 47 17 Typical Directivity of the Coupler Red Trace as measured on an HP8714B Network Analyzer blue trace is calibrated measurement limit of the 8714 Airwave Inc 2 Specifications 8920 20 4 Directional Coupler Impedance epe ORO o m P Gt d 500 Frequency of oido ovans Uude 0 1 1000 Mhz DD ROB RIO BE EB eg DERE See Plot at Left Coupling 19 5 Insertion Loss Typical ES Rare 0 7 dB Maximum Continuous Input Power at 1 Mhz or 33 dBm 2 W Maximum Intermittent Input Power 1 Mhz 10 Seconds On I Minute 38 dBm 6 W AWR 2050 Resistive Power Divider ek ee he Ds Ae ROR OA Ae bias See See beh E 50 Q Frequency Of Operation eee petierit eene DC 2000 Mhz Isolation BR SUE ee NIU Ine UBI eee 6 6 dB Insertion Loss Above 6 dB Typical pct te RERO Hehe seder eten 0 3 dB Phase Unbalance Typical tete rete RUE RR p eere ERE 27 Amplitude Unbalance Typical 0 2 dB Matched Power Rating Ge DEFERRI 1W Internal load dissipation oet ere ie I tree ne eng o bee eee er E 0 125 W Attenuators Impedance co aeogerodat up eon ats ode
11. RL Experience has shown that these errors are almost always less than the above maximums and unless you are using a specialized spectrum analyzer or network analyzer are usually insignificant compared to the frequency response errors almost certain to exist in your measurement instrument Directivity error is the collective imperfections within the directional coupler that allow a signal from the source to leak directly to the measurement port and limit the directivity of the test set Directivity error is the most significant error term for RL measurement Directivity Error limits the effective measurement range of the test setup and contributes errors to readings primarily beyond 25 dB RL With an RL reading of 25 dB directivity error will contribute an uncertainty of about 1 0 dB and at an RL of 35 dB uncertainty of about 3 to 2 dB As a rule of thumb if the directivity of the coupler is about 10 dB greater than the reading at the frequency of interest the measurement will be reasonably accurate Be sure to see the measurement comparison test results in the appendix 1 2 3 4 To obtain the highest degree of accuracy possible from the return loss test set setup as usual without attaching any adapters or jumper cables if needed to the test port just yet Normalize the display by performing the Save B A B analyzer function if available or by tracing the displayed line on the analyzer wit
12. Velocity of 3 227 491 7855 0 695 7 13440625 Distance in Feet Frequency in Mhz to Fault See Above When an unterminated cable is connected to the Source port a standing wave pattern is displayed on the analyzer screen whose frequency of repetition is related to the length of the cable under test or the distance to a fault The longer the cable the higher the frequency of repetition If the span of the spectrum analyzer you are using is too narrow or the length of cable under test is too short this pattern may not seem evident at first Using an IFR 1200 for example 10 Mhz span maximum any cable less than about thirty five feet long will be too short to see the standing wave pattern To view the wave the center frequency of the generator can be varied to find a dip in the analyzer trace Make a note of this frequency and find the next adjacent dip then calculate the frequency difference between the two dips This is the half wave frequency The length of the cable can now be found by the following 3 D 1 f Where D Distance to fault or end of cable C Speed of Light 983 571 for ft per second or 299 792 for m per second Vr Velocity of Propagation of the cable under test f Frequency in Mhz determined by the above test and calculations The speed of light is expressed in feet or meters per second and will yield results in the same unit of measure The Velocity of Propagation can
13. adjust the input inter stage if a dual type and output tuning capacitors of the isolator for lowest indicated overall insertion loss do not adjust the load port capacitor s at this time 2 Now drive the antenna port and monitor the isolator input port Adjust the isolator load port capacitor s for the greatest isolation 3 If the isoplexer is equipped with a 2nd harmonic filter drive the isolator input at 2X the transmit frequency while monitoring this frequency at the duplexer antenna port Adjust the filter tuning capacitor to place it s notch at the harmonic frequency Note If the isolator is broadband or fixed tuned device check losses and tune the harmonic filter as in step 3 above Hints and Kinks Errata Often if a duplexer has been seriously detuned cables damaged etc it will be best to pretune each cavity separately for pass or pass reject characteristics Care must also be used to avoid exchanging cables since all cables are critical in length If a cable must be replaced use the exact cable type and connector types and make sure that the cable is the exact length as the original Cavities having rotatable adjustable loops should not be changed under frequency change procedures since these adjustments can be very critical and the effective electrical length changes as the loop coupling factor is changed Note that it is rare that calibrations placed on rotatable loops are accurate over a range of loop coupling adjustme
14. at the output port of a preamp can also be measured if the power levels involved do not exceed the ratings of the test set or the analyzer Before tuning test the isolator at the factory tuned frequency and make note of its performance Measure the insertion loss of the isolator both forward and reversed Then measure the return loss at the input and output ports Make sure the isolator load is connected Compare this performance with the isolator after retuning to be sure performance is acceptable Also be sure to perform an RL test of the isolator termination s to be sure of their acceptable performance RL of 26 dB is optimal Set up your spectrum analyzer and tracking generator as shown The 6 dB attenuators serve to move the measurement plane directly to the isolator and remove the test leads from the measurement This setup is recommended if the test leads exceed 1 20 Remember to account for the 12 dB loss in your readings or perform a normalization function with a Airwave Inc 17 C2 Output Single Isolator CI C2 C3 C4 Output C6 Dual Isolator Duplexers and Filters barrel connector in place of the isolator Set the sweep width to cover both the old frequency and the new frequency if possible Tune capacitors and C2 C2 C3 and C4 for a dual isolator to move the pass band from the old frequency to the new tuning for lowest loss Reduce the sweep width and continue adjusting u
15. broad selectivity characteristic centered on the transmit and receive frequencies The coupling loop is resonated by a series capacitance to form a notch element The notch in the receiver branch is tune to reject transmitter in the transmitter branch is used to trap out residual transmitter wide band noise existing at or near the receiving frequency With a given cavity size the spacing between transmit and receive frequencies decreases the notch depth becomes less and throughput losses become greater As T and R frequencies are brought closer together more cavities are required to provide needed rejection of transmitter noise and carrier powers as needed to yield interference free duplex isolation and resulting branch losses increase The benefits of this duplexer type include lowest possible loss in each branch use of smaller cavity resonator dimensions smallest overall duplexer size and lowest cost to manufacture The disadvantages are that the pass responses are very broad providing very little protection against the radiation of harmonics or spurious emissions present in the transmitter s output and little or no improvement in the receiver s front end selectivity EMR Corporation manufactures band reject duplexers for all bands from 136 Mhz through 960 Mhz as standard models and for frequencies below 136 Mhz on special order Airwave Inc 35 Pass Reject Duplexer Types This duplexer design is similar to the straight band reject typ
16. dB 53 4696 34 8496 7 50 dB 462 3496 82 2296 1 88 dB 54 1796 35 14 7 60 dB 475 44 82 62 1 90 dB 54 88 35 43 7 70 dB 488 84 83 02 1 92 dB 55 60 35 73 7 80 dB 502 56 83 40 1 94 dB 56 31 36 03 7 90 dB 516 6096 83 7896 1 96 dB 57 04 36 32 8 00 dB 530 96 84 15 1 98 dB 57 76 36 61 8 10 dB 545 6596 84 5196 2 00 dB 58 4996 36 9096 8 20 dB 560 69 84 86 2 10 dB 62 18 38 34 8 30 dB 576 08 85 21 2 20 dB 65 96 39 7496 8 40 dB 591 8396 85 5596 2 30 dB 69 8296 41 1296 8 50 dB 607 9596 85 8796 2 40 dB 73 7896 42 4696 8 60 dB 624 4496 86 2096 2 50 dB 71 8396 43 77 8 70 dB 641 3196 86 5196 2 60 dB 81 9796 45 0596 8 80 dB 658 5896 86 8296 2 70 dB 86 2196 46 3096 8 90 dB 676 2596 87 1296 2 80 dB 90 5596 47 5296 9 00 dB 694 3396 87 4196 2 90 dB 94 9896 48 7196 9 10 dB 712 8396 87 7096 3 00 dB 99 5396 49 8896 9 20 dB 731 7696 87 9896 3 10 dB 104 1796 51 0296 9 30 dB 751 1496 88 2596 3 20 dB 108 9396 52 1496 9 40 dB 710 9696 88 5296 3 30 dB 113 8096 53 2396 9 50 dB 791 2596 88 7896 3 40 dB 118 7896 54 2996 9 60 dB 812 0196 89 04 3 50 dB 123 87 55 33 9 70 dB 833 25 89 28 3 60 dB 129 09 56 35 9 80 dB 854 99 89 53 3 70 dB 134 42 57 34 9 90 dB 877 24 89 77 3 80 dB 139 88 58 31 10 00 dB 900 00 90 00 3 90 dB 145 47 59 26 10 10 dB 923 29 90 23 4 00 dB 151 19 60 19 10 20 dB 947 13 90 4596 4 10 dB 157 0496 61 1096 10 30 dB 971 5296 90 6796 4 20 dB 163 0396 61 98 10 40 dB 996 48 90 88 4 30 dB 169 15 62 85 10 50 dB 1022 02
17. edd ee det hi diens 500 Frequency of Operation rette dte ctetu DC 1500 Mhz Nominal Value encre tibi pee ete ert f eee ttp ere Re ese meten teh 0 3 dB Flatness To 1000 Mh2 uti eicere 0 6 dB VSWR TO 1000 Mhh ncetbo inet tat eimi tese ettet licet EE 1 5 1 Termination s ups 500 Frequency of Operation eo acest Gate DC 2000 Mhz Return 055 5 is elei Up ERIS 30 dB Typical 40 dB 500 Mhz Maximum Input 0 25 W Airwave Inc 3 Airwave Inc 4 Kit Contents Care and Handling Warranty Limitation of Warranty Unpacking The standard AW8920A Return Loss and Cable Fault Test Kit is supplied with the following Items Directional Coupler Resistive Power Divider Two 2 6 dB Attenuators Precision 50 Termination Two 2 Low Loss Test Leads Carry Case Users Manual and Quick Start Guide QI GN Que Dr Every effort has been made to insure durability of all kit components They remain however delicate electronic devices The directional coupler is by far the most sensitive part in the kit NEVER drop the coupler on a hard surface and NEVER remove the cover The physical placement of all the internal parts that make up the coupler the wires transformers etc are very critical A hard shock to the coupler could adversely affect performance Other components of the kit are far less sensiti
18. fW 0 056 uV 7 199 5 uW 99 88 mV 70 100 0 pw 70 71 uV 133 0 050 fW 0 050 uV 8 158 5 uW 89 02 mV 71 79 4 pW 63 02 uV 134 0 040 fW 0 045 uV 9 125 9 uW 79 34 mV 72 63 1 pW 56 17 uV 135 0 032 fW 0 040 uV Airwave Inc 44 Appendix F Decibels to Percentage Gain or Loss dB Change Gain Loss 0 10 dB 2 3396 2 2896 0 12 dB 2 8096 2 73 0 14 dB 3 28 3 17 0 16 dB 3 75 3 62 0 18 dB 4 23 4 06 0 20 dB 4 71 4 50 0 22 dB 5 20 4 94 0 24 dB 5 68 5 38 0 26 dB 6 17 5 81 0 28 dB 6 66 6 24 0 30 dB 7 1596 6 6796 0 32 dB 7 6596 7 1096 0 34 dB 8 1496 7 5396 0 36 dB 8 6496 7 9696 0 38 dB 9 1496 8 3896 0 40 dB 9 6596 8 8096 0 42 dB 10 1596 9 22 0 44 dB 10 66 9 64 0 46 dB 11 17 10 05 0 48 dB 11 69 10 46 0 50 dB 12 20 10 87 0 52 dB 12 72 11 28 0 54 dB 13 24 11 69 0 56 dB 13 76 12 10 0 58 dB 14 29 12 50 0 60 dB 14 82 12 90 0 62 dB 15 35 13 30 0 64 dB 15 88 13 70 0 66 dB 16 41 14 10 0 68 dB 16 95 14 49 0 70 dB 17 49 14 89 0 72 dB 18 03 15 28 0 74 dB 18 58 15 67 0 76 dB 19 12 16 05 0 78 dB 19 67 16 44 0 80 dB 20 23 16 82 0 82 dB 20 78 17 21 0 84 dB 21 34 17 59 0 86 dB 21 90 17 96 0 88 dB 22 46 18 34 0 90 dB 23 03 18 72 0 92 dB 23 59 19 09 0 94 dB 24 17 19 46 0 96 dB 24 74 19 83 0 98 dB 25 31 20 20 1 00 dB 25 89 20 57 1 02 dB 26 47 20 9396 1 04 dB 27 06 21 30 1 06 dB 27 64 21 66 1 08 dB 28 23 22 02 1 10 dB 28 82 22 38 1 12 dB 29 42 22 73 1 14 d
19. handling rating of the duplexer 3 Ranges of the covity resonator tuning and loop adjustment methods if a band reject or pass reject type 4 Range over which the duplexer may be tuned without modification of jumper cables loop sizes etc 5 Availability of proper test equipment in terms of frequency stability display measurement range both maximum and minimum 6 The correct procedure to be used to most effectively accomplish the retuning procedure The following points might be of help in determining these variables A If the duplexer is to be moved to frequencies within no more than 1 of its nominal frequency range 9 1 5 Mhz in the 150 Mhz range 4 5 Mhz in the 450 Mhz range or 7 8 Mhz in the 800 Mhz band and the T R spacing is the same as originally supplied it can probably be retune successfully Note that broad banded duplexers are usually optimized with loops and cables required for the exact band pass and T R spacing as factory tuned Such models are best returned to the factory for retuning B Attempts at retuning a duplexer with inadequate test equipment proper instructions and knowledge of how the particular duplexer functions will usually result in failure We regularly retune duplexers of our own manufacture or those made by other companies and can attest to their condition of tuning when received if such has been attempted under improper procedures C Before trying to retune or even to touch up the tunin
20. is always best to avoid using adaptors or jumpers whenever possible Once connected and setup as described above the spectrum analyzer will display the return loss of anything connected to the Device test port of the set Since return loss is a measure of the reflected power from the device under test a lower trace on the analyzer display indicates a better impedance match to 50 ohms Since spectrum analyzers are calibrated in decibels and since return loss is a logarithmic expression the analyzer reads return loss directly To see the approximate measurement limits of the test setup connect the 50 precision termination to the test port after following setup procedures as outlined above The resulting display is an approximate limit of measurement The actual measurement limit can only be found by using a special calibration termination It is assumed that most users of our kit will not have access to an instrument of this class If you happen to be fortunate setup as shown in the diagram and perform the calibrations as described in your user s manual By using a network analyzer reflection measurements can be made with great precision and accuracy Enjoy Airwave Inc Cables Base Antennas 1 J Measurement Procedures The following are some examples of how the return loss test set can be used to perform some useful tests Many more uses are possible than are listed here Generally any passive network
21. or low power amplifier designed for 50 ohms can be characterized using this return loss test set When testing a device with more than one port it is important to terminate all unused ports with a 50 ohm termination The directional coupler can also act as an isolating combiner combining two signals into one with the signal sources isolated from each other The following examples assume that setup and any calibration s as described previously have been performed Setup the test set with a 0 dB reference line as described under the section Improving Accuracy page 21 Attach one end of the cable under test to the coupler The other end should be unterminated or shorted either way is fine Use a shorting termination not a piece of wire Divide the measurement reading by two to find the approximate loss of the attached cable and its connectors Perform a cable fault check to be sure there are no breaks in the cable since this measurement would not indicate this except in the possible case of abnormal results Before attempting antenna measurements the location of the antenna to be tested must be considered If high power transmitters are anywhere within a few thousand feet it is possible that excessive power may be present at the connector of the antenna to be tested This must be checked before proceeding Terminate a wattmeter with a dummy load and connect it to the antenna connector Any power measured must be less than 2 wa
22. spacings The recommended procedure for tuning band reject and pass reject duplexers is as follows 1 Normalize your test setup as covered under band pass auolexer tuning 2 Drive the duplexer transmit port monitor at the duplexer antenna port and terminate the receiver port with a 50 ohm load Adjust the cavity tuning rods for lowest insertion loss and best return loss at the desired transmit frequency 3 Drive the receive port at the receive frequency with the transmit port terminated and adjust the cavities for lowest insertion loss and best available return loss 4 While driving the receiver port and monitoring at the antenna port tune to the transmit frequency and adjust the notch tuning of the receive cavities to place the notches exactly on the transmit frequency 5 Now drive the transmitter port again and adjust the transmit cavity notch capacitors to place the notches on the receive frequency 6 Repeat steps 2 through 5 Note that the cavity main tuning and notch tuning are somewhat inter relative With fairly close spaced duplexers three or four times through the procedures may be needed to secure best overall performance The return loss at both the transmit and receive ports should be 26 or better If not some compromise in cavity tuning may be required to secure this even at some slight expense of insertion loss Note that any time a cavity is adjusted it s loop must again be adjusted to re position the notch 7 No
23. 1 e a a a c v v we 74 Ul 8920 View of screen prior to performing normalization 300 kHz 501 00000 RNRLYZER BH Marker Frea Normalized a L D JE 0 00 Ref ER A LAL 4 4 Screen 1 4 DE Same test setup after performing a Save B normalization function Airwave Inc
24. 2 6 fW 0 793 uV 16 39 8 mW 1 41 47 20 0 nW 1 00 mV 110 10 0 fW 0 707 uV 15 31 6 mW 1 26 48 15 8 nW 890 19 uV 111 7 9 fW 0 630 uV 14 25 1 mW 1 12 49 12 6 nW 793 39 uV 112 6 3 fW 0 562 uV 13 20 0 mW 1 00 V 50 10 0 nW 707 11 uV 113 5 0 fW 0 501 uV 12 15 8 mW 890 19 mV 51 7 9 nW 630 21 uV 114 4 0 fW 0 446 uV 11 12 6 mW 793 39 52 6 3 nW 561 67 uV 115 3 2 fW 0 398 uV 10 10 0 mW 707 11 mV 53 5 0 nW 500 59 uV 116 2 5 fW 0 354 uV 9 7 9 mW 63021 mV 54 4 0 nW 446 15 uV 117 2 0 fW 0 316 uV 8 6 3 mW 561 67 mV 55 3 2 nW 397 64 uV 118 1 6 fW 0 282 uV 7 5 0 mW 500 59 mV 56 2 5 nW 354 39 uV 119 1 3 fW 0 251 uV 6 4 0 mW 446 15 mV 57 2 0 nW 315 85 uV 120 1 0 fW 0 224 uV 5 3 2 mW 397 64 mV 58 1 6 nw 281 50 uV 121 0 794 fW 0 199 uV 4 2 5 mW 354 39 mV 59 1 3 nW 250 80 uV 122 0 631 fW 0 178 uV 3 2 0 mW 315 85 mV 60 1 0 nW 223 601 uV 123 0 501 fW 0 158 uV 2 1 6 mW 281 50 mV 61 794 3 pW 199 20 uV 124 0 398 fW 0 141 uV 1 1 3 mW 250 89 mV 62 631 0 pW 177 62 uV 125 0 316 fW 0 126 uV 0 1 0 mW 223 600 mV 63 501 2 pW 158 30 uV 126 0 251 fW 0 112 uV 1 794 3 uW 199 29 mV 64 398 1 pW 141 09 uV 127 0 200 fW 0 100 uV 2 631 0 uW 177 62 mV 65 316 2 pW 125 74 uV 128 0 158 fW 0 089 uV 3 501 2 uW 158 30 mV 66 251 2 pw 112 07 uV 129 0 126 fW 0 079 uV 4 398 1 uW 141 09 mV 67 199 5 pw 99 88 uV 130 0 100 fW 0 071 uV 5 316 2 uW 125 74 mV 68 158 5 pw 89 02 uV 131 0 079 fW 0 063 uV 6 251 2 uW 112 07 mV 69 125 9 pW 79 34 uV 132 0 063
25. 20 Reliable Measurement Range Sources of Errors e N Y MEASUREMENT ERRORS Z d Unknown Measured Data Improving Accuracy A consideration in the quest for precision is the resolution and accuracy of your display instrument Most low cost spectrum analyzers the kind found in communications service monitors and the kind for which this test set was primarily intended will yield excellent results when measuring return loss from between 5 to 30 dB and will provide reasonable accuracy when measuring from around 1 or 2 dB to as much as 40 or 45 dB depending on the test frequency Most spectrum analyzers are inadequate for measurements much outside this range however They lack the tracking stability and resolution and most importantly the advanced calibration techniques necessary for that latitude of measurement When the 8920 is used with a network analyzer with vector calibration capability RL measurements from 0 001 dB to 60 dB or more can be made with great accuracy Try to keep in mind real world situations when determining the need for accuracy In most cases someone else has already designed the thing and it s your job to decide if it s still working Keep the RL to SWR conversion table handy and refer to it often Note that the difference between a return loss of 30 dB when compared to one of 40 dB means that
26. 4 11 2 1 760 0 2754 88 01 28 41 37 8 1 026 0 0129 51 31 48 73 24 44 1 128 0 0603 56 41 44 32 11 0 1 785 0 2818 89 24 28 01 37 6 1 027 0 0132 51 34 48 70 24 2 1 131 0 0617 56 57 44 19 10 8 1 811 0 2884 90 53 27 62 37 4 1 027 0 0135 51 37 48 67 24 0 1 135 0 0631 56 73 44 06 10 6 1 837 0 2951 91 87 27 21 37 2 1 028 0 0138 51 40 48 64 23 8 1 138 0 0646 56 90 43 94 10 4 1 865 0 3020 93 27 26 81 37 0 1 029 0 0141 51 43 48 61 23 6 1 141 0 0661 57 07 43 80 10 2 1 894 0 3090 94 72 26 39 36 8 1 029 0 0145 51 47 48 58 23 4 1 145 0 0676 57 25 43 67 10 0 1 925 0 3162 96 25 25 97 36 6 1 030 0 0148 51 50 48 54 23 2 1 149 0 0692 57 43 43 53 9 8 1 957 0 3236 97 84 25 55 364 1 031 0 0151 51 54 48 51 23 0 1 152 0 0708 57 62 43 39 9 6 1 990 0 3311 99 51 25 12 362 1 031 0 0155 51 57 48 47 22 8 1 156 0 0724 57 81 43 24 9 4 2 025 0 3388 101 25 24 69 36 0 1 032 0 0158 51 61 48 44 22 6 1 160 0 0741 58 01 43 10 9 2 2 062 0 3467 103 08 24 25 35 8 1 033 0 0162 51 65 48 40 224 1 164 0 0759 58 21 42 95 9 0 2 100 0 3548 104 99 23 81 35 6 1 034 0 0166 51 69 48 37 22 2 1 168 0 0776 58 42 42 80 8 8 2 140 0 3631 107 01 23 36 35 4 1 035 0 0170 51 73 48 33 220 1 173 0 0794 58 63 42 64 8 6 2 182 0 3715 109 12 22 91 35 2 1 035 0 0174 51 77 48 29 218 1 177 0 0813 58 85 42 48 8 4 2221 0 3802 111 34 22 45 35 0 1 036 0 0178 51 81 48 25 21 6 1 181 0 0832 59 07 42 32 8 2 2 274 0 3890 113 68 21 99 34 8 1 037 0 0182 51 85 48 21 21 4 1 186 0 0851 59 30 42 16 8 0 2 323 0 3981 116 14 21 53 34 6 1 038 0 0186
27. 46 17 14 6 1 458 0 1862 72 88 34 30 1 2 14 500 0 8710 724 98 3 45 27 8 1 085 0 0407 54 25 46 09 14 4 1471 0 1905 73 54 34 00 1 0 17 391 0 8913 869 55 2 88 27 6 1 087 0 0417 54 35 46 00 14 2 1 484 0 1950 74 22 33 68 0 8 21 730 0 9120 1086 50 2 30 27 4 1 089 0 0427 54 46 45 91 14 0 1 499 0 1995 74 93 33 37 0 6 28 964 0 9333 1448 22 1 73 27 2 1 091 0 0437 54 56 45 82 13 8 1 513 0 2042 75 66 33 04 0 4 43 437 0 9550 2171 86 1 15 27 0 1 094 0 0447 54 68 45 72 13 6 1 528 0 2089 76 41 32 72 0 2 86 863 0 9772 4343 14 0 58 26 8 1 096 0 0457 54 79 45 63 13 4 1 544 0 2138 77 19 32 39 0 0 oo 1 0000 oo 0 00 Airwave Inc 43 Appendix E dBm to Power or Voltage at 50 ohms dBm Power Voltage dBm Power Voltage dBm Power Voltage 53 199 53 99 88 10 100 0 uW 70 71 mV 73 50 1 pw 50 06 uV 52 158 49 W 89 02 11 79 4 uW 63 02 mV 74 39 8 pw 44 62 uV 51 125 89 W 79 34 12 63 1 uW 56 17 mV 15 31 6 pw 39 76 uV 50 100 00 W 70 71 V 13 50 1 uW 50 06 mV 76 25 1 pw 35 44 uV 49 79 43 W 63 02 V 14 39 8 uW 44 62 mV TI 20 0 pw 31 59 uV 48 63 10 W 56 17 V 15 31 6 uW 39 76 mV 78 15 8 pw 28 15 uV 47 50 12 W 50 06 V 16 25 1 uW 35 44 mV 79 12 6 pw 25 09 uV 46 39 81 W 44 62 V 17 20 0 uW 31 59 mV 80 10 0 pw 22 36 uV 45 31 62 W 39 76 18 15 8 uW 28 15 mV 81 7 9 pw 19 93 uV 44 25 12 W 35 44 V 19 12 6 uW 25 09 mV 82 6 3 pw 17 76 uV 43 19 95 W 31 59 20 10 0 uW 22 36 mV 83 5 0 pw 15 83 uV 42 15 85 W 28 15 V 21 7 9 uW 19 93 mV 84 4 0 pw 14 11 u
28. 51 90 48 17 21 2 1 191 0 0871 59 54 41 99 7 8 2 375 0 4074 118 74 21 05 34 4 1 039 0 0191 51 94 48 13 21 0 1 196 0 0891 59 78 41 82 7 6 2 430 0 4169 121 49 20 58 34 2 1 040 0 0195 51 99 48 09 20 8 1201 0 0912 60 04 41 64 74 2 488 0 4266 124 39 20 10 34 0 1 041 0 0200 52 04 48 04 20 6 1 206 0 0933 60 29 41 46 7 2 2 549 0 4365 127 47 19 61 33 8 1 042 0 0204 52 08 48 00 204 1 211 0 0955 60 56 41 28 7 0 2 615 0 4467 130 73 19 12 33 6 1 043 0 0209 52 13 47 95 20 2 1217 0 0977 60 83 41 10 6 8 2 684 0 4571 134 19 18 63 33 4 1 044 0 0214 52 18 47 91 20 0 122 0 1000 61 11 40 91 6 6 2 758 0 4677 137 88 18 13 33 2 1 045 0 0219 52 24 47 86 19 8 1 228 0 1023 61 40 40 72 6 4 2 836 0 4786 141 80 17 63 33 0 1 046 0 0224 52 29 47 81 19 6 1 234 0 1047 61 70 40 52 6 2 2 920 0 4898 145 99 17 12 32 8 1 047 0 0229 52 34 47 76 19 4 1 240 0 1072 62 00 40 32 6 0 3 010 0 5012 150 48 16 61 32 6 1 048 0 0234 52 40 47 71 19 2 1 246 0 1096 62 32 40 12 5 8 3 106 0 5129 155 28 16 10 32 4 1 049 0 0240 52 46 47 66 19 0 1 253 0 1122 62 64 39 91 5 6 3 209 0 5248 160 44 15 58 32 2 1 050 0 0245 52 52 47 60 18 8 1 259 0 1148 62 97 39 70 54 3 320 0 5370 166 00 15 06 32 0 1 052 0 0251 52 58 47 55 18 6 1266 0 1175 63 31 39 49 52 3 440 0 5495 172 00 14 54 318 1 053 0 0257 52 64 47 49 18 4 1 273 0 1202 63 67 39 27 5 0 3 570 0 5623 178 49 14 01 31 6 1 054 0 0263 52 70 47 44 18 2 1281 0 1230 64 03 39 05 4 8 3 711 0 5754 185 54 13 47 31 4 1 055 0 0269 52 77 47 38 18 0 1 288 0 1259 64 40 38 82 4 6 3 864 0 5
29. 888 193 22 12 94 31 2 1 057 0 0275 52 83 47 32 17 8 1 296 0 1288 64 79 38 59 44 4 032 0 6026 201 61 12 40 31 0 1 058 0 0282 52 90 47 26 17 6 1 304 0 1318 65 18 38 35 4 2 4 216 0 6166 210 82 11 86 30 8 1 059 0 0288 52 97 47 20 17 4 1 312 0 1349 65 59 38 11 4 0 4 419 0 6310 220 97 11 31 30 6 1 061 0 0295 53 04 47 13 17 2 1 320 0 1380 66 01 37 87 3 8 4 644 0 6457 232 21 10 77 30 4 1 062 0 0302 53 11 47 07 17 0 1 329 0 1413 66 45 37 62 3 6 4 894 0 6607 244 72 10 22 30 2 1 064 0 0309 53 19 47 00 16 8 1 338 0 1445 66 90 37 37 3 4 5 174 0 6761 258 72 9 66 30 0 1 065 0 0316 53 27 46 93 16 6 1 347 0 1479 67 36 37 11 32 5 490 0 6918 274 50 9 11 29 8 1 067 0 0324 53 34 46 87 16 4 1 357 0 1514 67 84 36 85 3 0 5 848 0 7079 292 40 8 55 29 6 1 068 0 0331 53 42 46 79 16 2 1 367 0 1549 68 33 36 59 2 8 6 258 0 7244 312 89 7 99 29 4 1 070 0 0339 93 91 46 72 160 1 377 0 1585 68 83 36 32 2 6 6 731 0 7413 336 56 7 43 29 2 1 072 0 0347 53 59 46 65 15 8 1 387 0 1622 69 36 36 05 2 4 7 284 0 7586 364 21 6 86 29 0 1 074 0 0355 53 68 46 57 15 6 1 398 0 1660 69 90 2 2 7 938 0 7762 396 92 6 30 28 8 1 075 0 0363 53 77 46 50 15 4 1 409 0 1698 70 46 35 48 2 0 8 724 0 7943 436 21 5 73 28 6 1 077 0 0372 53 86 46 42 15 2 1421 0 1738 71 03 35 19 1 8 9 686 0 8128 484 28 5 16 28 4 1 079 0 0380 53 95 46 34 15 0 1 433 0 1778 71 63 34 90 1 6 10 888 0 8318 544 40 4 59 28 2 1 081 0 0389 54 05 46 26 14 8 1 45 0 1820 72 24 34 60 1 4 12 435 0 8511 621 76 4 02 28 0 1 083 0 0398 54 15
30. 91 09 4 40 dB 175 42 63 69 10 60 dB 1048 15 91 29 4 50 dB 181 84 64 52 10 70 dB 1074 90 91 49 4 60 dB 188 40 65 33 10 80 dB 1102 26 91 68 4 70 dB 195 12 66 12 10 90 dB 1130 27 91 87 4 80 dB 202 0096 66 89 11 00 dB 1158 93 92 06 Airwave Inc 45 Appendix G Velocity of Propagation for RG U Cable Types RG U Vr RG U Vr RG U Vr RG U Vr 5 659 74 659 174 659 235 695 6 659 79 84 177 659 293 659 7 659 84 659 178 695 294 659 8 659 85 659 179 695 295 659 9 659 87 695 180 695 302 695 10 659 94 695 183 91 303 695 11 659 108 659 187 695 304 695 12 659 111 659 188 695 306 8 13 659 115 695 195 695 307 8 14 659 116 695 196 695 316 695 17 659 117 695 211 695 323 8 18 659 118 695 212 659 324 8 19 659 119 695 213 659 332 8 20 659 120 695 214 659 333 8 21 659 122 659 215 659 334 8 22 659 130 659 216 659 335 8 29 659 131 659 217 659 336 8 34 659 140 695 218 659 360 8 35 659 141 695 219 659 376 8 54 659 142 695 220 659 388 659 55 659 143 695 221 659 393 695 57 659 144 695 222 659 397 695 58 659 147 659 223 659 400 695 59 659 159 695 224 659 401 695 62 84 161 695 225 695 402 695 63 84 164 659 226 695 403 695 70 659 165 695 227 695 404 695 71 84 166 695 228 695 Other Cable Types If the type of cable you are testing is not listed here keep in mind the following The velocity of propagation for Teflon
31. AW8920A Return Loss amp Cable Fault Test Set From Airwave Inc evision 4 Blank Page AIR E Communications amp Electronics AW8920A Return Loss And Cable Fault Test Kit User s Guide By Bryan K Blackburn Edition 4 0 Copyright 1993 1994 1995 1996 2006 Bryan K Blackburn All Rights Reserved Reproduction without prior written permission prohibited AIR E Communications amp Electronics Blank Page Table of Contents 8 225 M 3 5 ER EE 5 CARE AND HANDEING Gre ORO ENIRO USER EG NORUNT URINE OUO MENTI EEG 5 WARRANTY sere HER D RIA RET En Er OX E s 5 LIMITAMON OF WARRANTY eee titt tetto iter tete te Put re Ite teen gr PM et Pere n eerte Een 3 QUICK START RE ROLE UL OO 7 225255255 555555 660 R 9 lt X EE DAI LOSS Inpedante issus dut Edo ep EE SWR elei eee DER d op WREST SETUP
32. B 30 02 23 09 1 16 dB 30 62 23 44 1 18 dB 31 22 23 79 1 20 dB 31 83 24 14 1 22 dB 32 43 24 49 1 24 dB 33 05 24 84 1 26 dB 33 66 25 18 1 28 dB 34 28 25 53 1 30 dB 34 90 25 87 1 32 dB 35 52 26 21 dB Change Gain Loss dB Change Gain Loss 1 34 dB 36 1496 26 5596 4 90 dB 209 0396 67 6496 1 36 dB 36 77 26 89 5 00 dB 216 23 68 38 1 38 dB 37 40 27 22 5 10 dB 223 59 69 10 1 40 dB 38 04 27 56 5 20 dB 231 13 69 80 1 42 dB 38 68 27 89 5 30 dB 238 84 70 49 1 44 dB 39 32 28 22 5 40 dB 246 74 71 16 1 46 dB 39 96 28 55 5 50 dB 254 81 71 82 1 48 dB 40 60 28 88 5 60 dB 263 0896 72 4696 1 50 dB 41 2596 29 2196 5 70 dB 271 54 73 08 1 52 dB 41 91 29 53 5 80 dB 280 19 73 70 1 54 dB 42 56 29 85 5 90 dB 289 05 74 30 1 56 dB 43 2296 30 1896 6 00 dB 298 1196 74 8896 1 58 dB 43 8896 30 5096 6 10 dB 307 3896 75 45 1 60 dB 44 54 30 82 6 20 dB 316 87 76 01 1 62 dB 45 21 31 13 6 30 dB 326 58 76 56 1 64 dB 45 88 31 45 6 40 dB 336 52 77 09 1 66 dB 46 55 31 77 6 50 dB 346 68 71 6196 1 68 dB 47 2396 32 0896 6 60 dB 357 09 78 12 1 70 dB 47 91 32 39 6 70 dB 367 74 78 62 1 72 dB 48 59 32 70 6 80 dB 378 63 79 11 1 74 dB 49 28 33 01 6 90 dB 389 78 79 58 1 76 dB 49 97 33 32 7 00 dB 401 19 80 05 1 78 dB 50 66 33 63 7 10 dB 412 86 80 50 1 80 dB 51 36 33 93 7 20 dB 424 81 80 95 1 82 dB 52 05 34 23 7 30 dB 437 03 81 38 1 84 dB 52 76 34 54 7 40 dB 449 5496 81 8096 1 86
33. Band Reject and Pass Reject Duplexers eese eee enne 40 Tuning Pass Reject with Added Band Pass Element Duplexers esee eese 40 Tuning Duplexers Isoplexers with Isolators Transmit Branch eese tenentem eene 41 Hintsand Kinks Errata uiii aee tees eic rete cet hee 4I NIU IL aT P 41 APPENDIX EQUATIONS CONVERSIONS c 42 APPENDIX D RETURN LOSS SWR REFLECTION COEFFICIENT AND IMPEDANCE 2 seen 43 APPENDIX E DBM TO POWER OR VOLTAGE AT 50 OHMS eseensvensvenseensennennennsennnennesnnesnnennnennnvnnnennsvensnnnsennennsennsennesnnennnennneennennnennneene 44 APPENDIX F DECIBELS TO PERCENTAGE GAIN OR LOSS eese eese eese ense sts sins sense tuse 45 APPENDIX G VELOCITY OF PROPAGATION FOR RG U CABLE TYPES 46 Other Cable Types bere p Adeo OR d ttu d teta 46 Airwave Inc i Airwave Inc 1 51 Ref lection Log Mag 180 8 dB Ref 04 dB 92 Transmission M Log Mag 18 8 dB Ref 40 080 dB Feide Ch2 Mkr4 gdg gg MHz 47 17 dB LJ 1T LIII OBEDIRE 17 q U Wt VAT 11 apna patna JP 1 Stop 1 080 0808 MHz on AAG 48
34. CITY OF PROPAGATION ie dr ete eei I e PR EU eR PER 27 CUTTING CABLE TO A DESIRED enne teen ntn tat 28 iade ente eter teet ERU e tH coches ee rhe erbe HERD E 28 Gp IM M 28 APPENDIX A TEST DDCA d Bo 29 Airwave Inc i APPENDIX B MAINTENANCE AND RETUNING PROCEDURES FOR ANTENNA DUPLEXERS eese ee eee enne tn neta 35 DUPLEXER TYPES AND OPERATING FREQUENCY 5 35 PASS LV Pe i iio eR RE EE 35 Band Reject Duplexers eae E anv Seapine oo ees Tbe A ete He ee eene EM 35 Pass Reject Duplexer do he tr ANS eA ae Gen 36 Pass Reject Band Pass D uplexers 5 ue e e Ue e eee Ue EGS a aE 36 Duplexer Isolator Combin ations iiec aae eee it erp ei rigen 36 APPLICATION OF DUPLEXERS t tee rte ERE APO 36 IMPEDANCE MATCH BETWEEN THE DUPLEXER TRANSMITTER AND 9 9 99 37 IDUPEEXER RETUNINGS rave ee p GRUPPEN TED OV E NNN 37 Test Equipment Requirements ie e t ERN ERU 38 Tuning Band P ss Duplexers ss sss ta oe ho seabed HoT 38 Tuning
35. CODER e 5 RL reading of the same filter at the same frequency and span Airwave Inc 31 10 0 dB Ref 10 0 dB Ref bli Reflection Log Mag 22 Transmission Log Mag dB 10 1 2 28 38 48 58 68 70 88 90 Abs BRL Test Tekmination Cpmparison Start 8 308 MHz Stop 1 000 0800 MHz 1 Mkr MHz dB 2 Mkr MHz dB T 10 00 ES TL 1 0 00 1 63 150 00 2 150 00 21 27 3 468 88 211 3 460 00 21 07 820 00 2 29 u 820 00 2 28 gt 1000 00 3 23 5 1000 00 2 69 Above is a comparison plot of a 2 0 dB test termination performed with an HP8714B network analyzer The blue trace is of the termination through a vector calibrated channel of the network analyzer The red trace is of the termination through the directional coupler normalized but uncalibrated identical to the reading that would be obtained with a tracking generator and spectrum analyzer This plot shows the comparative accuracy of the coupler at low level RL readings 1 Reflection Lag Mag 10 0 dB Ref 4 64 dB b2 Transmission M Log Meg 10 0 dB Ref 8 00 dB 39 B RL Terminatfon Chi Mke2 1 5 000 MHz T
36. Kit Connections Setup 5 5 Directional Coupler 1 1 6 dB Attenuator Y Normalizing Device Under Test Unused Ports Testing Terminate Lower Trace Better Match Return Loss Make connections as shown in the diagram allowing power reflected from the device under test to be separated and measured independently from the incident signal 1 Set the spectrum analyzer tracking generator controls to sweep the desired frequency range Smaller span settings are preferred for more exact readings 2 Set RF Amplitude to 0 dBm or near the high side of the generators ability 3 Set the input reference level if available to 20 dB or set the attenuator vertical gain or position and IF gain controls until the displayed line is even with one of the upper graticules 4 Normal Sensitivity at 10 dB per division Normalize the analyzer using Save B A B if available or use a grease pencil or dry erase marker to trace this reference line on the screen Connect the device to be tested to the Device test port of the directional coupler The amount by which the displayed line drops in dB is the return loss of the device under test DUT This is plotted on the analyzer display as a function of frequency Tracker Port Analyzer Port Device Port Airwave Inc 7 Automated Te
37. Other service monitors that offer a cable fault test function such as the IFR 1500 and IFR 1200 Super S may benefit by substituting the resistive power divider in place of a T connector specified in the instruction manual This presents a 50 ohm impedance not only to the service monitor ports but also to the cable under test allowing a more accurate pinpointing of the fault 1 Connect the tracking generator output to 1 of the power divider the analyzer to Port 2 and precision termination to the Source port note that all ports of the Resistive Power Divider are identical and can be interchanged labeling is for convenience 2 Set the tracking generator and spectrum analyzer to the widest sweep possible The generator output should be as high as possible but not greater than about 10 dBm 3 If your spectrum analyzer offers a normalization function set the input attenuation for the analyzer to match the generator output 10 dBm output 10 dB attenuation and normalize the display 4 Now set the analyzer input attenuation to a level 10 to 20 dB higher than the signal generator output The trace displayed should be relatively flat and about a graticle or two from the top line Airwave Inc Testing Example Display Results of a 2 6 5 Cable 67 625 Mhz 202 03125 Mhz Halfwave Frequenc F 134 40625Mhz 4 One half Speed of Light Cable
38. V 41 12 59 W 25 09 V 22 6 3 uW 17 76 mV 85 3 2 pw 12 57 uV 40 10 00 W 22 36 23 5 0 uW 15 83 mV 86 2 5 pw 11 21 uV 39 7 94 W 19 93 V 24 4 0 uW 14 11 mV 87 2 0 pw 9 99 uV 38 6 31 W 17 76 V 25 3 2 uW 12 57 mV 88 1 6 pw 8 90 uV 37 5 01 W 15 83 26 2 5 uW 11 21 mV 89 1 3 pw 7 93 uV 36 3 98 W 14 11 V 27 2 0 uW 9 99 mV 90 1 0 pw 7 07 uV 35 3 16 W 12 57 V 28 1 6 uW 8 90 mV 91 794 3 fW 6 30 uV 34 2 51 W 11 21 V 29 1 3 uW 7 93 mV 92 631 0 fW 5 62 uV 33 2 00 W 9 99 V 30 1 0 uW 7 07 mV 93 501 2 fW 5 01 uV 32 1 58 W 8 90 31 794 3 nW 6 30 mV 94 398 1 fW 4 46 uV 31 1 26 W 7 93 V 32 631 0 nW 5 62 mV 95 316 2 fW 3 98 uV 30 1 0 W 7 07 33 501 2 nW 5 01 mV 96 251 2 fW 3 54 uV 29 794 3 mW 6 30 V 34 398 1 nw 4 46 mV 97 199 5 fW 3 16 uV 28 631 0 mW 5 62 V 35 316 2 nW 3 98 mV 98 158 5 fW 2 82 uV 27 501 2 mW 5 01 V 36 251 2 nW 3 54 mV 99 125 9 fW 2 51 uV 26 398 1 mW 4 46 37 199 5 nW 3 16 mV 100 100 0 fW 2 24 uV 25 316 2 mW 3 98 V 38 158 5 nW 2 82 mV 101 79 4 fW 1 99 uV 24 251 2 mW 3 54 V 39 125 9 nW 2 51 mV 102 63 1 fW 1 78 uV 23 199 5 mW 3 16 40 100 0 nW 2 24 mV 103 50 1 fW 1 58 uV 22 158 5 mW 2 82 V 41 79 4 nW 1 99 mV 104 39 8 fW 1 41 uV 21 125 9 mW 2 51 42 631 nw 1 78 mV 105 31 6 fW 1 26 uV 20 100 0 mW 2 24 V 43 50 1 nW 1 58 mV 106 25 1 fW 1 12 uV 19 79 4 mW 1 99 44 39 8 nw 1 41 mV 107 20 0 fW 1 00 uV 18 63 1 mW 1 78 45 31 6 nw 1 26 mV 108 15 8 fW 0 890 uV 17 50 1 mW 1 58 V 46 25 1 nW 1 12 mV 109 1
39. and pass duplexers are returned to manufacturer for retuning or repair and tuning for The same reasons Tuning Band Reject and Pass Reject Duplexers As previously mentioned these duplexer types function by placing the notches of one or more cavities in each branch such that the transmitter carrier is notched out in the receive branch and transmitter noise at receiving frequency is notched out in the transmit branch Simple two cavity duplexers can be used for low power transmit systems with wide T R spacings Where 65 or so is sufficient for duplex operation this can be secured with two carefully coupled and tuned cavities Where higher transmitter power and narrower T R spacing are present two three or even four cavities and large covities providing higher Q may be needed in each branch This is particularly true where T R spacings are very narrow such as down to 180 200 Khz in the 150 Mhz range and in similar special situations Notch depths required for interference free duplex operation increase as transmitter power yielding more noise increases and the receive frequency is brought closer to the transmitter carrier where the amount of noise power increases sharply Before attempting to tune a duplexer of these types for a T R spacing closer that it was factory tuned you must consult the manufacturer s data sheets or contact the manufacturer s engineering department to determine whether or not it can function at closer
40. any connectors any losses and a standing wave pattern related to the length of the cable between the test set and the antenna and finally the match at the end of the cable the antenna Whew For most purposes this reading is enough to determine whether or not you have a problem If the RL reading seems poor increase the span of the spectrum analyzer or vary the center frequency up and down enough to see the composite wave effect of the antenna and cable Poor RL with no wave pattern may indicate an open or shorted cable pattern may be very difficult to see with short antenna cables It is also possible that if the transmission line is cut to the wrong fraction of a wavelength at the frequency of interest the standing wave pattern on the feed line can make an acceptable RL from the antenna appear unacceptable at the end of the cable By just shaving a few inches off the feed line or by changing the length of a jumper the RL that the transmitter or receiver sees some cases be improved A SWR reading of 1 5 1 is equal to a return loss reading of 14 dB In most cases this is the value that manufactures specify as a minimum performance level for their antennas usable bandwidth of such an antenna is the span between the 14 dB points Airwave Inc 16 Portable Antennas Preamps and receivers Isolators Although portable antennas can be measured us
41. ations 1 A wave analyzer preferably with a transmission reflection test set or an accurate R F bridge source of 50 ohms and a return loss measurement range capability 40 aB or greater Suitable analyzers are manufactured by Hewlett Packard Wiltron Textronix Rhode Schwartz General Instruments and others Models with dynamic ranges of 80 dB are suitable for tuning and optimizing most duplexers however a range of 100 or more is needed to correctly adjust the more high performance duplexer models Most such analyzers have in addition to 10 dB per division major range resolution expanded ranges with resolution down to as exacting as 0 1 dB per display graticule division built in step attenuators polar display capability and other desirable capabilities Wave analysis equipment of this class cost from 25 000 to as high as 75 000 per setup on today s market depending on ranges capabilities added features such as S Parameter measurement pen or digital recorders etc It is a rare two way shop that has this class of equipment on hand 2 Barring the availability of a suitable wave analyzer the next best choice is a spectrum analyzer with an integral swept signal source often called a tracking generator If the frequency source is not provided by a synthesized crystal oscillator reference that is accurate to 50 Hz or better an accurate frequency source such as a good quality service monitor can be used to check calibratio
42. be determined from the table in the appendix or experimentally as described below Example Consider the example shown at left This was a section of RG U 142 cable with a measured length of exactly 2 5417 feet 2 6 5 including connectors The measured frequency of the first dip is 67 625 Mhz the second dip is at 202 03125 Mhz The difference between the two is 134 40625 Mhz this is the half wave frequency The published Velocity of Airwave Inc 26 Velocity of propagation Propagation for RG U 142 is 69 596 plugging into the equation _ 491 7855 0 695 134 40625 _ 341 790 134 40625 2 5438 As can be seen from this example the results are quite accurate The Velocity of Propagation is the speed at which the RF signal travels through a cable This number is required to find the distance to a cable fault as described in the previous section It follows then that if all other quantities are known in the equation above Velocity of Propagation can be found from the equation D Vr f 5 Using the numbers from the previous example _ 2 543 134 40625 491 7855 0 695 This is the published Velocity of Propagation number for this cable See appendix for Velocity of Propagation table Once you have found Vr by using a known length sample of the cable to be tested you can then perform the distance to fault test as described previously Airwave Inc 27 lt
43. cedures for Antenna Duplexers is included in appendix B We are grateful to Mr Lieske for his permission to include this work as a part of our user manual A complete copy of Technical Papers can be obtained by calling EMR Corp at 602 581 2875 Also ask for a price list and catalog of products Some of the best equipment available in the industry is Made at EMR Airwave Inc 18 Termination Tracker Port Site Noise and Receiver Sensitivity Device Port Signal Generator Analyzer Port The sensitivity of a receiver on the bench will always be better than the same receiver connected to an antenna due to site noise Power lines nearby transmitters sunspots and other sources of noise are everywhere So how do these noise levels effect receiver sensitivity To find out set up the test set as in the diagram Be sure any associated transmitter s on the same line as the coupler are disabled for this test and it may be wise to measure the received power at the coupler insertion point see base antennas section above for details before proceeding Adjust the generator output for 12 dB receiver SINAD with the termination in place and compare the generator level to that required to obtain a 12 dB SINAD with the antenna in place Remember that the coupler has about a 20 dB loss in line with the generator so subtract 20 dB from the measured values to find the actual generator l
44. cident lt Reflected Directional Coupler Reflection Coefficient Return Loss Reflection Measurements The directional coupler in the AW8920A test kit is a signal separation device It provides a sample of the power traveling in one direction only The coupler has three ports an input port a test port and the measurement sample port fourth port is internally terminated in a precision 50 ohm load An incident signal applied to the input or Tracker port of the coupler is passed to the Device or test port unattenuated less the insertion loss signal reflected at this port will be passed back to the input port with a sample 20 dB down directionally isolated from the incident signal also present at the measurement or Analyzer port When compared to the incident signal This directionally isolated reflection sample provides the basis for calculating reflection coefficient return loss SWR and impedance See Appendix D for conversions Reflection coefficient is the most basic of reflection measurement values and is simply the ratio of reflected power to incident power This number varies from zero for a perfect match to one for a total mismatch If your spectrum analyzer offers a choice between linear and log displays you will be able to read this value directly from the screen The symbol for reflection coefficient is p magnitude only or magnitude and phase The logarithmic expression o
45. cted as described 6 dB loss in the attenuator and 20 dB loss in the coupler from the Device test port to the Analyzer measurement port Airwave Inc 13 Adaptors and Jumpers Testing Lower Trace Better Match Network Analyzers Terminate Unused Ports Splitter Directional Coupler Device Under Test plus any test cables losses analyzer must compensate for this by using an increased sensitivity level or by increasing the generators output With a higher output level the spectrum analyzer has a stronger signal to work with and is easier to use and read Although the coupler will operate at levels as high as 38 dBm at 1 Mhz or above generator levels about 10 to 20 dB below the highest output level obtainable from your tracking source usually between 20 dBm and 15 dBm are preferred as this is usually a more stable and leveled range for the signal generator If an adapter or jumper cable must be used between the Device test port and the DUT connect it now Keep in mind that the test set will add any mismatch in the adapters or jumpers to your reading effectively limiting the measurement range of the test setup A single average quality adapter can limit the measurement range of the test setup to as little as 20 dB Jumpers longer than 1 20 become part of the DUT no longer just a jumper It
46. dielectric cables is typically 0 695 and for typical cables with polyethylene dielectric 0 659 Some foam dielectric cables have Vr ratings from 0 78 0 88 and air dielectrics from 0 90 0 93 Airwave Inc 46 Blank Page Airwave Inc bryan bkblackburn com
47. e except that lighter coupling into the cavity field is provided by smaller loop geornetry s and placements When properly designed above and below resonant loop notch responses are used to yield a pseudo band pass effect Excellent isolation notch depths are provided along with notches above and below the desired pass bands Although a slightly higher branch loss results compared with the strict band reject type the pass bands of both branches provide valuable selectivity to help attenuate the radiation of transmitter noise harmonics and spurs and improve effective receiver front end selectivity For application at moderately and highly populated sites this duplexer provides the desired aspects of the band reject type in terms of small size low loss and low cost to manufacture with some of the benefits of tne bandpass type in terms of selectivity EMR Corporation manufactures pass reject type duplexers in all frequency bands from 136 through 960 Mhz as standard models and special models for 50 through 136 Mhz ranges Pass Reject Band Pass Duplexers This type of duplexer is suited for the most difficult site installation Generally a pass reject type arrangement followed by one or more band pass cavities in each branch The benefits of deep notch response is further enhanced by the use of band pass elements to provide the ultimate in protection for both receivers and transmitters Relatively close T R spacings can be accommodated and maximum rece
48. evels if desired The difference between the two noted generator levels is the amount by which the site noise degrades the receiver sensitivity So to find the actual receiver sensitivity of the system during use take the antenna system gain or loss minus the site noise as determined above and subtract the results from or add them to the receiver bench sensitivity Rx Sens Bench Sens Ant Gain or Loss Noise Example antenna with 10 dB gain is used with a cable having a loss of 3 dB The measured site noise degradation is 4 dB and the bench sensitivity of the receiver is 118 dBm The actual system sensitivity is Rx Sens 118 dBm 10 dB 3 dB 4 dB 118 dBm 3 dB 121 dBm In this example if the cable is replaced with one having 1 dB loss instead of the current 3 dB loss the measured site noise would increase by 2 dB to 6 dB since site noise is also attenuated by cable losses The resulting system sensitivity would be 121 dB Thus system sensitivity would not necessarily benefit by upgrading the transmission line As can be seen this could be a valuable test to perform Note also that site noise is not a static value but is constantly changing day by day and varies with the time of day and the time of year Site noise studies must therefore be conducted over a long enough period of time to be sure the results are true and reliable Airwave Inc 19 Airwave Inc
49. exers already in service it is best to order the complete isoplexer at the onset as random cable lengths between isolator and duplexer can lead to impedance matching problems Adding an isolator will improve the overall performance of any of the four duplexer types with only a small increase in transmitter power loss under 0 3 for a single stage isolator and under 0 5 dB for a dual stage isolator In the band reject and pass reject type duplexers the isolator should be followed by a 2nd harmonic or low pass filter since 2nd harmonic rejection characteristics of tnese duplexers are usually insufficient to suppress the 2nd harmonic responses which contribute to 3rd and 5th order intermodulation products Application of Duplexers Unless specially manufactured and supplied in a weather resistant or weather proofed enclosure all EMR Corporation duplexers are intended for indoor protected installation Most models are arranged for mounting in standard EIA relay racks or cabinets Unless specially ordered all models use Type N female input and output connectors because of critical cable lengths duplexers in 1296 Mhz range have BNC or TNC connectors For best performance the duplexer should be placed as near to the associated transmitter and receiver as possible Use of double shielded flexible or solid outer conductor high quality cables for connection between the duplexer and repeater is recommended Receive and transmit lines should be stru
50. f the reflection coefficient is the return loss and its value is given in decibels A return loss of 0 dB represents a total mismatch and one of 40 dB or more a near perfect match Since spectrum analyzers are usually calibrated in decibels reflection measurements are read from the screen directly in return loss The abbreviation for return loss is RL R L or R L Use the equations RL 20108 p 5 p 10 20 to convert between return loss and reflection coefficient Airwave Inc 9 Impedance SWR Reflected Power For every measured value of there is a corresponding value of impedance The two are directly related their relationship in a 50 Ohm system is shown by the equation eT To find reflection coefficient from impedance Zi DS 1 50 Reflected signals on a transmission line form standing waves on the line Every half wave along the line high voltage and low current points occur Halfway between the high voltage points will be low voltage high current points The ratio of these voltages or currents is the Standing Wave Ratio or SWR SWR is also related to return loss impedance and reflection coefficient as shown by the equations 1 1082 29 SWR E 1082 20 SWR 1 p and SWR sd 50 2 2 Since power is proportional to or E the power reflected will be proportional the square of the reflection coefficient or 2 reflected p P forwa
51. g of any duplexer be sure that it s operation is understood both in theory and in application Airwave Inc 37 D When following tuning instructions don t try any short cuts In the instructions to follow we will describe the procedure that we would follow either in plant or in the field It is important that these are followed exactly if the full performance capobilities of tne duplexer are to be secured Test Equipment Requirements Although skilled technicians have tuned duplexers for years using receiver responses and other tricks the availability of modern highly stable service monitors field portable spectrum analyzers and similar equipment have simplified bench or field tuning of duplexers of all types Few two way shops have true wave analyzers having the measurement accuracy and dynamic range of those used in manufacturing in their test equipment inventory To tune even the simplest form of duplexer you must be able to generate a signal that is very accurate in frequency and level adjustment Since you will be dealing with insertion losses as low as 0 5 and signal response rejections of 75 to 120 dB according to duplexer type and application it is rather pointless to attempt tuning duplexers with equipment incapable of displaying the results of adjustments to these limits and with reasonable accuracy Accordingly we offer the following test equipment types as those required to properly retune duplexers to factory specific
52. h a grease pencil or dry erase marker Next establish 0 dB reference as follows Connect a short circuit termination not included with the kit to the test port One half the return loss measured for the short circuit termination from the normalized line 1s the O dB reference If you are using an HP8920A you can enter this number as the reference at the menu field Lvl If your spectrum analyzer does not have a reference set function make a note of the 0 dB reference point or use a grease pencil to trace a reference line on the analyzer screen Reference your test results to this line Airwave Inc 22 Using an Adapter or Jumper When using an adaptor or jumper at the test port signal reflections from impedance mismatches and losses within the adaptor or jumper tend to limit the measurement range of the test setup and contribute errors to the measurement If for instance the adaptor exhibits a small inductive reactance and the test device exhibits an equal capacitive reactance the two will cancel each other out The result will be either a better than expected reading or worse depending on the non reactive element of the DUT impedance It is also important to understand that if a jumper is used whose length is a significant portion of a wavelength at the frequency of interest longer than say 1 20 A the return loss being measured will not be of the intended device The measurement will instead be of the te
53. he center frequency of the monitor to the dip frequency found from the following frequency 0257 4 4 Trim the cable for a dip on the display making sure that the cut end remains open not shorted during measurements Keep in mind that the length of any adapters used at the test port or connectors not yet installed will add length to the cable These lengths are more significant at higher frequencies Airwave Inc 28 Appendix A Test Examples The following examples are of actual measurements made using the AW8920A test kit An HP8920A communications test set and an HP8714B network analyzer were used to produce the hardcopy BW 300 kHz Marker Frea 501 00000 SPECTRUM RHRLYZER 4
54. ill vary exhibiting a lower output impedance at higher than rated level or a higher output impedance at below rated power level Further where a mismatch exists and the jumper cable from the P A to the duplexer happens to be at or near an electrical 1 4 wavelength any mismatch may be made worse The effect is that even though the duplexer was designed for a 50 ohm match the combination of P A and cable mismatch will cause power to be reflected instead of conducted toward the antenna This situation may also exist when long random lengths of cable are used with isolator duplexer combinations One way to correct this situation is through experimenting with cable lengths between the transmitter and duplexer until an optimum of signal power transfer is found The quickest and most effective way of accomplishing this is through the use of an adjustable impedance correction network EMR Corporation manufactures such units called marchers which are actually adjustable PI networks having an impedance transformation ratio of 2 1 or greater for each of the popular land mobile frequency bands The recommended method for using line matchers is as follows 1 First adjust the amplifier output to desired level using a through line watt meter and suitable 50 Ohm test load termination 2 Next install the line matcher right at the transmitter s output jack with an adapter or short jumper cable is necessary and connect the jumper cable from the line matche
55. ing this test set obtaining an accurate reading is tricky A test fixture must be made to hold the antenna over a ground plane that simulates a portable radio in real world use Except for manufacturing this may not be an economically feasible venture compared to simply replacing a suspect antenna To do a simple test connect the antenna to the coupler test port through an adapter if needed and watch the analyzer display Hold the coupler with the antenna near your head as if it were on a radio in use Notice the degree of signal variance with only small changes in how the coupler is held in the hand After testing several known good antennas you should at least have an idea of what to expect when testing unknowns Connect the test set to the input of the preamp or front end to be tested In the case of the preamp terminate the unused port with a 50 ohm termination If the receiver front end is part of a transceiver disable the transmitter before proceeding It is also important to apply power to the preamp The trace on the analyzer display is the plot of return loss versus frequency tune the front end for a minimum of about 14 dB RL across the entire operating band of the device or for the best reading possible at the frequency of interest Usually only the slugs or trimmers preceding the first amplifier can be tuned with this method Disconnect the test set and continue tuning the remainder of the device conventionally The RL
56. iver selectivity enhancement is provided with a reasonable amount of branch losses Although the cost to manufacture and physical size of this duplexer type increases it is often the only type that will permit a given repeater to operate on highly populated high I M level sites EMR Corporation manufactures pass reject band pass duplexers for all of the popular land mobile frequency bands Duplexer Isolator Combinations The addition of an RF isolator between the transmitter and the input port of a duplexer provides several system advantages These include 1 Protecting the system from intermodulation problems through attenuation of signals from other nearby transmitters they may mix in the transmitter power amplifier stage to produce intermodulation products 2 Providing a resistive match for the power amplifier compared to the somewhat inductively reactive characteristic of the duplexer cavity resonator input 3 Added isolation between the transmitter and receiver operating with the duplexer The cover of this booklet shows an EMR Corporation duplexer with an added dual stage RF isolator Isolator duplexers or Isoplexers are supplied in all frequency ranges with either single or dual stage isolators according to the character of the site in terms of equipment density For best performance the jumper cable between the isolator and the duplexer s TX cavity port must be optimized for correct matching While isolators can be added to dupl
57. n by injecting pirdie markers The addition of an accurate 50 ohm bridge source and optimized cable types and lengths are definite assets The spectrum analyzer must have a dynamic measurement range of at least 80 dB for signal reject measurements and should also have a resolution of 2 dB or less on expanded ranges 3 Several high quality service monitors on today s market have highly accurate signal generation capability along with swept source or tracking generator options and integral spectrum analysis capabilities Several have 80 or greater dynamic display ranges however only one or two have expanded resolution ranges of 1 dB or lower A reasonably good job of duplexer tuning may be done with these instruments particularly if a good R F bridge is used for measurements that may be translated to VSWR 4 The very minimum equipment should include a spectrum analyzer with an 80 dB dynamic range plus a stable signal source such as a good service monitor Again a suitable RF bridge is most valuable to observe VSWR using return loss measurement during the tuning procedures 5 In every case high quality double shielded test cables with Type N or BNC connectors as applicable and high grade adapters to meet other duplexer connector types such as UHF or TNC types will be needed Each cable set must be optimized for the band in which the duplexer is to operate Accurate 50 ohm test loads having a VSWR of 1 05 1 or better are a must Rand
58. ncreased to center the traces bl Reflection Log Mag 1 dB Ref dB 92 Transmission M Log Mag 10 0 dB Ref DE Mr dB 2 dB MHz 20 2 6 dB 30 5 60 7 88 9 Abs Compatson Pilot of UHF Nagi 2ft Cable Start 8 308 MHz Stop 1 080 088 MHz 1 Mkr MHz dB 2 Mkr MHz dB ug 0 IS 1 31 150 00 0 20 2 150 00 0 27 3 160 00 23 01 3 60 00 23 86 E 820 00 8 83 820 00 sdb gt 1000 00 egg 5 1000 00 2 61 Comparison plot of a UHF yagi antenna with a 2ft feed line bl Reflection Log Mag 1 dB Ref dB 0 00 dB 2 Transmission M Log Mag 10 0 dB Ref dB 18 20 38 5 60 70 80 90 Abs UHF onl Suftlof Cable Start 8 300 MHz Stop 1 800 088 MHz 1 MHz dB 2 Mkr MHz 1 40 00 2 08 I 30 00 1 88 150 00 2 77 2 1580 00 2 69 3 460 00 28 9 3 460 08 28 56 820 80 7 71 620 00 7 7 gt 1808 00 6 11 5 1008 00 6 72 Comparison plot of a UHF yagi with a 54 ft feed line The interference pattern seen is related to the length of the cable bl Reflection Log Mag 10 0 dB Ref 4 64 dB 0 0 00 2 Transmission M Log Mag 10 0 dB Ref
59. ned we find that most duplexers will provide return losses of at lest 26 dB at all ports which translates to a VSWR of about 1 1 1 a reflection coefficient of only 596 It is for these reasons that we stress that measuring return loss is most important in duplexer tuning Even though a measure loss appears to be low through a transmit or receive branch a bad match between that port and the radio equipment can and often will result in lowered system performance The following procedure is recommended for tuning a band pass duplexer 1 Normalize the test equipment such that display indication is set to top of scale with a calibrated generator signal output For most analyzers and many swept type measurement systems 1 milli watt dB is available We assume here that the duplexer to be tune or re tuned has been operating satisfactorily 2 Terminate the receive port with a test termination 3 Set the generator center frequency to the present frequency of the transmit branch to verify insertion loss as originally tuned 4 Drive the transmit port with generator signal output and monitor at the antenna port Measured loss should be close to the duplexer s rated loss 5 Expand the analyzer bandwidth if necessary and measure the response at the originally tuned receive frequency This defines the rejection of transmitter noise rejection at the receiver s frequency For transmitters under 100 watt output power this should be at least 75
60. ng at least 6 inches apart since T to R port isolations from 75 to more than 120 dB are provided by the duplexer and cable to cable coupling can nullify these isolations Each EMR Corporation duplexer is factory tuned using wave analysis techniques to specified frequencies and supplied with a test data sheet showing losses in each branch transmitter carrier rejection or isolation at receiver frequency transmitter noise rejection or isolation at receiver frequency VSWR s at all ports at all frequencies and mid band isolation between T and R frequencies No field adjustment should be required or attempted at time of installation All components used in manufacture are of high quality and cavity resonators are designed with inherent temperature compensation Unless damaged in shipment or tampered with every duplexer may be expected to provide a high level of system performance for an indefinite period since all elements are passive and fixed Airwave Inc 36 Impedance Match Between the Duplexer Transmitter and Receiver Often it will be found that the loss through a duplexer seems higher than expected This is usually due to the fact that the power amplifier output does not meet a true 50 ohm impedance at the desired system power level Modern solid state power amplifiers are designed to match 50 ohm systems at their rated power output and if driven or adjusted for power levels other than their rated output level the actual output impedance w
61. nt Should it be necessary to adjust a band pass cavity resonator for a given loss coupling factor the availability of an impedance bridge is most desirable The procedure to adjust band pass cavity coupling loss is as follows 1 If the loops have calibrations in dB of loss set them to the indicated coupling factor desired e g 0 5 1 1 5 etc asa starting point 2 Set the equipment to the desired pass frequency drive one loop and monitor at the other loop Observe the loss through the cavity and the return loss at the driven loop It should be 18 or better Now reverse the test cables and check the return loss at the other port 3 It will De necessary to carefully adjust each loop alternately to finally secure the desired coupling factor and at the same time have identical return losses at both ports Often three or four reversals of the cables will be required to arrive at this optimum point of tuning The return losses with most cavities will be from 16 to 25 dB depending on the cavity design the Q and the coupling factor desired Other suggestions include making certain that all connector barrels are properly tightened cables are tied down and the cavities are properly secured to their mounting bars or brackets When retuning a duplexer do yourself and the next technician a favor by labeling the unit with its operating frequencies Also a record of the performances as measured is most valuable in the even of
62. ntil no further improvement is noted The fall off response should be fairly symmetrical above and below the tuned frequency Reverse the connections at the isolator and adjust C3 C5 and C6 on a dual for highest loss Now terminate the isolator output port with a precision termination Set up for return loss measurement and measure return loss at the input port of the isolator and tune capacitors and C2 C2 and for a dual isolator for best return loss at the transmit frequency Only minor adjustment should be necessary and a RL of around 26 dB should be the goal Now reverse the connections at the isolator place the precision termination at the input port and the measurement set at the output port Adjust C3 C5 and C6 on a dual for best RL at the output port Again only minor adjustments here for around 26 dB or better RL We recommended this method of tuning conventional first second because it is possible for an improperly tuned isolator to exhibit a seemingly acceptable RL the applied signal is dissipated primarily within the isolator Unacceptable insertion losses and performance would be the result Duplexers and Cavity Filters Bill Lieske of EMR Corporation in Phoenix Arizona has written what may be the most comprehensive guide available on the subject of duplexer retuning From Mr Lieskes manual Technical Papers a complete copy of the chapter entitled Maintenance and Retuning Pro
63. om cable lengths and types may cause erroneous readings and single shielded cables may inadvertently have sufficient leakage to cause improper results 6 Many duplexers currently manufactured or built during past years for use at VHF and UHF frequencies are equipped with UHF PL 258 or SO 239 connector types Good quality adapters or optimized cable sets equipped with UHF connectors will be needed to tune these along with test loads having UHF connectors Occasionally duplexers equipped with RCA phono type TNC SMA and special connectors are found particularly in mobile duplexer designs Cables adapters and test loads must be secured to suit Tuning Band Pass Duplexers This type of duplexer is the easiest to tune particularly if it is set up for single transmit single receiver operation As stated earlier this duplexer performs by virtue of pure band pass cavity selectivity Their tunable ranges are generally restricted to less than 0 5 of originally set frequencies due to the critical nature of loop adjustment and cable lengths Obviously major changes of frequency can be accomplished through complete re adjustment of all loop settings and making up new cables as required We caution against attempting this as loop setting and cables lengths are interactive and overall adjustment procedures are lengthy and tricky at best Airwave Inc 38 Remember for low signal loss and interference free duplex operation the duplexer must do
64. on terminations exhibit a nearly flat RL of about 50 dB They are available for N SMA and BNC connector types and are priced according to the difficulty involved in construction and tuning inquire Calibration terminations are rarely necessary and used mostly for laboratory work termination included with the kit is suitable for nearly any application including most manufacturing situations Airwave Inc 23 Airwave Inc 24 Fault Location Signal Analyzer Input Jo X Test Setup f Resistive Power Divider N Cable Under Test Normalize with 1 Termination Cable Tests The resistive power divider is used to combine a swept signal from a tracking generator with a reflected signal from the cable under test The resultant standing wave trace on the analyzer display can be used to find such information as distance to a fault velocity of propagation of a known length of cable and the exact length of cable needed to form 1 4 A 1 2 A etc stubs or jumpers Some service monitors such as the HP8920A the IFR 1500 the Motorola 2600 and others offer built in cable fault checking These monitors use the FFT to find the distance to a cable fault When using the 8920 run the cable fault test program from the Tests screen and follow the instructions provided with the software System Support Tests Instructions are provided on screen
65. only 0 0898 more of the forward power is reflected from the load reflected power forward power x reflection coefficient Most of the errors encountered when using a spectrum analyzer with this kit are from e Frequency response errors from within the analyzer and the interconnecting cables to the test set These errors vary depending on the actual quality of your analyzer check your analyzer specs and the interconnecting cables used with the test set Their effects are most noticeable with readings between 0 dB to 5 dB RL The best thing you can do to reduce these errors is use high quality high frequency low loss test cables Source match errors result from impedance mismatches between the tracking generator output and the test set input This is minor error term Source match errors affects accuracy of measurements primarily between 0 dB and 5 dB RL and are minimized by using a 6 dB attenuator at the input of the directional coupler When the kit Airwave Inc 21 Measured Return Loss dB Max Source Match Error using supplied attenuators Max Directivity Error at 40 dB directivity Measurement Uncertainties Establish a Reference Line Open Termination 0 dB Reference Shorted Termination 0 dB Reference Line is used with the supplied attenuators the maximum effect of source match error on an RL reading of 5 dB is about 0 5 dB increasing to about 0 75 dB for a reading of 2 dB
66. op 1 888 888 MHz Wide sweep of an open or shorted cable test set is capable of generating the tracking signal through a high power test port it is possible that this port may be used instead of the attenuator Usually though signals generated from this port will be less accurately leveled causing errors in your readings Avoid this method if possible If the levels you encounter are greater than 2 watts your only options are to turn off the offending transmitter s or reduce their output power CAUTION The maximum input power at the Tracker or Device ports of the bridge is 6 watts under intermittent operating conditions Any sustained use at power levels above 2 Watts could damage the coupler and will void the warranty For this reason 2 Watts is listed as the maximum input level for the above tests The maximum power that may be applied to the Analyzer port of the coupler is 125 mW Also pay attention to the maximum power ratings of the attenuators Attenuators supplied with the kit are rated at watt maximum input power Once precautions have been taken the return loss of the base antenna is measured the same as a mobile antenna See below Measure return loss by connecting the test set to the antenna cable of the antenna under test The reading is the same quality of match the transmitter or receiver sees when connected to the transmission line and is a composite signal of the return loss of the antenna the cable
67. pectrum analyzer tracking generator controls to sweep the desired frequency range Use the smallest span setting that will allow you to see the desired band set the bandwidth wider for wide span settings and for tests on devices connected by long feed lines Set the sweep rate quick enough to see rapid changes on the analyzer display the HP8920A for example sweep rate is a function of the span setting therefore it is best to use an 18 Mhz span width rather than 10 Mhz and 1 5 Mhz rather than 800 Khz see HP8920A owner s manual under Spectrum Analyzer for more on span and sweep rate relationships in the HP8920A 2 Set the RF Amplitude to 0 dBm or near the high side of your tracking generator s output capability At this point in the setup you should see a fairly flat trace near the top of the analyzer display 3 Set the input reference level to 20 dBm If your monitor does not have a reference setting adjust the input attenuator the vertical position and IF gain controls until the displayed line is even with one of the upper division lines 4 Set the display range to read decibels at 10 dB per division If your spectrum analyzer offers a Save B or normalization function perform that now Otherwise use a grease pencil or dry erase marker to trace the line on the screen if desired The RF amplitude level is not very critical Just remember that there is a minimum loss of 26 dB in the system when conne
68. r to the duplexer 3 Place the in line wattmeter between the aup exer antenna port and the 50 ohm test load termination 4 Key the transmitter up and alternately adjust the line matcher capacitors until maximum power is obtained The duplexer branch loss may then be calculated For example If the transmitter is set 100 watts output and 80 watts is measured out of the duplexer loss calculates to 1 dB through the duplexer see chart at end of the booklet To use the chart divide power out of the duplexer by the input power and compare the nearest loss ration to find loss through the duplexer in dB 5 Connect the antenna feedline to the wattmeter and check the power reading It should be within a watt or two if the antenna system VSWR is 1 2 1 or better A line matcher can also be used in the receiver branch to secure best receiver sensitivity To accomplish this a 12 dB SINAD measurement should be used feeding the duplexer antenna port with the signal generator and adjusting the matcher and the receiver Input tuning to secure best available sensitivity Duplexer Retuning The occasion may arise through system frequency changes equipment transfers to meet customer needs etc that a duplexer must be retune Before attempting to retune any duplexer several things must be determined including 1 Suitability of tne duplexer for service at the new frequencies and under the site density conditions to be experienced 2 Transmitter power
69. race 2 ip an Type Coup yer 38 4 Ch2 Mkr2 58 080 MHz 36 7b dB 30 2 ug 1 58 68 70 80 90 Abs Comparison pf Type W Vertor Galibrated HP8714B Start 8 3080 MHz Stop 1 800 0808 MHz Start 300 MHz Stop 1 MH 1 Mkr MHz dB 2 Mkr MHz dB 38 9 48 08 37 46 gt 150 00 38 0 2 150 00 36 76 3 460 08 38 94 3 560 00 37 26 H 800 00 38 97 800 00 36 61 Comparison plot of a 39 8 dB test termination This plot shows the comparative accuracy of the coupler at high RL readings bi Reflection Log Mag 10 0 dB Ref dB 22 Transmission M Log Mag 10 0 dB Ref 0 00 Chi MkrS 1400 040 MHz 17 28 dB j Ch2 Mkrs 1400 040 MHz 20 4 30 58 6 7 9 Abs est Termination Comparison Start 8 308 MHz Stop 1 000 000 MHz 1 Mkr MHz dB 2 Mkr MHz dB 16 30 0 00 16 31 150 00 16 41 2 1580 08 16 26 3 468 88 16 56 3 460 08 17 11 820 00 17 01 820 00 17 58 gt 1000 00 17 28 5 1088 08 17 16 ep gt bs Another comparison plot this time of a 16 3 dB test termination This plot shows the comparative accuracy of the coupler at mid level RL readings bli Reflection Lag Mag 92 Transmission M Log Mag 1 0 dB Ref 1 dB 1 0 dB Ref 1 dB 9
70. rd Airwave Inc 10 For example a source impedance of 50 and load impedance of 100 produces SWR of 2 1 and a reflection coefficient of 0 3333 square of 0 3333 is 0 1111 or 1 9 fractional This means that eight ninths of the power indicated by an in line wattmeter would actually be delivered to the load The remaining one ninth is reflected from the load The reflected power is reactive power volt amperes is not actually dissipated Airwave Inc 11 Airwave Inc 12 Spectrum Analyzer Signal Analyzer Input J Directional Coupler d 6 dB Attenuator Y Device Under Test Terminate Unused Ports Normalized Display Settings Normalizing Settings Notes Test Setup Make connections as shown in the diagram allowing power reflected from the device under test to be separated and measured independently from the incident signal The Tracker input port of the coupler is connected to the tracking generator output of the spectrum analyzer The Analyzer measurement port is connected to the spectrum analyzer input The 6 dB attenuator is used to reduce errors caused by mismatches between the directional coupler and the signal source It should be placed nearest the coupler rather than your measurement instrument The Device test port should be left open at this time 1 Setthe s
71. rt between SWR Reflection Coefficient and Return Loss RL 20108 0 SWR 1 SWR 1 SWR 1 RL 201og 810 SWR 41 p 10 5842 50 p 20 102 0 z P s pao E d 50 SWR 1tP RL 20 SWR 14107772 Z 5023 mg 1 7 Z 50SWR SWR 50 1 10 5220 2 1 10 052 20 P 1 P SWR P 1 r P Airwave Inc 42 Appendix D Return Loss to SWR Reflection Coefficient and Impedance RL SWR p 2 29 ZZ RL SWR p ZZ ZZ RL SWR p ZZ ZZ 40 0 1 020 0 0100 51 01 49 01 26 6 1 0908 0 0468 54 91 45 53 13 2 1 560 0 2188 78 00 32 05 39 8 1 021 0 0102 51 03 48 99 26 4 1 101 0 0479 55 03 45 43 13 0 1 577 0 2239 78 84 31 71 39 6 1 021 0 0105 51 06 48 96 26 2 1 103 0 0490 55 15 45 33 12 8 1 594 0 2291 79 72 31 36 39 4 1 022 0 0107 51 08 48 94 26 0 1 106 0 0501 55 28 45 23 12 6 1 612 0 2344 80 62 31 01 39 2 1 022 0 0110 51 11 48 92 25 8 1 108 0 0513 55 41 45 12 12 4 1 631 0 2399 81 56 30 65 39 0 1 023 0 0112 51 13 48 89 25 6 1 111 0 0525 55 54 45 01 12 2 1 651 0 2455 82 53 30 29 38 8 1 023 0 0115 51 16 48 86 254 1 114 0 0537 55 68 44 90 12 0 1 671 0 2512 83 54 29 92 38 6 1 024 0 0117 51 19 48 84 25 2 1 116 0 0550 55 81 44 79 11 8 1 692 0 2570 84 60 29 55 384 1 024 0 0120 51 22 48 81 25 0 1 119 0 0562 55 96 44 68 11 6 1 714 0 2630 85 69 29 17 38 2 1 025 0 0123 51 25 48 78 24 8 1 122 0 0575 56 11 44 56 11 4 1 737 0 2692 86 83 28 79 38 0 1 025 0 0126 51 27 48 76 24 6 1 125 0 0589 56 26 44 4
72. several things 1 Through sufficient selectivity of cascaded band pass cavity branches the carrier power of the transmitter must be reduced below the Threshold sensitivity of the receiver 2 The wide band noise generated in the transmitter must also be reduced to a level below the receiver s threshold 3 The lowest possible loss should exist in both branched to keep transmitter power loss down and to preserve receiver sensitivity 4 Co incident with low loss is the electrical match between each port of the duplexer and transmitter output impedance receiver input impedance and the antenna impedance A measured return loss of at least 26 a VSWR of 1 1 1 or better should be attained Lower return losses higher VSWR s simply indicate a mismatch with the associated devices meaning that power will be reflected causing higher losses Other things can also happen Certain amplifiers may become spurious if connected to a poor match or through integral protective circuitry reduce the amplifiers output power where bad match exists Obviously a poor match between the receiver s input circuits and the duplexer means that less signal will be transferred reducing effective receiver sensitivity Note that many manufacturers specify VSWR s as 1 5 1 a return loss of 14 dB or better as an acceptable matching impedance Consider that 1 5 1 VSWR represents a mismatch in which 2096 of the power will be reflected If properly designed and properly tu
73. st cable as terminated with a device of unknown impedance this information is very useful if the test cable also happens to be the feed line to an antenna for example In order to obtain an accurate measurement under these conditions the phase relationships and losses involved must be known Using this information along with a Smith chart and a little math the jumper can be calibrated out of the measurement It is assumed that most users of our test kit will not have easy access to a vector analyzer and therefore it is recommended that all test leads at the device port of the bridge be kept to 1 20 X or less This limits the practicable use of jumpers to frequencies of around 50 Mhz or less It is preferable to lengthen the test leads from the analyzer to the coupler and then use a high quality adapter at the device port if necessary If an adapter is used have the right one handy and use only one If you would like to see the approximate measurement range of the test setup with an adaptor or jumper in line attach using no further adapters a precision termination to the end of your adapter or jumper Unless you have a good selection of precision termination s this is not always possible The trace displayed is the approximate measurement limit of your test setup with the adapter or jumper in line To find the true measurement limit of the test setup a specially made calibration termination must be used Airwave calibrati
74. sting Manual Testing 4 Resistive Power Divider T Cable Under Test 67 625 Mhz 202 03125 Mhz F5 134 40625 MHz Cable Fault If your monitor offers an automated cable fault test use the Resistive Power Divider and follow the instructions provided for this test in your manual ports of the Resistive Power Divider are identical and can be interchanged 1 Make connections as shown at left and set tracking generator output at or near 0 dBm 2 Connect the cable to be tested to the open power divider port 3 Select analyzer span and input attenuation controls for a standing wave pattern similar to the example Short cables require wide span settings 4 Find the frequency difference between two adjacent dips 5 Find the velocity of propagation from manufacturer data or from Appendix G 6 Plug these two numbers into the equation below and calculate the distance to the cable end or fault See Cable Tests page 25 for more details and how to determine velocity of propagation from a cable sample One half Speed of Light Cable Velocity of 3 aoa 254 _ 491 7855 0 695 134 40625 Distance in Feet to Fault Frequency in Mhz See Above Airwave Inc 8 Measurement Internal 50 ohm Termination Sample 2 Input Q Test In
75. system problems or if the duplexer is to be placed in storage for later use Summary Antenna duplexers currently provide many thousands of repeaters with the system isolations needed for successful duplex operation Most duplexers manufactured during the past ten to fifteen years are capable of long term operation without maintenance The EMR Corporation line of antenna duplexers was developed over several years of design work Our choice of square format cavities was determined by looking for an optimum of physical size versus performance requirements in today s land mobile system market The square shapes and cavity lengths are optimum for the frequency ranges of the traditional land mobile band allocations and package very well for relay rack and in cabinet mounting Every effort is made to use the best materials careful attention to internal resonating element construction and use of silver plating to reduce losses of the elements and loop assemblies High quality double shielded cable is used with high grade cable connectors We use Type N connectors primarily for their constant impedance characteristics extremely low loss and low signal leakage Every cavity is carefully temperature compensated to ensure stable long term and trouble free performance under wide extremes of ambient temperature and transmit duty cycles up to 100 Airwave Inc 41 Appendix C Equations Conversions The following mathematical equations allow one to conve
76. tts to insure safety of the coupler watt if using attenuators supplied with the kit and in most cases less than 640 mW to insure the safety of most spectrum analyzers 640 mW through the 6 dB attenuator results in 160 mW into the duplex out port of the spectrum analyzer At this level measurements can safely be made Be sure that any suspect transmitters are operating when you make this measurement and be sure that your wattmeter is capable of the full frequency range of all the suspect transmitters If the levels encountered are less than 2 watts but greater than 640 mW a high power attenuator will be needed Use a 10 or 12 dB high quality attenuator one with good flatness across the frequency band of interest Place the attenuator between the duplex out port of the spectrum analyzer and the tracker input port of the directional coupler If your Airwave Inc 15 bl Reflection Lag Mag 18 8 dB Ref 8 00 dB 1 MHz 18 q 28 A 3 ug 58 68 78 88 98 Abs UHF yaoi onl suftlof Cable Start 0 308 MHz Stop 1 880 888 MHz Wide sweep of a good antenna and cable Mobile Antennas bli Reflection Log Mag 18 8 dB Ref 8 0 dB C dB 18 28 38 40 56 68 70 88 98 Abs Start 8 308 MHz St
77. ve to shock but should be handled with care to prevent damage to their connectors NEVER apply DC current to the directional coupler DC current will destroy the coupler and void your warranty The minimum frequency of operation for the coupler is 100 Khz at no more than 0 5 watts below 1 Mhz Clean the connectors often using pure TF solvent The painted surfaces can be cleaned with glass cleaner components of the return loss and cable fault test kit are warranted to be free from defects in material and workmanship for a period of one year from the date of shipment except test leads which are warranted for a period of 90 days During the warranty period Airwave Inc will at its option repair or replace at no charge any kit item found to be defective provided the item is returned shipping prepaid to Airwave Inc Airwave Inc shall pay return shipping charges to the buyer This warranty shall not apply to any item found to have been subjected to abuse misuse or improper care NO OTHER WARRANTY EXPRESS OR IMPLIED IS GIVEN AIRWAVE INC SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTIES OR WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE Repair or replacement of the defective item is buyers sole and exclusive remedy AIRWAVE INC SHALL NOT BE LIABLE FOR DIRECT INDIRECT INCIDENTAL OR CONSEQUENTIAL DAMAGES Airwave Inc 5 Airwave Inc 6 Quick Start Instructions For 8920 Test
78. w terminate the antenna port drive the transmit port and monitor at the receive port Expand the swept width to view both the receive and transmit frequencies This will display the two notches and the mid band isolation curve between the receive and transmit frequencies 8 Drive the antenna port monitor the transmit port and terminate the receive port Observe the return loss at both transmit and receive frequencies It should be 26 or better at either frequency Tuning Pass Reject with Added Band Pass Element Duplexers The recommended procedure for tuning this type duplexer is similar to the pass reject type tuning the pass cavities during the pass reject cavity sequences as covered As noted earlier this type of duplexer is used generally at high density communications sites and can provide reject notches of 120 or greater in addition to enhanced receiver protection and transmitter spurious harmonic and intermodulation protection Great care must be used in tuning procedures to secure the best operation characteristics Airwave Inc 40 Tuning Duplexers Isoplexers with Isolators in Transmit Branch First retune the duplexer according to the instructions for the duplexer type with the isolator disconnected After tne duplexer has been tuned satisfactorily re connect the isolator and retune as follows 1 Drive the isolator input at the transmitter frequency with the signal source and monitor the antenna port Alternately
79. xer types application notes system impedance matching testing tuning re tuning and trouble shooting Duplexer Types and Operating Frequency Bands Four distinct types of duplexers are manufactured by EMR Corporation Band Pass Band Reject Pass Reject Pass Reject Band Pass The distinguishing features of each type are as follows Band Pass Type This duplexer type consists of two or more band pass cavity resonators with suitable connecting cables in the transmit and receive branches to secure desired rejection of transmitter carrier and noise powers as required for full duplex operation The two branches are connected to two ports of a three way tee connector using selected cable lengths The antenna is connected through its coaxial cable feed line to the third port of the tee connector The size and number of the cavity resonators coupling loop design and adjustment and cables lengths between the cavities are determined by the operating frequency band and the frequency spacing between the transmitter and receiver frequencies Where multi frequency or multicoupled receivers multi frequency or combined transmitters are to be served by a single duplexer special coupling and tuning methods along with critical cable lengths permit duplexing of expanded pass bands within certain limits Standard EMR Corporation duplexers are available for single frequency TX and RX stations in the 66 68 Mhz 88 108 Mhz 118 136 Mhz 136 150 Mhz

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