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1. 6 deus gab 6 ANTENNA 6 INTELLIGENT REFERENCE TM 4 2 0 7 CONNECTION A PERSONAL 7 POWER INPUT 5 7 SECTION 3 QUICK START INSTRUCTIONS 9 SECTION 4 OPERATING MODES AND 17 START UP SEQUENCES i 11 OSGILEATOR MODES diate salt ie a a ee 12 TIMING MODES Dead geet ead 12 MASK ANGLE a a aa aada i 13 MAP DATUMS 2 pno naea ria E nate EEE E S EE ney aA 13 USER TIME ira area a Gate eee ea ie waa pie A E ak 14 ASCII SERIAL 5 0 000 14 EVENT Govt A a aa 15 PROGRAMMED OUTPUT PULSE 2 16 HARDWARE FAULT MONITORING 16 IRIG OR OTHER SERIAL TIME CODE
2. 29 EVENT TIME TAG 29 PROGRAMMED OUTPUT PULSE OPERATION 30 REMAINING OPERATIONS ye 2 ce dadana tate cag badelaeastdaks aah inet 30 lil SECTION 6 COMMUNICATING WITH THE 31 GONTROL PORT debian 31 COMMUNICATION MODES 31 MESSAGE FORMATS AND 2 31 MESSAGES FROM THE HOST 32 MESSAGES FROM THE INTELLIGENT REFERENCE TM 4 36 SECTION 7 a HARDWARE FRONT PANEL sak aa ede 42 LED COMBINATIONS AND THEIR 65 43 REAR PANEL CONNECTORS AND 2 43 OTHER HARDWARE 65 46 SECTION 8 IN CASE OF DIFFICULTY BERR RRR RR RR RRR RRR RRR RRR 49 CONTACTING nn innit 49 EIMITED WARRANTY E N a 49 RETURNING EQUIPMENT FOR REPAIR APPENDIX A 5 51 iv SECTION 1 INTRO
3. 17 NETWORK TIME PROTOCOL 17 AUXILIARY FREQUENCY OUTPUT 0 0 17 SYNTHESIZED TIMING PULSE OUTPUT 18 ACCURACY 18 OPERATING SUGGESTIONS 21 STAND ALONE 21 MASTER RESET 22 SECTION 5 OPERATION OF THE INTELLIGENT 4 23 SOFTWARE OVERVIEWS 23 COMPUTER REQUIREMENTS 2 426 a 23 INITIALIZATION FILE 23 MAIN SCREEN seine steed 24 RECEIVER STATUS PANEL 25 6 24 TIME AND DATE T soda 26 POSITION DATA PANEL 26 TIMING STATUS PANEL ee a 27 ALARMS AND INDICATORS 27 OPERATIONAL 28 28 SETTING OPMONS
4. 4 INSTALLATION There are no special requirements for the location of the unit itself other than the obvious considerations of access to the rear panel for cable connections and visibility of the front panel LEDs Avoid electromagnetic interference EMI keep the unit and its cabling away from sources of strong radio frequency RF energy such as radio transmitter cables and antennas Also keep the unit away from sources of heat Normally no special cooling provisions are required as long as adequate clearance is provided around the unit so that internally generated heat can dissipate by natural air convection CONNECTION TO A PERSONAL COMPUTER The Intelligent Reference TM 4 is connected to a personal computer by means of the HD 15 D sub connector located on the rear of the unit There are several ways to make connections to the unit Spectrum offers an optional breakout board that allows access to every pin and function of the unit If you only require power and connection to a personal computer for control Spectrum also offers an optional power and data cable Or you may make your own connections If you use the breakout board or cable assembly connect the Intelligent Reference TM 4 to the 15 pin connector and connect your computer to the 9 pin connector If you wish to use the supplied control software you must use a 32 bit Windows based computer with a free serial port Since the message output from the Intelligent Reference TM 4
5. OPERATING CURRENT 135 mA 24 VDC typical Page 53
6. Page 15 Event times are passed to host computer over control channel as quickly as possible Since events may occur closely spaced in time and in bursts the Intelligent Reference TM 4 buffers up to 23 event times in its memory passing them on to the host by unloading the buffer as quickly as possible Certain limitations on ETT operation are imposed by the design of the related hardware and software in the TM 4 1 To ensure that an event will not be missed the minimum latency time between any two events is 4 milliseconds 2 The maximum continuous rate of events is 30 per second to avoid overflowing the event buffer and losing events The buffer holds up to 23 events 3 The pulse width of the external event signal must be greater than 10 ns to ensure that it is recognized by the hardware 4 The input signal must be a valid TTL or CMOS logic level PROGRAMMED OUTPUT PULSE POP Another important capability of the Intelligent Reference TM 4 is its ability to generate precisely timed pulses on an external signal line This is called Programmed Output Pulse POP operation Pulses can be programmed with a resolution of 100 ns The TM 4 must achieve the Time Valid condition in order for this function to become available Two operating modes are provided POP One Shot Mode and POP Repeat Mode In the one shot mode only a single pulse is generated at the specified time and date In the repeat mode the time and date
7. X 6 for baseband IRIG if installed 7 for baseband NASA 36 if installed MESSAGE 15 SET SERIAL TIME MESSAGE FORMAT 15 XCRLF where X 0 for standard Spectrum ASCII serial time message X 1 for Type 11 NTP compatible format if installed X 2 for NMEA messages MESSAGE 16 SET MODULATED SERIAL TIME CODE FORMAT 16 XCRLF where X 0 for IRIG X for NASA 36 NOTE This message is enabled only in units with more than time code installed Page 34 MESSAGE 17 SET POLLING MODE 17 XCRLF where X 0 for BROADCAST standard operating mode X 1 for POLLING MESSAGE 18 Reserved MESSAGE 19 INITIALIZE POSITION AND ALTITUDE 19 WWWW WW X YYYYY YY Z SAAAAACRLF where W decimal latitude DDMM MM X hemisphere N or S Y decimal longitude DDDMM MM Z hemisphere or W S sign or A altitude in meters 5 digits MESSAGE 20 Reserved MESSAGE 21 SET POP PARAMETERS Simultaneous ETT POP units NOTE Non simultaneous POP ETT TM 4 s must use message 11 to set POP parameters 4 21 X P MMDDYYYY HHMMSS SSSSSSS RRRRRRRR WCRLF where X 0 POP Off X for POP One Shot X 2 for POP Repeat for positive polarity P for negative polarity MMDDYYYY is the POP date UTC HHMMSS SSSSSSS is the POP time UTC RRRRRRRR 15 the POP repeat interval in milliseconds W 0 for 1 us pulse width W 1 for 10 us pulse width W 2 for 100 us pul
8. disconnected at any time in which case the unit will continue to operate normally with the configuration in effect at that time Subsequent power on starts use the last configuration in effect when power was turned off with the exception of POP settings POP settings are not restored after a power cycle The TM 4 features two timing modes static and dynamic Static timing mode may be used when the user is stationary and position and altitude are known Up to twelve satellites are used to derive timing information however only one satellite needs to be tracked to operate in this mode Dynamic timing mode is used when the user is not stationary or when position or altitude is not known In this mode the unit continuously computes the position and derives timing information from as many as twelve satellites The TM 4 also supports Auto Survey mode where 10 000 position measurements are averaged and the unit then automatically put into static timing mode A GPS disciplined ovenized crystal oscillator OCXO is incorporated in the Intelligent Reference TM 4 to provide a very precise and stable frequency reference After a few hours of tracking GPS signals the accuracy of this source approaches that of the Cesium clocks on the GPS satellites The output frequency is 10 MHz and both sine wave and TTL outputs are provided The sine wave output is of Page 3 extremely high quality in terms of phase noise and spectral purity and is ideal for use a
9. is simple ASCII you may also easily create your own control software You can use a longer serial cable up to 50 feet but make sure that it is fully shielded in order to prevent unwanted radiation from the cable Many computer suppliers carry shielded monochrome monitor cables 9 pin in various lengths that are suitable for this application If the serial port on your computer has a DB25 connector instead of a DB9 connector use a DB9 to DB25 adapter available from most any computer supplier In the case where a serial port is not available as is the case with many newer laptop computers you may use a serial to USB adapter If you plan to use a port other than COM1 make a note of the port you choose so that you can set the software to match POWER INPUT EXTERNAL SOURCE Power is supplied to the unit via the 15 pin HD D sub connector See the pinout table on page 7 for the input pin connection You may supply power to the Intelligent Reference TM 4 from any source that can supply a clean DC voltage in the range of 9 to 35 VDC at 1 ampere Use caution when supplying power and see Section 7 of this manual for more information on operation from external DC sources Page 7 ADAPTOR BREAKOUT BOARD DATA CABLE ASSEMBLY The simplest way to supply power to the Intelligent Reference TM 4 is by use of an AC adaptor and either the breakout board or data cable The board cable and adaptor are all optional accessories and may be ordere
10. the absolute timing accuracy is enhanced by averaging out its effects An additional sine or square wave output is available as a factory set option This signal is slaved to the primary frequency output and can be either identical to the primary frequency or a different frequency Standard features of the Intelligent Reference TM 4 include simultaneous Event Time Tag ETT and Programmed Output Pulse POP function Note that some TM 4 units do not offer simultaneous capability In these units only one function may be enabled at any given time The programmed output pulse feature allows the host computer to specify a date time repetition rate polarity and pulse width for generating an output pulse with 100 ns resolution The external Event Time Tag feature marks the date and time of occurrence of an external event with 100 ns resolution The polarity of the input pulse is selectable Multiple events are buffered and supplied to the host computer as simple ASCII messages and the control software allows events to be archived An optional IRIG serial time code generator is available in the Intelligent Reference TM 4 and provides precise time outputs in the industry standard IRIG B format Two outputs are available IRIG Page 4 002 a pulse width modulated logic signal and IRIG 122 1 kHz amplitude modulated carrier Other time codes are also available consult the factory for details The TM 4 can optionally supply Net
11. to find them It will typically find satellites in a few seconds then spend the next 30 seconds collecting the ephemeris information for each satellite The first fix is then produced a few seconds later Under these conditions the first fix is typically obtained in about 40 seconds or less Page 11 HOT START If the unit has been turned off for only a short time less than about an hour the precise ephemeris previously found for the currently visible satellites will still be valid and start up can take place without having to spend the 30 seconds required to collect ephemeris data This is known as a Hot Start and cuts the time to first fix down to about 15 seconds under typical conditions It is important to note for all start up modes that TTFF does not always correspond to the time it takes for Time Valid to occur This is because in order to declare that time is valid the offset from UTC must be known In the GPS system this offset value is transmitted only once every 12 5 minutes OSCILLATOR MODES The ovenized oscillator is controlled by sophisticated algorithms in the TM 4 As the unit operates the control of the OCXO involves several stages and processes The various operating modes are described below Mode 1 Warm up The oven in the oscillator is being preheated to bring the OCXO to the desired operating temperature Until this temperature is reached the oscillator cannot be tuned or controlled This mode can take anywhere
12. INFORMATION This section of the manual provides detailed information on the Intelligent Reference TM 4 hardware including power specifications input output signal definitions and specifications connector and pin assignments and other miscellaneous hardware details FRONT PANEL The front panel of the TM 4 consists of three LED indicators that provide operating and system status These LEDs may be off steadily illuminated or they may flash Important information about the unit is conveyed by various combinations of the states of these indicators The table on the following page will also help you to understand the various combinations possible and how they relate to the current status of the unit ALARM LED This LED indicates the general status of GPS Under useable operating conditions it will be off During the initialization sequence it will rapidly flash momentarily and then illuminate steadily while the unit acquires GPS satellites and waits for the Time Valid condition Once time is valid this LED will turn off Subsequently this LED may flash or illuminate steadily depending upon GPS condition and the mode the TM 4 was in prior to a change in conditions If the unit was in coarse or fine tuning Modes 2 or 4 respectively mode and GPS is lost this LED will flash There is also a defined condition called Coast Alarm in which the TM 4 has achieved Mode 4 but has lost GPS and has been in the fine tuning hold mode Mode 5 for longe
13. MHz output fault may indicate that there has been a failure of the 10 MHz frequency output electronics or that the 10 MHz output level has dropped significantly below its 10 dBm nominal level If any of the alarm conditions occurs the POWER LED flashes the alarm status message Message 65 is updated the alarm status byte in the ASCII serial time message is updated and the auxiliary port alarm signal pin 8 is asserted to indicate that an alarm condition has occurred If the alarm condition subsequently clears these alarm indicators return to their normal condition and the TM 4 resumes normal operation Page 16 IRIG OR OTHER SERIAL TIME CODE OPTION The IRIG serial time code option provides the Intelligent Reference TM 4 with the capability to generate and output a serial time code based on the precise time obtained from GPS IRIG is the most commonly used of the standard serial time codes and is used to distribute precise time information to other equipment in a system or network or to time stamp data being recorded The specifications for IRIG B and the other IRIG time codes are available from a number of sources Other IRIG formats and other time codes are available as options Consult the factory for details The IRIG option provides two types of output signals baseband and modulated carrier On power up the IRIG outputs are disabled until valid time has been obtained by the GPS receiver Once this has occurred the outputs are c
14. Part 15 of the Federal Communications Commission Rules amp Regulations These limits are assigned to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment This equipment generates uses and can radiate radio frequency energy and if not installed and used in accordance with this user manual may cause harmful interference to radio communications Operation of this equipment in a residential area may cause harmful interference in which case the user will be required to correct at his own expense DC POWER CONNECTION Exercise caution when connecting a power source to the Intelligent Reference TM 4 Make sure to observe the correct polarity voltage and pin connection Applying power to the unit with incorrect polarity or voltage or to the incorrect pin will damage the unit and it will then require factory repair Damage due to incorrect powering of the Intelligent Reference TM 4 is not covered by the warranty Refer to Section 7 of this manual for complete information ii TABLE OF CONTENTS SECTION 1 1 HOW USE THIS 4 THE GLOBAL POSITIONING SYSTEM 6 5 4 INTRODUCTION TO THE INTELLIGENT 4 2 SECTION 2 UNPACKING AND
15. average error of a series of measurements with respect to the correct value in an absolute sense Stability refers to the statistical nature of the errors with respect to an average of the measurements Page 19 In Dynamic Timing Mode time is derived as one of the three or four dependent variables that are solved for in the navigation solution Geometry selective availability and other factors can affect the time accuracy by approximately the same amount as they affect the position accuracy In Static Timing Mode the effect of geometry is eliminated because position is known In this case we would expect to see timing errors cut in half no multiplier of 2 due to PDOP HDOP For best accuracy users are encouraged to operate the TM 4 in static mode whenever possible Tests of the TM 4 against a Rubidium atomic standard have verified that the quoted accuracies are achieved a large percentage of operating time However short term excursions from these accuracies can be expected due to a variety of causes such as ionospheric errors and other factors In the case of a GPS timing receiver a specification of absolute accuracy must account for any bias in the measurements The Intelligent Reference TM 4 is specified to have an absolute accuracy of 25 ns with respect to UTC SA off This means that if you could measure the error of the 1 PPS output with respect to the UTC second an average of a number of such measurements would yield a result
16. cable to connect to the host computer or other controlling device 2 Use shielded and terminated cables to connect signals from the TM 4 to other equipment 3 Runa ground wire from the TM 4 s chassis to an earth ground point in your system such as an AC safety ground or ground rod A solder lug placed under one of the connector retention nuts of the DB15 connectors on the rear panel is a good way to connect such a ground line 4 Apply a ferrite sleeve to the AC adaptor wire at the DC plug 5 Use a shielded cable to supply external DC power to the unit if you are not using the AC adapter 6 Locate the unit as far away as possible from any other equipment in your system that may be particularly sensitive to interference particularly receivers antenna cables and antennas These same precautions will also be helpful in avoiding adverse effects on the operation of the TM 4 from other nearby equipment Page 48 SECTION 8 IN CASE OF DIFFICULTY NOTE Should you have difficulty with the installation or operation of your TM 4 please take a few minutes to look through this manual You will find the answers to most of your questions here If you are still having difficulty after reviewing the manual please contact us for technical support and assistance CONTACTING SPECTRUM If you need to contact Spectrum please telephone or write to us at Spectrum Instruments Inc 570 East Arrow Highway Suite D San Dimas California 91773 Phon
17. details see the help file included with the application OPERATIONAL SESSION This section of the manual walks through a typical operational session with the Intelligent Reference TM 41 Jt assumes that you have connected the unit to your and have made the necessary power and data connections START UP Apply input power to the unit Note that Spectrum recommends that you do not connect the 15 pin connector to the unit with power already on it The initial inrush of current can cause an arc and repeatedly connecting the cable to the connector in this fashion may eventually burn or damage the power input pin Connect the cable and then apply power At first the three LEDs will flash indicating that the unit is going through its initialization tasks After initialization is complete the POWER and ALARM LEDs will illuminate continuously Start the control display software After the software initializes and the opening screen closes you can begin to use the application To check that the TM 4 and the host computer are communicating look at the GPS Receiver Status Screen currently being displayed and note that there is now information being displayed in the various fields on the screen The TM 4 is now searching for satellites As the unit finds and tracks satellites SQ numbers will be displayed When enough satellites have been found and their ephemeris data collected the Receiver Mode field will show Calculating Position indicatin
18. from three to six minutes depending on which oscillator is installed Mode 2 Coarse tuning The OCXO is being tuned in relatively large steps This mode may last anywhere from a few to twenty minutes or more depending on the initial error of the frequency when this mode began Mode 3 Coarse tuning hold Tuning in coarse mode is suspended due to an error condition of some sort usually due to GPS unavailability The tuning value is reset Mode 4 Fine tuning The OCXO is being tuned in very fine steps This is the normal operating mode of the unit and is indicated by the illumination of the READY LED This mode always starts with the accuracy of the primary frequency better than 1x10 and as the unit tunes the accuracy becomes greater and greater approaching that of the cesium clocks on the satellites themselves Mode 5 Fine tuning hold Fine tuning is suspended due to an error condition of some sort usually due to GPS unavailability Intelligent Holdover takes control of the unit in this mode and provides excellent holdover characteristics This mode is indicated by the ALARM and READY LEDs flashing with the POWER LED remaining illuminated TIMING MODES Two timing modes are provided in the TM 4 for maximum accuracy and flexibility In the Dynamic Timing Mode the reference position for the purpose of determining precise time is the current position as determined by the GPS position solution This mode is provided to accommodate
19. incoming signal a receiver can recover the carrier read the data stream and measure the propagation time of the signal from the satellite to the receiver relative to the receiver s own internal clock This time is directly related to the distance from receiver to satellite known as the pseudo range by the speed of light With this information available from three satellites the receiver can first calculate the exact position of the satellites at the time of transmission and then determine the receiver position in two dimensions as well as time by essentially solving three equations in three unknowns If the information is available from four satellites the receiver can determine the receiver position in three dimensions as well as time by essentially solving four equations in four unknowns INTRODUCTION TO THE INTELLIEGNT REFERENCE TM 4 The Intelligent Reference TM 4 is a complete GPS time amp frequency system offering the following features and performance State of the art 12 channel GPS technology Spectrum s exclusive FastStart technology offers high accuracy within just minutes of start up Intelligent Holdover function provides near Rubidium stability during GPS unavailability GPS disciplined ovenized oscillator with very low phase noise High spectral purity 10 MHz sine wave output Stratum 1 compliance with frequency accuracy of 1 10 12 long term Timing accuracy of 25 ns rr Standard one p
20. indicator in the software will also illuminate The Intelligent Reference TM 4 will now continue to fine tune as long as GPS remains available to its maximum accuracy of better than 1 x 10 Now that you have the TM 4 up and running you should read the remainder of this manual to familiarize yourself with the various features operating modes and functions that have been designed into the unit Page 10 SECTION 4 OPERATING MODES AND FUNCTIONS This section of the manual provides information on the various operating modes and functions of the Intelligent Reference TM 4 START UP SEQUENCES In order for a GPS receiver to quickly find and track satellites it needs four pieces of information Date Time Initial Position Almanac Depending on which pieces of information are known to the receiver at start up the Intelligent Reference TM 4 will enter one of three start up sequences The amount of time required to get started known as the time to first fix is highly dependent on which start up sequence is required COLD START The worst possible situation occurs when the receiver has no information at all about date time user position or satellite constellation In this case a Cold Start is required which involves the following steps 1 The receiver performs a systematic search for satellites 2 When one satellite is found the receiver gets the time and date from that satellite and starts collecti
21. this output may require that the unit enter the Time Valid state before it is made available OTHER HARDWARE CONSIDERATIONS AC ADAPTOR The optional AC adaptor requires an AC input supply voltage of 105 to 130 VAC at 55 65 Hz Other worldwide adaptor units are available Consult the factory for details ANTENNA POWER The optional antenna for the TM 4 requires approximately 15 mA of current at an input voltage of 5 0 VDC The unit supplies this voltage on the center pin of the antenna connector from a current limited source This power is supplied only when the unit is operating Page 46 SIGNAL CABLES AND TERMINATIONS TTL outputs from the 4 are designed to drive 50 ohm shielded cables terminated at the end with a 50 ohm resistive load to ground We highly recommend this practice Other cable arrangements such as twisted pairs and non terminated high impedance loads will work but the user will observe ringing and distortion of the pulse shapes which are not present when using shielded cables that are properly terminated IRIG B SERIAL TIME CODE OPTION The IRIG serial time code option provides the Intelligent Reference TM 4 with the capability to generate and output a serial time code based on the precise time obtained from GPS IRIG B is the most common of the standard serial time codes and is used to distribute precise time information to other equipment in a system or network or to time stamp data being recorded The s
22. tuning status at least once The retention of configuration information also allows the unit to come up from a power off condition and operate with the configuration in effect prior to removing power Page 47 The battery is not user replaceable Current is drawn from battery only when power is not being supplied to the unit and the battery is recharged when power is applied A full charge from a depleted state takes approximately 24 hours of operating time The backup time is approximately 30 days of non operation after a full charge If the battery is allowed to completely discharge the GPS receiver will lose all of the information that it ordinarily stores in order to start rapidly In this case a cold start will take significantly longer than usual since the receiver will have to retrieve all GPS parameters including an almanac and UTC offset RACK MOUNTING An optional rack mount adapter kit is available for the Intelligent Reference TM 4 which allows the mounting of as many as four units in a standard 19 inch equipment rack This adapter occupies one rack height 1U of space ELECTROMAGNETIC INTERFERENCE AND COMPATIBILITY The Intelligent Reference TM 4 radiates very little electrical noise and should not create interference problems in most installations It has been tested and found to comply with FCC Part 15 Class A requirements In critical situations consider the following precautions 1 Always use a fully shielded
23. warranty Page 45 There is one to six minute depending type of oscillator installed and its temperature at start up period during which the unit requires more power than that normally required when operating Note that the period of higher current consumption can be shorter than the fixed oscillator warm up period Mode 1 time if the oscillator is already warm Typical warm up and operating currents are shown below WARM UP OPERATING CURRENT CURRENT 325 mA 175 mA 270 mA 135 mA 215 mA 110 mA POP This is the Programmed Output Pulse output signal The polarity and pulse width of this signal is software selectable Rise and fall times are less than 10 ns and the output driver will supply TTL levels into 50 ohm load POP is disabled until the unit has reached the Time Valid condition MUXOUT2 Multiplexer 2 can supply the following outputs 10 MHz Frequency Output e Mux mirror e PPS e Optional outputs 1 5 The output is user selectable via either ASCII command or the supplied control software and will supply TTL levels at 50 ohms This output is not available until the TM 4 has achieved Time Valid IN1 Reserved in the standard version of the TM 4 This is an input for custom applications OUTI IRIG IN2 Reserved in the standard TM 4 If the IRIG function is included modulated time code will appear on this pin This pin may also function as either a custom input or output Depending upon the configuration
24. 5 RH non condensing ENVIRONMENTAL OPTIONAL TIMING ANTENNA OPERATING TEMPERATURE 45 to 85 C HUMIDITY Water resistant All weather PERFORMANCE GPS RECEIVER TYPE Twelve parallel channel code and carrier tracking CA code L1 carrier TIME TO FIRST FIX Hot Start lt 15 seconds typical valid almanac time date position and ephemeris Warm Start lt 40 seconds typical valid almanac time date and position Cold Start lt 60 seconds typical no information POSITION UPDATE RATE Once per second nominal MAXIMUM VELOCITY 1000 knots 515 m s MAXIMUM ACCELERATION 2 g POSITION ACCURACY Less than 15 M SEP PERFORMANCE TIME Conditions Time Valid 1 PPS OUTPUT Referenced to UTC Accuracy 25 ns ere 1 PPS TIME MESSAGE Serial Spectrum format ASCII date and time of next 1 PPS epoch Page 51 PERFORMANCE FREQUENCY GPS CORRECTED 10 MHz SINE WAVE FREQUENCY OUTPUT Conditions Time Valid Tuning in Mode 4 Long term Stability while tracking 1x1 0 12 after 24 hours of tracking At 24 hours Short term Stability 1 10711 At 1 second Accuracy while coasting lt 5x1 0711 per day after 3 days of locked operation Phase Noise 1 Hz Bandwidth 1 Hz lt 85 dBc 10 Hz lt 115 dBc 100 Hz lt 135 dBc 1 kHz lt 145 dBc 10 kHz lt 155 dBc Harmonic Outputs lt 50 dBc Spurious Outputs lt 70 dBc Level 10 dBm nominal into 50 ohms INPUTS amp OUTPUTS 1 PPS OUTPUT CONNECTOR BNC
25. DRIVE TTL levels into 50Q PULSE WIDTH Positive pulse 1 ms nominal Rising edge on time RISE TIME 10 ns maximum Connector can be factory reconfigured to deliver IRIG or multiplexer output in lieu of PPS 10 MHz OUTPUT CONNECTOR BNC DRIVE High spectral purity sine wave 10 dBm into 50Q 2dB Connector can be factory reconfigured to deliver a custom output in lieu of 10 MHz CONTROL AND AUXILIARY CONNECTOR DB 15HD female SERIAL CONTROL I O RS 232C 9600 bps 8 N 1 ALARM OUTPUT Open collector 25 mA current capability SERIAL TIME MESSAGE RS 232C 1200 38400 bps 8 N 1 NETWORK TIME PROTOCOL Optional compatible with Type 11 public domain drivers NMEA MESSAGES GPZDA GPRMC GPGGA not all fields of all messages are provided EXTERNAL EVENT INPUT TTL CMOS level edge triggered Active edge is software selectable PROGRAMMED OUTPUT PULSE Drive TTL levels into 50Q Rise amp Fall Time 10 ns maximum Pulse Width 20 usec nominal Polarity Selectable MULTIPLEXER OUTPUT Drive TTL levels into 500 Rise amp Fall Time 10 ns maximum 1 1 kHz 10 kHz 100 kHz 1 MHz 5 MHz 10 MHz PPS optional baseband IRIG Mux2 10 MHz Mux1 mirror PPS optional custom outputs Mux2 output pin may also be factory reconfigured for IRIG output or as an additional input OPTIONAL TIME CODE OUTPUT Type TTL and modulated Output Level 3 0 Voi into 6000 Modulation Level 3 3 1 Time Code IRIG B NASA 36 other codes availabl
26. DUCTION HOW TO USE THIS MANUAL You are strongly encouraged to read this manual thoroughly before installing and operating the Intelligent Reference TM 4 The instrument coupled with the supplied computer software provides a number of advanced and useful features To achieve maximum performance these features require a degree of understanding on the part of the user This manual is organized into logical sections and can be read straight through from cover to cover However each section covers a single topic or related set of topics and you may feel free to skip around if you wish If you are not familiar with GPS timing instruments and the Intelligent Reference family of products in particular you should read this manual carefully before attempting to install or operate the Intelligent Reference 41 Pay particular attention to Section 2 for unpacking and installation instructions Section 4 for operating modes and functions Sections 5 amp 6 for operating instructions and Section 7 for hardware information If you are an experienced user you should read the last part of this section entitled Introduction to the Intelligent Reference TM 4 It will quickly familiarize you with the functional capabilities of the instrument You can then browse the remainder of the manual to get a feel for its contents and organization THE GLOBAL POSITIONING SYSTEM GPS The Global Positioning System GPS consists of a constellation of sat
27. F X 1 for POP One Shot X 2 for POP Repeat X 3 for ETT P for positive polarity for negative polarity 0 when mode is OFF MMDDYYYY is the POP date UTC HHMMSS SSSSSSS is the POP time UTC RRRRRRRR is the POP repeat interval Page 38 MESSAGE 64 OSCILLATOR TUNING MODE 64 XCRLF where X 1 for Mode 1 oscillator warm up X 2 for Mode 2 course adjust X 3 for Mode 3 course adjust standby X 4 for Mode 4 fine adjust 5 for Mode 5 fine adjust hold MESSAGE 65 ALARM STATUS 65 X Y ZCRLF where X 0 no coast condition 1 coast alarm condition Y 0 antenna good Y antenna fault condition Zz 0 10 MHz frequency output good Z 1 10 MHz frequency output fault condition MESSAGE 66 Reserved MESSAGE 68 MULTIPLEXER 2 STATUS 68 XCRLF where X 0 for 10 MHz output X 1 for mirror 2 for PPS 3 for output option 1 4 for output option 2 5 for output option 3 X 6 for baseband IRIG if installed 7 for baseband NASA 36 if installed MESSAGE 69 TRACKING CHANNEL STATUS 69 VV W X Y VV W X Y ZCRLF where VV PRN of satellite being tracked W constellation status 0 not included in current constellation 1 included in current constellation X tracking status A acquisition reacquisition S searching Page 39 0 9 SQ ephemeris status 0 not collected 1 coll
28. INTELLIGENT 4 TIME FREQUENCY SYSTEM USER MANUAL MANUAL PART NUMBER 40013 001 SPECTRUM INSTRUMENTS INC 570 ARROW HIGHWAY SUITE D SAN DIMAS CA 91773 Copyright 2004 SPECTRUM INSTRUMENTS INC Spectrum makes every effort to insure that the information in this document is accurate but makes no claim to that effect and does not guarantee accuracy This information is offered as is and Spectrum cannot be held responsible for any inaccuracies Specifications features and operational characteristics of the described product are subject to change without notice WARNINGS AND NOTICES NAVIGATING WITH THE PRODUCT The Intelligent Reference TM 4 is intended to be used primarily as a precise time and frequency instrument even though it is capable of position location and navigation using the GPS system Users are strongly advised to use good judgment if using this instrument for navigation The user should never rely solely on any one source of information for navigation and should be aware that the position accuracy obtained from any GPS receiver can be affected by numerous sources of error such as satellite geometry selective availability satellite health and electromagnetic interference Published accuracy specifications are to be used only as a guide and are not guaranteed FCC NOTIFICATION This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to
29. POSITION ACCURACY The accuracy of position and time obtained from any GPS receiver is determined by the nature of the signal used the characteristics of the propagation medium the geometry of the particular situation at the time and various hardware and software factors in the receiver itself Using only the C A Code signal the more precise P Code signal is not generally available to civilian users presents a fundamental limit on accuracy due to the resolution of range measurement implied by the spreading code rate of 1 023 MHz This factor translates into an accuracy limit of about 15 meters in position and 50 ns in time A sequence of measurements can be averaged to improve this accuracy somewhat In the past C A Code receivers could not always achieve this accuracy due to intentional degradation of the signal by the United States Department of Defense This degradation is called Selective Availability SA and its intent was to limit the accuracy available to civilian users of the system to a value much less than that which can be achieved using the C A Code without degradation This was achieved by intentionally introducing errors into the clock timing and the transmitted satellite ephemeris data The past Department of Defense policy was to degrade the accuracy for C A Code users to 100 meters 2 drms or less under normal operating conditions As of this writing SA has been deactivated and is not expected to reappear in the future The t
30. Vere The carrier and baseband signals are synchronous and the one second epoch is synchronized to the positive zero crossing of a carrier cycle to within 2 microseconds On power up the IRIG outputs are disabled until valid time has been obtained by the GPS receiver Once this has occurred the outputs are continuously available even when the unit enters coast mode A TM 4 with the IRIG option installed enables these functions automatically without any need for operator action Note however that since MUXOU1A defaults to output the PPS signal unless changed the user would need to switch its function to IRIG in order to get baseband IRIG output from it Note that in units equipped with more than one time code function the unit will recall the last one used whenever power is cycled BACK UP BATTERY AND NON VOLATILE MEMORY Two methods are used to retain operating parameters in the Intelligent Reference TM 4 The GPS receiver contains a small rechargeable lithium battery which supplies a back up voltage to retain certain critical information in memory and to allow time keeping in the total absence of input power The TM 4 also incorporates a non volatile backup memory device that stores various operating parameters of the unit It is this retention of critical data and time that allows the TM 4 to have a very short time to first fix and high precision under normal conditions after the unit has been operated and allowed to achieve Mode 4 fine
31. and the POWER LED remaining illuminated If the TM 4 enters coast mode while in Mode 4 fine tuning the POWER LED will remain illuminated but the ALARM and READY LEDs will flash A coast condition will also be reflected by the status byte in the ASCII serial time message If the unit remains in the Coast Mode for 60 continuous minutes another condition called Coast Alarm occurs This condition is reflected by the ALARM and POWER LEDs illuminating and the READY LED extinguishing This condition will also be reflected in the alarm status message Message 65 a status byte in the serial time message and by activation of a hardware signal on the auxiliary port connector Note that in all coast conditions if there is a hardware fault antenna or 10 MHz output defective the POWER LED will not operate as described above but will instead flash The coast alarm is reset once the Time Valid condition has again been achieved While in Coast Mode the time and frequency outputs from the TM 4 degrade very slowly for two reasons One is that the GPS receiver continues to supply precise time from its internal tracking loops using the loop parameters in effect when timing information was lost The second is that the Intelligent Holdover function takes control of the OCXO and keeps precision high After 3 days of locked operation the TM 4 will degrade no more than 5 x 10 parts 24 hours during a GPS outage Shorter GPS blackouts of a few seconds or eve
32. are or by sending ASCII message 10 see Section 6 If the unit has been configured to provide NMEA messages the format is as follows SGPZDA hhmmss 00 dd mm O csCRLF where hhmmss 00 is UTC time dd mm yyyy is UTC date represents a null character two nulls in this sentence cs is the character and two byte checksum CRLF is a carriage return followed by a line feed Page 14 SGPRMC hhmmss 00 a ddmm mmmm n dddmm mmmm w ZZZ ZZ O csSCRLF where hhmmss 00 is UTC time a is the time valid status A valid V invalid ddmm mmmm is latitude in degrees and decimal minutes is north or south N S dddmm mmmm is longitude in degrees and decimal minutes w is west or east W E 222 22 is speed over ground in knots is course over ground in degrees represents a null character two nulls in this sentence cs is the character and two byte checksum CRLF is a carriage return followed by a line feed SGPGGA hhmmss 00 ddmm mmmm n dddmm mmmm w 5 uu pp p aaaaa a m 0 0 O cSCRLF where hhmmss 00 is UTC time ddmm mmmm is latitude in degrees and decimal minutes is north or south N S dddmm mmmm is longitude in degrees and decimal minutes w is west or east W E is GPS status 0 fix not valid 1 fix valid uu is number of satellites used in navigation solution 0 12 is estimated horizontal dilution of precision 0 99 9 is a
33. ased computer with at least 256 colors The software is supplied on a compact disc The TM 4 connects to a standard serial port on the PC and the baud rate for communication is fixed at 9600 The Event Time Tag feature requires special consideration The occurrence of an event causes only a single time tag message to be sent to the PC Thus the PC must be fast enough to stay up with the message output rate if no events are to be lost To be safe we recommend a 233 MHz or faster machine when using the Event Time Tag feature and dedicating the machine to that purpose while events are to be captured INITIALIZATION FILE The program utilizes a small initialization file to save certain user options so that these options do not have to be set each time the program is started on the same computer If no initialization file is present in the directory containing the program executable the software sets these options to the factory default settings Each time you change one of these settings the initialization file is written to the application directory saving the current options The software makes no changes to the Windows registry except for DLL registrations CHANGING THE COMMUNICATIONS PORT The Control Display software defaults to if no initialization file is present If the Intelligent Reference TM 4 has been connected to a different port you ll need to change the software to point it to correct port In the menu choose Co
34. ating position and has received the offset from UTC information this value can take up to 12 5 minutes from the first fix to receive the Time Valid indicator in the software will illuminate The READY LED on the front panel will flash the POWER LED will illuminate steadily and the ALARM LED will extinguish When this occurs the pulse per second PPS output becomes locked to GPS and the following functions become available e ASCII serial time message Spectrum NMEA or optional NTP output e Programmed Output Pulse amp Event Time Tag features Multiplexed frequency synthesizer outputs e Optional IRIG or other time code serial time code generator output e Optional synthesized timing pulse output e Optional auxiliary PLL clock output If the OCXO warm up period has expired the unit will enter the coarse tuning mode Mode 2 at this point and will begin to tune the OCXO Note that if you have a TM 4 equipped with a VCXO instead of an OCXO the unit is now ready to use of the above functions are active and in this case the TM 4 will display a front panel status as described in 11 below 11 After completion of coarse tuning the TM 4 will enter the fine tuning Mode 4 mode At this point the main 10 MHz output and all of its derived outputs has reached an accuracy of better than 1 in 10 parts The READY and LEDs will illuminate continuously indicating that the TM 4 is now in Reference Ready state The REF READY
35. ble in the unit Two of the most advanced features of the unit are the Intelligent Holdover function and Spectrum s exclusive FastStart technology Intelligent Holdover is an advanced oscillator control method that learns the unique operating characteristics of the particular oscillator incorporated into each individual TM 4 This allows for near Rubidium holdover characteristics during the absence of GPS signals while maintaining all the benefits of a quartz oscillator FastStart is Spectrum s proprietary method of oscillator control at initial startup Under typical operating conditions FastStart will bring the unit to very high precision and stability within just minutes after applying power This is a significant improvement over the typical hour or longer of tuning normally required by previous and competing products Another unique feature of the Intelligent Reference TM 4 is the availability of a filtered timing pulse output This output is available as a factory option and may be set to virtually any frequency up to 100 kHz including frequencies such as 216 2 3 Hz It is coherent with the 10 MHz clock and has the same accuracy and stability as the primary 10 MHz output The leading edges of this signal are synchronized to the average value of the PPS signal from the GPS receiver Also the nature of the filtering is such that this signal has extremely low jitter Even when Selective Availability is active no longer likely
36. ck source The performance of this output in the absence of GPS signals coasting is excellent due to the Intelligent Holdover function and very high quality ovenized oscillator incorporated in the unit This function only becomes available after the TM 4 has achieved the Time Valid condition WIDE RANGE FREQUENCY SYNTHESIZER OUTPUT OPTION The very wide range frequency synthesizer option allows the TM 4 to generate a factory set frequency of the user s choice slaved to the primary frequency reference This output retains the precision and quality of the primary reference and can be almost any frequency desired up to approximately 40 MHz The signal is output on pin 15 OUT 1 on the 15 pin D sub connector and it may also be routed to the PPS connector if desired Spectrum must be consulted with requirements prior to this feature being available in the unit Page 17 SYNTHESIZED TIMING PULSE OUTPUT OPTION The synthesized timing pulse output option enables the Intelligent Reference TM 4 to generate and output a timing pulse that is coherent with the 10 MHz clock and has the same accuracy and stability as the primary 10 MHz output This factory set frequency can be virtually any value up to 100 kHz including frequencies such as 216 2 3 Hz and the leading edges of this signal are synchronized to the average value of the PPS signal from the GPS receiver Because of the nature of the filtering applied these signals also have extremely low
37. d from Spectrum The adaptor plugs into any 120 volt AC outlet and provides a suitable DC voltage source for the unit The input requirements for the AC adaptor are 105 to 130 VAC 55 to 65 Hz The connector on the end of the adaptor cable plugs directly into the power jack on the breakout board or adapter cable and the breakout board or cable connects to the TM 4 by means of the HD 15 pin D sub cable See page 44 for a full description of the pin functions and connections coments INC INTELLIGENT REFERENCE 4 aarm PoweR READY TM 4 FRONT PANEL SYSTEM oera 10 MHz 1 PPS 5 1 e KKE ANTENNA 0 212 22 22224274 154 4 REAR PANEL SIGNAL FUNCTION 1 OUT2 10 MHZ TTL OUTPUT or CUSTOM OUT 2 GND SIGNAL POWER GROUND 3 CPTXD232 RS 232 SERIAL DATA TO HOST 4 CPRXD232 RS 232 SERIAL DATA FROM HOST 5 PPS AUX232 PPS CUSTOM SEE DESCRIPTION 6 TPTXD232 TIME PORT RS232 OUTPUT 7 MUXOUTIA MULTIPLEXER 1 A OUTPUT 8 ALM ALARM OUTPUT 9 GND SIGNAL POWER GROUND 10 EVENT EVENT INPUT 11 DCIN POWER IN 9 35 VDC 12 POP PROGRAMMED OUTPUT PULSE 13 MUXOUT2 MULTIPLEXER 2 OUTPUT 14 RESERVED SEE DESCRIPTION 15 2 OUTPUT TIME CODE CUSTOM INPUT HD 15 D SUB CONNECTOR PIN FUNCTIONS Page 8 SECTION QUICK START INSTRUCTIONS The following instructions will allow the more experienced user to begin using the Intell
38. e Page 52 OPTIONALWIDE RANGE FREQUENCY SYNTHESIZER OUTPUT Frequency Almost any desired frequency up to 40 MHz Factory set Drive TTL levels into 5002 Accuracy Same as for 10 MHz sine wave output Meets Stratum 1 MTIE specifications Rise amp Fall Time 10 ns maximum Output 50 duty cycle OPTIONAL AUXILARY CLOCK OUTPUT Frequency Almost any standard frequency including T1 E1 Factory set Drive TTL levels into 500 Accuracy Same as for 10 MHz sine wave output Meets Stratum 1 MTIE specifications Rise amp Fall Time 10 ns maximum Output 50 duty cycle OPTIONAL SYNTHESIZED TIMING PULSE OUTPUT Frequency Virtually any frequency up to 100 kHz such as 1 Hz 25 Hz and 216 2 3 Hz Factory set Drive TTL levels into 500 Accuracy Same as for 10 MHz sine wave output Meets Stratum 1 MTIE specifications Rise amp Fall Time 10 ns maximum Characteristics Coherent with 10 MHz output Leading edge synchronized to average value of PPS from GPS Extremely low jitter Pulse Width Positive pulse 500 usec nominal Rising edge on time OPTIONAL SECONDARY SINE WAVE OUTPUT Frequency Identical to or independent of primary output frequency Drive High spectral purity sine wave 10 dBm into 500 2dB ANTENNA INPUT CONNECTOR TNC DC POWER INPUT CONNECTOR Pin 11 of DB 15HD CAUTION NEVER APPLY INPUT POWER TO OTHER PINS ON THE DB 15 CONNECTOR POWER INPUT SUPPLY VOLTAGE 9 to 35 VDC WARM UP CURRENT 270 mA 24 VDC typical
39. e 909 971 9710 E mail support spectruminstruments com Before you call please have the following information available so that we may better assist you in trying to resolve the problem immediately 1 Model number and serial number of the unit 2 Purchase date 3 An accurate description of the problem LIMITED WARRANTY This product is warranted to be free from defects in material and workmanship for a period of one year from date of shipment During the warranty period Spectrum Instruments Inc Spectrum will at its option either repair or replace products which prove to be defective The repaired or replaced product will be warranted for the longer of either 1 A period of 90 days from the date of return shipment 2 The balance of the original warranty extended by the amount of time that the unit was out of service To obtain repair under this warranty the buyer must obtain a Return Authorization Number from Spectrum and return the product to a designated repair location freight prepaid Spectrum shall pay shipping costs to return the product to the buyer In the case of products returned from a country other than the United States of America the buyer shall pay all applicable duties or taxes required and freight charges both ways EXCLUSIONS This warranty shall not apply to defects caused by abuse neglect accident improper repair alteration or modification unreasonable use of the product by the buyer or damage in sh
40. e improperly due to corrupted memory contents Page 22 SECTION 5 OPERATION OF THE INTELLIGENT REFERENCE TM 4 WITH THE CONTROL DISPLAY SOFTWARE This section of the manual assumes that you have performed the unpacking and installation steps outlined in Section 2 and are now ready to operate the unit using the Control Display software SOFTWARE OVERVIEW The Intelligent Reference TM 4 Control Display software package is a control and display program which allows you to fully access the capabilities of the TM 4 without the need to develop special software for this purpose The Control Display software features windows menus and dialog boxes similar to those found on many commonly available software packages Users should have no trouble becoming familiar with the software relatively quickly Most of the functionality of the software is accessed through the use of menus dialog boxes and standard navigational conventions The software will run on most Windows based personal computers that are equipped with a serial port available for connection to the TM 4 The software does not support versions of Windows earlier than 95 COMPUTER REQUIREMENTS The computer requirements to operate the Intelligent Reference TM 4 using the Control Display software are relatively minimal Spectrum recommends 233 MHz or faster Pentium II or higher based machine with at least 16 bit color The minimally acceptable platform is a 100 MHz Pentium b
41. e setting Time Code setting ETT operation setting ASCII serial time message Spectrum NMEA or optional NTP output setting Note that the Programmed Output Pulse POP parameters are not saved POP will continue to operate with the host computer disconnected but will not be enabled if power is removed and then reapplied Also note that items pertaining to the GPS receiver almanac time date and position are not saved in non volatile memory but rather are retained by the receiver itself via a small rechargeable lithium backup battery The useable power off backup time of the battery is about 30 days The Intelligent Reference TM 4 can be operated right out of the box without connecting it to a host computer In this case it will execute the cold start sequence and will operate with the factory default settings for options and configuration MASTER RESET The Master Reset function which is initiated by Message 08 see Section 6 provides a complete reset of certain memory content in the Intelligent Reference TM 4 If you are using the Control Display software the Master Reset function is available in the Command Menu on the Receiver Status screen see Section 5 When executed the unit will initiate a cold start and adopt all factory default settings for options and configuration This feature should seldom if ever be required but is provided as a way of recovering in the event that a transient error causes the unit to operat
42. ected Z receiver status 2 search the sky 3 almanac collect 4 ephemeris collect 5 acquisition 6 position NOTE Vv W X Y repeats twelve times corresponding to each of the twelve channels MESSAGE 70 SERIAL TIME MESSAGE FORMAT 70 XCRLF where X 0 for standard output X 1 for NTP output optional X 2 for NMEA output MESSAGE 71 SERIAL TIME CODE FORMAT units with time code options 71 XCRLF where X 0 for IRIG B output X 1 for NASA 36 output MESSAGE 72 Reserved MESSAGE 73 ETT PARAMETERS Simultaneous ETT POP units 73 X PCRLF where X 0 ETT OFF X 1ETTON Page 40 MESSAGE 74 POP PARAMETERS Simultaneous ETT POP units 474 X P MMDDYYYY HHMMSS SSSSSSS RRRRRRRR WCRLF where 0 for POP Off X for POP One Shot X 2 for POP Repeat for positive polarity for negative polarity MMDDYYYY is the POP date UTC HHMMSS SSSSSSS is the POP time UTC RRRRRRRR 15 the POP repeat interval in milliseconds W 0 for 1 us pulse width W 1 for 10 us pulse width W 2 for 100 us pulse width 3 for 1 ms pulse width W 4 for 10 ms pulse width W 5 for 50 ms pulse width 17 6 for 100 ms pulse width W 7 for 250 ms pulse width W 8 for Level Hold MESSAGE 75 SPEED OVER LAND and HEADING 75 SSS SS HHH HCRLF where SSS SS indicates speed over land in meters sec HHH H indicates course in degrees decimal Page 41 SECTION 7 HARDWARE
43. ed or input altitude in either meters or feet Clicking on this field will show the Set Position and Altitude screen Satellites Used Value Indicates the number of tracked satellites for which the receiver has obtained a valid ephemeris Map Datum Item Fixed at WGS84 Page 26 TIMING STATUS PANEL Timing Mode Static Indicates that the receiver is in static timing mode In this mode the receiver assumes that the values it currently has for position and altitude are correct and derives precise time using these position coordinates Dynamic This mode is provided for users on a moving platform or who are starting from an unknown position In this mode the GPS receiver derives precise time information using the current position solution Clicking on the field will access the Timing Mode screen which will allow you to change timing modes Oscillator Mode 1 5 Indicates the current oscillator tuning algorithm mode Modes are described on page 12 of this manual User Time Bias 99 999 Indicates the current value of user time bias in nanoseconds Clicking on this field will access the User Time Bias screen which will allow you to set the user time bias ALARMS AND INDICATORS PANEL Time Valid Off Time is not yet valid or has become invalid Blue The TM 4 has obtained valid time information from GPS and the following functions if incorporated have been enabled 1PPS output ASCII serial time message Programmed Output Pu
44. egrees X 2 for 20 degrees 47 two digit map datum code fixed at WGS84 NOTE Map datum is not changeable in the TM 4 and will always be reported as WGS84 MESSAGE 56 USER TIME BIAS 56 SXXXXXCRLF where S sign or X bias value 5 digits MESSAGE 57 TIMING MODE 57 where X 0 for dynamic timing mode X 1 for static timing mode X 3 for Auto Survey mode MESSAGE 59 GEOMETRIC QUALITY AND ALMANAC STATUS 59 X YCRLF where GQ 0 9 Y 0 almanac Y 1 no almanac Y 2 almanac 15 old MESSAGE 60 TIME PORT DATA RATE AND MULTIPLEXER 1 STATUS 60 X YCRLF where X 0 1200 baud X 1 2400 baud X 2 4800 baud X 3 9600 baud Page 37 X 4 19200 baud X 5 38400 baud Y 0 for 10 MHz output Y 1 for 5 MHz output Y 2 for 1 MHz output Y 3 for 100 kHz output Y 4 for 10 kHz output Y 5 for 1 kHz output Y 6 for IRIG output if installed 7 for PPS output MESSAGE 61 TIMING STATUS 61 WCRLF where W 0 time not valid 1 time valid MESSAGE 62 EVENT TIME TAG 62 MMDDYYYY HHMMSS SSSSSSSCRLF where MMDDYYYY UTC date of event HHMMSS SSSSSSS UTC time of event MESSAGE 63 POP ETT STATUS NOTE This message is obsolete and has been replaced by Message 74 It is valid only for TM 4 units that do not support simultaneous POP ETT 63 X P MMDDYYYY HHMMSS SSSSSSS RRRRRRRRCRLF where X 0 for ETT POP OF
45. ellites orbiting at altitudes of approximately 10 900 nautical miles along with ground stations which monitor and control the system The system consists of 21 active satellites and three in orbit spares each of which orbit the earth twice per day The design of the constellation is such that at least four satellites are in view at all times from all places on the earth thus providing continuous world wide three dimensional navigational capabilities Each satellite continuously transmits encoded signals in what is called the L Band at 1575 42 MHz L1 and 1227 6 MHz L2 Most commercial GPS receivers use only the L1 signal Each satellite modulates its L1 signal with a unique pseudo random spreading code PRN It is this unique modulation that allows a receiver to track a particular satellite while ignoring the others even though all satellites broadcast on the same frequency There is also a 50 bit per second data message superimposed on the L1 signal which contains information necessary for a receiver to provide navigation and time transfer For two dimensional navigation a receiver must track a minimum of three satellites This allows the receiver to determine the position latitude amp longitude and time The 21 satellite constellation provides very reliable two dimensional navigation for a user whose antenna has a reasonably clear view of the sky For three dimensional navigation a receiver must track a minimum of four satellites This allo
46. erfere with reception of the satellite signals If several suitable locations are available select the one with the best view of the sky MOUNTING OPTIONAL SPECTRUM ANTENNA KIT For flush mounting first select a suitable flat surface Using the antenna template mark the mounting and clearance holes Then drill the four mounting holes and cut out the center clearance hole The mounting holes in the antenna are metric Use M4 screws and be sure that they do not penetrate the antenna by more than 8mm If water intrusion is a possibility seal the bottom of the antenna and mounting surface with caulk silicone or black non drying automotive window sealant Connect the cable assembly and attach the antenna to the mounting surface For pole mounting feed one end of the cable up through the pole and mast adapter if provided and attach to the antenna There two types of pole mount antennas One uses a standard marine thread 1 0 14UNS2A and the other uses an adapter that screws onto the bottom of the antenna suitable for larger diameter poles For the marine thread model simply thread the antenna onto the corresponding pole For the large diameter version attach the mast mount adapter to the antenna with the provided four screws Attach the mast adapter to the pole with the two set screws The mast adapter will accommodate a pole of up to 1 25 in diameter If the pole you wish to use is too small for the set screws to grab insert a
47. ers You must provide noise and kick back suppression as dictated by good engineering practice for this type of circuit GND Power and or signal ground connection EVENT This connection is for the Event Time Tag input and accepts CMOS or TTL levels The receiving logic is edge sensitive and the active edge is software selectable Events are not recognized until the unit has achieved the Time Valid condition DC IN Power to the TM 4 may be supplied by the optional AC adaptor or from an external DC source In the later case the source must be a stable and clean source of DC in the range of 9 to 35 VDC over a load current range of 200mA to 1A See the chart to get an approximation of the current requirement near your desired operating voltage The correct polarity must always be observed Applying power to the unit in reverse polarity will damage it WARNING Exercise caution when connecting a power source to the TM 4 Make sure to observe the correct polarity and voltage at all times Applying power with incorrect polarity or voltage will damage the unit and it will then require factory repair Spectrum also recommends that you not connect the 15 pin connector to the unit with power already on it The initial input rush of current may cause an arc and repeated arcing over a period of time will likely damage the pin Connect the cable and then apply power Damage due to incorrect powering of the TM 4 or contact arcing is not covered by the
48. ese cases the help system will start with the help file s table of contents 7 If you get an error message saying that the software can t see TM 4 check that you have selected the correct port that both cables are seated properly and that the TM 4 is on Otherwise you should now see sensible information appearing on the main screen Page 9 8 The unit is now searching for satellites Observe the GPS Receiver Status panel and watch as the unit finds satellites as indicated by the SQ numbers and bar graphs being displayed When enough satellites have been found and their ephemeris data collected the Receiver Mode field will show Calculating Position indicating that the unit is now navigating 9 You should now display each of the user selectable options and change parameters to suit your requirements The following list shows the choices with the factory default shown in parentheses Mask Angle 5 Degrees 15 Degrees or 20 Degrees Local Time Offset Integral Hours Default is 0 Position Format Degrees and Minutes or Degrees Minutes and Seconds Altitude Units Feet or Meters User Time Bias Bias in tnanoseconds Default is 0 Timing Mode Static or Dynamic Multiplexer Outputs Any two of several outputs Default is PPS Output for Mux2 ASCII Time Message Baud Rate 1200 2400 4800 9600 19200 or 38400 Communications Port COM1 2 6 10 Once the unit is operating calcul
49. g that the unit is now navigating The position will be updated every couple of seconds When the unit is operating calculating position and has received the UTC offset data the ALARM LED will extinguish indicating a normal Time Valid condition Page 28 When this occurs PPS output becomes locked to GPS and the following time related functions if incorporated become available ASCII serial time message Spectrum NMEA or optional NTP output Programmed Output Pulse amp Event Time Tag features Multiplexed frequency synthesizer outputs Optional IRIG B serial time code generator outputs Optional filtered timing pulse output Optional auxiliary PLL clock output SETTING OPTIONS If you have not previously done so you should now set the user selectable options and parameters to suit your requirements The following list shows the choices with the factory default shown in parentheses Mask Angle 5 Degrees 15 Degrees or 20 Degrees Local Time Offset Integral Hours Default is 0 Position Format Degrees and Minutes or Degrees Minutes and Seconds Altitude Units Feet or Meters User Time Bias Bias in tnanoseconds Default is 0 Timing Mode Static or Dynamic Multiplexer Outputs Any one of available outputs Default is PPS ASCII Time Message Baud Rate 1200 2400 4800 9600 19200 or 38400 Communications Port COM1 2 6 EVENT TIME TAG OPERATION To use the Event Time Tag feature ETT perfor
50. ias is a parameter that allows you to introduce a user specified bias into all timing related functions in the TM 4 The range of bias you can enter is 99 999 ns Negative values cause the timing functions to occur later in absolute time while positive values cause them to occur earlier The primary use for User Time Bias is to compensate for antenna cable length where absolute accuracy of PPS is important Another use is to adjust the absolute timing of the unit to match other system components or standards Changing the value of User Time Bias may introduce a perturbation in the time tracking loops that requires a few seconds to dampen out This will manifest as a momentary dropout of the time valid status while the loops stabilize ASCII SERIAL TIME MESSAGE NTP NMEA MESSAGES Once the Time Valid condition has been reached either a standard ASCII serial time message a subset of 0183 NMEA messages are transmitted on the TPTXD232 time port pin 6 at the user selected baud rate The Spectrum standard serial time message is formatted as follows MMDDYYYY HHMMSS X YCRLF where MMDDYYYY is UTC date HHMMSS is UTC time X is the time valid status O coasting 1 time valid Y is the alarm status O off 1 CRLF is a carriage return followed by a line feed NOTE time broadcast in this message is the time associated with the next PPS pulse The default baud rate is 9600 bps and may be changed either with the control softw
51. igent Reference TM 4 in a minimum amount of time using a Windows based personal or compatible computer the breakout board or power data cable AC adaptor and the supplied control display software If you encounter difficulty at any point please consult the appropriate sections of this manual for more detailed instructions and information 1 Unpack the Intelligent Reference TM 4 and any accessories 2 Set the unit near the computer and connect them together with the cables The HD 15 D sub cable will connect between the TM 4 and the connector on the breakout board and the 9 pin cable connects to the serial communications port on the computer COM1 6 and the other connector on the breakout board In the case of the power data cable the 15 pin connector will mate with the connector on the TM 4 and the 9 pin connector will mate with the serial communications port on the computer 3 Choose an outdoor location that has a reasonably clear view of the sky and set the antenna in an upright position Connect one end of the supplied antenna cable to the TNC connector on the antenna Connect the other end to the Intelligent Reference TM 4 antenna connector the rear panel 4 Install the software Insert the CD in the drive and open Windows Explorer Select the drive and click on SETUP EXE Follow the prompts to finish the installation To launch the software click on the desktop shortcut or the entry in the Start Programs Spectrum Co
52. ion Because they re derived from messages sent from the host to TM 4 they 1 be incorrectly formed if the incoming message is faulty in some fashion If the host fails to receive the acknowledge message within a reasonable time out interval and is expecting it the input message should be transmitted again or some other action such as executing an error processing routine should be taken Messages from the TM 4 to the host are broadcast with no acknowledge expected or required MESSAGES FROM THE HOST The following messages are defined for control of the Intelligent Reference TM 4 by a host computer Note that in cases where input data is shorter than the required number of digits for any given message the data must be padded with zeros MESSAGE 05 SET MASK ANGLE 05 XCRLF where X 0 for 5 degree mask angle X 1 for 15 degree mask angle X 2 for 20 degree mask angle MESSAGE 06 SET USER TIME BIAS 06 SXXXXXCRLF where S sign or X bias value 5 digits MESSAGE 07 SET TIMING MODE 07 XCRLF where X 0 for dynamic timing mode X 1 for static timing mode 3 for Auto Survey mode MESSAGE 08 MASTER RESET 08 1CRLF Page 32 MESSAGE 09 SET MULTIPLEXER 1 OUTPUT 09 XCRLF where X 0 for 10 MHz output X 1 for 5 MHz output 2 for 1 MHz output 3 for 100 kHz output 4 for 10 kHz output 5 for kHz output X 6 for baseband IRIG output if insta
53. ipment to Spectrum for repair Spectrum shall make the evaluation of the unit and shall be the sole determiner of its eligibility for or exclusion from warranty coverage Page 49 Software included with this product is intended but not guaranteed to run Windows95 or higher based computers and is provided solely for the convenience of the buyer It is supplied as is and is expressly excluded from any warranty LIMITATIONS amp DISCLAIMER The remedies provided by this warranty are the buyer s sole and exclusive remedies Spectrum shall not be liable for any direct indirect special incidental or consequential damages resulting from the buyer s use of this product or software supplied by Spectrum NO OTHER WARRANTY IS EXPRESSED OR IMPLIED SPECTRUM SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE It is the buyer s sole responsibility to determine the suitability of this product for the intended use prior to purchase Some states do not allow limitations on warranties so some or all of the above limitations may not apply to you RETURNING EQUIPMENT FOR REPAIR Should it become necessary for you to return equipment for repair please take the following steps 1 Contact us to obtain a Return Material Authorization RMA number We can only accept repair returns if an RMA has been obtained 2 Carefully pack the equipment and clearly mark the RMA number on the outside
54. jitter Even when SA is active no longer considered likely the absolute timing accuracy is enhanced by averaging out its effects This signal is output on pin 1 OUT 2 on the 15 pin D sub connector The TM 4 must have achieved Time Valid in order for this output to be enabled ACCURACY CONSIDERATIONS There are a number of factors that can influence the accuracy of position and precise time information obtained from the Intelligent Reference TM 4 An appreciation of these factors will help you optimize the results obtained under various conditions PPS OUTPUT ACCURACY The 1PPS signal at the BNC output jack is made available immediately after the TM 4 completes its initialization tasks However the user must take into consideration that the accuracy of this signal is not reliable until the unit has reached the Time Valid condition Until the TM 4 reaches this state the GPS receiver is relying upon its own internal references to generate PPS rather than using time information derived from the GPS satellites Do not allow critical applications to rely upon PPS until the Time Valid condition is obtained If you have an application where PPS accuracy is critical but operation of the TM 4 cannot be monitored or verified consider using PPS from the multiplexer outputs Because the multiplexer outputs are disabled until the unit has Time Valid PPS from these sources will always be accurate once they become available GENERAL INFORMATION amp
55. lled 7 for PPS output MESSAGE 10 SET SERIAL TIME PORT BAUD RATE 10 XCRLF where X 0 for 1200 baud X 1 for 2400 baud X 2 for 4800 baud X 3 for 9600 baud X 4 for 19200 baud X 5 for 38400 baud MESSAGE 11 SET POP ETT PARAMETERS NOTE This message is obsolete and has been replaced by Message 21 Itis valid only for TM 4 units that do not support simultaneous POP ETT 11 X P MMDDYYYY HHMMSS SSSSSSS RRRRRRRRCRLF where X 0 for ALL OFF X 1 for POP One Shot X 2 for POP Repeat X 3 for ETT for positive polarity for negative polarity MMDDYYYY is the POP date UTC 55 5555558 is the POP time UTC RRRRRRRR 15 the POP repeat interval in milliseconds NOTE In ETT mode POP parameters do not need to be sent POP One Shot mode the repeat interval does not need to be sent Page 33 MESSAGE 12 MODIFY BROADCAST OUTPUT 12 XCRLF where X 0 to output all messages X 1 to output Event Time Tag Message 62 and Acknowledge Message 50 messages only MESSAGE 13 REQUEST MESSAGE OUTPUT 13 XXCRLF where XX Two digit message number for the desired message NOTE This message is only enabled when the TM 4 is set to polling mode MESSAGE 14 SET MULTIPLEXER 2 OUTPUT 14 where X 0 for 10 MHz output X 1 for mirror output X 2 for PPS 3 for optional output 1 X 4 for optional output 2 5 for optional output 3
56. lows OUT2 10 MHz TTL CMOS output in the standard configuration This output may be used for the optional synthesized timing pulse output signal which will appear as a 500 us wide nominal positive pulse This pin may also be used for the optional auxiliary clock function or a custom factory configured output The output driver will supply CMOS or TTL levels into a 50 ohm load Depending upon the configuration this output may require that the unit enter the Time Valid state before it is made available GND Power and or signal ground connection CPTXD232 CPRXD232 These are the serial communication lines for control of the unit via a host computer and for receiving status messages from the TM 4 This interface is standard RS 232C 232 is the transmit line for sending commands to the TM 4 CPRDX232 is the input line for receiving data from the unit The communications parameters for these pins are 9600 baud 8 data bits e No parity One stop bit PPS AUX232 In the standard TM 4 this pin supplies an RS232 compatible PPS signal PPS availability requires that the TM 4 has achieved Time Valid TPTXD232 This 15 the output signal for the serial time port The interface levels for this signal are standard RS 232 and the output driver is capable of driving up to five standard RS 232 loads The output signal transmits the standard Spectrum ASCII serial time message or NMEA sentence subset using the following co
57. lse Event Time Tag multiplexed frequency synthesizer outputs IRIG B serial time code output filtered timing pulse and auxiliary frequency output Reference Ready Off The unit has not yet achieved minimum accuracy levels Blue The unit has reached minimum accuracy levels of 1 x 10 and is in Fine Tuning Mode 4 mode ETT Status Off ETT is not activated Orange ETT is activated but no events have been detected Green ETT events have been detected Antenna Fault Off Antenna circuits are operating normally Page 27 Red The unit has determined that the antenna circuits are not operating normally This can be caused by an antenna that is defective or not connected or by an antenna cable that is shorted or otherwise damaged POP Status Off No pulse is scheduled Yellow A single pulse is scheduled but has not been generated Orange Multiple repeating pulses have been scheduled but have not been generated Green The scheduled pulse has occurred Red The time to generate a scheduled pulse has passed but the TM 4 has not achieved the Time Valid state and thus now cannot generate it The POP function must be reinitialized with new values 10 MHz Output Fault Off The 10 MHz frequency output is operating normally Red The unit has determined that the output level of the 10 MHz frequency output is very low or absent The individual sub screens are mostly self explanatory and will not be described here For more
58. ltitude in meters 0 18000 m is altitude units always meters M represents a null character four nulls in this sentence CRLF is a carriage return followed by a line feed If the TM 4 is optionally configured to produce Network Time Protocol and NTP output is selected by the user it appears on this output instead of the other messages The message emulates Type 11 device such as an Arbiter 1088A B The message format is 26 ASCII 24 printing characters long and is as follows CRLFI YY DDD HH MM SS 000bbb where CRLF is a carriage return followed by a line feed T is the synchronization flag blank locked unlocked YY is year of century DDD is day of year HH MM SS is hours minutes and seconds 000 is fraction of second not used bbb is three trailing spaces for message fill EVENT TIME TAG ETT An important capability of the TM 4 is its ability to notate external events This is called Event Time Tag operation or ETT The TM 4 tags events with a resolution of 100ns This feature is not available until the unit achieves the Time Valid condition In this mode the unit monitors an external event signal line looking for a logic transition The TM 4 may be configured to look for either a positive going or negative going transition When a transition is detected the unit snapshots the date and time and stores this in its internal memory as an event time It then continues to watch for additional events that may occur
59. m the following steps 1 Connect the desired external signal to the EVENT signal pin pin 10 on the 15 pin port connector This must be a CMOS or TTL compatible signal Open the ETT sub screen via the Command menu or by clicking on the ETT Status indicator or the toolbar icon Select the ETT mode and polarity Observe the event times displayed on the screen This is the only sub screen in the software that can be minimized rather than closed Event times can be logged by the host computer connected to the control port Select the Log to File option on the ETT sub screen and choose a filename if necessary This filename must conform to the standard MS DOS 8 3 format Long filenames are not supported The file will be located in the same folder to which the application has been installed usually C TM4 In some implementations of the Intelligent Reference TM 4 it is not possible to use both the ETT and POP functions at the same time If your TM 4 has simultaneous ETT POP capability then both functions can operate coincidentally Page 29 Note there is another operation mode that disables message broadcast and sets unit to only output ETT and acknowledge messages This is recommended for advanced users only See the section on message 12 page 34 for details PROGRAMMED OUTPUT PULSE OPERATION To use the Programmed Output Pulse feature POP perform the following steps 1 Open the POP sub screen by clicking on
60. mmunications parameters Page 44 8 data bits No parity One stop bit The data rate is software selectable at 1200 2400 4800 9600 19200 and 38400 baud The default value is 9600 baud If the TM 4 is optionally configured for NTP the user may toggle this output between the standard time message formats and NTP This output is only enabled after the unit has entered the Time Valid condition MUXOUTIA The output of multiplexer 1 can appear in two places In a standard TM 4 the A output for Mux appears on this pin Optionally Mux1 s output can be factory configured to appear at the BNC connector for PPS in lieu of the 1 PPS signal normally present Multiplexer 1 can supply the following outputs e 1 10 100 kHz Frequency Output 1 5 10 MHz Frequency Output e PPS Output Baseband IRIG serial time code optional The output is user selectable via either ASCII command the supplied control software and will supply TTL levels at 50 ohms This output is disabled until Time Valid has been obtained ALM This is the alarm output signal It is driven by an open collector NPN transistor The user should supply an external high side load to a positive voltage no greater than 20 volts The drive capability is 25 mA The sense of this output is low impedance to ground for the alarm condition and high impedance for the no alarm condition NOTE Use special care when driving inductive loads such as relays buzz
61. n a few minutes have will have essentially no noticeable effect on timing data The unit returns to the Time Valid condition as soon as the GPS receiver starts supplying timing data from tracking loops that have been refreshed with new information from the GPS system MASK ANGLE Most GPS receivers provide some control over mask angle Mask angle is defined as the angle above the horizon below which the receiver will not try to acquire a satellite In the Intelligent Reference TM 4 this is controlled by issuing a mask angle command either with the control software or with an ASCII command The three choices of 5 Degrees 15 Degrees and 20 Degrees provide starting mask angles of 5 15 and 20 degrees respectively This sets the angle below which the receiver will not start using a satellite If a satellite is already being used it can drop to as low as 5 degrees in any mode before it is dropped For most applications we recommend a mask angle setting of 5 degrees unless the user has a specific reason to use one of the other settings Marine users and users at fixed locations with a clear view of the sky should use 5 degrees Choose 15 degrees for conditions where the view of the sky is mostly unobstructed A selection of 20 degrees would be appropriate for land mobile users in difficult terrain MAP DATUMS Map datums are coordinate transformations that allow the user to transform the position outputs of the Intelligent Reference TM 4 into a c
62. nfiguration Set Communications Options and choose the appropriate port You can also use the corresponding icon on the toolbar The communications port setting is saved in the initialization file Page 23 MAIN SCREEN Almost all of the information pertinent to the operation status and control of the Intelligent Reference TM 4 are on the main screen You can navigate to sub screens using either the menu functions the toolbar at the bottom or in the case of fields where the mouse pointer changes from an arrow to a hand by clicking on those Most of the functions are very simple and self explanatory If you need assistance with an item on the main screen you can call up help via the menu or by pressing 1 sub screens in most cases right clicking on the item will bring up context sensitive help MAIN SCREEN DETAILED DESCRIPTION The information and data that is displayed on each main display screen is relatively self explanatory The following sections describe the information displayed in more detail RECEIVER STATUS PANEL This panel reports various types of information relating to the satellite receiver and its current status Satellite ID This identifies which satellite is being tracked or sought by the channel An asterisk in this field indicates that the channel is currently not being utilized by the receiver Bar Graph This is an indication of the relative signal quality signal to noise ratio of the received sa
63. ng the current almanac Almanac collection is a process that takes approximately 12 5 minutes 3 While collecting the almanac the remaining receiver channels continue to search for additional satellites With luck the receiver will find two more satellites and start navigating in the two dimensional 2D mode while the remainder of the almanac is collected Since the receiver does not have any knowledge of user position finding the first position fix is a somewhat tedious process and may take a minute or two though the time is typically under 60 seconds This is because the receiver must perform additional calculations to rule out possible false solutions and determine which position is correct The entire cold start process will typically take approximately 10 minutes but can take longer Fortunately you should rarely encounter the need for a cold start The Intelligent Reference TM 4 is shipped with a current almanac in memory In addition the receiver retains the almanac and updates time and date for up to 30 days when not powered so it should usually have time date and almanac available at start up WARM START The start up sequence most often encountered is the Warm Start where the unit has the almanac time date and a reasonably accurate position that was either left over from previous operation or entered by the user In this case the receiver knows exactly which satellites to search for and where in frequency and the code phase
64. ns are offered to help the user obtain the best performance possible from the unit 1 Mount the antenna in a good location with the best possible view of the sky 2 Use Static Timing Mode if you are in a fixed location 3 Leave power on the unit unless you are not going to be using it for an extended period of time STAND ALONE OPERATION Once the Intelligent Reference TM 4 has been configured and the user options have been selected the host computer may be disconnected at any time The unit will continue to operate just as it did with the host connected The only exception is if you are using the Event Time Tag ETT feature In this case the host must be left connected to collect the event times Otherwise events will be lost All important configuration information and parameters are saved in non volatile memory so that power can be removed from the TM 4 without losing this data When power is reapplied the unit utilizes the parameters saved in memory to determine how it should operate This allows the unit to be configured one time by the user and eliminates the need for the unit to be connected to a host computer The following information is retained when power is removed from the Intelligent Reference TM 4 Almanac UTC Time and Date Page 21 Last position Mask angle selection Timing mode selection Time port baud rate selection Multiplexer output selection User Time Bias setting Polling Broadcast mod
65. ntrol Software menu 5 Connect the coaxial plug of the adaptor to the power connector on the breakout board or power data cable and plug the adaptor into a 120 VAC source Move the power switch on the breakout board to the ON position Note that Spectrum recommends that you do not connect the 15 pin connector to the unit with power already on it The initial inrush of current can be high enough to cause an arc and repeatedly connecting the cable to the connector in this fashion may eventually burn or damage the power input pin Connect the cable and then apply power All three LEDs should rapidly flash momentarily finishing with the POWER and ALARM LEDs illuminating steadily 6 Start the software If the TM 4 has been connected to a port other than COM1 the computer you will need to change the communications port setting using the Set Communications Options screen available from either the menu or the toolbar Almost all of the information pertinent to the operation status and control of the unit are on the main screen You can navigate to sub screens using either the menu functions the toolbar at the bottom or in the case of fields where the mouse pointer changes from an arrow to a hand by clicking on those Most of the functions are very simple and self explanatory If you need help with an item in most cases right clicking on it will bring up context sensitive help You can also call up help with the menu or by pressing F1 In th
66. of the first pulse to be generated is specified exactly as in the one shot mode A repeat interval is also specified as an integral number of milliseconds eight digits After the initial pulse is generated subsequent pulses will occur at the specified repeat interval The output signal is a TTL CMOS compatible pulse of user selectable width and polarity In POP One Shot mode the pulse may also be held indefinitely at a selected logic level Note that in POP Repeat mode the repeat interval must always be 1 one millisecond larger than the desired output pulse width HARDWARE FAULT MONITORING The Intelligent Reference TM 4 continuously monitors the performance of critical hardware circuits and reports any abnormal operation as an alarm condition There are three types of fault monitoring 1 Coast Alarm A coast alarm is reported if the unit has been in the coast condition for more than 60 minutes This may indicate a GPS receiver or antenna failure or that the view of the sky has become obstructed 2 Antenna Fault The TM 4 monitors the antenna input and reports an alarm condition if certain parameters are not correct An antenna fault may indicate that there is no antenna connected to the unit or that there has been a failure of the GPS antenna or power supply electronics 3 10 Frequency Output Fault The TM 4 monitors the 10 MHz frequency output and reports alarm condition if signal parameters are not within limits A 10
67. of the package 3 Ship the package freight or postage prepaid insurance is recommended to the above address unless you have been given an alternate shipping address at the time the RMA number was assigned Be sure to include any items or accessories that we have asked to have included and any information that may be helpful in resolving the problem Also be sure to include your name and information on how to contact you so that we can get additional information from you if needed and let you know when the equipment has been repaired We will make every effort to repair your equipment and have it on its way back to you within five working days from the time it arrives at our repair facility Page 50 APPENDIX SPECIFICATIONS PHYSICAL 4 HEIGHT 1 50 38 1mm WIDTH 4 125 in 104 8 mm DEPTH 4 50 in 114 3 mm excluding connectors WEIGHT 0 75 lbs 34 kg PHYSICAL 4 HEIGHT 1 00 in 25 4 mm FOOTPRINT 4 875 in x 3 875 in 123 8 mm x98 4 mm including connectors and LEDs WEIGHT 0 25 Ibs 11 kg PHYSICAL OPTIONAL ANTENNA HEIGHT 5 0 in 126 6 mm DIAMETER 3 54 in 90 0 mm WEIGHT 0 66 Ibs 0 30 kg MOUNTING Marine thread 1 0 14UNS2A pole mount Optional flush and 1 25 mast mount CABLE RG 58 50 ft with TNC connectors standard Longer cables optional ENVIRONMENTAL TM 4 STORAGE TEMPERATURE 40 to 85 C OPERATING TEMPERATURE 20 to 70 C HUMIDITY Up to 9
68. onitor and control the Intelligent Reference TM 4 from host computers not running the TM 4 Control Display Software CONTROL PORT The control port is a standard RS 232 serial channel which accommodates a wide variety of host computers and equipment The control port can be used to monitor and control the unit from any device using the ASCII message formats described in this section The communication parameters are 9600 baud Eight data bits No parity One stop bit Messages from the TM 4 to the host appear on pin 3 of the HD 15 pin D sub connector Messages to the TM 4 from the host must be applied to pin 4 of the HD 15 pin D sub connector COMMUNICATION MODES The Intelligent Reference TM 4 normally broadcasts the entire set of status messages on a repeating basis without any requests from the host computer The control display software is designed to utilize these messages and display the information contained within them in a meaningful fashion There are two user settable communication modes in which the TM 4 does not broadcast messages in the ordinary fashion One is a modified broadcast mode in which only ETT events and the acknowledge message are supplied The other is called polling mode and each desired message must be requested individually by the host computer using Message 13 Request Message Output The TM 4 cannot be put into either of these modes via the control display software since the software
69. ontinuously available even when the unit enters the coast mode A TM 4 with the IRIG option installed provides these functions automatically without any need for user action If the unit incorporates more than one time code option the user must choose which one appears at the output by either using the control software or sending ASCII control message 16 These optional functions require that the unit has entered the Time Valid state before they become available NETWORK TIME PROTOCOL OPTION After achieving Time Valid a TM 4 equipped with the Network Time Protocol option will supply NTP in place of the standard serial time messages on pin 6 of the DB 15 connector if NTP output is selected This output emulates a Type 11 compliant device such as the Arbiter 1088A B Appropriate public domain daemons may be obtained at http www eecis udel edu ntp ftp ftp udel edu pub ntp http www glen ellyn iit edu clocks clocks ntp ntp htm1 AUXILIARY FREQUENCY OUTPUT OPTION The auxiliary frequency output option adds a phase locked loop PLL synthesizer to the Intelligent Reference TM 4 and provides a clock output that retains the accuracy and stability of the primary 10 MHz output This signal is output on pin 1 OUT 2 on the 15 pin D sub connector and virtually any common frequency is available including widely used frequencies such as 1 544 MHz and 2 048 MHz The stability of this output meets the MTIE requirement for a Stratum 1 primary clo
70. oordinate system used by a particular chart or map so that positions can be plotted with accuracy There are literally hundreds of different map datums in use around the world as different geographical areas have adopted different earth models for the purpose of creating maps The differences in position from one datum to another can be as large as hundreds of meters The internal representation of position in the TM 4 is referenced to the WGS84 datum Since the TM 4 is designed as a time and frequency reference and not as a primary navigation tool the map datum is fixed and cannot be changed For timing applications as opposed to positioning applications map datum would only be Page 13 important if you were trying to enter a fixed position for operation in the Static Timing Mode by reading that position from a map and not allowing the receiver to ever operate dynamically In this case Spectrum would suggest that you allow the unit to temporarily operate dynamically after entering position information and then switch to static mode once the receiver has corrected position For North American users it may be helpful to know that the National Oceanic and Atmospheric Administration NOAA is presently converting its charts to NAD 83 which is essentially the same as WGS84 The bulk of NOAA charts now use are referenced to NAD 27 as are most of the existing United States Geological Survey USGS topographic maps USER TIME BIAS User Time B
71. pecifications for IRIG B and the other IRIG time codes are available from a number of sources IRIG B encodes the day of year hours minutes and seconds in a 100 pulse per second serial data stream that repeats once per second The data is formatted as binary coded decimal BCD and is transmitted least significant digit first The IRIG serial time code option available in the TM 4 provides two types of output signals baseband and modulated carrier The baseband signal is IRIG 002 pulse width coded BCD time only and is available as one of the multiplexed output signals on the MUXOUTIA pin 7 If the PPS BNC connector has been reconfigured at the factory to output signal from Mux1 baseband IRIG may appear there as well This output is TTL level and will drive a 50 ohm load The baseband signal consists of positive pulses mark high space low with three pulse widths 2 ms space 5 ms mark 8 ms timing pulse The rising edge of one particular timing pulse identified as the Reference Element defines the one second epoch The encoded time data following the epoch is the time UTC of that epoch The modulated carrier signal is IRIG B122 a 1000 Hz sinusoidal carrier that is amplitude modulated with the baseband signal and made available on the OUTI IRIG IN2 pin 15 on the HD 15 connector This signal has a 3 3 1 modulation ratio mark space It is typically able to drive a 600 ohm grounded load with a mark amplitude of 3 0
72. phemeris for this satellite NAV An illuminated indicator in this field indicates that the GPS receiver is using this satellite in its navigation solution The Receiver Status panel also displays other information relevant to the operation of the GPS receiver Receiver Mode Searching for Satellites The receiver is performing a systematic search to locate satellites This mode is used during cold starts and whenever the receiver is lacking any of the information it needs in order to know which satellites to look for Collecting Almanac The receiver has found at least one satellite and is in the process of collecting an almanac to replace an old or nonexistent one Receiving Ephemeris The GPS receiver is collecting the ephemeris data from one or more satellites This usually takes about 30 seconds Acquiring Satellites The receiver is verifying the usability of one or more satellites it wants to use Calculating Position The receiver is producing position and timing information from GPS Static Position The receiver is utilizing position information it already has or that which has been supplied by the user Almanac Status None The receiver currently does not have a valid almanac Old The receiver has determined that the current almanac is old OK The almanac is current and complete Geometric Quality 0 9 GQ is an indication of the relative geometric quality of the satellite constellation currently being utilized and i
73. put pulses will occur 150 ns late with respect to the 1 PPS signal of the unit This can be offset by adopting a User Time Bias of 150 ns however this will cause the 1 PPS signal to be 150 ns early If this effect is undesirable another method to back POP bias out would be to subtract 150 ns from the desired POP start time when entered into the TM 4 CORRECTION FOR ANTENNA CABLE LENGTH Since not all users will use the same length of antenna cable the PPS output from the TM 4 is not calibrated for any specific value In cases where absolute in time accuracy of PPS is required the user must calculate the specific User Time Bias for his antenna cable length In cases where Spectrum has supplied a 50 foot RG 58 cable a User Time Bias of 77 ns is correct For different cable lengths an appropriate User Time Bias should be adopted To calculate this bias you need to know the type and length of antenna cable being used in your particular installation Coaxial cables using polyethylene inner insulation have a delay of 1 54 ns per foot while those with cellular poly insulation commonly called polyfoam have a delay of 1 30 ns per foot To compensate for cable length simply multiply the appropriate delay by the length of the antenna cable The resulting number is the required User Time Bias You can enter this value via either the control software or with a Message 06 see Section 6 ASCII command OPERATING SUGGESTIONS The following suggestio
74. r than 60 minutes In this case the LED will illuminate steadily POWER LED This LED is software controlled and its primary function is to indicate the power status of the TM 4 During the initialization sequence it will rapidly flash momentarily and then illuminate steadily If this indicator is off it indicates that there is no input power being supplied to the unit or that there is some sort of microprocessor problem When the LED is on it indicates that the unit is operating This LED also doubles as a hardware fault indicator In the case of a detected hardware fault antenna antenna cable failure or 10 MHz output failure this LED will change from steady illumination to a flashing state READY LED This LED glows steadily to indicate that the TM 4 has reached a minimum acceptable accuracy level of 1 in 10 parts It also is flashed to indicate certain operating cautions During the initialization sequence it will rapidly flash momentarily and then extinguish until the TM 4 acquires GPS Once the unit has entered coarse tuning mode this indicator will flash It will extinguish if a condition arises that interrupts Mode 2 tuning and will remain off until the condition is corrected and tuning begins again at which point it will resume flashing Once the TM 4 enters the fine tuning mode the LED will illuminate steadily If the unit subsequently enters the fine tuning hold mode 5 condition this indicator will again flash If the TM 4 ente
75. ransmission medium is another source of error over which the user has no control Receivers that utilize only one of the two transmitted carriers L1 or L2 must rely on a mathematical model for correction of the change in path length due to ionospheric refraction bending of the signal as it propagates from the satellite Page 18 to receiver The accuracy will be degraded by this effect to extent that the actual propagation differs from the model at any given time Another important consideration is dilution of precision due to geometry All radio navigation systems have a fundamental defect in that errors inherent in the basic measurements are magnified by varying amounts depending upon the geometrical relationship between the user and the signal sources In the case of GPS the satellites are the signal sources and the geometrical relationship to the receiver is always changing even for a fixed user due to the motion of the satellites Algorithms in the receiver software attempt to minimize these effects by selecting the best set of available satellites to use for navigation Nonetheless there is always a precision error that can range from very small to very large depending upon the geometry PDOP position dilution of precision and HDOP horizontal dilution of precision are measures of the dilution of precision in 3D and 2D positions respectively These numbers are the factors by which measurement errors are magnified in a GPS po
76. requires a continuous stream of information in order to function The user must set and unset these modes directly via Messages 12 and 17 either with a serial communications program or via his own application MESSAGE FORMATS AND PROTOCOL A series of compact ASCII messages are used to control the TM 4 and to monitor its performance The general format for messages between the host and the unit is NN XXXXX XXXX XX XXXCRLF where NN is the message number designates various data fields CRLF is a carriage return followed by a line feed NOTE Spaces are not allowed in the messages and all punctuation shown must be included Page 31 Unless set to polling mode unit acknowledges each received message with the following message 50 1CRLF This indicates that the message was received the message number was legal the line feed character was received and that the message length did not exceed the maximum message length for that message number Message 50 is not indicative that the received message was legal or correct only that it met the criteria listed above Exercise caution and care when sending messages to the TM 4 It is possible to send an illegal or ill formed message and still receive message 50 Behavior is not always consistent with an illegal message Usually the unit will ignore a bad message and not change corresponding modes or outgoing messages but the POP output messages are an except
77. roduce time offset and time rate frequency terms which are used to correct the 1 PPS signal with respect to UTC This is a continuous process as long as the receiver is tracking satellites static timing mode or is calculating position fixes dynamic timing mode If the receiver finds that it cannot update the tracking loops it enters coast mode and the unit signals this by dropping the Time Valid indication The receiver continues to correct time using the loop parameters that were in place at the time coasting began In coast mode time will gradually drift off because these loops are not closed The drift rate for a VCXO equipped TM 4 will typically be 4x10 In the case of a standard TM 4 equipped with an OCXO the Intelligent Holdover algorithm detects the loss of GPS signals and enters a frequency hold mode in which the tuning is corrected with learned and stored predictive values significantly improving frequency and PPS accuracy during holdover The drift rate is typically 5x10 day after 3 days of locked operation Page 20 PROGRAMMED OUTPUT PULSE 8 EVENT TIME TAG The basic accuracy and stability of the Programmed Output Pulse POP and Event Time Tag ETT functions is determined by the accuracy of timing as described earlier The only additional consideration is that the POP function has a built in hardware bias that may need to be considered in the most precise applications The POP function has a bias of 150 ns that is out
78. rs Coast Alarm the LED will turn off See the chart on the following page for an at a glance explanation of TM 4 operating status Page 42 LED COMBINATIONS AND THEIR MEANINGS ALARM READY POWER TM 4 STATUS rapid flash rapid flash rapid flash Start up The unit is completing initialization tasks on off on flash Warm up GPS is not supplying valid time information off off on flash Warm up GPS is supplying valid time information off flash on flash Oscillator coarse tuning Mode 2 GPS is normal flash off on flash Coarse tuning hold Mode 3 Unit is in coast mode due to lack of input from GPS off on flash Oscillator fine tuning Mode 4 Accuracy better than 1x10 GPS is normal flash on flash Fine tuning hold Mode 5 Unit is no longer fine tuning due to lack of input from GPS but is using Intelligent Holdover technology to maintain oscillator accuracy In hold mode for less than 60 minutes on flash Coast Alarm Same as above but unit has been in this condition for more than 60 minutes POWER LED will indicate hardware faults in these modes by flashing Bold indicates priority of indication REAR PANEL CONNECTORS AND FUNCTIONS ANTENNA CONNECTOR The antenna connector is a standard TNC jack and is the input connector for the antenna cable 1 PPS CONNECTOR This BNC connector supplies the 1 PPS pulse per second output signal which is a 1 ms nominal positive pulse The driver circuit
79. s designed to be attached to a standard marine thread 1 0 14UNS2A pole Options include a flush mounted version an adapter that allows attachment to an unthreaded pole up to 1 25 in diameter and various antenna mounts Pre amplifier power is supplied from the unit over the coaxial cable center conductor Control and operation of the Intelligent Reference TM 4 is handled through the control interface Consisting of a standard RS 232 serial channel implemented in a VGA style HD 15 D sub connector this accommodates a wide variety of host computers and equipment including any personal computer or compatible with a serial communications port The user may make use of the port either by wiring up his own cable or connection or by using the optional breakout board or adapter cable which will bring the serial connections out to a standard 9 pin D sub connector All communications to and from the unit utilize a series of compact ASCII messages which allow the host to make changes to the operating parameters and read GPS tracking status and timing information The Intelligent Reference TM 4 is capable of autonomous operation without connection to a host computer Once power is applied the unit requires no intervention to acquire satellites and provides the basic time and frequency functions based on factory default settings A host computer may be connected for initialization purposes and left connected to monitor the system operation The host may be
80. s represented with a 0 9 scale A value of nine indicates the best geometric quality and low PDOP Position Dilution of Precision GQs of 7 9 allow good accuracy with PDOPs of 1 5 A value of 4 6 give fair accuracy and corresponds with PDOPs of 5 10 with values lower than 4 indicating poor accuracy and PDOPs of greater than 10 Page 25 Mask Angle 5 10 15 Shows the current value being used by the receiver for mask angle Satellites below the selected value will not be acquired by the receiver If a satellite is currently being tracked it can drop to 5 degrees before it is no longer used You can click on this value to access the Mask Angle screen and change the mask angle setting TIME AND DATE PANEL Local Time Local Date Time Date This is obtained by adjusting UTC time and date by a value specified by the user in the Local Time Offset screen Clicking on either of these fields will access this screen which also allows you to change time modes If you select 12 hour mode the time field shows time as AM PM UTC Time UTC Date Time Date UTC time and date obtained from the GPS receiver POSITION DATA PANEL Latitude Position Displays the receiver s current calculated or user input latitude in either degrees and decimal minutes or degrees minutes and seconds Clicking on this field will bring up the Set Position and Altitude screen Longitude Position Same as latitude Altitude Altitude Shows the receiver s current calculat
81. s the primary source for driving local oscillator synthesizers in wireless communications systems There two user settable multiplexer outputs incorporated in the Intelligent Reference TM 4 Mux1 generates a precise TTL frequency output that is slaved to the primary 10 MHz output One of six frequencies may be selected for output 1 kHz 10 kHz 100 kHz 1 MHz 5 MHz 10 MHz Also Mux1 can be programmed to output PPS or optional IRIG time code The second multiplexer can supply a 10 MHz TTL signal PPS a mirror of the output of Mux an optional custom signal The Intelligent Reference TM 4 provides for an auxiliary frequency output generated by a phase locked loop PLL synthesizer in the unit This output is available as a factory option and virtually any common frequency is available Examples include frequencies such as 1 544 MHz and 2 048 MHz This output retains the accuracy and stability of the primary 10 MHz output and its stability meets the MTIE requirement for a Stratum 1 primary clock source Another advanced feature of the TM 4 is an optional very wide range frequency synthesizer This allows the TM 4 to generate a factory set frequency of the user s choice slaved to the primary frequency reference This output retains the precision and quality of the primary reference and can be almost any frequency desired up to approximately 40 MHz Spectrum must be consulted with requirements prior to this feature being availa
82. se width 3 for 1 ms pulse width W 4 for 10 ms pulse width W 5 for 50 ms pulse width W 6 for 100 ms pulse width W 7 for 250 ms pulse width W 8 for Level Hold only valid POP One Shot mode Page 35 NOTE In Repeat mode repeat interval must be least one millisecond longer than selected pulse width MESSAGE 22 SET ETT PARAMETERS NOTE Non simultaneous POP ETT TM 4 s must use message 11 to set ETT parameters 22 X PCRLF where X 0 for ETT OFF X 1 ETT ON for positive polarity P for negative polarity MESSAGES FROM THE INTELLIGENT 4 The following messages have been defined for transfer of information from the TM 4 to a host computer MESSAGE 50 ACKNOWLEDGE 50 1CRLF MESSAGE 51 DATE AND TIME 51 MMDDYYYY HHMMSSCRLF where MMDDYYYY is UTC month day and year HHMMSS is UTC hours minutes and seconds MESSAGE 52 POSITION 452 WWWW WW X YYYYY YY 2Z A NCRLF where W latitude in DDMM MM X hemisphere N or S Y longitude in DDDMM MM Z hemisphere W GBPS availability 0 not available 1 available N number of satellites used 0 9 A 10 B 11 C 12 MESSAGE 53 ALTITUDE 53 SXXXXX MCRLF Page 36 where S sign or X altitude 5 digits M altitude units meters MESSAGE 55 MASK ANGLE AND MAP DATUM SETTING 55 X 47CRLF where X 0 for 5 degrees X 1 for 15 d
83. sheet of rubber or flexible plastic in the space on the opposite side of the set screws to fill the space and then tighten Spectrum recommends the application of a weatherproof connector sealant available at most electronic supply stores RTV silicone or automotive window sealant at the junction of the connector and antenna to prevent water intrusion and corrosion Other mounting and antenna options are available Contact Spectrum for more details CABLE LENGTHS AND TYPES The antenna cable normally supplied with the optional antenna kit is a 50 foot length of RG 58 Belden 8240 with TNC connectors attached to both ends Page 6 You can use up to 115 feet of solid core RG 58 without suffering any appreciable performance loss sure that the cable you are planning to use is of good quality and that the connectors are attached correctly Also be sure that the center conductor is solid as opposed to stranded as the stranded types have much higher signal loss at GPS frequencies For longer cable runs it will be necessary to convert all or part of the run to a cable with lower signal loss such as RG 213 or RG 8 The critical issue with cable length is the total cable loss at 1575 MHz This loss must be kept less than 24dB in order to avoid performance degradation Consult the factory for help in configuring longer cable runs We can also supply cables in custom lengths and configurations if required INTELLIGENT
84. sition solution due to geometrical considerations PDOP is generally greater than HDOP thus position accuracy will be better in 2D where altitude is known than in 3D The best thing a user can do to minimize the effects of geometry is to locate the antenna such that it has a clear view of the sky This will allow the GPS receiver to track all satellites above the horizon and will give the satellite selection algorithm the best choices for minimizing errors In the Intelligent Reference TM 4 the variable called GQ is a relative measure of geometric quality on a 0 to 9 scale with 9 representing the best geometry This relates to PDOP or HDOP as shown in the following table oe a E E 4 Under identical circumstances two GPS receivers will achieve slightly different results due to differences in hardware and software designs Fortunately the error contribution due to receiver design considerations is very small in modern receiver designs such as the one incorporated into the TM 4 TIME ACCURACY The same factors that affect position accuracy also affect timing accuracy although degradation in timing accuracy due to geometry and previously SA is different in the two timing modes Static and Dynamic In discussing timing accuracy it is important to distinguish between absolute accuracy and relative accuracy or stability Absolute accuracy refers to the error of a single measurement or the
85. tellite signal SQ is measured using a 0 9 scale with nine being the highest quality Under most conditions you can expect signal qualities ranging from 7 9 Lower values can occur due to the satellite being low on the horizon or partially blocked by one or more objects or a less than ideal antenna cable condition An S in this field indicates that the receiver is currently searching for an identified satellite utilizing this channel An A in this field indicates that a satellite has been found and its signal is being acquired by the receiver The signal quality display consists of 12 bar graph type indicators which change both length and color depending upon signal quality The bar indicates red for signal qualities of zero to one yellow for conditions of greater than one and up to four and green for SQ s greater than four These indicators are updated every two seconds and thus will not show instantaneous changes in signal strength SQ This is a numeric indication of signal strength S in this field indicates that the receiver is currently searching for an identified satellite utilizing this channel An in this field indicates that a satellite has been found and its signal is being acquired by the receiver SQ relates to the signal to noise ratio carrier to noise density ratio or C No according to the following table EPH lit indicator in this field indicates that the GPS receiver has a valid e
86. the POP Status indicator the toolbar icon or via the Command menu 2 Enter a POP UTC date and time This is the time that you want the first pulse to be generated 4 If you have selected the POP Repeat Mode enter a repeat interval number of milliseconds between pulses 4 Choose output pulse polarity 5 Choose a suitable pulse width If you are using the POP Repeat mode note that the repeat interval must be at least 1 millisecond longer than the pulse width you have selected 6 Click on OK to activate the POP feature The pulse will be generated at the specified time and if the unit is set to POP Repeat Mode at the specified intervals thereafter NOTE minimum repeat interval is 1 ms and the maximum repeat interval is 99 999 999 ms approximately 27 78 hours In some implementations of the Intelligent Reference TM 4 it is not possible to use both the ETT and POP functions at the same time If your TM 4 has simultaneous ETT POP capability it does not have this limitation REMAINING OPERATIONS At this point an OCXO equipped unit should continue to tune and progress through the various operating stages It will first enter the Mode 2 coarse tuning phase and then enter the fine tuning Mode 4 phase See the chart on page 43 explaining LED combinations for the indications that denote these modes Page 30 SECTION 6 COMMUNICATING WITH THE TM 4 This section of the manual provides the information necessary to m
87. ulse POP functions each with 100 ns resolution Note that some TM 4 units do not offer simultaneous capability In these units only one function may be enabled at any given time e Optional Type 11 Network Time Protocol output e Optional IRIG or other time code serial time code output TTL and modulated e Windows based control display software e Front panel indicators for power status reference ready and alarm status 9 to 35 VDC operation with rechargeable lithium battery back up for GPS data The Intelligent Reference TM 4 consists of a twelve channel GPS timing receiver integrated with proprietary microprocessor controlled timing and interface logic A separate GPS antenna is required The GPS receiver simultaneously tracks all available satellites The microprocessor controlled timing and interface logic derives precise timing information from these satellites and provides additional features including the standard 1 PPS output and associated ASCII serial time message external event time tag programmed output pulse optional IRIG B serial time code generator and other optional features and outputs The timing and interface logic also controls an ovenized 10 MHz crystal oscillator or VCXO and additional clock features The standard timing antenna if supplied is an all weather high performance high noise immunity patch design with an integrated low noise preamplifier It is supplied with 50 feet of RG 58 cable and i
88. ulse per second 1 PPS output with separate ASCII serial time message Static and dynamic timing modes Auto Survey position averaging mode Timing information derived from all satellites tracked with only one satellite required in static timing mode RS 232 control interface for control by a host computer Optional low cost VCXO in place of OCXO Two multiplexer outputs Mux output 1 supplies one of six selectable TTL outputs slaved to the primary frequency reference 1 10 and 100 kHz and 1 5 and 10 MHz In addition Mux also supply a TTL level PPS output or optionally be configured to supply baseband IRIG time code Mux output 2 can supply 10 MHz or PPS at TTL levels mirror Mux1 s output or may optionally be configured to supply a custom output e NMEA message capability subset Optional very wide range frequency synthesizer output slaved to primary reference Consult factory for specific application Optional second sine wave output either identical to or independent of primary frequency up to 100 MHz Optional auxiliary frequency output such as 1 544 MHz or 2 048 MHz slaved to the primary frequency reference Virtually any common frequency may be chosen Optional synthesized timing pulse output coherent with 10 MHz output and synchronized to 1 PPS This may be virtually any frequency up to 100 kHz including frequencies such as 216 2 3 Hz Page 2 e Simultaneous Event Time Tag ETT and Programmed Output P
89. users who require precise timing while operating on a moving platform When operating in the Static Timing Mode the TM 4 uses a fixed position as the reference for deriving time In this case the position may be user entered or previously derived from GPS Information from all satellites tracked is used for timing and time remains valid as long as at least one satellite is tracked A related function is the Auto Survey mode If you plan to operate the unit in one location you may wish to invoke this function Auto Survey takes the average of 10 000 position measurements and then automatically switches the unit to static timing mode The Auto Survey function takes about 3 hours to complete Page 12 Once Intelligent Reference TM 4 has obtained precise time from the GPS system it declares Time Valid and enables all functions that are dependent on the availability of precise time The Time Valid condition is indicated by a status byte in the ASCII serial time message output on the time port by Message 64 and by combinations of front panel LEDs in various operating modes If the unit subsequently finds that it cannot supply corrected precise time it enters Coast Mode Coast mode will be indicated differently depending on what mode the TM 4 was in prior to entering the coast condition If the unit was in Mode 2 coarse tuning when it entered coast this will normally be indicated by the READY LED extinguishing the ALARM LED flashing
90. will supply TTL levels into a 50 ohm load and the rising edge of this signal is the on time epoch Rise and fall times are less than 10 ns Additionally this connector may be reconfigured at the factory to provide modulated IRIG time code a mirror of MUXOUTIA or some other custom output in lieu of the 1 PPS signal The PPS signal is supplied as soon as the TM 4 finishes its initialization tasks but is not locked to GPS until the unit achieves the Time Valid condition 10 MHz OUT CONNECTOR This BNC connector is the disciplined 10 MHz sine wave output signal The driver circuit will supply a level of 10 dBm nominal into a 50 ohm load This connector may be factory reconfigured to a custom output Page 43 HD 15 D SUB CONNECTOR This connector provides for input DC power and access to a variety of functions as listed below SIGNAL FUNCTION 1 OUT2 10 MHZ TTL OUTPUT or CUSTOM OUT 2 GND SIGNAL POWER GROUND 3 CPTXD232 RS 232 SERIAL DATA TO HOST 4 CPRXD232 RS 232 SERIAL DATA FROM HOST 5 PPS AUX232 PPS CUSTOM SEE DESCRIPTION 6 TPTXD232 TIME PORT RS232 OUTPUT 7 MULTIPLEXER 1 A OUTPUT 8 ALM ALARM OUTPUT 9 GND SIGNAL POWER GROUND 10 EVENT EVENT INPUT 11 DCIN POWER IN 9 35 VDC 12 POP PROGRAMMED OUTPUT PULSE 13 MUXOUT2 MULTIPLEXER 2 OUTPUT 14 RESERVED SEE DESCRIPTION 15 OUT1 IRIG IN2 OUTPUT TIME CODE CUSTOM INPUT The definitions and specifications for these signals are as fol
91. within 25 ns of UTC If the effect of SA were to be included this value would be more like 125 ns although this cannot be definitively specified The stability of timing measurements is specified as 12 5 ns RMS without SA in static timing mode In summary when operating in static mode a large number of measurements of the time of the 1 PPS output with respect to true UTC should have a mean value within 12 5 ns of UTC and have a standard deviation of 5 ns 68 within 5 ns of the mean FREQUENCY ACCURACY The accuracy of the primary 10 MHz output and other outputs is dependent upon the interval over which the accuracy is measured For longer intervals greater than one hour the accuracy is controlled by the oscillator discipline algorithm which uses information derived from GPS and the built in intelligence to accurately tune the ovenized crystal oscillator OCXO on frequency In this case the accuracy will continue to approach that of the Cesium clocks on the satellites for the length of the measurement period For short intervals less than an hour the accuracy is weighted more by the inherent stability of the OCXO itself though the tuning action is still important The accuracy specifications given in Appendix A include these various effects The specified accuracies are those that would be measured by an ideal frequency counter perfect time base infinite resolution COASTING There are tracking loops in the GPS receiver that p
92. work Time Protocol in a format compatible with widely available public domain drivers The front panel of the unit incorporates three LED status indicators to indicate power tuning status and alarm status All connections to the Intelligent Reference are made with standard connectors located on the rear panel The Intelligent Reference TM 4 comes with control display software and this user s guide Optional accessories include GPS antennas and cables an AC power adaptor a breakout board for easy connection of the unit and access to features and outputs and a power data adapter cable Page 5 SECTION 2 UNPACKING AND INSTALLATION PACKING LIST Every TM 4 shipment includes a packing list showing the contents of the shipment After unpacking this list should be checked to make sure that all of the items listed are present and undamaged In some cases a special or custom item may have been included or substituted for a standard item If your order includes any special items these will be listed on the packing list ANTENNA INSTALLATION LOCATION Before attempting to install an antenna give careful consideration to its location and placement as this can affect the overall performance of the Intelligent Reference TM 4 The primary goal is to locate the antenna in a place where it has a clear view of the sky A secondary goal is to locate the antenna away from radio transmitters or other sources of noise that could possibly int
93. ws the receiver to determine the position latitude longitude amp altitude and time The 21 satellite constellation provides excellent three dimensional navigation with only occasional outages as long as the antenna has a clear view of the sky and is not obstructed If navigation is not required because the user position is known precise time can be derived by tracking only one satellite In this case it is easy to see that the reliability of time information will be very high even in situations where the antenna has an obstructed view of the sky The satellites have on board Cesium atomic clocks which provide a very stable time reference for determining the time synchronization of the radio transmissions from the satellite In addition ground stations closely monitor the performance of these clocks and provide fine corrections to the on board time keeping These corrections are available in the transmitted data stream for use by receivers on the ground Page 1 Each satellite broadcasts 50 bit per second data stream which contains an almanac for entire constellation and precise ephemeris data for that particular satellite Also transmitted is the precise time of transmission of a particular epoch in the data stream The carrier is modulated with this data stream and also with a pseudo random spreading code which is unique to that satellite By correlating an internally generated but time shifted replica of the spreading code to the

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