ET6000, ET6010, ET6500
ExacTime GPS Time Code
And Frequency Generator
Covering Configurations:
ET6000, ET6010, ET6500-TCXO
ET6000, ET6010, ET6500-OCXO
ET6000, ET6010, ET6500-RB1
Revision C
User’s Guide
8500-0105
June, 2005
ET6000, ET6010, and ET6500
EXACTIME GPS TIME CODE AND FREQUENCY GENERATOR
TABLE OF CONTENTS
SECTION PAGE
CHAPTER ONE
GENERAL INFORMATION
1.0 INTRODUCTION ................................................................................................................1-1
1.1 USER'S GUIDE SUMMARY ..............................................................................................1-1
1.2 NAVSTAR/GPS DESCRIPTION ........................................................................................1-2
1.3 PRODUCT DESCRIPTION.................................................................................................1-3
1.4 SPECIFICATIONS...............................................................................................................1-4
1.4.1 GPS SUBSYSTEM................................................................................................ 1-4
1.4.2 TIMING OUTPUTS..............................................................................................1-4
1.4.3 ACCURACY .........................................................................................................1-7
1.4.4 TIMING INPUTS..................................................................................................1-7
1.4.5 J12 RS-232 I/O INTERFACE ............................................................................... 1-8
1.4.6 INTERNAL TIME BASE......................................................................................1-8
1.4.7 PRIMARY POWER ............................................................................................1-11
1.4.8 DIMENSIONS..................................................................................................... 1-13
1.4.9 WEIGHT..............................................................................................................1-13
1.4.10 ENVIRONMENT.............................................................................................. 1-13
1.5 ADDITIONAL SPECIFICATIONS................................................................................... 1-14
1.5.1 ANTENNA/PREAMP.........................................................................................1-14
1.5.2 GPS RPU AND ANTENNA................................................................................1-14
1.6 FUNCTIONAL CHARACTERISTICS.............................................................................. 1-14
1.6.1 ACQUISITION....................................................................................................1-14
1.6.2 SIGNAL INTERRUPTION.................................................................................1-15
1.6.3 POSITION AND VELOCITY SOLUTION........................................................1-15
1.6.4 DYNAMIC CAPABILITY.................................................................................. 1-16
1.6.5 RF JAMMING RESISTANCE AND BURN-OUT PROTECTION................... 1-16
1.6.6 SYSTEM STATUS AND DIAGNOSTICS ........................................................1-16
1.6.7 GPS SOLUTION MODES .................................................................................. 1-16
1.6.8 ELEVATION ANGLE MASK............................................................................1-17
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CHAPTER TWO
INSTALLATION
2.0 INTRODUCTION ................................................................................................................2-1
2.1 UNPACKING AND INSPECTION.....................................................................................2-1
2.2 RACK MOUNTING PROCEDURE.................................................................................... 2-1
2.2.1 TMRA....................................................................................................................2-1
2.2.2 ELEVATED AMBIENT OPERATING TEMPERATURE..................................2-1
2.2.3 REDUCED AIR FLOW.........................................................................................2-2
2.2.4 MECHANICAL LOADING.................................................................................. 2-2
2.2.5 CIRCUIT OVERLOADING ................................................................................. 2-2
2.2.6 RELIABLE EARTHING.......................................................................................2-2
2.3 ANTENNA/PREAMP INSTALLATION............................................................................2-2
2.4 ANTENNA/PREAMP INTERFACE CONNECTIONS......................................................2-2
2.5 PRIMARY POWER CONNECTION ..................................................................................2-3
2.6 GPS TIMING UNIT INTERFACE CONNECTIONS.........................................................2-6
2.6.1 RS-232 I/O INTERFACE J12 ............................................................................... 2-6
2.6.2 PRINTER OUTPUT PORT J11 ............................................................................2-7
2.6.3 TIMING OUTPUTS..............................................................................................2-7
2.6.4 1PPS INPUT..........................................................................................................2-8
2.6.5 OSCILLATOR CONFIGURATION..................................................................... 2-8
CHAPTER THREE
OPERATION
3.0 INTRODUCTION ................................................................................................................3-1
3.1 OPERATIONAL STEPS......................................................................................................3-1
3.1.1 INITIALIZATION (UNKNOWN POSITION)..................................................... 3-1
3.1.2 INITIALIZATION (KNOWN POSITION)...........................................................3-3
3.2 OPERATIONAL CHARACTERISTICS............................................................................. 3-4
3.3 LIQUID CRYSTAL DISPLAY............................................................................................ 3-4
3.3.1 MAIN MENU SCREEN........................................................................................3-4
3.3.2 POSITION MENU SCREEN ................................................................................ 3-9
3.3.3 SET-UP MENU SCREEN................................................................................... 3-10
3.3.4 RS232 I/O CONFIGURATION MENU SCREEN .............................................3-15
3.3.5 MULTIPLE TIME CODE OUTPUTS MENU SCREEN...................................3-16
3.3.6 PRESET COINCIDENCE MENU SCREEN...................................................... 3-16
3.3.7 EXTERNAL FREQUENCY MEASUREMENT MENU SCREEN...................3-17
3.3.8 SINGLE EVENT LOG MENU SCREEN........................................................... 3-18
3.3.9 50/60HZ MEASUREMENT SCREEN ...............................................................3-19
3.3.10 AUTO DAYLIGHT SAVINGS MENU SCREEN ........................................... 3-20
3.3.11 MUX OUTPUT MENU SCREEN ....................................................................3-21
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3.3.12 PRINTER PORT CONFIGURATION MENU SCREEN.................................3-23
3.3.13 IEEE-488 I/O INTERFACE MENU SCREEN.................................................3-26
3.4 CONFIGURATION OF REAR PANEL BNC CONNECTORS J4-J9..............................3-26
CHAPTER FOUR
I/O PORT DATA INPUT/OUTPUT
4.0 INTRODUCTION ................................................................................................................4-1
4.1 SYMMETRICOM FIRMWARE VERSION........................................................................4-3
4.2 UTC SYNC........................................................................................................................... 4-4
4.3 GPS SYNC............................................................................................................................4-4
4.4 PRINT FREQUENCY OFFSET........................................................................................... 4-4
4.5 PRINT TIME, STATUS, ERROR CODE, AND SATELLITE VEHICLE NUMBERS..... 4-4
4.6 PRINT POSITION................................................................................................................4-6
4.7 CLEAR EVENT DATA ...................................................................................................... 4-7
4.8 PRINT EVENT DATA.........................................................................................................4-7
4.9 REQUEST ONE EVENT LOG DATA................................................................................ 4-8
4.10 ENABLE SINGLE EVENT LOG ...................................................................................... 4-9
4.11 DISABLE SINGLE EVENT LOG..................................................................................... 4-9
4.12 SELECT MODE.................................................................................................................4-9
4.13 ENABLE TIME INTERVAL...........................................................................................4-10
4.14 DISABLE TIME INTERVAL.......................................................................................... 4-10
4.15 REQUEST TIME INTERVAL.........................................................................................4-10
4.16 REQUEST ELEVATION MASK ANGLE...................................................................... 4-11
4.17 ENTER ELEVATION MASK ANGLE........................................................................... 4-11
4.18 ENABLE DISCIPLINING ...............................................................................................4-11
4.19 DISABLE DISCIPLINING.............................................................................................. 4-11
4.20 ENTER POSITION .......................................................................................................... 4-12
4.21 ENTER DAC VALUE...................................................................................................... 4-12
4.22 REQUEST DAC VALUE................................................................................................. 4-13
4.23 NUMBER OF POSITION AVERAGES.......................................................................... 4-13
4.24 ENTER LOCAL OFFSET................................................................................................ 4-13
4.25 ENTER CABLE DELAY.................................................................................................4-14
4.26 REQUEST CABLE DELAY............................................................................................ 4-14
4.27 RESYNCHRONIZE MINOR TIME................................................................................4-14
4.28 SELECT DEFAULT VALUES........................................................................................ 4-15
4.29 EXTERNAL FREQUENCY MEASUREMENT – SELECT INPUT FREQUENCY.....4-15
4.30 EXTERNAL FREQUENCY MEASUREMENT – ENABLE/DISABLE ........................4-16
4.31 EXTERNAL FREQUENCY MEASUREMENT – REQUEST DATA............................4-16
4.32 REQUEST SATELLITE SIGNAL SNR..........................................................................4-16
4.33 REQUEST UNIT OPERATING PARAMETERS........................................................... 4-17
4.34 ENABLE 50/60HZ MEASUREMENT............................................................................ 4-18
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TABLE OF CONTENTS
4.35 50/60HZ SELECTION .....................................................................................................4-18
4.36 ENTER 50/60HZ OFFSET DATA................................................................................... 4-18
4.37 REQUEST 50/60HZ MEASUREMENT DATA............................................................... 4-19
4.38 PRINTER – SET-UP CONFIGURATION.......................................................................4-19
4.39 PRINTER – REQUEST CONFIGURATION..................................................................4-20
4.40 PRINTER PORT MODE SELECTION........................................................................... 4-20
4.41 PRINTER – SELECT OUTPUT RATE...........................................................................4-21
4.42 PRINTER – REQUEST OUTPUT RATE........................................................................4-21
4.43 ENABLE/DISABLE & DATA SELECT......................................................................... 4-21
4.44 ENTER PRESET COINCIDENCE TIME .......................................................................4-23
4.45 REQUEST MUX OUTPUT ............................................................................................. 4-24
4.46 SET MUX OUTPUT ........................................................................................................4-25
4.47 SET MAJOR TIME – TOD (TIME OF DAY)................................................................. 4-25
4.48 SET YEAR........................................................................................................................4-25
4.49 AUTOMATIC DAYLIGHT SAVINGS TIME................................................................ 4-26
4.49.1 DISABLE AUTO DAYLIGHT SAVINGS TIME FUNCTION....................... 4-26
4.49.2 ENABLE AUTO DAYLIGHT SAVINGS TIME FUNCTION........................4-26
4.49.3 SET AUTO DAYLIGHT SAVINGS TIME DEFAULT INTERVAL ............. 4-26
4.49.4 REQUEST AUTO DAYLIGHT SAVINGS TIME INTERVAL......................4-27
4.49.5 SET AUTO DAYLIGHT SAVINGS TIME INTERVAL................................. 4-27
4.50 REQUEST UNIT SERIAL NUMBER............................................................................. 4-28
CHAPTER FIVE
MAINTENANCE/TROUBLESHOOTING
5.0 MAINTENANCE................................................................................................................. 5-1
5.1 ADJUSTMENTS..................................................................................................................5-1
5.1.1 INTERNAL OSCILLATOR CALIBRATION...................................................... 5-1
5.1.2 LCD ADJUSTMENT ............................................................................................5-3
5.1.3 AC CODE ADJUSTMENTS................................................................................. 5-3
5.1.4 10MHZ SINE WAVE............................................................................................5-3
5.1.5 10MHZ SQUARE WAVE..................................................................................... 5-3
5.2 TROUBLESHOOTING........................................................................................................ 5-4
5.2.1 GENERAL............................................................................................................. 5-4
5.2.2 POWER LED WILL NOT ILLUMINATE WHEN ON/OFF SWITCH IS
ACTIVATED........................................................................................................ 5-4
5.2.3 TRACKING LED DOES NOT ILLUMINATE.................................................... 5-4
5.2.4 LOCKED LED DOES NOT ILLUMINATE ........................................................ 5-5
5.2.5 UNIT DOES NOT TRACK SATELLITES, ERROR MESSAGE/CODE –
ANTENNA UNDERCURRENT ..........................................................................5-5
5.2.6 COLD RESET ....................................................................................................... 5-5
5.3 THEORY OF OPERATION................................................................................................. 5-6
5.3.1 GPS SYSTEM OPERATION................................................................................5-6
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ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
TABLE OF CONTENTS
5.3.2 MODES OF OPERATION....................................................................................5-6
5.3.3 EXACTIME INTERNAL CONFIGURATION....................................................5-8
5.3.4 MICROCOMPUTER PROGRAM THEORY OF OPERATION.........................5-9
APPENDIX A
ASCII CHARACTER CODE TABLE
PART ONE................................................................................................................................. A-1
PART TWO................................................................................................................................ A-2
PART THREE ............................................................................................................................ A-3
PART FOUR............................................................................................................................... A-4
APPENDIX B
GLOSSARY OF TERMS
A...................................................................................................................................................B-1
B...................................................................................................................................................B-2
C...................................................................................................................................................B-2
D...................................................................................................................................................B-3
E...................................................................................................................................................B-3
F ...................................................................................................................................................B-4
G...................................................................................................................................................B-4
H...................................................................................................................................................B-5
I....................................................................................................................................................B-5
J....................................................................................................................................................B-6
K...................................................................................................................................................B-6
L...................................................................................................................................................B-6
M..................................................................................................................................................B-7
N...................................................................................................................................................B-7
O...................................................................................................................................................B-8
P ...................................................................................................................................................B-8
Q...................................................................................................................................................B-9
R...................................................................................................................................................B-9
S ...................................................................................................................................................B-9
T.................................................................................................................................................B-10
U.................................................................................................................................................B-10
V.................................................................................................................................................B-10
W................................................................................................................................................B-11
X.................................................................................................................................................B-11
Y.................................................................................................................................................B-11
Z.................................................................................................................................................B-11
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TABLE OF CONTENTS
APPENDIX C
OPTION DESCRIPTIONS
GPS Opt 01/01A Three Channel Encoder .....................................................................C-1
GPS Opt 06A 1 MHz Sine Wave Shaper................................................................C-16
GPS Opt 07A 5 MHz Sine Wave Shaper................................................................C-17
GPS Opt 08CE 10-37VDC Dual Power Input ..........................................................C-18
GPS Opt 08G 38-73VDC Power Supply................................................................C-21
GPS Opt 08GP 38-73VDC Power Supply................................................................C-23
GPS Opt 10B Low Phase Noise Oscillator.............................................................C-28
GPS Opt 13A Parallel BCD Output (Days – Milliseconds) ...................................C-31
GPS Opt 14 IEEE-488 I/O Interface....................................................................C-36
GPS Opt 15A/15P Rubidium Time Base 10MHz Oscillator (LPRO) ...........................C-42
GPS Opt 15C Rubidium Time Base 10MHz Oscillator (X72)...............................C-45
GPS Opt 21A 10MHz Sine Wave Shaper...............................................................C-47
GPS Opt 23A/23B Lightning Arrestor (w/25 or 50 ft. Antenna Cable ..........................C-48
GPS Opt 27A,B,C,D Signal Distribution...........................................................................C-53
GPS Opt 33A 1.544/2.048MHz Square Wave Output............................................C-56
GPS Opt 33B/33C T1/E1 Framed Ones – Balanced Output ..........................................C-57
GPS Opt 33D/33E T1/E1 Framed Ones – Balanced Output w/Frame Marker etc. .......C-65
GPS Opt 40/40P GPS Option Motherboard (w/6 BNC outputs) ................................C-73
GPS Opt 40A/40AP GPS Option Motherboard (w/1 BNC output)..................................C-75
GPS Opt 40B/40BP GPS Option Motherboard (w/3 BNC outputs) ................................C-77
GPS Opt 48 Pulse Rate Module...........................................................................C-79
APPENDIX D
ANTENNA REPLACEMENT KIT
D.0 Antenna Replacement Kit................................................................. D-1
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ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
CHAPTER ONE
GENERAL INFORMATION
1.0 INTRODUCTION
This User’s Guide describes the installation and operation of the ExacTime ET6xxx Global
Positioning System (GPS) Time Code and Frequency Generator (TC&FG). Excluding options and
size, the only difference between the different configurations is the oscillator.
The following are the available configurations and their respective oscillators:
ET6000-TCXO 10MHz Voltage Controlled Temperature Compensated Crystal Oscillator.
ET6010-TCXO
ET6500-TCXO
ET6000-OCXO 10MHz Voltage Controlled Ovenized Crystal Oscillator.
ET6010-OCXO
ET6500-OCXO
ET6000-RB1 10MHz Rubidium Oscillator with an aging rate of 5E-11 per month.
ET6010-RB1
ET6500-RB1
1.1 USER'S GUIDE SUMMARY
This User’s Guide is divided into the following chapters:
A. CHAPTER ONE - GENERAL INFORMATION
This chapter includes a general description of the GPS Timing Unit and provides
technical specifications.
B. CHAPTER TWO - INSTALLATION
Describes initial inspection, preparation for use, interconnections to antenna/preamp,
power connections, and signal interconnections.
C. CHAPTER THREE - OPERATION
Describes the local operation of the unit.
D. CHAPTER FOUR - I/O PORT DATA INPUT/OUTPUT
Provides information on the protocol and data available through the RS-232C I/O
port.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-1
CHAPTER ONE
E. CHAPTER FIVE - MAINTENANCE/TROUBLESHOOTING
Provides a guide to the maintenance and troubleshooting of this instrument. A
description of the available adjustments is also provided.
F. APPENDIX A - ASCII CHARACTER CODES
Provides the cross reference of the ASCII character set to decimal, octal, and
hexadecimal numbers.
G. APPENDIX B - ACRONYMS AND ABBREVIATIONS
Provides a list of acronyms and abbreviations used in this User’s Guide.
H. APPENDIX C -OPTION DESCRIPTIONS
The Option Descriptions that are available with this instrument are located in this
Appendix.
I. APPENDIX D –ANTENNA REPLACEMENT KIT
Provides superseded model information.
1.2 NAVSTAR/GPS DESCRIPTION
The Navstar/GPS satellite-based timing and navigation system consists of a constellation of high
altitude satellites orbiting the earth every twelve sidereal hours, a group of ground-based
control/monitoring stations and the user equipment which may be located on land, sea and/or air.
The GPS System was completed in the early 1990’s and provides three dimensional positioning,
velocity, and time, on a continuous world-wide basis. The constellation is comprised of twenty-one
satellites and three spares. The satellites are located in six different orbital planes inclined
approximately sixty degrees to the equator at altitudes of 10,400 miles above the earth.
The GPS Timing Unit determines time and frequency by measuring the time of arrival of the
precise timing mark and measuring the Doppler effect from one satellite. A previously entered or
determined position allows computation of the receivers time offset. An accurate timing mark
(1pps) can be set, and an input 1pps pulse can be measured with respect to UTC. The satellite
positions are known within a few meters and the satellite clocks are calibrated within a few
nanoseconds so position can be computed within an absolute accuracy of better than 120 meters
(with current selective availability).
The GPS signal transmitted from a satellite consists of two carrier frequencies. L1 at a frequency of
1575.42 MHz and L2 at a frequency of 1227.6 MHz. The L1 signal is modulated with both a
precision (P) code and a coarse acquisition (C/A) code. The precision (P) code is available to
authorized users only. The GPS Timing Unit operates on the C/A code.
Each satellite transmits a unique C/A code that reflects the satellite identity for acquisition and
tracking. The C/A PRN code is a gold code of 1023 bits repeating at a one-millisecond rate.
1-2 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
GENERAL INFORMATION
The L1 and L2 frequency is also modulated with a fifty-bit-per-second data stream providing
satellite ephemerides, system time, satellite clock behavior, and status information on all satellites.
The data message is contained in a data frame that is 1,500 bits long.
Ground based control/monitoring stations track the satellites and provide an upload several times
each day to provide a prediction of each satellites ephemeris and clock behavior for the next day’s
operation.
1.3 PRODUCT DESCRIPTION
The GPS Timing Unit operates on the civilian L-band (1575.42MHz) utilizing C/A (Coarse
Acquisition) code transmissions to monitor time and frequency data from the Navstar satellite
constellation. Time and frequency is determined from satellite transmissions and calculations
referenced to USNO (United States Naval Observatory) through the GPS Master Clock system.
This link provides traceability to USNO and all international time scales through the use of
publications from NIST (National Institute of Standards Technology), USNO, and BIPM (Bureau of
International Des Poids et Measurements) in Servres, France.
The unit automatically acquires and tracks satellites based on health status and elevation angle. In
the Stationary mode, time and frequency monitoring requires only one satellite, once accurate
position data has been acquired or entered, although the receiver will use as many satellites as
available. In “AUTO” mode, and the “Dynamic” mode, a minimum of four satellites are required
for the GPS Timing unit to do three dimensional (latitude, longitude, and altitude) position fixes.
The basic GPS Timing Unit configuration includes the GPS Main Module, an antenna/preamp and
a coaxial cable for interconnection. A corrected 1pps output signal and a 10MHz Sine Wave are
provided. An RS-232 I/O Port is also provided in the basic configuration which can be used to
control the unit as well to get data from the unit. The basic unit has an LCD Display and a
keyboard. It generates IRIG B Serial Time Code, and has the capability of measuring the time
interval difference between the GPS 1pps and an externally input 1pps (or it can measure an
external frequency input – Models ET6000 and ET6010 only). It contains an RS-232 printer port.
Optional features listed in Appendix C are available to meet specific requirements. Refer to the
GPS Option/Connector Configuration sheet located in this manual for the options supplied with this
instrument. The Option Descriptions are located in Appendix C.
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-3
CHAPTER ONE
1.4 SPECIFICATIONS
The electrical, physical, and environmental specifications for the ExacTime are listed below.
1.4.1 GPS SUBSYSTEM
A. TIME ACCURACY
After power-up, when LOCKED and using 200 Position Averages, will be better
than ± 125 nanoseconds relative to UTC with SA on within:
4 hours using a Rubidium oscillator.
2 hours using an Oven oscillator.
1 hour using a TCXO oscillator.
B. FREQUENCY ACCURACY
90% of the time, better than: 1E-9 for TCXO
1.5E-10 for Oven (OCXO)
1E-11 for Rubidium
C. POSITION ACCURACY
100m 2dRMS with SA
Less than 25m SEP without SA.
D. MAXIMUM VELOCITY
515 meters/second. (1000 knotts/hour).
E. TRACKING CHANNELS
Eight parallel.
F. RECEIVER FREQUENCY
L1 1.575 GHz, C/A Code.
G. ACQUISITION TIME
Time to first fix is less than 5 minutes with timing accuracy better than two μS and
frequency accuracy better than 1E-8. Full system accuracy with oven (OCXO)
oscillator is provided within 2 hours after LOCKED.
1.4.2 TIMING OUTPUTS
Rear panel BNCs J4 through J9 can output a 10MHz sine wave, IRIG B (AC), various pulse rates,
or alarm outputs. The following is the standard output configuration for the rear panel BNC
connectors. To change the outputs from the factory set standard configuration, see the paragraph
titled “Timing Outputs” in Chapter Two and the paragraph titled “Optional Pulse Rate Outputs” in
this section of the User’s Guide. Each output is via a 50Ω driver.
1-4 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
GENERAL INFORMATION
A. J4 - TRACKING
This CMOS output level is “low” when the unit is actively acquiring data from
satellites. In the Stationary Mode, the unit has to track at least one satellite for the
Tracking level to go “low”. In the Dynamic Mode, the unit has to track at least four
satellites, for the Tracking level to go “low”, and all available satellites are used for
the time solution. The Tracking level is “high” when the unit is not acquiring data
from any satellite or the satellites are not used for the time solution (as in the
Flywheel Mode).
B. J5 - LOCKED
When this CMOS output level is “low” (LOCKED), the 1pps output is coherent to
the internal 10MHz Oscillator. The DAC voltage controls the 10MHz oscillator
from which the 1PPS is derived. When this CMOS output level is “high” (i.e., not
locked), the 1pps is constantly being corrected (jammed) to on time using the 1PPS
from the GPS Receiver Module. In this mode, the 1PPS output can jump.
C. J6 - 1PPS
This output is a thirty to fifty μsec wide pulse at CMOS levels. The rise and fall
times are ≤ 6 nanoseconds. It is positive (rising) edge on time, within ±125
nanoseconds relative to either UTC or GPS with six or more satellite averaging with
95% confidence.
D. J7 - 10MHz SINE WAVE
This output has a nominal amplitude of one volt RMS into a 50Ω load.
Note: The output amplitude of the 10MHz sine wave is dependent on the internal
time base. This amplitude specification is for the Voltage Controlled
Temperature Compensated Crystal oscillator.
J7 – COINCIDENCE OUTPUT (ET6500 ONLY)
The Preset Coincidence Pulse occurs 200 Nanoseconds late. Its pulse width is
approximately two (2) microseconds wide, positive edge on-time. It is capable of
driving 10 LSTTL loads.
To enable this output, on the GPS Main Assembly 100015, jumper J17 pins 7-8
(only). See Figure 2-3 in Chapter Two.
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CHAPTER ONE
E. J8 - IRIG B (AC)
This output is Amplitude Modulated IRIG B122 Serial Time Code. This output is
available only after the unit has tracked satellites and set time.
Carrier 1KHz
Modulation Ratio 3:1
Amplitude Three volts peak-to-peak on the Mark Pulse
Note: When enabled, the unit will output a modified IRIG B per IEEE Std. 1344
that has data in the Control Function bit area. Refer to Table One at the end
of this chapter for the Control Function Bit Assignments.
F. J9 - IRIG B (DC)
This output is Pulse Width Modulated IRIG B002 Serial Time Code at CMOS levels.
This output is available only after the unit has tracked satellites and set time
G. J11 – PRINTER OUTPUT PORT
This DB9 connector can output data to an RS232 compatible serial printer or
terminal.
It can be configured to operate in the Standard RS232 output or the One Second
RS232 ASCII Burst Mode output. For the operation and configurations, refer to
Chapters Three and Four.
H. OPTIONAL PULSE RATE OUTPUTS
The following is a list of optional pulse rate outputs available for selection on BNC
connectors J4-J9. They are positive (rising) edge on-time. The majority of these
rates have a 80/20 duty cycle with the exception of the 10MHz and the 5MHz which
are square waves, and the 1PPM which is 40/20.
10MHz 5MHz 1MHz
100KHz 10KHz/2PPH* 1KHz
100Hz 10Hz/1PPH* 1Hz
.1Hz 1PPM
Models ET6000 and ET6010 output 10KHz and 10Hz. Model ET6500 outputs
2PPH and 1PPH. For further clarification and/or configuration of the above outputs,
See Chapters Two and Three.
1-6 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
GENERAL INFORMATION
1.4.3 ACCURACY
The accuracy of the pulse rates listed in Section 1.4.2H is the same as that in Section 1.4.1A.
1.4.4 TIMING INPUTS
A. J10 - 1PPS INPUT (TIME INTERVAL MEASUREMENT) or
EXTERNAL FREQUENCY MEASUREMENT or
SINGLE EVENT LOG
TIME INTERVAL MEASUREMENT
Used to measure the time interval between the internally generated GPS 1PPS and an
external 1PPS input. The resolution of this measurement is 1 nanosecond with
accuracy better than 10 nanoseconds. At power-up, this feature is DISABLED. If
enabled, the measurement is displayed on the Second Menu Screen. Refer to
Chapter Three. Also see paragraphs entitled, “Enable Time Interval,” “Disable Time
Interval,” and “Request Time Interval,” in Chapter Four of this User’s Guide.
EXTERNAL FREQUENCY MEASUREMENT (MODELS ET6000 AND
ET6010 ONLY)
Frequency Range
1Hz to 10MHz (discrete, whole numbers - not fractional parts).
Input Wave Form From 1Hz to 10MHz
Rectangular or square wave (minimum pulse width fifty nanoseconds).
Amplitude Range:
Logic “0” +0.2V ±0.2VDC
Logic “1” +2.4V to +15VDC
Input Wave Form From 100KHz to 10MHz
Sinusoidal Amplitude Range: 1 - 5 volts peak-to-peak
SINGLE EVENT LOG
This option provides the capability of logging the time occurrences of up to 256
events from one input. A pulse on the event input will cause the time to be
logged/stored on either the rising (positive going) or falling (negative-going) edge of
the input pulse. The edge designated as on time is programmable via the front panel
keyboard or remotely via the RS-232 I/O. Each event will have a defining number
from zero to 255 and the channel identifier.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-7
CHAPTER ONE
The event memory can be read and/or cleared via the RS-232 I/O. Refer to Chapter
Four of this User's Guide. If the inputs exceed 256 events (occurrences), the new
data will be lost. If two events occur less than ten milliseconds apart, it is possible
that one of the events may be lost. This will be reported as a missed event in the
status code when the data is output. This event log option can also be enabled or
disabled. Refer to Chapter Four of this User’s Guide.
The event time resolution is from hundreds of nanoseconds through hundreds-ofdays.
1.4.5 J12 RS-232 I/O INTERFACE
Full remote control of all operating functions in a complete ASCII protocol. Baud rate, parity, word
length, and stop bits are selectable. See paragraph titled, “Fourth Menu Screen – RS232 I/O
Configuration” in Chapter Three of this User’s Guide. A description of the remote control
functions is contained in Chapter Four.
1.4.6 INTERNAL TIME BASE
This unit can have one of three internal time bases depending on customer requirements. Unless
otherwise specified, the following are the specifications for the oscillators used as the internal time
base - not the specifications of the unit’s 10MHz sine wave output.
A. VOLTAGE CONTROLLED TEMPERATURE COMPENSATED CRYSTAL
OSCILLATOR (Configuration –TCXO) with the following specifications:
OUTPUT FREQUENCY/WAVEFORM
10MHz Sine Wave.
OUTPUT AMPLITUDE OF CRYSTAL OSCILLATOR
1.0 volt peak-to-peak minimum clipped sine wave into 20KΩ load. Harmonics 20dBc maximum.
AGING RATE
1E-7 per day or ±1.0PPM maximum per year.
1-8 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
GENERAL INFORMATION
PHASE NOISE
The following specifications are for the 10MHz sine wave output available on rear
panel BNC connectors J4-J9:
1Hz -72 dBc/Hz
10Hz -93 dBc/Hz
100 Hz -115 dBc/Hz
1KHz -126 dBc/Hz
10KHz -136 dBc/Hz
100 KHz -136 dBc/Hz
TEMPERATURE RANGE AND STABILITY
±1.0PPM from -30o to +75oC.
ADJUSTMENT RANGE
±3.0PPM minimum by internal manual trimmer.
VOLTAGE CONTROL
±3.0PPM minimum from +0.5 to +4.5 VDC.
B. LOW NOISE OVEN OSCILLATOR (Configuration –OCXO) with the
following specifications:
OUTPUT FREQUENCY/WAVEFORM
10MHz Sine Wave.
OUTPUT AMPLITUDE OF CRYSTAL OSCILLATOR
1.0 volt RMS into 50 ohms.
AGING RATE
±5 x 10
-10
per day, ±5 x 10-8 per year.
TEMPERATURE STABILITY
-8
±1 x 10
over a temperature range of –20ºC to +75ºC.
OPERATING TEMPERATURE
–20ºC to +75ºC.
ALTITUDE
Sea level to +50,000 feet.
ELECTRICAL TUNING
±1PPM (minimum) / ±2PPM (maximum).
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-9
CHAPTER ONE
1Hz -100 dBc/Hz
10Hz -120 dBc/Hz
100Hz -140 dBc/Hz
1KHz -144 dBc/Hz
10KHz -144 dBc/Hz
100KHz -144 dBc/Hz
C. RUBIDIUM OSCILLATOR (either X72 or LPRO) with the following
CONTROL VOLTAGE
0 to +6 volts.
MECHANICAL FREQUENCY ADJUST
±1PPM (minimum) / ±3PPM (maximum).
The following specifications apply to the selected 10MHz sine wave output at a +13
dbm level:
HARMONICS
-45 dBc
SPURIOUS NOISE
>-70 dBc
PHASE NOISE
specifications:
OUTPUT FREQUENCY/WAVEFORM
10MHz Sine Wave.
OUTPUT AMPLITUDE OF OSCILLATOR
0.55VRMS ±0.05VRMS into 50 ohms.
AGING RATE
≤5 x 10
-11
per month, 5 x 10
-10
per year.
OPERATING TEMPERATURE
–20ºC to +70ºC measured at the base plate.
STORAGE TEMPERATURE
-55ºC to +85ºC
1-10 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
GENERAL INFORMATION
ALTITUDE
-200 feet to +40,000 feet (operating).
FREQUENCY CONTROL - INTERNAL TRIM RANGE
±1.5 x 10
-9
FREQUENCY CONTROL - EXTERNAL (ELECTRICAL) TRIM RANGE
±1.5 x 10
-9
(0V to +5V).
The following specifications apply to the selected 10MHz sine wave output at a +13
dbm level:
HARMONICS
-42 dBc
SPURIOUS NOISE
>-80 dBc
PHASE NOISE
1Hz -82 dBc/Hz
10Hz -91 dBc/Hz
100Hz -131 dBc/Hz
1KHz -144 dBc/Hz
10KHz -146 dBc/Hz
100KHz -147 dBc/Hz
1.4.7 PRIMARY POWER
Models ET6000 and ET6010 utilize a Power Entry Module and the Standard Power Supply.
Input Voltage AC = 85 to 264 VAC (47-440 Hz) @ less than thirty watts.
DC = +120 to 373 VDC
Input Frequency Range 47 to 440 Hz
Note: When using 120 VAC, install 1 Amp Line Fuses. When using 220 VAC, install ½ Amp
Line Fuses. Fuses are found in the Shipping Kit.
Model ET6500 utilizes a Power Entry and Alarm Relay Module (Assembly 55191) and the
Standard Power Supply.
This module takes a nominal input of 115 VAC or 125 VDC through a rear panel terminal strip and
provides +5 and ±12 VDC to power the GPS Time Code and Frequency Generator. It provides
timing and fault status relay closures.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-11
CHAPTER ONE
It also has the capability of measuring the frequency, phase angle, and elapsed time offset of an
externally applied 50 or 60Hz AC sine wave.
Input Voltage AC = 85 to 264 VAC (47-440 Hz) @ less than thirty watts.
DC = +120 to 373 VDC
Input Frequency Range 47 to 440 Hz
Fault Relay Closure on fault.
Timing Relay Closure when not locked.
Relay Contact Ratings 10 watts, 0.5 amps, 200 volts.
50/60Hz Measurement Input 85-250 VAC.
Note: When using 120 VAC, install 1 Amp Line Fuses. When using 220 VAC, install ½ Amp
Line Fuses. Fuses are found in the Shipping Kit.
All input/outputs from the 55191 are from a rear panel terminal strip TB1.
All input/outputs have metal oxide varistors for transient voltage suppression.
The pin assignments for TB1 are shown below (as viewed from the rear of the unit):
TB1-1 TB1-12
Pin Assignments
TB1-1 AC HI Input
TB1-2 AC LO Input
TB1-3 Chassis Ground
TB1-4 Fault Relay - Common Contact
TB1-5 Fault Relay - Normally Closed Contact
TB1-6 Timing Relay - Common Contact
TB1-7 Timing Relay - Normally Closed Contact
TB1-8 50/60Hz Measurement Input - HI
TB1-9 50/60Hz Measurement Input - LO
TB1-10 Not Used
TB1-11 Not Used
TB1-12 Not Used
1-12 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
GENERAL INFORMATION
This Power Entry and Alarm Relay Module has two relay closures to indicate timing/fault of the
unit. The fault relay output on the rear panel terminal strip TB1-4 and 5 will provide contact
closure upon the following conditions:
A processor error, from the GPS Receiver Module
Loss of +5VDC.
If the DAC value goes below 300 or above 65,000.
The timing relay (output on the rear panel terminal strip TB1-6 and 7) provides a contact closure
until the unit has achieved oscillator lock. For example, until the front panel LOCKED LED
illuminates.
1.4.8 DIMENSIONS
Chassis:
Height 1.75 Inches. Model ET6010 is 3.50 Inches.
Width 17 Inches.
Depth 12 Inches Maximum.
1.4.9 WEIGHT
ExacTime Unit Approximately ten pounds.
Antenna/Preamp Less than 1.5 pounds.
1.4.10 ENVIRONMENT
A. OPERATING TEMPERATURE
ExacTime Unit: 0oC to +50oC.
o
Antenna/Preamp: -40
C to +85oC.
B. STORAGE TEMPERATURE
ExacTime Unit: -20
Antenna/Preamp: -55
o
C to +70oC.
o
C to +100oC.
C. HUMIDITY
ExacTime Unit 95% (non-condensing) up to 40oC.
Antenna/Preamp Unlimited.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-13
CHAPTER ONE
1.5 ADDITIONAL SPECIFICATIONS
The following is additional information regarding the GPS RPU (Receiver Processing Unit) located
within the GPS Time Code and Frequency Generator, and the antenna/preamp.
1.5.1 ANTENNA/PREAMP
The antenna/preamp satisfies performance requirements at altitudes of up to +59,000 feet.
1.5.2 GPS RPU AND ANTENNA
The GPS RPU (Receiver Processor Unit) and antenna/preamp set has burn-out protection which
prevents damage from an RF signal at power densities of up to one watt at the antenna. The RF
signal must be 100MHz out of band. The C/A band of 1575.42MHz has a bandwidth of 20.48MHz.
1.6 FUNCTIONAL CHARACTERISTICS
The following is a description of the functional characteristics of the GPS RPU.
1.6.1 ACQUISITION
The GPS RPU position fix, acquisition and tracking processes feature the ability to determine its
own position (that of the antenna/preamp), not the TC&FG Module, utilizing a position averaging
technique and assuming the unit has been set to the “AUTO,” or “DYNAMIC” mode. See “Third
Menu Screen” in Chapter Three of this User’s Guide for selection and an explanation of each
MODE SELECTION using the front panel LCD and Keyboard. Mode selection may also be made
via the RS-232 Interface. See the paragraph titled “Select Mode” in Chapter Four for mode
selection using the RS-232 I/O.
The GPS RPU has an eight parallel channel design capable of tracking eight satellites
simultaneously. The module receives the L1 GPS signal (1575.42 MHz) from the antenna and
operates off the coarse/acquisition (C/A) code tracking. The code tracking is carrier aided.
Time recovery capability is inherent in the architecture.
The GPS RPU is designed specifically for precise timing applications.
Upon powering up the system, the unit begins a systematic search for satellites which are expected
to be above the horizon. In this start-up mode of operation it uses the last position data stored in the
battery backed RAM as a starting point. If it is in the A (Auto) mode, it will begin doing a running
average of position fixes. After 200 averages, the unit will have acquired its position and will
switch automatically to the S (Stationary) mode. The number of position averages is user selectable
via the RS-232 I/O. See paragraph titled “Number of Averages” in Chapter Four.
1-14 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
GENERAL INFORMATION
If in the D (Dynamic) mode, the unit will use the last position data stored in battery backed RAM as
a starting point to begin its systematic search for satellites. It will continue to do three dimensional
position fixes (latitude, longitude, and altitude) upon acquiring four or more satellites until the
mode is changed. If in the “STATIONARY” mode and a known position has been entered, the unit
will use the position information stored in battery backed RAM as a starting point to begin its
systematic search for satellites.
1.6.2 SIGNAL INTERRUPTION
During GPS ExacTime operation, should the signal from the satellites be interrupted, the antenna
disconnected or blocked, the reacquisition time is dependent upon events during the interruption.
For the first minute of the interruption, the GPS RPU continues to search for the last satellite signals
to which it was locked. If the signal is regained during this minute, reacquisition will be almost
immediate if the users velocity has not changed by more than fifty meters per second.
If the velocity has changed, the Doppler frequency has shifted. The GPS RPU must finish its search
of previous satellite signals and will then expand the search to reacquire. The search time will
depend on the amount of velocity change, but it is usually within fifteen seconds.
If the signal is regained within one minute, the expanding frequency search will already have begun
cycling. In this case, reacquisition may require a few minutes depending upon where the RPU is in
the frequency search when the signal is regained.
If the signal is regained within one hour, the same search must take place, then the new ephemeris
data must be collected. In this case, reacquisition will occur within a few minutes.
The user should realize that obstructions, shading of the antenna, and satellite transmission
interruptions can degrade the signal reception and length of acquisition times.
1.6.3 POSITION AND VELOCITY SOLUTION
The position and velocity, along with the time tag of the measurement, are digitally output from the
RPU to the GPS ExacTime Processor. The position data is three dimensional and available in a
latitude, longitude, and altitude (WGS-84) coordinate frame. The GPS solutions are computed at
typically less than one second intervals.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-15
CHAPTER ONE
1.6.4 DYNAMIC CAPABILITY
The following specifications are operational dynamic limits for GPS Timing Unit operation.
A. VELOCITY
The velocity of the user is limited to 515 m/sec for proper GPS Receiver operation.
B. ACCELERATION
User acceleration cannot exceed four 4g (39.2 m/sec2).
C. JERK
The rate of change of acceleration is not to exceed 5 m/sec3.
1.6.5 RF JAMMING RESISTANCE AND BURN-OUT PROTECTION
The GPS RPU provides resistance to all forms of jamming whose effect results in jamming to signal
power ratios of twenty-four dB or less as measured at the antenna/preamplifier interface when the
input signal is at -163 dBm. The GPS RPU/antenna set provides burn-out protection to prevent
damage at RF power densities up to one watt (CW) at the antenna, provided the signal is 100MHz
out of the GPS frequency band.
1.6.6 SYSTEM STATUS AND DIAGNOSTICS
All digital circuitry is tested to the greatest extent possible at power-up. This includes testing the
memory systems, and processor, as well as monitoring the performance of the channel processors.
Should a failure occur in any of these areas, it will be available as status on the RS-232 I/O and will
be displayed on the LCD Display as an error.
1.6.7 GPS POSITION SOLUTION MODES
The user may select either the Auto Mode or the Dynamic Mode for position solutions. (In the
Stationary Mode, the position is already predetermined.) See SELECT MODE in Chapter Three for
front panel LCD and keyboard selection. See Chapter Four for MODE SELECTION using the RS232 I/O.
The AUTO mode is actually a combination of the DYNAMIC and the STATIONARY modes.
When powered up in the AUTO mode, the unit will acquire some number of positions in the
DYNAMIC mode calculating an average latitude, longitude, and altitude when there are at least
four satellites in view. The factory set default number of averages is 200. These position averages
are loaded into battery backed memory for future use.
1-16 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
GENERAL INFORMATION
The number of positions used to calculate the averages is user selectable via the RS-232 I/O
interface. Once the average position has been determined, the unit will switch to the
STATIONARY mode. The AUTO mode provides an averaged solution of the time information
from as many satellites as the receiver is tracking.
In the DYNAMIC mode, the system will select the best available satellites based on PDOP
(Position Dilution Of Precision) and provide a continuous navigational solution in three dimensions
(latitude, longitude, and altitude). The DYNAMIC mode does not automatically switch to the
STATIONARY mode.
1.6.8 ELEVATION MASK ANGLE
This mask is used to specify the elevation angle below which the use of satellites is prohibited.
Signal integrity from satellites very low on the horizon can be degraded. Obstructions will block
the signal. For land-based applications where there are local obstructions (foliage, buildings, etc.)
system performance will be smoother with an elevation mask of fifteen to twenty degrees. For
marine or aircraft applications, it is usually possible to use the satellites very close to the horizon,
although the pitch/roll should be considered. The system default is that set by the user. Refer to
Chapter Four, paragraph titled “ENTER ELEVATION MASK ANGLE” for instruction on selecting
elevation mask.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-17
CHAPTER ONE
Table One
Control Function Bit Assignments
IRIG B
Positive ID
Control
Bit #
Designation Explanation
P50 1 Year, BCD 1 Last two digits of year in BCD.
P51 2 Year, BCD 2 IBID.
P52 3 Year, BCD 4 IBID.
P53 4 Year, BCD 8 IBID.
P54 5 Not Used Unassigned.
P55 6 Year, BCD 10 Last two digits of year in BCD.
P56 7 Year, BCD 20 IBID.
P57 8 Year, BCD 40 IBID.
P58 9 Year, BCD 80 IBID.
P59 N/A P6 Position identifier number six.
P60 10 Leap Second Pending
(LSP)
Becomes 1 up to 59 s BEFORE leap second
insert.
P61 11 Leap Second (LS) 0 = add leap second, 1 = delete leap second.
P62 12 Not Used
P63 13 Not Used
P64 14 Time Offset Sign Time offset sign 0 = +, 1 = P65 15 Time Offset - Binary 1 Offset from coded IRIG B time to UTC time.
P66 16 Time Offset - Binary 2 IRIG coded time plus time offset (including
P67 17 Time Offset - Binary 4 sign) equals UTC time at all times (offset will
change during daylight savings).
P68 18 Time Offset - Binary 8
P69 N/A P7 Position identifier number.
P70 19 Time Offset - 0.5 Hour 0 = none, 1 = additional 0.5 h time offset
P71 20 Time Quality 4 bit code representing approx. clock time error
P72 21 Time Quality 0000 = clock locked, maximum accuracy.
P73 22 Time Quality 1111 = clock failed, data unreliable.
P74 23 Time Quality
P75 24 PARITY Parity on all preceding data bits.
P76 25 Not Used Unassigned.
P77 26 Not Used Unassigned.
P78 27 Not Used Unassigned.
P79 N/A P8 Position identifier number eight.
1-18 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
CHAPTER TWO
INSTALLATION
2.0 INTRODUCTION
This section describes the unpacking, inspection, and installation of the GPS Timing Unit.
2.1 UNPACKING AND INSPECTION
The GPS Timing Unit is packaged in one shipping container. Inspect the unit for visible damage
(scratches, dents, etc.). If the instrument is damaged, immediately notify both Symmetricom Inc
and the responsible carrier. Keep the shipping container and packing material for the carrier’s
inspection.
Note: When communicating with either Symmetricom Inc or the responsible carrier regarding
shipping damage, refer to the serial number. This number is located on the rear panel of
the GPS Timing Unit.
2.2 RACK MOUNTING PROCEDURE
The GPS Timing Unit is designed for standard nineteen inch rack mounting.
Optional chassis slides are recommended if the unit is to be installed in an equipment rack. If
slides are not used, a supporting bar or tray should be provided for the rear of the instrument.
The chassis slides attach to the sides of the GPS Timing Unit. To mount it using the optional
slide mounting kit, use the eight #6 self tapping screws provided in the kit.
*** CAUTION ***
General Cautions/Hazards to be considered when installing the GPS Timing Unit into an
equipment rack:
2.2.1 TMRA – The maximum recommended ambient temperature (Tmra) that this equipment
is specified to operate in is 50°C.
2.2.2 ELEVATED OPERATING AMBIENT TEMPERATURE – If installed in a closed or
multi-unit rack assembly, the operating ambient temperature of the rack environment
may be greater than room ambient. Therefor, consideration should be given to installing
the equipment in an environment compatible with the maximum rated ambient
temperature (Tmra).
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 2-1
CHAPTER TWO
2.2.3 REDUCED AIR FLOW - The equipment has no cooling fans and depends on
convection for cooling. Installation in a rack may cause an excessive heat rise if sufficient air
flow is not available. Installation should be such that the amount of air flow required for safe
operation of the equipment is not compromised.
2.2.4 MECHANICAL LOADING – Mounting of the equipment in the rack should be such
that a hazardous condition is not achieved due to uneven mechanical loading.
2.2.5 CIRCUIT OVERLOADING – Consideration should be given to the connection of the
equipment to the supply circuit and the effect that overloading of circuits might have on
over current protection and supply wiring. Appropriate consideration of equipment
nameplate ratings should be used when addressing this concern.
2.2.6 RELIABLE EARTHING – Reliable earthing of rack-mounted equipment should be
maintained. Particular attention should be given to supply connections other than direct
connections to the branch circuit (e.g., use power strips).
2.3 ANTENNA/PREAMP INSTALLATION
The antenna/preamp is enclosed in a weatherproof housing suitable for permanent installation in
an exposed location. The unit should be located with an unobstructed view of the horizon for
optimum tracking conditions. The signal will not penetrate foliage. Multi-path signals may be
generated from vertical surfaces, which are above the plane of the base of the antenna/preamp.
The antenna/preamp, which is designed for fixed ground or marine applications, requires no
special ground plane, but a large metal surface below the antenna/preamp may reduce multi-path
effects. The unit may be mounted on any level surface or on a vertical pipe having ¾ - 14 NPT
threads. See Figures 2-1, and 2-4, “Antenna/Preamp Installation,” for mounting.
*** CAUTION ***
A high powered radar beamed directly at the antenna/preamp may damage it and a signal
within a few MHz of the carrier frequency may jam the GPS RPU.
2.4 ANTENNA/PREAMP INTERFACE CONNECTIONS
A fifty foot long RG-58A/U coaxial cable is provided to connect the antenna/preamp to the GPS
Timing Unit. For cable lengths greater than seventy-five feet, an optional low loss coaxial cable
(such as Belden 9913) must be used.
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
2-2 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
INSTALLATION
The antenna/preamp power is provided by the GPS Timing Unit via the coaxial cable. No
additional cabling is required to power the antenna/preamp.
Cables attached to the antenna/preamp should be strain relieved and secured to some permanent
fixture.
Cables attached to the antenna/preamp which are exposed to the elements should be wrapped
with a weather-proof tape after being connected.
Cables from the antenna/preamp should be secured as required with cable clamps and should not
put a strain on the antenna/preamp connector as it may damage the unit.
2.5 PRIMARY POWER CONNECTION
The GPS Timing Unit is operated from external AC power. The AC power specifications are
listed in the specification section in Chapter One of this User’s Guide.
Models ET6000 and ET6010 utilize a power cord that plugs into a Power Entry Module.
Note: Check the AC line fuses located in the power entry module on the rear panel and assure
the correct fuse is installed for the AC Line voltage being used to power the unit. The
AC line fuses should be 1 Amp for an AC input of 120 volts or ½ amp for an AC input of
220 volts.
Model ET6500 utilizes a terminal strip Power Entry and Alarm Relay Module (Assembly
55191).
Note: Check the AC line fuses located in the power entry module inside the unit and assure the
correct fuse is installed for the AC Line voltage being used to power the unit. The AC
line fuses should be 1 Amp for an AC input of 120 volts or ½ amp for an AC input of 220
volts.
The terminal strip pin designations are shown below:
REAR VIEW OF ET6500 SHOWING 55191
POWER ENTRY AND ALARM RELAY MODULE
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 2-3
19
TB1
CHAPTER TWO
PIN ASSIGNMENTS
TB1 Pin 1 AC High Input
TB1 Pin 2 AC Low Input
TB1 Pin 3 Chassis Ground
TB1 Pin 4 Fault Relay – Common Contact
TB1 Pin 5 Fault Relay – Normally Closed Contact
TB1 Pin 6 Timing Relay – Common Contact
TB1 Pin 7 Timing Relay – Normally Closed Contact
TB1 Pin 8 50/60Hz Measurement Input - High
TB1 Pin 9 50/60Hz Measurement Input - Low
This assembly has two relay closures to indicate timing/fault of the unit. The fault relay output
on the rear panel terminal strip TB1-4 and 5 will provide contact closure upon the following
conditions:
A processor error, Channel One error, or Channel Two error from the GPS receiver.
Loss of +5VDC.
If the DAC value goes below 300 or above 65,000.
The timing relay output on the rear panel terminal strip TB1-6 and 7 provides a contact closure
until the unit has achieved unit stabilization. For example, until the front panel LOCKED LED
illuminates.
If this unit is provided with a power supply other than the standard, its specifications will be
found in the Option Description envelope located on the inside cover of this User’s Guide.
2-4 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
INSTALLATION
Figure 2-1
Antenna/Preamp Installation
5000-0001 Bullet Antenna
(Mfg P/N 25045-10*)
* Dash number is the software revision. This
is subject to change without notice.
1704-9389 Type F to Type N
Connector Adapter
1. Material* PVC or CPVC Schedule 80, Gray Color.
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 2-5
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