MODEL 8194 GPS AGELESS™ OSCILLATOR

MODEL 8194 GPS AGELESS™ OSCILLATOR
MODEL 8194
GPS AGELESS OSCILLATOR
INSTRUCTION MANUAL
SPECTRACOM CORPORATION
95 METHODIST HILL DRIVE
SUITE 500
ROCHESTER, NY 14623
PHONE
FAX
585-321-5800
585-321-5218
Copyright  2004 Spectracom Corporation. All rights reserved.
Contents of this publication may not be reproduced in any form
without the written permission of Spectracom Corporation.
REVISIONS, IF ANY, ARE LOCATED AT THE END OF THE MANUAL
PART NUMBER 8194-5001-5000
MANUAL REVISION A
February 2004
5-Year Warranty
LIMITED WARRANTY________________________________
Spectracom warrants each new product manufactured and sold by
it to be free from defects in material, workmanship, and
construction, except for batteries, fuses, or other material normally
consumed in operation that may be contained therein, for five
years after shipment to the original purchaser (which period is
referred to as the "warranty period"). This warranty shall not
apply if the product is used contrary to the instructions in its
manual or is otherwise subjected to misuse, abnormal operations,
accident, lightning or transient surge, repairs or modifications not
performed by Spectracom.
The GPS receiver is warranted for one year from date of shipment
and subject to the exceptions listed above. The power adaptor, if
supplied, is warranted for one year from date of shipment and
subject to the exceptions listed above.
The Rubidium oscillator, if supplied, is warranted for two years
from date of shipment and subject to the exceptions listed above.
All other items and pieces of equipment not specified above,
including the antenna unit, antenna surge suppressor and antenna
pre-amplifier are warranted for 5 years, subject to the exceptions
listed above.
WARRANTY CLAIMS________________________________
EXCEPT FOR THE LIMITED WARRANTY STATED ABOVE,
SPECTRACOM DISCLAIMS ALL WARRANTIES OF ANY KIND
WITH REGARD TO SPECTRACOM PRODUCTS OR OTHER
MATERIALS PROVIDED BY SPECTRACOM, INCLUDING
WITHOUT LIMITATION ANY IMPLIED WARRANTY OR
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Spectracom shall have no liability or responsibility to the original
customer or any other party with respect to any liability, loss, or
damage caused directly or indirectly by an Spectracom product,
material, or software sold or provided by Spectracom,
replacement parts or units, or services provided, including but not
limited to any interruption of service, excess charges resulting from
malfunctions of hardware or software, loss of business or
anticipatory profits resulting from the use or operation of the
Spectracom product or software, whatsoever or howsoever
caused. In no event shall Spectracom be liable for any direct,
indirect, special or consequential damages whether the claims are
grounded in contract, tort (including negligence), or strict liability.
EXTENDED WARRANTY COVERAGE___________________
Extended warranties can be purchased for additional periods
beyond the standard five-year warranty. Contact Spectracom no
later than the last year of the standard five-year warranty for
extended coverage.
Spectracom's obligation under this warranty is limited to in-factory
service and repair, at Spectracom's option, of the product or the
component thereof, which is found to be defective.
If in
Spectracom's judgment the defective condition in a Spectracom
product is for a cause listed above for which Spectracom is not
responsible, Spectracom will make the repairs or replacement of
components and charge its then current price, which buyer agrees
to pay.
Spectracom shall not have any warranty obligations if the
procedure for warranty claims is not followed. Users must notify
Spectracom of the claim with full information as to the claimed
defect. Spectracom products shall not be returned unless a return
authorization number is issued by Spectracom. Spectracom
products must be returned with the description of the claimed
defect and identification of the individual to be contacted if
additional information is needed. Spectracom products must be
returned properly packed with transportation charges prepaid.
SPECTRACOM CORPORATION 95 METHODIST HILL DRIVE SUITE 500 ROCHESTER NY 14623 USA
+1.585.321.5800 FAX: +1.585.321.5218 www.spectracomcorp.com sales@spectracomcorp.com
TABLE OF CONTENTS
SECTION 1
1.0
1.1
1.2
1.3
1.4
1.5
INTRODUCTION .................................................................................................................... 1-1
FEATURES ............................................................................................................................ 1-2
WARRANTY INFORMATION AND PRODUCT SUPPORT.................................................. 1-2
MANUAL ERRATA AND SPECIAL DOCUMENTATION .....................................................1-3
UNPACKING.......................................................................................................................... 1-3
SPECIFICATIONS ................................................................................................................. 1-4
1.5.1 Receiver .................................................................................................................... 1-4
1.5.2 Standard Frequency Outputs .................................................................................... 1-4
1.5.3 Frequency Standard Stability .................................................................................... 1-5
1.5.4 1 PPS Output............................................................................................................. 1-6
1.5.5 Data Clock Timing Outputs ....................................................................................... 1-6
1.5.6 Indicator Lamps ......................................................................................................... 1-6
1.5.7 Alarms ........................................................................................................................ 1-7
1.5.7.1 Alarms Classifications ................................................................................... 1-7
1.5.7.2 Tracking Alarm Classifications ......................................................................1-8
1.5.7.3 Alarm Interface ............................................................................................. 1-9
1.5.8 RS-232 Communication Port.......................................................................................1-9
1.5.9 Input Power ............................................................................................................... 1-9
1.5.10 Mechanical ............................................................................................................... 1-9
1.5.11 Environmental..........................................................................................................1-10
1.5.12 Model 8225 GPS Antenna Specifications ...............................................................1-10
1.5.12.1 Electrical Specifications............................................................................1-10
1.5.12.2 Mechanical Specifications .........................................................................1-10
1.5.13 Model 8226 Impulse Suppressor.............................................................................1-10
1.5.14 Model 8227 Inline Amplifier .....................................................................................1-11
SECTION 2
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
GENERAL INFORMATION
INSTALLATION
INTRODUCTION .................................................................................................................... 2-1
MODEL 8225 GPS ANTENNA ..............................................................................................2-1
2.1.1 Antenna Installation ................................................................................................... 2-1
ANTENNA CABLE.................................................................................................................. 2-2
2.2.1 Cable Lengths ........................................................................................................... 2-3
MODEL 8226 IMPULSE SUPPRESSOR .............................................................................. 2-3
MODEL 8227 GPS INLINE AMPLIFIER................................................................................ 2-6
MODEL 8194 PREPARATION FOR USE ............................................................................. 2-8
2.5.1 Antenna Connection .................................................................................................. 2-8
2.5.2 AC Power .................................................................................................................. 2-8
2.5.3 Chassis Ground......................................................................................................... 2-8
INITIAL OPERATION............................................................................................................. 2-8
QUALIFYING THE INSTALLATION...................................................................................... 2-9
2.7.1 GPS Signal Status ....................................................................................................2-9
2.7.2 Tracking Histogram .................................................................................................2-10
FACTORY CONFIGURATION.............................................................................................2-12
SECTION 3
OPERATION
3.0
INTRODUCTION .................................................................................................................... 3-1
3.1
FRONT PANEL FUNCTIONS................................................................................................ 3-1
3.1.1 Status Lamps............................................................................................................. 3-1
3.1.1.1 Power ......................................................................................................... 3-1
3.1.1.2 Tracking GPS ............................................................................................. 3-1
3.1.1.3 Oscillator Locked ....................................................................................... 3-1
3.1.2 Alarm Lamps ............................................................................................................. 3-1
3.1.2.1 Major Alarm Lamp ...................................................................................... 3-2
3.1.2.2 Minor Alarm Lamp ...................................................................................... 3-2
3.1.3 RS-232 Com.............................................................................................................. 3-4
3.1.4 10-MHz Output ..........................................................................................................3-5
3.1.5 1PPS Output.............................................................................................................. 3-5
3.2
REAR PANEL FUNCTIONS .................................................................................................. 3-6
3.2.1 GPS Antenna............................................................................................................. 3-6
3.2.2 Frequency Outputs .................................................................................................... 3-6
3.2.2.1 Signature Control ........................................................................................ 3-6
3.2.2.2 Optional Output........................................................................................... 3-6
3.2.2.3 Simulcast Offsets ........................................................................................ 3-8
3.2.3 Data Clock Timing Outputs ....................................................................................... 3-9
3.2.3.1 RS-485 Outputs ........................................................................................3-10
3.2.3.2 Major Alarm Relay ....................................................................................3-11
3.2.4 Alarm Outputs..........................................................................................................3-11
3.2.5 AC Power ................................................................................................................3-12
3.2.6 Chassis Ground.......................................................................................................3-13
SECTION 4
4.0
4.1
4.2
SOFTWARE COMMANDS
INTRODUCTION .................................................................................................................... 4-1
RS-232 COMMANDS............................................................................................................. 4-1
RS-232 COMMAND DESCRIPTIONS ................................................................................... 4-2
4.2.1 ANTENNA CABLE DELAY........................................................................................ 4-3
4.2.2 ALARM TIMEOUTS................................................................................................... 4-4
4.2.3 CLEAR ALARM ......................................................................................................... 4-5
4.2.4 CONFIGURATION .................................................................................................... 4-6
4.2.5 DISPLAY ALARM LOG ............................................................................................. 4-7
4.2.6 DATE ......................................................................................................................... 4-8
4.2.7 DISPLAY FREQUENCY MEASUREMENT ..............................................................4-9
4.2.8 DISPLAY OSCILLATOR LOG.................................................................................4-10
4.2.9 DISPLAY TRACKING HISTOGRAM.......................................................................4-13
4.2.10 EVENT OUTPUT.....................................................................................................4-15
4.2.11 GPS SIGNAL STATUS.............................................................................................4-16
4.2.12 HELP .......................................................................................................................4-18
4.2.13 LOCATION ..............................................................................................................4-19
4.2.14 SIGNATURE CONTROL.........................................................................................4-20
4.2.15 SET MODE..............................................................................................................4-21
4.2.16 STATUS INFORMATION ........................................................................................4-22
4.2.17 TIME ........................................................................................................................4-23
4.2.18 TEST MODE............................................................................................................4-24
4.2.19 TIME ZONE OFFSET..............................................................................................4-25
4.2.20 UTC TO GPS TIME .................................................................................................4-26
4.2.21 VERSION ................................................................................................................4-27
4.2.22 FREQUENCY OFFSET...........................................................................................4-28
4.2.23 1PPS OFFSET ........................................................................................................4-30
SECTION 5
5.0
5.1
5.6
SECTION 6
6.0
6.1
6.2
SERVICE INFORMATION
INTRODUCTION .................................................................................................................... 6-1
RECEPTION TROUBLESHOOTING..................................................................................... 6-1
6.1.1 No Reception............................................................................................................. 6-1
6.1.2 Low GPS Quality .......................................................................................................6-3
OSCILLATOR ADJUSTMENT .............................................................................................. 6-4
6.2.1 Adjustment Procedure ............................................................................................... 6-4
APPENDIX A
A.0
A.1
A.2
OPTIONS AND ACCESSORIES
INTRODUCTION .................................................................................................................... 5-1
OPTION 03 BUILT IN DISTRIBUTION AMPLIFIER ............................................................. 5-1
5.1.1 System Components ................................................................................................. 5-1
5.1.1.1
Model 8140T Line Taps...........................................................................5-1
5.1.1.2
Model 8140Vt VersaTap Frequency Synthesizer.................................... 5-2
5.1.1.3
Model 8140TA Line Extender Amplifier................................................... 5-3
5.1.1.4
Model 8140MT MultiTap..........................................................................5-3
5.1.2 Design of Distribution Networks ................................................................................ 5-4
OPTION 11 - RACK MOUNT SLIDES.................................................................................. 5-9
OPERATION WITH LOW GPS QUALITY
INTRODUCTION ................................................................................................................... A-1
GPS QUALIFYING ALGORITHM SELECTION ................................................................... A-2
GQA COMMAND .................................................................................................................. A-2
TABLES
TABLE 1-1
MODEL 8195A ANCILLARY KITS................................................................................... 1-4
TABLE 2-1
DEFAULT SETTINGS....................................................................................................2-12
TABLE 3-1
TABLE 3-2
TABLE 3-3
TABLE 3-4
TABLE 3-5
RS-232 COMM PIN ASSIGNMENTS ..............................................................................3-5
UHF SIMULCAST OFFSETS .......................................................................................... 3-8
VHF HI SIMULCAST OFFSETS ...................................................................................... 3-9
DATA CLOCK PIN ASSIGNMENTS..............................................................................3-10
ALARM OPERATION ....................................................................................................3-12
TABLE 4-1
TABLE 4-2
TABLE 4-3
TABLE 4-4
ALPHABETICAL LIST OF RS-232 COMMANDS............................................................ 4-2
COMMON OFFSET VALUES........................................................................................4-25
UHF SIMULCAST OFFSETS SC1 ................................................................................4-28
VHF SIMULCAST OFFSETS SC2.................................................................................4-28
TABLE 5-1
TABLE 5-2
LINE TAP LOADS ............................................................................................................ 5-4
OPTION 11 CHECKLIST ................................................................................................. 5-7
TABLE A-1
TABLE A-2
TELEVISION STATIONS WITH GPS JAMMING POTENTIAL .......................................A-1
FM RADIO FREQUENCIES WITH GPS JAMMING POTENTIAL...................................A-1
ILLUSTRATIONS
FIGURE 1-1
MODEL 8195A AGELESS OSCILLATOR ....................................................................... 1-1
FIGURE 2-1
FIGURE 2-2
FIGURE 2-3
FIGURE 2-4
FIGURE 2-5
FIGURE 2-6
ANTENNA INSTALLATION ............................................................................................. 2-2
MODEL 8226 IMPULSE SUPPRESSOR ........................................................................ 2-3
GROUNDING PANEL INSTALLATION ........................................................................... 2-4
N CONNECTOR ASSEMBLY INSTRUCTIONS ................................................................ 2-5
MODEL 8227 INLINE AMPLIFIER................................................................................... 2-6
CABLE GUIDELINES ...................................................................................................... 2-7
FIGURE 3-1
FIGURE 3-2
FIGURE 3-3
FIGURE 3-4
FIGURE 3-5
FIGURE 3-6
FIGURE 3-7
FIGURE 3-8
MODEL 8194 FRONT PANEL ......................................................................................... 3-3
RS-232 COM PIN NUMBERING ..................................................................................... 3-4
MODEL 8194 REAR PANEL ........................................................................................... 3-7
DATA CLOCK CONNECTOR.......................................................................................... 3-9
RS-485 LINE DRIVER ...................................................................................................3-10
SINGLE-ENDED CONNECTION...................................................................................3-11
ALARM OUTPUTS TERMINAL BLOCK........................................................................3-11
AC POWER MODULE ...................................................................................................3-13
FIGURE 4-1
COMMAND STRUCTURE............................................................................................... 4-1
FIGURE 5-1
FIGURE 5-2
FIGURE 5-3
LINE TAP NUMBER AND DISTANCE CHART - OPTION 03......................................... 5-5
TYPICAL INTERCONNECTION DIAGRAM .................................................................... 5-6
SLIDES, OPTION 11 ....................................................................................................... 5-8
MODEL 8194
SECTION 1
GENERAL INFORMATION
1.0
INTRODUCTION
1.1
FEATURES
1.2
WARRANTY INFORMATION AND PRODUCT SUPPORT
1.3
MANUAL ERRATA AND SPECIAL DOCUMENTATION
1.4
UNPACKING
1.5
SPECIFICATIONS
GENERAL INFORMATION
1.0
INTRODUCTION
The patented Spectracom Model 8194 Ageless Oscillator*, shown in Figure 1-1, is an ovenstabilized highly accurate frequency source. Its outputs are locked to the United States Naval
Observatory via the NAVSTAR Global Positioning System (GPS). Spectracom’s field-proven
Ageless Oscillator technology provides continual automatic frequency control. A long-term
averaging algorithm compensates for oscillator aging and temperature drift.
The Model 8194 is ideally suited as a site master oscillator for communication systems. Typical
transmitter applications include land mobile simulcast, SMR (Specialized Mobile Radio), paging
simulcast, satellite/microwave communications links, cellular telephone, and broadcast
television. Other applications include use as a frequency standard in a Metrology Lab or as a
factory reference to lock test equipment to a common traceable time base.
FIGURE 1-1 MODEL 8194 AGELESS OSCILLATOR
* PATENT NO. 4,525,685
8194 Instruction Manual
Page 1-1
Section 1: General Information _____________________________________
1.1
FEATURES
The Spectracom Model 8194 offers the following features:
•
•
•
•
Accuracy: Continuous self-calibration to GPS provides ± 1.0 x 10-11 frequency accuracy.
Precise Offsets: The disciplined 10 MHz outputs can be offset in precise steps to improve
VHF - Hi simulcast and TV broadcasts.
Reliable Worldwide Operation: The Model 8194 can receive and track up to eight satellites
simultaneously. Receivers qualify the received GPS broadcast using T-RAIM. T-RAIM,
Time Receiver Autonomous Integrity Monitoring is an algorithm that disqualifies a satellite
from a solution if its message is not within a reasonable window of other satellites currently
tracked.
Frequency Distribution: With the addition of Option 03 Built-In Distribution Amplifier and
Model 8140T Line Taps, the Model 8194 provides a reference frequency to counters,
spectrum analyzers and signal generators located throughout a facility. Distributing the
accurate and traceable reference eliminates the need to buy expensive, high stability time
bases for each instrument.
1.2
WARRANTY INFORMATION AND PRODUCT SUPPORT
Warranty information is found on the leading pages of this manual. The Model 8194 contains a
GPS receiver that is not manufactured by Spectracom Corporation. Therefore the GPS receiver
carries a one-year warranty while the rest of the product is covered under a five-year warranty.
Should it become necessary to exercise the warranty, contact Spectracom Corporation to obtain a
replacement or service.
Spectracom continuously strives to improve its products and therefore greatly appreciates any
and all customer feedback given. Please participate in Spectracom’s Customer Satisfaction
Survey found on our web site at:
http://www.spectracomcorp.com
The online survey is also used for warranty registration of your new Spectracom products.
Technical support is available by telephone. Please direct any comments or questions regarding
application, operation, or service to Spectracom Customer Service Department. Customer
Service is available Monday through Friday from 8:30 A. M. to 5:00 P.M. Eastern time.
Telephone Customer Service at: 585-321-5800.
Page 1-2
8194 Instruction Manual
_____________________________________ Section 1: General Information
In addition, please contact customer service to obtain a Return Material Authorization Number
(RMA#) before returning any instrument to Spectracom Corporation. Please provide the serial
number and failure symptoms. Transportation to the factory is to be prepaid by the customer.
After obtaining an RMA# ship the unit back using the following address:
Spectracom Corporation
Repair Department, RMA# xxxxx
95 Methodist Hill Drive, Suite 500
Rochester, NY 14625
Product support is also available by e-mail. Questions on equipment operation and applications
may be e-mailed to Spectracom Sales Support at:
mailroom@spectracomcorp.com
Repair or technical questions may be e-mailed to Spectracom Technicians at:
techsupport@spectracomcorp.com
Visit our web page for product information, application notes and upgrade notices as they
become available at:
http://www.spectracomcorp.com
1.3
MANUAL ERRATA AND SPECIAL DOCUMENTATION
Information concerning manual corrections or product changes occurring after printing is found
in the Errata Section. The Errata Section, when required, is found at the end of this manual.
Please review and incorporate changes into the manual whenever an Errata Section is included.
Spectracom will make instrument modifications upon special request. A customer
documentation packet associated with the modification is included with this manual.
1.4
UNPACKING
Upon receipt, carefully examine the carton and its contents. If there is damage to the carton that
results in damage to the unit, contact the carrier immediately. Retain the carton and packing
materials in the event the carrier wishes to witness the shipping damage. Failing to report
shipping damage immediately may forfeit any claim against the carrier. In addition, notify
Spectracom Corporation of shipping damage or shortages, to obtain a replacement or repair
services.
Remove the packing list from the envelope on the outside of the carton. Check the packing list
against the contents to be sure all items have been received, including an instruction manual and
ancillary kit. Table 1-1 lists the items included in the various Model 8194 ancillary kits.
8194 Instruction Manual
Page 1-3
Section 1: General Information _____________________________________
Description
Part
Number
Standard
Power
Option 03
Distribution
Fuse, 1.5A Slo-Blo
F011R5
1
1
Line Cord
W01000
1
1
Terminal Block,
7 position
P13007
1
1
Terminator, 50-ohm
004492
4
0
Terminator,
DC isolated
004490
0
4
TABLE 1-1 MODEL 8194 ANCILLARY KITS
1.5
Specifications
This section contains specifications for the standard Model 8194 GPS Ageless Oscillator, Model
8225 GPS Antenna, Model 8226 Impulse Suppressor and the Model 8227 Inline Amplifier.
Specifications pertaining to the Model 8194 options are found in Section 5.
1.5.1
Receiver
Received Standard:
L1 C/A Code transmitted at 1575.42 MHz.
Satellites Tracked:
Up to 8 simultaneously.
Acquisition Time:
Cold start typically <20 minutes.
Acquisition Sensitivity:
-105 dBm to -137 dBm.
Tracking Sensitivity:
-139 dBm.
Optimum Gain Range:
11 to 33 dB at receiver input.
Timing Accuracy:
<50 nanoseconds while in Position Hold mode and SA on.
Typically <30 nanoseconds.
1.5.2
Standard Frequency Outputs
Signal:
10-MHz sinewave derived from GPS disciplined
Connector:
BNC female, one front panel, four rear panel.
Signal Level:
700 mV rms ±2 dB into 50 ohms.
Page 1-4
oscillator.
8194 Instruction Manual
_____________________________________ Section 1: General Information
Impedance:
50 ohms.
Harmonics:
Better than 30 dB down.
Spurious:
Better than 40 dB down.
Phase Noise:
<97 dBc @ 1 Hz.
<110 dBc @ 10 Hz.
<125 dBc @ 100 Hz.
<135 dBc @ 1000 Hz.
<138 dBc @ 10 kHz.
Signature Control:
The Frequency Outputs can be configured with Signature Control.
Under Signature Control, the outputs are removed whenever a
Major Alarm is asserted. The outputs are restored when the fault
condition is corrected. The Signature Control feature is set via the
RS-232 communication port.
Simulcast Offsets:
The disciplined oscillator output can be offset in precise steps to
minimize co-channel interference. The offsets provide steps of ±3,
5, 7, 9 Hz at VHF-HI frequencies, and ±1, 2, 3, 4 Hz at UHF
frequencies. Offsets are selected by software commands.
Output Options:
Option 03 Distribution Amplifier: Allows the Model 8194 to drive
Spectracom distribution products. This option adds a 12 Volt DC
offset to the rear panel Frequency Outputs.
1.5.3
Frequency Standard Stability
Oscillator Type:
10-MHz OCXO, SC cut.
Locked Accuracy:
±1 x 10-11, 24-hour average when locked to GPS and no frequency
offsets selected.
±1 x 10-10, 24-hour average when locked to GPS and frequency
offsets selected.
Unlocked Accuracy:
Corrections are applied to the oscillator based upon learned
oscillator aging characteristics. Holdover accuracy is <5
microseconds over 5 hours.
Recovery:
Two hours from holdover to oscillator lock.
Four hours from cold start.
Aging Rate:
<5 x 10-10/day after 30 days. Unit automatically corrects for
oscillator aging when locked to GPS.
8194 Instruction Manual
Page 1-5
Section 1: General Information _____________________________________
1.5.4
1 PPS Output
Signal:
One pulse-per-second square wave derived from the GPS receiver.
Connector:
BNC female, front panel.
Signal Level:
TTL compatible into loads >100 ohms.
Pulse Width:
200 milliseconds.
Accuracy:
Positive edge within ±50 nanoseconds of UTC when in Position
Hold Mode and NO DELAY selected.
Delay Control:
The 1PPS output can be delayed 0 - 1 second in 0.001 microsecond
steps. The delay value is entered via the
RS-232 or RS-485 communication port.
1.5.5
Data Clock Timing Output
Signal:
Connector:
Signal Level:
Duty Cycle:
Accuracy:
Additional Outputs:
1.5.6
1PPS derived from the GPS disciplined 10 MHz oscillator.
DB9 female, rear panel.
RS-485.
20% ±5%.
The Data Clock 1PPS is made leading edge synchronized to the
recovered GPS 1PPS. Using the 1PPS offset command, 1PO, the
Data Clock 1PPS output can be offset from 0 to 1 second in 0.1
microsecond steps. The Data Clock 1PPS shall be synchronized
within ±500 nanoseconds of other Model 8194/8195A/8197
receivers having the same 1PO offset.
Major alarm status is provided on this connector. Under normal
operation the alarm pin is Ground. Whenever a Major Alarm is
asserted, this pin is open an circuit.
Indicator Lamps
Front panel LEDs, when lit, indicate the following:
Power:
Primary power source is connected and switched ON.
Tracking GPS:
Receiver is tracking at least four qualified GPS satellites.
Oscillator Locked:
Oscillator is disciplined to the received GPS signal.
Major Alarm:
Alarm condition classified as “major” is active.
Minor Alarm:
Alarm condition classified as “minor” is active.
Page 1-6
8194 Instruction Manual
_____________________________________ Section 1: General Information
1.5.7
Alarms
Alarm relays allow remote monitoring of operational status. Relay contacts are provided for
Major Alarms and Minor Alarms. Alarm status is also included in performance and status logs
obtained using software commands.
1.5.7.1
Alarm Classifications
Major Alarm: A Major alarm is asserted when detected faults compromise output accuracy.
The alarm relays reset when the fault condition is corrected. Faults and conditions listed below
actuate a Major Alarm:
Frequency Error Alarm: Measured oscillator frequency error exceeds
1 x 10-8 or whenever an AT2 Alarm is asserted. A Frequency Alarm is also asserted at
Power On.
GPS Tracking Timeout 2: The AT2 time period allotted for operation without tracking
a minimum of four qualified satellites has expired. An AT2 Alarm is also asserted during
start-up.
GPS Tracking Timeout 3: The AT3 time period allotted for operation without tracking
a minimum of four qualified satellites has expired. An AT3 Alarm is also asserted during
start-up.
CPU Fault: The CPU is unable to communicate with the GPS receiver.
Test Mode: Unit has been placed in TEST MODE operation.
Free Run: The automatic frequency control feature has been disabled.
Short Gate: Gate time is shortened for test purposes, measurement resolution is
reduced.
Minor Alarm: A minor alarm is asserted when failures detected do not immediately affect
output accuracy. The alarm relays reset when the fault condition is corrected. Faults and
conditions listed below actuate a Minor Alarm:
Output Fault: No output is detected from one or more of the four rear panel Frequency
Outputs. Fault could be caused by a shorted cable, reflections due to an unterminated
cable or removed by a Major Alarm when Signature Control is enabled.
Oscillator Adjust: Warns that oscillator is operating within 10% of the minimum or
maximum control setting. The oscillator requires manual adjustment.
8194 Instruction Manual
Page 1-7
Section 1: General Information _____________________________________
GPS Tracking Timeout 1: The AT1 time period allotted for operation without tracking
a minimum of four qualified satellites has expired. An AT1 Alarm is also asserted during
start-up.
Low Quality Alarm: Warns of low GPS signal quality. The alarm is asserted whenever
the "Q" value in Tracking Histogram is below 3000.
Frequency Offset: An initial or new simulcast offset value has been entered. The alarm
remains active until the standard oscillator has corrected for the offset.
Test Mode: Unit is placed in Test Mode operation from RS-232 communication port.
Antenna Problem: Warns that the antenna is not connected or a cable short or open is
detected.
1.5.7.2
Tracking Alarm Classifications
Three configurable alarm tracking timeouts, AT1, AT2, and AT3, indicate how long the Model
8194 has been unable to receive qualified GPS satellites. Countdown timers are started
whenever the receiver is not tracking a minimum of four qualified satellites. As the period
configured for each Alarm Timeout expires, the associated Tracking Alarm is asserted. The
alarm timeouts are configured via the RS-232 and RS-485 communication ports. Timeout range
is 1 second to 999 days. Alarm tracking status is provided to the communication ports using the
STAT and DAL commands.
AT1 (Alarm Tracking Timeout 1): Period of time the receiver has not tracked at least four
qualified satellites has expired. Factory default is 1 minute. This is a Minor Alarm that also
extinguishes front panel TRACKING GPS lamp. The AT1 Alarm resets upon acquisition of at
least four qualified satellites for one minute.
AT2 (Alarm Tracking Timeout 2): Period of time the receiver has not tracked at least four
qualified satellites has expired. Factory default is 2 hours 30 minutes. This condition is
classified as a Major Alarm. An AT2 alarm asserts a frequency alarm and extinguishes the OSC
LOCK lamp. The AT2 Alarm resets when the receiver has reacquired a minimum of four
qualified satellites for one minute.
AT3 (Alarm Tracking Timeout 3): Period of time the receiver has not tracked at least four
qualified satellites has expired. Factory default is 30 days. This is a Major Alarm. The AT3
Alarm resets when the receiver has reacquired a minimum of four qualified satellites for one
minute.
Page 1-8
8194 Instruction Manual
_____________________________________ Section 1: General Information
1.5.7.3
Alarm Interface
Alarm relay contacts are provided on the Alarm Outputs and Data Clock connectors.
Alarm Outputs:
Connector:
Contacts:
Contact Rating:
Major Alarm, Minor Alarm.
7-position terminal block, rear panel.
NO, NC, and Common.
30 VDC, 2 Amps.
Data Clock:
Connector:
Contact Rating:
Major alarm.
DB9 Female, rear panel.
30 VDC, 500 milliamps.
1.5.8
RS-232 Communication Port
The front panel RS-232 Com port is used to monitor and set operational parameters.
Signal:
RS-232C, DCE.
Connector:
DB9 female, front panel.
Bit Rate:
9600 Baud.
Character Structure:
ASCII, 1 start, 8 data, 1 stop, no parity, xon/xoff flow control.
1.5.9
Input Power
AC Input:
90 to 264 VAC, 50/60 Hz, 20 Watts.
Option 03, Built-in Distribution Amplifier, requires an additional
25 Watts.
Fuse:
1.5 Amp, 250V, Slo-Blo.
Connector:
3-conductor, IEC 320 C-13, rear panel.
1.5.10
Mechanical
Dimensions:
3.5H x 19.0W x 12.5D inches.
(89H x 483W x 315D mm).
Weight:
9 lbs.(6.8 kg) maximum.
Shipping Weight:
12 lbs. (9.1 kg).
Rack Mount:
EIA 19”, front panel drilled for two standard rack units.
Optional:
Option 11 Rack Mount Slides.
8194 Instruction Manual
Page 1-9
Section 1: General Information _____________________________________
1.5.11
Environmental
Operating Temperature:
-30 to +60°C.
Storage Temperature:
-40 to +85°C.
Humidity:
95% R. H. non-condensing.
1.5.12
Model 8225 GPS Antenna Specifications
1.5.12.1 Electrical Specifications
Type:
Frequency:
Temperature Range:
Gain:
Connector:
Recommended Cable:
Maximum Cable Length:
Power:
Active.
1575.42 MHz.
-30° to 80° C (-22° to 176°F).
30 dB.
N type, Female.
LMR-400.
350 feet or 20 dB cable loss before additional preamplifier is
required.
5 Volts, 27 milliamps, powered by receiver.
1.5.12.2 Mechanical Specifications
Assembled Length:
Housing Diameter:
Housing Material:
Assembled Weight:
Shipping Weight:
Mounting:
1.5.13
24 inches (61 cm).
3.5 inches (8.9 cm).
PVC.
1.3 lbs. (.60 kg).
3.5 lbs. (1.6 kg).
Hose clamps (furnished) on vent pipe
Model 8226 Impulse Suppressor
Connectors:
Turn On Time:
Turn On Voltage:
Frequency Range:
VSWR:
Insertion Loss:
Page 1-10
Type N Female
4 nanoseconds for 2 kV/ns
+7 V, -1 VDC
1.2 to 2.0 GHz
1.1:1 or better
0.1 dB maximum
8194 Instruction Manual
_____________________________________ Section 1: General Information
1.5.14
Model 8227 Inline Amplifier
Connectors:
Gain:
VSWR:
Power:
8194 Instruction Manual
Type N Female
20 ±3 dB
≤1.5:1
3 - 9 VDC, 7.5 ±1 milliamps
Page 1-11
MODEL 8194
SECTION 2
INSTALLATION
2.0
INTRODUCTION
2.1
MODEL 8225 ANTENNA
2.2
ANTENNA CABLE
2.3
MODEL 8226 IMPULSE SUPPRESSOR
2.4
MODEL 8227 INLINE AMPLIFIER
2.5
MODEL 8194 PREPARATION FOR USE
2.6
INITIAL OPERATION
2.7
QUALIFYING THE INSTALLATION
2.8
FACTORY CONFIGURATION
INSTALLATION
2.0
INTRODUCTION
This section describes the installation of the Model 8225 GPS Antenna and related
accessories. This section also describes the Model 8194 preparation for use, initial
operation, installation qualification and factory configuration. To ensure proper
operation, please read this section prior to equipment installation and usage.
Refer to Section 5 of this manual for information on installing the Option 11 Rack Mount
Slides.
2.1
MODEL 8225 GPS ANTENNA
The Model 8225 is an active antenna tuned to receive the GPS 1575.42 MHz L1 band
satellite broadcast. The received signals are passed through a narrow band pass filter and
preamplifier within the antenna. The active antenna circuitry provides 30 dB of gain and
requires +5 VDC at 27 milliamps. The Model 8194 receiver provides this over the
antenna coax. Each antenna is terminated with a type “N” female connector. The Model
8225 features a compact weatherproof design measuring 3.5 inches in diameter.
2.1.1
Antenna Installation
The GPS antenna must be installed outdoors in a location where an unobstructed view of
the sky exists. Rooftops generally make good locations due to clear overhead sky with
views to the horizon. This type of location allows the antenna to see and track the
maximum number of satellites throughout the day. Installations with obstructed views
may prove operational, but can experience reduced reception quality and the inability to
simultaneously track the maximum number of satellites. In addition to clear sky
coverage, select a site, which would not allow the antenna to become buried in drifted or
accumulated snow or ice. Avoid placing the GPS antenna in close proximity to broadcast
antennas whenever possible.
Each antenna includes a mating PVC mast assembly and two hose clamps to simplify
installation. The hose clamps can be used to affix the mast assembly to a vent pipe.
Spectracom offers an antenna base, Model 8213, for installations where vent pipe
mounting is not practical or desired. The Model 8213 is constructed of aluminum and is
furnished with ballast for stability. Both mounting methods are illustrated in Figure 2-1.
8194 Instruction Manual
Page 2-1
FIGURE 2-1 ANTENNA INSTALLATION
2.2
ANTENNA CABLE
Spectracom recommends low loss coax, such as Times Microwave LMR-400, for the
GPS antenna cable. To simplify the installation process, Spectracom offers GPS cable
assemblies terminated with Type N Male connectors. Specify part number CAL7xxx,
where xxx equals the length in feet.
If the antenna cable is purchased locally, select coax suitable for outdoor use. Consider
the cable's weather ability, temperature range, UV resistance, and attenuation
characteristics.
Do not allow the antenna cable to be placed in standing water, as water may permeate
through the coax jacket over time. On flat roof installations, the coax can be suspended
by cable hangers or placed in sealed PVC conduit. Apply a weather proofing sealant or
tape over all outdoor connections.
Installation of a surge protection device in the antenna line is recommended to protect the
Model 8194 receiver and connected devices from lightning damage. Spectracom offers
the Model 8226 Impulse Suppressor to shunt potentially damaging voltages on the
antenna coax to ground. Refer to Section 2.3 for a complete description of the Model
8226.
Page 2-2
8194 Instruction Manual
2.2.1
Cable Lengths
Using Spectracom CAL7xxx or LMR-400 coax, the maximum antenna cable length
permitted is 350 feet. These cables attenuate the GPS signal by 5.4 dB per 100 feet of
coax. Installations requiring longer antenna cables may use the Model 8227 Inline
Amplifier or lower loss cable. Refer to Section 2.4 for additional information on the
Model 8227.
When selecting alternate antenna cable sources, the attenuation characteristics at the GPS
frequency of 1575.42 MHz must be known. To ensure optimum receiver performance,
the total antenna cable attenuation must not exceed
20 dB. Cable attenuations greater than 20 dB require the use of a Model 8227 Inline
Amplifier.
2.3
MODEL 8226 IMPULSE SUPPRESSOR
Spectracom recommends the use of an inline coaxial protector for all products with an
outside antenna. Spectracom offers the Model 8226, Surge Suppressor, to protect the
receiver from damaging voltages occurring on the antenna coax. Voltages exceeding the
impulse suppresser trip point are shunted to the system ground. The Model 8226 is
designed to withstand multiple surges.
Install the suppressor indoors, preferably where the coax enters the building. Connect the
largest gauge grounding wire available to the Model 8226 ground stud. Optionally the
suppressor can be mounted to a grounding panel or bulkhead using the BF adapter
bracket as shown in Figure 2-2. Spectracom offers the bracket under part # MP10-00000002.
FIGURE 2-2 MODEL 8226 IMPULSE SUPPRESSOR
8194 Instruction Manual
Page 2-3
Page 2-4
8194 Instruction Manual
In addition, Spectracom offers a copper grounding panel, part number MP10-0000-0001,
as a single point ground connection for the antenna surge suppressor, equipment rack,
GPS receiver and other surge protection devices to a perimeter ground system. A single
point ground system is recommended to provide optimum protection from lightning
strikes.
Each grounding panel includes mounting hardware, hardware to secure protective
devices to the copper plate, 20 feet of 1.5 inch wide copper strap, two strap clamps and
copper paste.
Mount the grounding panel indoors, preferably close to where the antenna coax enters the
building and direct access to the system ground is available. Refer to Figure 2-3 for
installation guidelines. The ground panel must be connected to a low impedance (both
low resistance and low inductance) ground system to assure proper operation of the surge
protection equipment. To minimize the inductance between the ground plate and system
ground interconnection keep the copper grounding strap as straight as possible, limit
bends to a radius of 8 inches or larger. Thoroughly clean the copper panel to remove any
oxidation or contaminants prior to installation. Apply the supplied copper paste to all
junctions on the copper panel to maintain a low impedance connection.
FIGURE 2-3 GROUNDING PANEL INSTALLATION
8194 Instruction Manual
Page 2-5
Each Model 8226 includes two clamp type male N connectors. These connectors can be
used to splice the Model 8226 into the antenna coax. The connectors are compatible with
Spectracom CAL7xxx cable assemblies and Times Microwave LMR-400 equivalent
coax. Connector assembly instructions are shown below in Figure 2-4.
Assembly Instructions
Part Number P051-0001-0100 Type N Connectors
The table below lists the recommended tools needed to assemble the connectors. Verify
all parts of the connector have been received as shown in connector diagram below.
Tools Required
Sharp Knife or Razor
Cable Cutter
Soldering Iron and Solder
Ruler
Wire Cutters/Scissors
5/8” Open End Wrench
11/16” Open End Wrench
Multimeter
Step 1
Cut the cable end squarely and
place the nut, washer, and gasket
onto the cable as shown. Make
certain the gasket’s “V” groove is
oriented towards the end of the
cable. Cut the cable jacket back to
dimension A of 0.359 inches (9.1
mm). Do not cut or knick the braid.
Step 2 Comb out the braid and fold back
to expose the dielectric. Cut the
dielectric back to dimension B of
0.234 inches (6.0 mm). Do not cut
or knick the center conductor.
Step 3
Comb the braid forward and slide
the clamp onto the cable as shown.
Make certain that the beveled edge
of the clamp is oriented towards the
gasket “V” groove to form a
weatherproof seal.
Page 2-6
8194 Instruction Manual
Step 4
Fold the braid back over the clamp.
Comb the braid to evenly distribute
it over the clamp and trim to the
proper length as shown.
Step 5 Verify there is no braid or dielectric
foil that may short against the center
conductor. Tin the center conductor
and then solder on the male contact
as shown.
Step 6
Insert the cable assembly into the
connector body. Verify the gasket
“V” grooves fit into the clamp edges.
Hold the body with the 11/16”
wrench and tighten the nut using the
5/8” wrench. Using the multimeter,
measure continuity of the center
conductors on each end of the cable.
It should be close to 0 Ω. Measure
the continuity between the center
conductor and connector body. It
should be an open circuit.
FIGURE 2-4 N Connector Assembly Instructions
2.4
MODEL 8227 GPS INLINE AMPLIFIER
An inline amplifier is required whenever GPS antenna cable lengths cause greater than
20 dB attenuation. Using Spectracom CAL7xxx or LMR-400 coax, an amplifier is
needed whenever antenna cable lengths exceed 350 feet.
The Model 8227 GPS Inline Amplifier, shown in Figure 2-5, extends the maximum cable
length to 600 feet. The Model 8227 provides 20 dB of gain and is powered by the
NetClock/GPS receiver.
FIGURE 2-5 MODEL 8227 INLINE AMPLIFIER
8194 Instruction Manual
Page 2-7
Each Model 8227 includes two clamp type male N connectors. These connectors can be
used to splice the Model 8227 into the antenna coax. The connectors are compatible with
LMR-400 type coax such as Spectracom CAL7xxx or LMR-400. Refer to Figure 2-4 for
connector assembly instructions.
A five-foot long coaxial cable is also provided with each Model 8227. This cable
connects the amplifier to the surge suppressor. This cable is rated for indoor usage only.
Refer to Figure 2-6 for Model 8227 installation guidelines. The cable lengths shown in
Figure 2-6 represent Spectracom CAL7xxx cable. The equivalent cable loss expressed in
dB, is provided for use with other cables.
Place the inline amplifier within 200 feet (10 dB cable loss) of the antenna to optimize
the signal to noise ratio. Whenever possible install the inline amplifier indoors and after
the impulse suppressor. Connect the surge suppressor to the inline amplifier using the
supplied 5-foot cable. The amplifier can be installed outdoors, providing care is taken to
weatherproof the connections.
FIGURE 2-6 CABLE GUIDELINES
Page 2-8
8194 Instruction Manual
2.5
MODEL 8194 PREPARATION FOR USE
This section outlines the set-up procedure to prepare the Model 8194 for operation.
2.5.1
Antenna Connection
Install the Model 8225 Antenna and related accessories as outlined previously in this
section. Connect the antenna cable to the rear panel GPS ANT connector.
2.5.2
AC Power
The standard Model 8194 receives primary power from a 90 to 264 VAC 50/60 Hz power
source. A detachable line cord is furnished in the ancillary kit. The supplied line cord is
compatible with AC receptacles (NEMA 5-15R) commonly found in the United States
and Canada. Alternate type line cords may be obtained locally. Connect the line cord to
the rear panel AC module and a properly grounded power receptacle.
NOTE: The Model 8194 accepts the complete range of 90 to 264
VAC without a change in instrument setup. Do not change the AC
fuse or line voltage selector.
2.5.3
Chassis Ground
The chassis ground lug allows the Model 8194 chassis to be connected to an earth ground
in addition to the power line safety ground. Connecting the chassis to a single point
ground system may be required in some installations to ensure optimum lightning
protection. A separate earth ground is also recommended in installations where
excessive noise on the power line degrades the Model 8194 receiver performance.
2.6
INITIAL OPERATION
Upon completing antenna and power connections, turn on the power switch. Observe the
front panel POWER lamp turns on. The Major and Minor Alarm lamps are also turned
on during initial operation. The receiver will now acquire and lock to GPS satellites
currently in view of the antenna. The TRACKING GPS lamp turns on and the Minor
Alarm lamp turns off when the receiver acquires a minimum of four satellites and has
achieved a 3-D fix for one minute. This typically takes less than 20 minutes to
accomplish during initial installation. Once the receiver has a 3-D fix in its new location,
the position information is loaded into non-volatile RAM. Having current position
information greatly reduces the time to first fix on subsequent power cycles to less than
one minute. The ovenized oscillator requires a minimum of 4 hours to reach operational
temperature and stabilize. The OSC LOCK lamp turns on and the Major Alarm lamp
turns off when the ovenized oscillator is disciplined to the GPS reference. The unit will
now operate in accordance with the specifications listed in this manual.
8194 Instruction Manual
Page 2-9
2.7
QUALIFYING THE INSTALLATION
Typically, the front panel Tracking GPS lamp illuminates within 20 minutes of turn on.
This lamp indicates that receiver is tracking at least 4 qualified satellites and a 3-D
position fix has been obtained. If the Tracking GPS lamp does not turn on, a cable or
reception problem may exist. Refer to Section 6 Service Information, for troubleshooting
assistance.
Reception quality can be evaluated using the performance and status logs provided by the
receiver. Commands to retrieve operational information are issued through the front
panel RS-232 Comm port. To communicate with the receiver, a terminal or computer
with terminal emulation software (i.e. Procomm Plus, Hyper-Terminal, etc.) is required.
Configure the terminal for ANSI emulation, 9600 baud and a character structure of 1
start, 8 data, and 1 stop with no parity. Flow control is not required, though xon/xoff is
supported.
2.7.1
GPS Signal Status
The GPS Signal Status command, GSS, provides an instantaneous view of the GPS
reception quality. This command is used to verify proper antenna placement and receiver
performance of an installation. The GSS response indicates the number of satellites the
receiver is currently tracking and their relative signal strength. The resulting GPS quality
and Position Fix Status are also included. A complete description of the GSS command
can be found in Section 4 of this manual.
Issue the GSS command as shown below.
Type: GSS <ent>
An example response is shown below:
TRACKING 6 SATELLITES
GPS STATE= 3D-FIX DOP= 03.7
LATITUDE= N 43 06 59.746 LONGITUDE= W 077 29 15.242 HEIGHT= +00110 METERS
QUALITY= PASSED
CHAN VID MODE STREN STAT
01 24 08
053
AA
02 04 08
052
AA
03 10 08
053
AA
04 05 08
053
AA
05 18 08
044
AA
06 30 00
000
00
07 01 07
047
28
08 06 00
000
00
Page 2-10
8194 Instruction Manual
Tracking: The receiver must track at least 4 qualified satellites to operate. Typically the
receiver shall track 6 or more satellites.
GPS State: Under normal operation the receiver will indicate either 3-D Fix or Position
Hold. A Searching or 2-D Fix message indicates that fewer than 4 qualified satellites are
currently tracked.
DOP: Dilution of Precision indicates the degree of uncertainty of a Position Fix. The
DOP value shall be 0≤DOP<10 when in 3-D Fix mode and 0.0 when in Position Hold
mode.
Quality: A passed message indicates the receiver is tracking at least 4 qualified
satellites. A failed message indicates the received GPS signals did not meet minimum
requirements.
Satellite Data: Data on each satellite currently tracked is provided in table form.
The CHAN column represents the GPS Receiver Channel Number, 1 through 8. VID is
the Vehicle (satellite) Identification Number, 1 through 37.
The MODE column provides the Channel Tracking Mode for each satellite. The GPS
qualifying algorithm accepts only satellites having a Mode value of 08.
The relative signal strength of each satellite currently tracked is found in the STREN
column. The minimum acceptable level is 40, maximum level is 55.
The satellite status flag code is found in the STAT column. Typically the STAT value is
A2.
If the receiver does not meet the minimum requirements described above, refer to Section
6 Service Information, for troubleshooting assistance.
2.7.2
Tracking Histogram
The Display Tracking Histogram command, DH, is used to evaluate the long-term
reception quality. The tracking histogram records the number of satellites tracked and
qualified every second. At the end of the hour, a log is created and the counters are
restarted. The command responds with the last four hourly entries and the histogram
currently in process. A complete description of the DH command is found in Section 4
of this manual.
8194 Instruction Manual
Page 2-11
Allow the receiver to operate for at least 5 hours before evaluating the tracking
histogram. Issue the DH command as shown below:
Type: DH <ent>
An example response is shown below:
TIME= 12:00:00 DATE= 2000-03-21 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00019 7= 01537 8= 02044 Q= 03600
TIME= 13:00:00 DATE= 2000-03-21 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00016 7= 01004 8= 02580 Q= 03600
TIME= 14:00:00 DATE= 2000-03-21 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 00067 8= 03533 Q= 03600
TIME= 15:00:00 DATE= 2000-03-21 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 00083 8= 03517 Q= 03600
TIME= 15:01:59 DATE= 2000-03-21 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 00000 8= 00118 Q= 00118
In this example, the receiver tracked six satellites for 19 seconds, seven satellites for
1537 seconds and eight satellites for 2044 seconds for the hour ending 12:00:00. The
"Q" value of 3600 indicates the receiver had tracked at least four qualified satellites for
the entire hour (3600 seconds). Note the partial histogram shown in the time stamp of
15:01:59.
For optimum performance, the receiver should consistently track four or more satellites.
The Q value should typically be 3600 for most entries. Occasional drops below 3600 are
considered acceptable. If the majority of the histograms show tracking less than four
satellites, or Q values less than 3000, the receiver may not provide reliable operation.
Refer to Section 6 Service Information, for recommendations.
Page 2-12
8194 Instruction Manual
2.8
FACTORY CONFIGURATION
Several of the Model 8194 outputs and operational parameters are configurable using the
RS-232 communication port and set-up DIP-switches. Table 2-1 lists the selectable
parameters, factory default, and if it is command or switch selectable. Refer to Section 3,
Operation, for a complete description of the various outputs and set-up switches. Refer
to Section 4, Software Commands, for information on the various commands.
FUNCTION
FACTORY DEFAULT
COMMAND
Antenna Cable Delay
No Delay
ACD
Alarm Timeout AT1
1 Minute
AT1
Alarm Timeout AT2
2.5 Hours
AT2
Alarm Timeout AT3
30 Days
AT3
Event Output
OFF
EO
Signature Control
OFF
SC
Set Mode
OFF
SM
Test Mode
OFF
TM
Time Zone Offset
No Offset
TZO
10-MHz Offset
No Offset
1FO
One PPS Offset
No Offset
1PO
TABLE 2-1 DEFAULT SETTINGS
8194 Instruction Manual
Page 2-13
MODEL 8194
SECTION 3
OPERATION
3.0
INTRODUCTION
3.1
FRONT PANEL FUNCTIONS
3.2
REAR PANEL FUNCTIONS
OPERATION
3.0
INTRODUCTION
This section describes the front and rear panel functions, and operational information for
the Model 8194 GPS Ageless Oscillator.
3.1
FRONT PANEL FUNCTIONS
The front panel of the Model 8194 is shown in Figure 3-1. The paragraphs below
describe the indicators and connectors found on the front panel.
3.1.1
Status Lamps
3.1.1.1
Power
This green lamp indicates that the unit is connected to the primary power source and is
turned on.
3.1.1.2
Tracking GPS
During initial operation the TRACKING GPS lamp turns on when the receiver has
tracked at least four qualified satellites for one minute. The lamp turns off when fewer
than four qualified satellites are tracked and Alarm Timeout 1, AT1, expires. The lamp
turns back on when at least four satellites are reacquired and qualified for one minute.
3.1.1.3
Oscillator Locked
The green OSC LOCKED lamp is off during start-up. The lamp turns on when the
standard oscillator is phase locked to the GPS reference. Entering a new frequency
offset, an Alarm Timeout 2 (AT2) or Frequency alarm turns this lamp off until oscillator
phase lock is achieved.
3.1.2
Alarm Lamps
The Model 8194 divides alarm conditions into two categories, Major and Minor. A
Major Alarm is asserted when fault conditions exist which affect the operation or
accuracy of the unit. A Minor Alarm warns of conditions having no immediate effect on
total operation, but may require corrective action.
8194 Instruction Manual
Page 3-1
Section 3: Operation ______________________________________________
Major and Minor Alarm conditions are communicated by the front panel lamps and relay
contacts on the rear panel Alarm Output connector. In addition Major alarm relay
contacts are found on the Data Clock connector. Alarm status may also be monitored
using the front panel RS-232 communication port. Refer to Section 4 for a complete
listing of alarm status and alarm clearing commands.
3.1.2.1
Major Alarm Lamp
This lamp turns on when any of the Major Alarm condition is present. The lamp turns off
when the fault condition is corrected. A Major Alarm is asserted when the following
conditions exist:
Frequency Error: Measured oscillator frequency error exceeds1 x 10-8 or whenever
an AT2 Alarm is asserted. A frequency alarm is also asserted during start-up.
GPS Tracking Timeout 2: The period of time (AT2) allotted for operation without
tracking a minimum of four qualified satellites has expired. Factory default period is
2.5 hours. An AT2 Alarm is also asserted during start-up.
GPS Tracking Timeout 3: The period of time (AT3) allotted for operation without
tracking a minimum of four qualified satellites has expired. Factory default period is
30 days. An AT3 Alarm is also asserted during start-up.
CPU Fault: The CPU is unable to communicate with the GPS receiver.
Test Mode: Unit has been placed in TEST MODE operation.
Free Run: While in Test Mode, the automatic frequency control feature has been
disabled.
Short Gate: While in Test Mode, gate time has been configured for 10 seconds,
measurement resolution is reduced.
3.1.2.2
Minor Alarm Lamp
This lamp turns on whenever a Minor Alarm condition is present. The lamp turns off
when the fault condition is corrected. A Minor Alarm is asserted when:
Output Fault: No output is detected from one or more of the four rear panel
frequency outputs. The fault could be caused by a shorted cable, reflections due to
an unterminated cable or Signature Control removed the outputs.
Oscillator Adjust: Warns that oscillator is operating within 10% of the minimum or
maximum control setting. The oscillator requires manual adjustment. Refer to
Section 6, Service Information, for the oscillator adjustment procedure.
Page 3-2
8194 Instruction Manual
______________________________________________ Section 3: Operation
FIGURE 3-1 MODEL 8194 FRONT PANEL
8194 Instruction Manual
Page 3-3
Section 3: Operation ______________________________________________
GPS Tracking Timeout 1: The period of time (AT1) allotted for operation
without tracking a minimum of four qualified satellites has expired. Factory default
=1.0 minute. An AT1 Alarm is also asserted during start-up.
Low Quality Alarm: Warns of low GPS signal quality. The alarm is asserted
whenever the "Q" value in the Tracking Histogram is below 3000.
Frequency Offset: An initial or new simulcast offset value has been entered. The
alarm remains active until the standard oscillator has corrected for the offset.
Antenna Problem: Antenna sense circuitry warns when the antenna is not
connected or a cable short or open is detected.
Test Mode: Unit is placed in Test Mode operation.
3.1.3
RS-232 Com
This is the RS-232 serial communication port. Commands to configure selectable
parameters, output operational status and events, and Test Mode functions are entered
here. Refer to Section 4.2 for a complete description of the RS-232 commands and
responses.
The RS-232 COM connector is a 9-pin series D female. Connector pin numbering is
shown in Figure 3-2. Pin assignments are listed in Table 3-1.
The RS-232 Com port transmits and receives ASCII characters at 9600 baud structured as
1 start, 8 data, 1 stop, no parity and xon/xoff flow control.
FIGURE 3-2 RS-232 COM PIN NUMBERING
Page 3-4
8194 Instruction Manual
______________________________________________ Section 3: Operation
PIN
SIGNAL
I/O
DESCRIPTION
2
RXD
O
Receive Data
3
TXD
I
Transmit Data
5
GND
-
Signal Common
6
DSR
O
Data Set Ready
7
RTS
*
Request to Send
8
CTS
*
Clear to Send
*Pins 7 and 8 are connected together internally.
TABLE 3-1 RS-232 COM PIN ASSIGNMENTS
The RS-232 Com port is configured as data communication equipment (DCE). Data is
output on Pin 2, RXD and commands are input on Pin 3, TXD. When interfacing to data
terminal equipment, DTE, (i.e. a personal computer) a one-to-one cable is used.
Interfacing to a DCE requires reversing Pins 2 and 3 or a null modem connection. The
RS-232 COM port does not require hardware handshaking. The Request to Send and
Clear to Send signals are internally connected together, and the DSR signal is held high
through a pull-up resistor.
3.1.4
Frequency Output
This BNC connector outputs a 10-MHz sine wave signal derived from the disciplined
oscillator. The 10-MHz output can be user-configured for simulcast paging. Refer to the
Ten MHz Offset command, 1F0, found in Section 4.2 for additional information.
3.1.5
1PPS Output
This BNC connector outputs a GPS one pulse-per-second TTL-compatible signal. The
leading edge of the signal is the on time point adjusted by any cable or offset delays that
have been user-configured. Refer to the Antenna Cable Delay command, ACD, and the
One PPS Offset command, 1PO, descriptions found in Section 4.2 for additional
information.
8194 Instruction Manual
Page 3-5
Section 3: Operation ______________________________________________
3.2
REAR PANEL FUNCTIONS
The rear panel of the Model 8194 is shown in Figure 3-3. The following paragraphs
describe each of the rear panel functions.
3.2.1
GPS Antenna
This type N connector is the antenna input to the GPS receiver. The Model 8225 GPS
Antenna and the Model 8227 Inline Preamplifier receive operational power, +5 VDC,
from this connector.
3.2.2
Frequency Outputs
The Frequency Outputs are derived from the GPS disciplined oscillator. Four BNC
outputs at 10.0 MHz are provided. The signal is 700 mV rms sinewave into a 50-ohm
load. The harmonic suppression is 30 dB.
3.2.2.1
Signature Control
The Frequency Outputs may be placed under signature control. Signature Control
removes the outputs whenever a Major Alarm occurs. The outputs return when the fault
condition is cleared. The Model 8194 is shipped with this feature disabled. The
Signature Control feature may be enabled using the front panel RS-232 Com port. Refer
to the Signature Control command, SC, found in Section 4, Software Commands.
3.2.2.2
Optional Output
Option 03 adds a 12-volt DC offset to the four rear panel 10 MHz outputs. This option
allows the Model 8194 to drive Spectracom distribution products such as the 8140T
LineTap, 8140MT MultiTap and the Model 8140VT VersaTaps. Refer to Section 5,
Options and Accessories, for a complete description of Option 03 and related accessories.
Page 3-6
8194 Instruction Manual
______________________________________________ Section 3: Operation
FIGURE 3-3 MODEL 8194 REAR PANEL
8194 Instruction Manual
Page 3-7
Section 3: Operation ______________________________________________
3.2.2.3
Simulcast Offsets
In simulcast radio systems, it is desirable to cover large geographic areas with multiple
base station transmitters. Simulcasting requires precise control of transmitter frequencies
to reduce interference between adjacent transmitters on the same channel.
Ineffective transmitter frequency control can reduce system coverage and cause "dead
spots," "false pages," and message distortion. These adverse effects are reduced or
eliminated by providing a carrier frequency offset between adjacent transmitters. The
offset values are selected to minimize co-channel interference. To assure maximum
performance of the system, the effects of transmitter oscillator "aging" must be
neutralized by periodically checking and adjusting the transmitter oscillators to maintain
the desired frequency offsets.
The Spectracom Model 8194 Simulcast Transmitter Offset provides an accurate,
controlled frequency reference that is continuously "frequency locked" to GPS. This
reference can be used by synthesized transmitters to provide "ageless" frequency control,
including offsets, ±1.0 x 10-10.
The simulcast offsets are divided into two groups; Simulcast 1 (SC1) and Simulcast 2
(SC2). Simulcast 1 has offset steps sized for UHF as listed in
Table 3-2. Simulcast 2 has offset steps sized for VHF Hi as listed in Table 3-3. Within
each group exist four positive offset steps and the complimentary negative offset steps.
The simulcast offsets are selected using software commands. Refer to the
10-MHz Offset command, 1F0, found in Section 4 for additional information.
Offset Name
Offset ∆fs
Output Frequency
Offset @
450 MHz
SC1 + 1
+1.1E-9
10,000,000.011 Hz
+0.5 Hz
SC1 + 2
+2.2E-9
10,000,000.022 Hz
+1.0 Hz
SC1 + 3
+3.3E-9
10,000,000.033 Hz
+1.5 Hz
SC1 + 4
+4.4E-9
10,000,000.044 Hz
+2.0 Hz
SC1 - 1
-1.1E-9
9,999,999.989 Hz
-0.5 Hz
SC1 - 2
-2.2E-9
9,999,999.978 Hz
-1.0 Hz
SC1 - 3
-3.3E-9
9,999,999.967 Hz
-1.5 Hz
SC1 - 4
-4.4E-9
9,999,999.956 Hz
-2.0 Hz
TABLE 3-2 UHF SIMULCAST OFFSETS
Page 3-8
8194 Instruction Manual
______________________________________________ Section 3: Operation
Offset ∆fs
Output Frequency
SC2 + 1
+2.0E-8
10,000,000.200 Hz
+3.0 Hz
SC2 + 2
+3.4E-8
10,000,000.340 Hz
+5.0 Hz
SC2 + 3
+4.7E-8
10,000,000.470 Hz
+7.0 Hz
SC2 + 4
+6.0E-8
10,000,000.600 Hz
+9.0 Hz
SC2 - 1
-2.0E-8
9,999,999.800 Hz
-3.0 Hz
SC2 - 2
-3.4E-8
9,999,999.660 Hz
-5.0 Hz
SC2 - 3
-4.7E-8
9,999,999.530 Hz
-7.0 Hz
SC2 - 4
-6.0E-8
9,999,999.400 Hz
-9.0 Hz
Offset Name
Offset @
150 MHz
TABLE 3-3 VHF HI SIMULCAST OFFSETS
The frequency offset at the carrier frequency is determined by the formula:
∆fc = Fc x ∆fs
where:
∆fc = carrier offset
Fc = carrier frequency
∆fs = offset of 10 MHz standard (from the tables)
3.2.3
Data Clock Timing Outputs
This connector provides an RS-485 one pulse per second (1PPS) and Major Alarm relay
contacts. The connector is a 9-pin series D numbered as shown in Figure 3-4. Data
Clock pin assignments are listed in Table 3-4.
FIGURE 3-4 DATA CLOCK CONNECTOR
8194 Instruction Manual
Page 3-9
Section 3: Operation ______________________________________________
PIN
SIGNAL
NOTES
3
+ 1 PPS
RS-485 B Terminal
4
Major Alarm
Ground = Normal
5
Ground
Cable Shield
8
- 1 PPS
RS-485 A Terminal
9
Ground
Cable Shield
TABLE 3-4 DATA CLOCK PIN ASSIGNMENTS
The Data Clock timing signal is derived from the 10 MHz GPS disciplined oscillator.
The 1PPS output is made leading edge synchronized to the GPS 1 PPS output. Using the
1PPS offset command; 1PO, the outputs can be offset from 0 to 1 second in 0.1
microsecond steps. Refer to Section 4 for additional information on the 1PO Command.
3.2.3.1
RS-485 Outputs
RS-485 is a balanced differential transmission requiring twisted pair cable. Cable lengths
up to 4000 feet are possible when using cables specifically designed for RS-485
applications, like Belden 9844 or equivalent. These cables have a braided shield,
nominal impedance of 120 ohms, and a capacitance of 12 to 15 picofarads per foot.
Refer to Figure 3-5 for a schematic representation of an RS-485 line driver. Relative to
RS-485 specifications the A Terminal (-) is negative with respect to the B Terminal (+)
for a Binary 1. The A Terminal (-) is positive to the B Terminal for a Binary 0.
B
A
+
-
RS-485 OUTPUT
FIGURE 3-5 RS-485 LINE DRIVER
The RS-485 output driver can provide a TTL-compatible clock signal when connected in
a single-ended configuration. Connect as shown in Figure 3-6 for a TTL clock reference.
Page 3-10
8194 Instruction Manual
______________________________________________ Section 3: Operation
FIGURE 3-6 SINGLE-ENDED CONNECTION
The 100-ohm termination resistor is required at the cable destination to prevent ringing
and reflections.
3.2.3.2
Major Alarm Relay
Major Alarm status can be monitored using Pin 4 of this connector. Under normal
operation, Pin 4 is connected to ground. When a Major Alarm is asserted, Pin 4 switches
to a high impedance (open circuit). Refer to Section 3.1.2 for a complete description of
Major Alarms.
3.2.4
Alarm Outputs
The Alarm Outputs connector provides relay contact closures for Major and Minor
alarms. Relay contacts are rated at 2 Amps, 30 VDC. The mating 7-position terminal
block, shown in Figure 3-17, is furnished in the ancillary kit.
1
2
3 4
5
6
7
FIGURE 3-7 ALARM OUTPUTS TERMINAL BLOCK
8194 Instruction Manual
Page 3-11
Section 3: Operation ______________________________________________
A Major Alarm is asserted when any of the following Alarm conditions exist:
Frequency, Tracking Alarm 2, Tracking Alarm 3, CPU or the unit is placed in Test Mode.
During normal operation the Major Alarm relay is energized. The energized relay causes
continuity between common contact, Pin 2, and the normally open contact, Pin 3.
A Major Alarm or power failure de-activates the relay causing continuity between
common, Pin 2, and the normally closed contact, Pin 1.
A Minor Alarm is asserted when any of the following alarm conditions exist: Output
Fault, Adjust Oscillator, Tracking Alarm 1, Low GPS Quality, Antenna Problem,
Frequency offset or the unit is placed in Test Mode operation. During normal operation
the Minor Alarm relay is de-activated. This causes continuity between common, Pin 5,
and the normally closed contact, Pin 6.
When a Minor Alarm is asserted the relay is activated causing continuity between
common, Pin 5, and the normally open contact, Pin 4.
Table 3-5 lists the Alarm status and the corresponding contact status. The relay contacts
remain in the alarm condition until the fault is corrected or a Clear Alarm, CA, command
is issued.
ALARM STATUS
PINS SHORTED
PINS OPEN
Major Alarm Off
2,3
1,2
Major Alarm On
1,2
2,3
Minor Alarm Off
5,6
4,5
Minor Alarm On
4,5
5,6
Ground is found on Pin 7
TABLE 3-5 ALARM OPERATION
3.2.6
AC Power
The standard Model 8194 receives primary power from a 90 to 264 VAC 50/60 Hz power
source. A detachable line cord is furnished in the ancillary kit. The supplied line cord is
compatible with AC receptacles (NEMA 5 - 15R) commonly found in the United States
and Canada. Alternate type line cords may be obtained locally. Connect the line cord to
the rear panel AC module and a properly grounded power receptacle.
The AC power module is equipped with a power switch, line voltage selector, EMI
filtering, and a fuse. Figure 3-8, AC POWER MODULE, illustrates fuse replacement.
Page 3-12
8194 Instruction Manual
______________________________________________ Section 3: Operation
The AC fuse requires a 1.5 Amp, 250V Slo-Blo fuse. A spare is found in the ancillary
kit.
230V
115V
NOTE: The Model 8194 accepts the complete range of
90-264 VAC without a change in instrument setup. Do not
change the AC fuse value or line voltage selector. The 115
label must appear in the cover cut-out.
FIGURE 3-8 AC POWER MODULE
3.2.6
Chassis Ground
The chassis ground lug allows the Model 8194 chassis to be connected to an earth ground
in addition to the power line safety ground. Connecting the chassis to a single point
ground system may be required in some installations to ensure optimum lightning
protection. A separate earth ground is also recommended in installations where
excessive noise on the power line degrades the Model 8194 receiver performance.
8194 Instruction Manual
Page 3-13
MODEL 8194
SECTION 4
SOFTWARE COMMANDS
4.0
INTRODUCTION
4.1
RS-232 COMMAND STRUCTURE
4.2
RS-232 COMMAND DESCRIPTIONS
SOFTWARE COMMANDS
4.0
INTRODUCTION
This chapter describes commands that are asserted through the front panel RS-232
COMM port.
4.1
RS-232 COMMANDS
From the front panel RS-232 COMM port the user may configure, control and monitor
the 8194. Table 4-1 lists the RS-232 commands available to provide user access to the
operation of the unit. These commands contain a hierarchy of Read, Set and Test modes.
Figure 4-1 illustrates the Model 8194 command structure. Read Mode is the base level
and when in Read Mode the user may access standard commands. From Read Mode the
user may select to enter Test or Set Mode. Set Mode allows the user to not only access
standard commands, but in addition, allows them to make changes to certain 8194
functions. Test Mode allows the user access to special test commands, as well as all
standard commands. After entering Set Mode or Test Mode, the unit will time out and
return to Read Mode after 15 minutes of inactivity.
Read Mode:
Read Standard
Information
Set Mode On
Test Mode On
Test Mode Off
Set Mode Off
Time Out
Time Out
Set Mode:
Read or Set Standard
Information
Test Mode:
Read or Set Standard
Plus Test Information
Test Mode On
FIGURE 4-1 COMMAND STRUCTURE
8194 Instruction Manual
Page 4-1
Section 4: Software Commands
COMMAND
ACD
ATx
CA
CONF
DAL
DATE
DFM
DOL
DH
EO
GSS
H,Help,?
LOC
SC
SM
STAT
TIME
TM
TZO
U2G
VER
1FO
1PO
DESCRIPTION
Antenna Cable Delay
Alarm Time Out
Clear Alarms
Configuration
Display Alarm Log
Date
Display Frequency Measurement
Display Oscillator Log
Display Tracking Histogram
Event Output
GPS Signal Status
Help
Location
Signature Control
Set Mode
Status Information
Time
Test Mode
Time Zone
UTC to GPS Time Offset
Version
Frequency Offset
One PPS Offset
MODE
READ/SET
READ/SET
SET
READ
READ
READ/SET
READ
READ/TEST
READ/TEST
READ/SET
READ
READ
READ/SET
SET
--READ
READ/SET
--READ/SET
READ
READ
READ/SET
READ/SET
SECTION
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
4.2.8
4.2.9
4.2.10
4.2.11
4.2.12
4.2.13
4.2.14
4.2.15
4.2.16
4.2.17
4.2.18
4.2.19
4.2.20
4.2.21
4.2.22
4.2.23
TABLE 4-1 ALPHABETICAL LIST OF RS-232 COMMANDS
4.2
RS-232 COMMAND DESCRIPTIONS
In the following command descriptions, characters in Bold Italics are keys typed by the
user. Terminate all command lines with the enter key. The enter key is represented by
<ent>. The responses from the Model 8194 are in Italics. A new line is represented by
the carriage return symbol <cr> . Configure the terminal for ANSI, 9600 baud and
xon/xoff flow control. The character structure is ASCII, 1 start, 8 data, 1 stop and no
parity.
Page 4-2
8194 Instruction Manual
Section 4: Software Commands
4.2.1
ANTENNA CABLE DELAY
The command, ACD, reads or sets the antenna cable delay value expressed in
microseconds. The on-time point is offset by the delay value entered to compensate for
antenna cable and in-line amplifier delays. The expected cable and amplifier delays are
typically negligible. The ACD command is intended for advanced user setup. The
advanced user can calculate the delay based upon the cable manufacturer’s specifications.
Range:
Default Value:
Resolution:
0.000 to 999.999 microseconds
0.000 microseconds
1 nanosecond
To read the antenna cable delay, issue the ACD command as shown below:
Type:
Response:
Where:
ACD <ent>
ANT CABLE DELAY = XXXXXX.XXX MICROSECONDS
XXXXXX.XXX = 000000.000 to 000999.999 microseconds.
To enter a cable delay, place the clock in Set Mode operation, issue the ACD command as
follows:
Type:
Where:
ACD XXXXXX.XXX <ent>
XXXXXX.XXX = 000000.000 to 000999.999 microseconds.
NOTE: It is not necessary to fill every digit space when
entering a delay value. The delay value can range from 1
to 9 digits long.
The clock then responds with the antenna cable delay value entered.
Example, The calculated cable delay for 100 feet of LMR-400 cable is 119 nanoseconds.
Follow the example below to compensate the on-time point by the antenna cable delay.
Type:
Response:
Type:
Response:
SM ON <ent>
SET MODE ON
ACD 0.119 <ent>
ANT CABLE DELAY = 000000.119 MICROSECONDS
Cable delay can be calculated using the formula:
D = LxC
V
Where:
D = Cable delay in nanoseconds.
L = Cable length in feet.
C = Constant derived from velocity of light; 1.016.
V = Nominal velocity of propagation expressed as a
decimal, ex. 85% = .85
Value is provided by cable manufacturer.
8194 Instruction Manual
Page 4-3
Section 4: Software Commands
4.2.2
ALARM TIMEOUTS
The command ATx reads or sets the time out period allotted for tracking alarms AT1,
AT2 and AT3. The default time out periods are AT1 = 1 minute, AT2 = 2 1/2 hours, and
AT3 = 30 days. When the receiver is unable to track at least four qualified satellites a
count down timer is started. If the receiver is unable to reacquire qualified satellites
within the assigned time out periods the expired time out alarm is asserted. An AT1
alarm is classified as a Minor alarm. AT2 and AT3 are Major alarms. To read the
current time out values issue the ATx command as follows:
Type:
Response:
ATx <ent>
Where x = 1, 2, 3.
ALARM TIMEOUT x = DDD HH:MM:SS
Where x = 1, 2, 3
DDD = Days 000 … 366
HH = Hours 00 … 23
: = Colon Separator
MM = Minutes 00 … 59
SS = Seconds 00 …59
To Change the alarm time out periods place the unit in set mode and issue the ATx
command as shown below:
Type:
Response:
Page 4-4
ATx DDD HH:MM:SS
ALARM TIMEOUT x = DDD HH: MM:SS
8194 Instruction Manual
Section 4: Software Commands
4.2.3
CLEAR ALARM
The Clear Alarm command, CA, resets the Major and Minor Alarm relays even though
the fault conditions are still present. If a new alarm condition arises the appropriate
alarm relay will be reasserted. The front panel alarm lamps are not reset by this
command. The indicator alarm lamps remain on until the fault condition is corrected.
When a CA command is issued the unit responds with a change in status report. This
report time stamps when the relays were reset and lists the active alarms.
To reset the alarm relays, place the unit in Set Mode and issue the CA command as
follows:
Type: CA<ent>
Example Response:
TIME= 13:44:06 DATE= 2001-11-03 STATUS CHANGE <TEMP= +36.0>
COOLING FAN= OFF
ALARM RELAYS: MAJOR= OFF MINOR= OFF
ACTIVE ALARMS: MAJOR
FREQUENCY
8194 Instruction Manual
Page 4-5
Section 4: Software Commands
4.2.4
CONFIGURATION
The Configuration command, CONF, provides a listing of all user selectable parameters
and their current values. The RS-485 address and baud rate selection is made using the
rear panel set up switches. All other parameters are configured using RS-232 or RS-485
command sets.
To retrieve configuration information issue the CONF command as shown below:
TYPE:
CONF<ent>
Default Response: TIME ZONE= +00:00
1PPS OFFSET= 000000.000 MICROSECONDS
ANT CABLE DELAY= 000000.000 MICROSECONDS
10 MHZ OFFSET= NONE
SIGNATURE CONTROL= OFF
EVENT OUTPUT= ON
RS-485 ADDRESS= 00 BAUD RATE= 9600
ALARM TIME OUT 1= 000 00:01:00
ALARM TIME OUT 2= 000 02:30:00
ALARM TIME OUT 3= 030 00:00:00
Page 4-6
8194 Instruction Manual
Section 4: Software Commands
4.2.5
DISPLAY ALARM LOG
An alarm log entry is made each time there is a change in the alarm relay status. The
alarm log can be viewed by using the Display Alarm Log command DAL. The log
contains a time and date stamp of when the alarm status change occurred, alarm relay
status and active alarms.
To retrieve the alarm log issue the DAL command as shown below:
Type:
DAL<ent>
Example Response:
TIME= 12:57:53 DATE= 2001-11-03 STATUS CHANGE <TEMP= +43.0>
COOLING FAN= OFF
ALARM RELAYS: MAJOR= OFF MINOR= ON
ACTIVE ALARMS: MINOR
ANTENNA PROBLEM
TIME= 12:58:54 DATE= 2001-11-03 STATUS CHANGE <TEMP= +43.5>
COOLING FAN= OFF
ALARM RELAYS: MAJOR= OFF MINOR= ON
ACTIVE ALARMS: MINOR
TRACKING ALARM 1
ANTENNA PROBLEM
TIME= 13:00:39 DATE= 2001-11-03 STATUS CHANGE <TEMP= +43.5>
COOLING FAN= OFF
ALARM RELAYS: MAJOR= OFF MINOR= OFF
ACTIVE ALARMS: NONE
8194 Instruction Manual
Page 4-7
Section 4: Software Commands
4.2.6
DATE
The DATE command reads or sets the date of the Model 8194. To retrieve the current
UTC date, issue the DATE command as shown below:
Type:
Response:
Where:
DATE <ent>
DATE = YYYY - MM - DD
YYYY = Year value, 1999, 2000, etc.
MM = Month value, 01 to 12, 01= January, 04= April
DD = Day of the month, 01 to 31
- = Hyphen
To set the date, place the clock in Set Mode, then issue the DATE command as follows:
Type:
Where:
DATE YYYY-MM-DD <ent>
YYYY-MM-DD = As defined above.
The clock responds with the date message reflecting the date entered.
NOTE: The date can not be set on receivers tracking GPS
satellites. The set date is overwritten with the received date
information.
Example:
Set the date for May 9, 2001.
Type:
Response:
Type:
Response:
Page 4-8
SM ON <ent>
SET MODE ON
DATE 2001-05-09 <ent>
DATE =2001-05-09
8194 Instruction Manual
Section 4: Software Commands
4.2.7
DISPLAY FREQUENCY MEASUREMENT
The average 24-hour frequency accuracy can be displayed using the DFM command.
The frequency accuracy is determined by subtracting the accumulated phase drift
measured at midnight from the previous midnight value. To display the last frequency
measurement, issue the DFM command as shown below:
Type:
Example Response:
DFM <ent>
DFM
DRIFT = 0003 ns = 3.5E-14 2001-11-03
Adding the "ALL" parameter to the DFM command displays up to 5 days of accuracy
measurement.:
Type:
Example Response:
DFM ALL <ent>
DRIFT = 0024 ns = 2.7E-13 2000-03-22
DRIFT = 0060 ns = 6.9E-13 2000-03-23
DRIFT = 0003 ns = 3.5E-14 2001-11-03
If the phase lock process was interrupted, the message "NOT AVAILABLE" will appear in
the response.
8194 Instruction Manual
Page 4-9
Section 4: Software Commands
4.2.8
DISPLAY OSCILLATOR LOG
The Oscillator Log is a compilation of the last 25 log entries made, or approximately one
hour's worth of data. In Test Mode the number of entries is expanded to 1,278, or
approximately 3.5 days worth of data. Due to the large number of entries, this command
is available with a page parameter [P]. This allows the log to be output one page at a
time with an option to continue or exit after each page.
The Oscillator log can be used to determine overall receiver and oscillator performance.
There are 14 different log entries, which may be included in the current oscillator log
response. These are listed below:
1. Frequency Measurement: occurs every 1000 seconds and reports frequency
error.
2. Automatic Frequency adjustment: when 3 of last 4 frequency measurements agree to
within 6 parts in 10-10 an adjustment is made. These adjustments only occur during
the frequency lock process NOT during phase lock.
3. Manual DAC adjustment: occurs when the Test Mode command DA is used to alter
the DAC setting.
4. Reset: occurs when the Test Mode reset command is used to reset the GPS receiver,
gates, RAM contents, etc.
5. Start-up: occurs at power on.
6. First satellite found: occurs when the 8194 detects a satellite for the first time since
power on. This entry does not happen after a loss of satellites.
7. 3D-Fix: This occurs when the GPS receiver has a 3D-Fix for a period of 1 minute.
When the unit is powered on this message coincides with the turning on of the
Tracking GPS light. Throughout operation if the unit loses a 3D-Fix and regains it
for 60 consecutive seconds this entry will occur again. Also, in the phase process the
unit is in position hold, if the receiver drops to less than 4 qualified satellites it is
considered to have lost a 3D-Fix. A log entry will occur when the receiver tracks 4
qualified satellites for 60 consecutive seconds. Once an initial 3D-Fix is acquired
these log entries are inconsequential unless all satellites are lost. If a lot of 3D-Fix
entries are in the log there is a reception problem.
8. Battery Check: occurs at 00:00:00 every day or when initiated by the Test Mode
command TB.
9. Phase Calibration: occurs at initial entrance to the phase process and every 15 hours
after.
10. Tight Phase Lock: occurs shortly after Phase Calibration.
Page 4-10
8194 Instruction Manual
Section 4: Software Commands
11. Phase Center adjust: occurs every 5 hours after Phase Calibration.
12. 24 hour phase measurement: occurs at 00:00:00 every day while in Phase Lock.
13. Phase adjustment: occurs every 6 minutes.
14. Free Run Test: this is a factory test procedure to verify the stability of the ovenized
oscillator.
15. Rubidium Lock Status: not applicable to the Model 8194.
16. Exit From Phase Lock: provides the reason the unit exited from the phase lock
process. The possible causes are tracking 0 satellites, CPU alarm, Frequency Error
>1.0x10-9 or Frequency Offset selected.
To retrieve the Oscillator Log issue the DOL command as shown below:
Type:
DOL<ent>
or
DOL P <ent> Paged Output
Example Response:
SPECTRACOM CORPORATION GPS DISCIPLINED OSCILLATOR 8194
SOFTWARE VERSION 1.00 DATE:OCTOBER 09, 2001 10:12:03
UNIT STARTED 12:47:07 2001-11-03
BAUD GENERATOR 1 = VERSION 2.01
BAUD GENERATOR 2 = VERSION 2.01
BAUD GENERATOR 3 = VERSION 2.01
GPS RECEIVER = 8 CHANNEL UT VERSION 3
TIME= 11:34:43 DATE= 2001-11-03 PHASE ADJUSTMENT
AVG LEN= 0168 TOTAL= 0001653A
DAC= B201(69%) TEMPERATURE= +37.5
PHASE ERROR= +129.55 nSEC
TIME= 11:36:07 DATE= 2001-11-03 D/A= B201(69%) FREQ ERROR=
+1.00E-10
LONG GATE 10MHZ OFFSET= NONE INTERNAL TEMP= +37.5
FREQ CNT= 10,000,000,001
TIME= 11:40:43 DATE= 2001-11-03 PHASE ADJUSTMENT
AVG LEN= 0168 TOTAL= 00012001
DAC= B1FE(69%) TEMPERATURE= +37.5
PHASE ERROR= +104.44 nSEC
MORE<ANY> QUIT<ESC>
8194 Instruction Manual
Page 4-11
Section 4: Software Commands
When in Test Mode, the oscillator log can be sorted for a specific log entry type. Each
log entry type is assigned a number, 1 through 16, as shown in the above description.
Logs may also be viewed from a specified time and date parameter. The DOL response
may be sorted using the command structure shown below:
Type:
Where:
DOL P TYPE YYYY-MM-DDD HH:MM:SS <ent>
P=
Type =
YYYY-MM-DD =
HH:MM:SS =
Page 4-12
Paged parameter
Log entry type, 1 through 14.
Start date of sort
Start time of sort
8194 Instruction Manual
Section 4: Software Commands
4.2.9
DISPLAY TRACKING HISTOGRAM
The Display Histogram command, DH, provides the tracking histogram. The histogram
records the number of satellites tracked each second. At the end of every hour a log entry
is created and the counters start again. In Read Mode the command responds with the
last four entries of the histogram and current histogram in process. While in Test Mode,
this command responds with the entire histogram log, which provides tracking data
collected over the past six days. The page parameter, P, causes the histogram to display
one page at a time. In paged mode the user may quit or continue the display after each
page is displayed. The tracking histogram is useful in verifying receiver and antenna
performance.
Type:
DH <ent>
- OR DH P <ent> (paged output)
The tracking histogram is output in the following format:
TIME= HH:MM:SS DATE= YYYY-MM-DD TRACKING HISTOGRAM
0= XXXXX 1= XXXXX 2= XXXXX 3= XXXXX 4= XXXXX
5= XXXXX 6= XXXXX 7= XXXXX 8= XXXXX Q=QQQQQ
Where:
HH:MM:SS =
YYYY-MM-DD =
XXXXX =
QQQQQ =
8194 Instruction Manual
UTC time log was created.
Date log was created.
Number of seconds the receiver tracked the
listed quantity of satellites since the
beginning of the hour, 0...3600.
Number of seconds since the beginning of
the hour the GPS signal was qualified,
0…3600.
Page 4-13
Section 4: Software Commands
Example: To view the satellite tracking histogram type the following:
Type:
Response:
DH <ent>
TIME= 10:00:00 DATE= 2001-11-03 TRACKING HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 02878 8= 00722 Q= 03600
TIME= 11:00:00 DATE= 2001-11-03 TRACKING HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00055 7= 02478 8= 01067 Q= 03600
TIME= 12:00:00 DATE= 2001-11-03 TRACKING HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 00724 8= 02876 Q= 03600
TIME= 13:00:00 DATE= 2001-11-03 TRACKING HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 00061 8= 03539 Q= 03600
TIME= 13:54:18 DATE= 2001-11-03 TRACKING HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 00008 8= 03249 Q= 03257
END OF LOG
Page 4-14
8194 Instruction Manual
Section 4: Software Commands
4.2.10
EVENT OUTPUT
The Model 8194 maintains logs on alarm conditions, satellite tracking, oscillator
performance and corrections. Entries made to these logs are automatically output to the
RS-232 port they are generated. The Event Output command, EO, can enable or disable
the automatic output of these entries. The Model 8194 is factory shipped with the event
output disabled.
To view the Event Output configuration issue the EO command as follows:
Type:
Response:
EO<ent>
EVENT OUTPUT ENABLED
- OR EVENT OUTPUT DISABLED
To enable or disable the Event Output feature, place the unit in Set Mode and issue the
following command:
Type:
Response:
EO ON<ent>
Type:
Response:
EO OFF<ent>
EVENT OUTPUT ENABLED
- OR EVENT OUTPUT DISABLED
8194 Instruction Manual
Page 4-15
Section 4: Software Commands
4.2.11
GPS SIGNAL STATUS
The GPS Signal Status command, GSS, lists the parameters used in qualifying the
received GPS signal. This command is useful in verifying proper antenna placement and
receiver performance in an installation.
The GSS response provides overall tracking and mode status, as well as a table
containing individual satellite date.
Issue the GPS Signal Status command as shown below:
Type:
GSS<ent>
An example response is shown below:
TRACKING 8 SATELLITES
GPS STATE= POS-HOLD DOP= 00.0
LATITUDE= N 43 07 01.942 LONGITUDE= W 077 29 15.050 HEIGHT= +00095 METERS
QUALITY= PASSED
CHAN VID MODE STREN STAT
01
08 08
050
A2
02
27 08
049
A2
03
31 08
052
A2
04
03 08
048
A2
05
15 08
051
A2
06
18 08
051
A2
07
13 08
049
A2
08
19 08
051
A2
The overall tracking and mode status is presented in the format shown below:
TRACKING N SATELLITES
GPS STATE = SSSSS DOP=##.#
QUALITY = QQQQQ
WHERE:
N=
SSSSS =
##.# =
QQQQQ =
Page 4-16
Number of satellites currently tracking, 0…8.
Fix Mode, 2-D fix, 3-D fix, Hold, Other
Dilution of Precision, 00.0…99.9.
This value indicates the degree of uncertainty in a position fix. When in Position Hold
Mode, this value shall be 00.0. In all other Fix Modes, the lower the DOP value,
except 00.0, the lower the degree of uncertainty.
Results of GPS qualification, Passed, Failed.
The received quality of the GPS signal is continuously monitored. The criteria used in
qualifying the GPS signal is listed below:
Dilution of Precision, 0 ≤DOP<10
Vehicle Identification Number, VID>1
Channel Tracking Mode, MODE=08
Relative Signal Strength, STREN>40
Position Fix Bit Set, BIT7=1
8194 Instruction Manual
Section 4: Software Commands
The GPS signal is qualified whenever four or more satellites meet the above criteria for
one minute.
Information on each satellite the receiver is currently tracking is presented in table form.
The table columns are described below:
CHAN =
VID =
MODE =
Where:
Example:
Channel Number of the GPS receiver, 01...08
Vehicle (satellite) Identification Number, 01...37
Channel Tracking Mode, 01...08.
00 - Code Search 05 - Message Sync Detect
01 - Code Acquire 06 - Satellite Time Avail
02 - AGC Set
07 - Ephemeris Acquire
03 - Freq Acquire 08 - Avail for Position
04 - Bit Sync Detect
STREN =
Signal strength value relative to SNR, 00...55. The higher the
number, the greater the received signal. The minimum
acceptable level is 40.
STAT =
Channel status flag. Convert the hexadecimal code word to
binary to find the status flags set.
(MSB)
Bit 7: Using for Position Fix
Bit 6: Satellite Momentum Alert Flag
Bit 5: Satellite Anti-Spoof Flag Set
Bit 4: Satellite Reported Unhealthy
Bit 3: Satellite Reported Inaccurate (>16 meters)
Bit 2: Spare
Bit 1: Spare
(LSB)
Bit 0: Parity Error
HEX code word A0 translates to the following flags set.
Bit 7: Using for Position Fix
Bit 5: Satellite Anti-Spoof Flag Set
8194 Instruction Manual
Page 4-17
Section 4: Software Commands
4.2.12
HELP
Help provides a list of commonly used commands and command parameters. Help is
available by using the following commands:
Type:
HELP <ent>
- OR -
? <ent>
- OR -
H <ent>
Response:
SPECTRACOM CORPORATION GPS DISCIPLINED OSCILLATOR 8194
COMMAND LIST FOLLOWS (SET MODE MUST BE ON TO CHANGE PARAMETERS)
CONF= DISPLAY THE CONFIGURATION <DC>
DAL [P]= DISPLAY ALARM LOG <DP>
DOL [P]= DISPLAY THE PERFORMANCE LOG, DFM= DAILY FREQUENCY MEASUREMENT
DH [P]= DISPLAY THE HISTOGRAM LOG
STAT= DISPLAY STATUS INFORMATION <DS>
GSS= GPS SIGNAL STATUS <DSS> <SS>
DATE [YYYY-MM-DD]= CURRENT DATE <D>
TIME [HH:MM:SS]= CURRENT TIME <T>, U2G= UTC TO GPS OFFSET
TZO [+/-HH:MM]= READ OR SET THE TIME ZONE
LOC [D DD MM SS.sss D DDD MM SS.sss]= CURRENT LOCATION
1PO [XXXXXX.XXX]= 1PPS OFFSET
ACD [XXX.XXX]= ANTENNA CABLE DELAY
1FO [SCn so]= 10MHZ OFFSET
ATx [DDD HH:MM:SS]= ALARM TIME OUTS x= 1,2 OR 3
SC [ON|OFF]= SIGNATURE CONTROL
CA= CLEAR ALARMS
EO [ON|OFF]= EVENT OUTPUT
SM [ON|OFF]= SET MODE
VER= SOFTWARE VERSION NUMBERS
FOR FURTHER INFORMATION PLEASE CONSULT YOUR MANUAL
Page 4-18
8194 Instruction Manual
Section 4: Software Commands
4.2.13
LOCATION
The command, LOC, is for reading or setting the current location of the receiver. This
command displays the current latitude and longitude calculated by the GPS receiver.
During initial installation it may speed up the time to first fix if the user inputs an
approximate position using this command. The GPS receiver constantly calculates its
position based on the satellites it is receiving. Once the unit has acquired its first fix,
entering a new position using this command has no effect. Also, after initial installation
the receiver will keep its current position in Non-Volatile RAM so that on subsequent
power cycles the unit will reach first fix much faster than at initial installation.
To view the current receiver location, issue the LOC command as shown below:
Type:
Example Response:
LOC <ent>
CURRENT LOCATION:LATITUDE = N 43 07 00.407 LONGITUDE = W 077 29 13.442
To enter a new location place the clock in Set Mode and issue the LOC command as
follows:
Type:
LOC [N:S] [DD MM SS.SSS][E:W] [DDD MM SS.SSS] <ent>
Where:
N =
S =
DD MM SS.SSS =
E =
W =
DD MM SS.SSS =
8194 Instruction Manual
North Latitude
South Latitude
Latitude Degrees:Minutes:Seconds
East Longitude
West Longitude
Longitude Degrees:Minutes:Seconds
Page 4-19
Section 4: Software Commands
4.2.14
SIGNATURE CONTROL
The command SC reads or selects the Signature Control feature. Signature Control
removes the front and rear panel 10-MHz outputs whenever a Major Alarm is asserted.
The Model 8194 is factory shipped with Signature Control off.
To read the Signature Control configuration issue the SC command as follows:
Type:
Response:
SC <ent>
SIGNATURE CONTROL ON
- OR SIGNATURE CONTROL OFF
To configure Signature Control place the unit in Set Mode and issue the SC command as
shown below:
Type:
Response:
SC ON <ent>
SIGNATURE CONTROL ON
- OR -
Type:
Response:
Page 4-20
SC OFF <ent>
SIGNATURE CONTROL OFF
8194 Instruction Manual
Section 4: Software Commands
4.2.15
SET MODE
This command is used to read or enter Set Mode operation. As a safeguard, the unit must
be placed into Set Mode whenever operational parameters are entered. The units “times
out” of Set Mode and returns to Read Mode operation if no commands are issued for 15
minutes. To read the Set Mode status (ON or OFF), issue the SM command as shown
below:
Type:
Response:
SM <ent>
SET MODE ON
- OR SET MODE OFF
To place the unit into Set Mode:
Type:
Response:
SM ON <ent>
SET MODE ON
To return the unit to Read Mode:
Type:
Response:
SM OFF <ent>
SET MODE OFF
8194 Instruction Manual
Page 4-21
Section 4: Software Commands
4.2.16
STATUS INFORMATION
The STAT command provides the current operational status of the Model 8194. The
Status Log includes a time and date stamp, oscillator status, GPS tracking status,
position, temperature, and alarm status.
To retrieve operational status information issue the STAT command as follows:
Type:
STAT <ent>
-ORDS <ent>
Example Response:
TIME= 14:54:18 DATE= 2001-11-03
OSCILLATOR STATUS= LOCKED
GPS SIGNAL= QUALIFIED
INTERNAL TEMP= +37.5 DEGREES C
ALARM RELAYS: MAJOR= OFF
MINOR= OFF
ACTIVE ALARMS: NONE
Page 4-22
8194 Instruction Manual
Section 4: Software Commands
4.2.17
TIME
The command, TIME, reads or sets the time of the Model 8194.
To retrieve the current UTC time, issue the TIME command as shown below:
Type:
Response:
Where:
TIME <ent>
TIME = HH:MM:SS
HH =
UTC hours 00...23
MM = Minutes 00...59
SS = Seconds 00...60
To set the time, place the clock in Set Mode and issue the TIME command as follows:
Type:
Where:
TIME HH:MM:SS <ent>
HH:MM:SS = As defined above.
The clock responds with a time message reflecting the time entered.
NOTE: Receivers tracking GPS satellites can not be set
using this command. The received time data overwrites the
set time.
Example:
Manually set the TIME 13:45:00.
Type:
Response:
Type:
Response:
SM ON <ent>
SET MODE ON
TIME 13:45:00 <ent>
TIME = 13:45:00
8194 Instruction Manual
Page 4-23
Section 4: Software Commands
4.2.18
TEST MODE
This command is used to read or enter Test Mode operation. Test Mode commands are
used in factory testing and field trouble shooting. The unit “times out” of Test Mode and
returns to Read Mode operation if no commands are issued for 15 minutes. Major and
Minor alarms are asserted whenever the clock is in Test Mode.
To read the Test Mode status ( ON or OFF), issue the TM command as shown below:
Type:
Response:
TM <ent>
TEST MODE ON
- OR TEST MODE OFF
To place the clock into Test Mode operation, issue the TM command as follows:
Type:
Response:
TM ON <ent>
TIME= 14:57:54 DATE= 2001-11-03 STATUS CHANGE <TEMP= +37.5>
COOLING FAN= OFF
ALARM RELAYS: MAJOR= ON MINOR= ON
ACTIVE ALARMS: MAJOR
IN TEST MODE
- OR TEST MODE= ON
Page 4-24
8194 Instruction Manual
Section 4: Software Commands
4.2.19
TIME ZONE OFFSET
The TZO command reads or sets a Time Zone Offset value from UTC. This command
allows all time stamps provided by the Model 8194 to reflect local time.
NOTE: Daylight saving time corrections are not
automatically performed. DST/STD time changes requires
changing the Time Zone Offset value.
The factory default value is +00:00 offset from UTC.
Table 4-2 lists the North American Time Zone offset values for periods of Standard time
and Daylight Saving time.
TIME ZONE
STANDARD TIME
(October -April)
Atlantic
Eastern
Central
Mountain
Pacific
-04:00
-05:00
-06:00
-07:00
-08:00
DAYLIGHT SAVING
TIME
(April - October)
-03:00
-04:00
-05:00
-06:00
-07:00
TABLE 4-2 COMMON OFFSET VALUES
To read the current Time Zone Offset value, issue the TZO command as shown below:
Type:
Response:
Where:
TZO<ent>
Time Zone = SHH:MM
S = + or - offset from UTC
HH = Hours 00 to 12
MM = Minutes 00 to 59
A Time Zone Offset may be entered by placing the unit in set mode and issuing the TZO
command as follows:
Type:
Where:
TZO ± HHMM<ent>
± HHMM = As described above
A response reflecting the selected offset value is output.
8194 Instruction Manual
Page 4-25
Section 4: Software Commands
4.2.20
UTC TO GPS TIME
The U2G command displays the offset in seconds between UTC and GPS times. This
offset is due to leap seconds that have occurred since the GPS system was launched.
To view the UTC to GPS offset, issue the U2G command as shown below:
Type:
Sample Response:
Page 4-26
U2G <ent>
UTC TO GPS OFFSET= +013 SECONDS
8194 Instruction Manual
Section 4: Software Commands
4.2.21
VERSION
The VER command provides the software version levels of the main and baud generator
programs. Included in the response message is the time and date the unit was turned on
and GPS receiver type. To retrieve version information, issue the VER command as
shown below:
Type:
Sample Response:
VER <ent>
VER
SPECTRACOM CORPORATION GPS DISCIPLINED OSCILLATOR 8194
SOFTWARE VERSION 1.00 DATE: OCTOBER 09, 2001 10:12:03
UNIT STARTED 12:47:07 2001-11-03
BAUD GENERATOR 1 = VERSION 0.00
BAUD GENERATOR 2 = VERSION 2.01
BAUD GENERATOR 3 = VERSION 0.00
GPS RECEIVER = 8 CHANNEL UT VERSION 3
8194 Instruction Manual
Page 4-27
Section 4: Software Commands
4.2.22
FREQUENCY OFFSET
The 1FO command allows the user to read or set the 10 MHz offset. The simulcast
offsets are divided into two groups; Simulcast 1 (SC1) and Simulcast 2 (SC2). Simulcast
1 has offset steps sized for UHF as listed in Table 4-3. Simulcast 2 has offset steps sized
for VHF Hi as listed in Table 4-4. Within each group exist four positive offset steps and
the complimentary negative offset steps. Section 5.8 defines the Option 31 TV offset
selections. The default offset value is none.
Offset Name
Offset ∆fs
Output Frequency
Offset @
450 MHz
SC1 + 1
+1.1E-9
10,000,000.011 Hz
+0.5 Hz
SC1 + 2
+2.2E-9
10,000,000.022 Hz
+1.0 Hz
SC1 + 3
+3.3E-9
10,000,000.033 Hz
+1.5 Hz
SC1 + 4
+4.4E-9
10,000,000.044 Hz
+2.0 Hz
SC1 - 1
-1.1E-9
9,999,999.989 Hz
-0.5 Hz
SC1 - 2
-2.2E-9
9,999,999.978 Hz
-1.0 Hz
SC1 - 3
-3.3E-9
9,999,999.967 Hz
-1.5 Hz
SC1 - 4
-4.4E-9
9,999,999.956 Hz
-2.0 Hz
TABLE 4-3 UHF SIMULCAST OFFSETS SC1
Offset ∆fs
Output Frequency
SC2 + 1
+2.0E-8
10,000,000.200 Hz
+3.0 Hz
SC2 + 2
+3.4E-8
10,000,000.340 Hz
+5.0 Hz
SC2 + 3
+4.7E-8
10,000,000.470 Hz
+7.0 Hz
SC2 + 4
+6.0E-8
10,000,000.600 Hz
+9.0 Hz
SC2 - 1
-2.0E-8
9,999,999.800 Hz
-3.0 Hz
SC2 - 2
-3.4E-8
9,999,999.660 Hz
-5.0 Hz
SC2 - 3
-4.7E-8
9,999,999.530 Hz
-7.0 Hz
SC2 - 4
-6.0E-8
9,999,999.400 Hz
-9.0 Hz
Offset Name
Offset @
150 MHz
TABLE 4-4 VHF HI SIMULCAST OFFSETS SC2
Page 4-28
8194 Instruction Manual
Section 4: Software Commands
The frequency offset at the carrier frequency is determined by the formula:
∆fc = Fc x ∆fs
where:
∆fc = carrier offset
Fc = carrier frequency
∆fs = offset of 10 MHz standard (from the tables)
To read the 10 MHz offset value issue the 1FO command as shown below:
Type: 1FO <ent>
Default Response: 10MHZ OFFSET = NONE
To select a 10 MHz simulcast offset, place the unit in Set mode and issue the 1FO
command as follows:
Type: 1FO SCn so<ent>
Where: n = Simulcast Offset Group: 1 or 2.
s = Sign, positive or negative: + or -.
o = Offset #: 1,2,3 or 4.
To remove a 10 MHz simulcast offset and return the unit to no offset operation, place the
unit in Set mode and issue the 1FO command as follows:
Type: 1FO 0<ent>
Examples:
Configure the Model 8194 10 MHz outputs for a VHF 150 MHz simulcast offset of –7
Hz. From Table 4-4 this offset value is equivalent to SC2 –3.
To enter in the 10 MHz offset value place the unit in Set Mode to allow configuration
changes then issue the 1FO command as shown below:
Type:
Response:
Type:
Response:
SM ON <ent>
SET MODE ON
1FO SC2 -3 <ent>
The unit responds with a message stating that Phase Lock
Process has been halted and a frequency offset has been
specified.
8194 Instruction Manual
Page 4-29
Section 4: Software Commands
4.2.23
1PPS OFFSET
The relative phase of the recovered GPS 1PPS output can be offset using the 1PO
command. The offset range is 0 - 1 second in .001 microsecond steps. In addition, the
Data Clock 1PPS output signal is leading edge synchronized to the GPS 1PPS and
therefore, will follow the offset value.
To read the 1PPS offset value issue the 1PO command as shown below:
Type: 1PO <ent>
Default Response: 1PPS Offset = 000000.000 Microseconds
To select a 1PPS offset, place the unit in Set mode and issue the 1PO command as
follows:
Type:
1PO XXXXXX.XXX <ent>
Where:
XXXXXX.XXX = 000000.000 TO 000999.999 microseconds
NOTE: It is not necessary to fill every digit space when
entering an offset value. The offset value can range from 1
to 9 digits long. The maximum offset value is 999.999
microseconds.
Page 4-30
8194 Instruction Manual
MODEL 8194
SECTION 5
OPTIONS AND ACCESSORIES
5.0
INTRODUCTION
5.1
OPTION 02, INTERNAL BATTERY BACKUP
5.2
OPTION 11, RACK MOUNT SLIDES
OPTIONS AND ACCESSORIES
5.0
INTRODUCTION
This section describes the following options and accessories that are available for the Model
8194.
•
Internal Distribution Amplifier - Option 03
•
Slides for Rack Mount - Option 11
5.1
OPTION 03 BUILT IN DISTRIBUTION AMPLIFIER
Option 03 allows counters and synthesizers throughout a facility to use the GPS disciplined
outputs from a Model 8194 as a common time base. Allowing equipment to share an accurate
common time base eliminates the need to buy expensive, high stability time bases for each
instrument or remove them from service for periodic calibration.
Units equipped with Option 03 may drive up to 25 remote stations. Multiple outputs are
provided on the rear panel so that signals may be sent in several different directions. A Line Tap
at each remote station receives DC power and the 10-MHz from the main coaxial trunk line
cable. The signal is buffered then divided to the frequency needed at that station. After filtering,
the signal is available at the Line Tap output. New stations are easily added to the system by
inserting additional Line Taps.
5.1.1
System Components
A frequency distribution system may use Model 8140T Line Taps, Model 8140VT VersaTaps,
Model 8140TA Line Extender Amplifiers or Model 8140MT MultiTaps. The following
paragraphs describe each of these units.
5.1.1.1 Model 8140T Line Taps.
These devices, powered by DC on the coaxial cable, are attached to the coaxial distribution
network and provide an output frequency of 1 MHz, 5 MHz, or 10 MHz.
Input: Buffered high input impedance causes negligible mismatch on main trunk line
distribution cable. Accepts signal levels provided by the base station equipped with Option 03.
Output Level: 600 mV rms sinewave into 50 ohms.
Output Frequencies: 10, 5.0, or 1.0 MHz. Specify frequency for each Line Tap ordered.
Harmonic Distortion of Output: -40 dB.
8194 Instruction Manual
Page 5-1
Section 5: Options and Accessories
Cross talk (Isolation): 80 dB minimum.
Output Phase Noise: Typically less than -130 dB/Hz 1 kHz from carrier for
10 MHz input to base station amplifier.
Line Tap Size: 5.25 L x 2.63 W x 1.71 H inches. (133 L x 67 W x 43 H mm). Mounting hole
pattern: 4.75 x 1.75 inches (121 x 44 mm).
5.1.1.2 Model 8140VT VersaTapTM Frequency Synthesizer
The VersaTapTM is a single-frequency synthesizer whose output is factory-set to any frequency
between 1 kHz and 16 MHz in 1-kHz increments and up to 20 MHz in 2 kHz increments. Some
special frequencies can be furnished, such as the 3.5795454...MHz TV color sub-carrier. Exact
frequencies must be specified at time of order.
Input: Buffered high impedance input. Accepts 10.0 MHz with signal level between 100
millivolts and 5.5 V p-p on a DC voltage of 7 to 12 VDC. The DC current requirement is 110
milliamps at +12 VDC.
Output A: A sine wave of 600 mV rms at the specified frequency into a 50-ohm load for
frequencies greater than 60 kHz. A TTL output for frequencies below 60 kHz with a source
impedance of 50 ohms (SN74S140) driver.
Output B: A TTL output at the specified frequency with a source impedance of 50 ohms
(SN75S140 driver). If the internal jumper, W6, is moved to location W5, Output B is HIGH
when the VersaTapTM is phase locked to the incoming reference and LOW when it is unlocked.
Lock LED: The LED will light when the VersaTapTM is locked to the incoming reference. The
LED will blink if the DC input is low, which may cause the VersaTapTM to malfunction. The
LED will be unlit when the VersaTapTM is not locked to the incoming reference.
VersaTapTM Size: 8.3 L x 4.2 W x 1.7 H inches. (211 L x 107 W x 43 H mm). Mounting hole
pattern 8.88 x 2.75 inches (225.4 x 69.9 mm).
Page 5-2
8194 Instruction Manual
Section 5: Options and Accessories
5.1.1.3 Model 8140TA Line Extender Amplifier
The Line Extender Amplifier must be used to boost the output signal when the coaxial
distribution network is more than 1500 feet (457 m) long. The Line Extender will drive an
additional 1500-feet (457 m) of RG58 coaxial cable with Model 8140 Line Taps installed along
its length.
Two DC-isolated 50-ohm terminators must be used: one at the input tee connector of the Line
Extender Amplifier and one at the far end of the cable connected to the output of the Line
Extender Amplifier.
See the “Typical Interconnection Diagram” at the end of this section for an approved method of
interconnection.
5.1.1.4 Model 8140MT MultiTap
The Spectracom Model 8140MT MultiTap is a programmable frequency divider/buffer. Three
outputs can be configured to the same frequency or set independently. When used as part of
your Spectracom Distribution System it decreases the cost per output and allows future
modifications as requirements change.
Frequency Outputs: Three square wave outputs per MultiTap. 1.5V p-p into 50 ohms. Once a
group is chosen, any divisor in a group may be individually selected.
Table of output divisors:
Group A
1
2
10
50
250
B
C
D
1
2
20
100
500
5
10
50
250
1250
5
10
100
500
2500
For a 10-MHz input, the available outputs in MHz are:
Group A
10.0
5.0
1.0
0.2
0.04
8194 Instruction Manual
B
10.0
5.0
0.5
0.1
0.02
C
2.0
1.0
0.2
0.04
0.008
D
2.0
1.0
0.1
0.02
0.004
Page 5-3
Section 5: Options and Accessories
Power Requirements: When driven by a Distribution Amplifier, the DC load equals three Line
Taps. Option 40, which is required for stand-alone operation, reduces the distribution load to
one Line Tap equivalent, and is required whenever output frequencies are below 100 kHz.
Maximum current is less than 150 mA.
MultiTap size:
5.25L x 2.63W x 1.71H inches.
(133L x 67W x 43H mm)
Mounting hole:
4.75 x 1.75 inches. (121 x 44 mm)
5.1.2
Design of Distribution Networks
This section provides guidelines for using the Option 03 distribution outputs. In planning a
system installation follow the guidelines listed below:
1. A maximum of 25 Line Tap loads may be driven from one base station. More than 25 loads
are not permitted due to power supply limitations and impedance matching. Table 5-1, LINE
TAP LOADS, lists the equivalent number of loads and current each distribution device
consumes. The receiver may provide up to 1.2 Amps total to the distribution network.
DEVICE
8140T All Versions
8140TA
8140VT Standard
8140VT w/Opt 45
8140VT w/Opt 48
8140VT w/Opt 62
8140MT
LOADS
1
1
3
5
4
4
3
CURRENT (mA)
45
45
150
250
200
200
150
TABLE 5-1 LINE TAP LOADS
If more than 25 Line Tap loads are required you may:
Add a Model 8140 Frequency Distribution Amplifier. The Model 8140 contains an internal
power supply and will feed an additional 25 Line Tap loads. A Line Tap is required (typically 10
MHz) to provide the input frequency source to the Model 8140. This “Daisy Chaining” may be
continued indefinitely.
2. Voltage drops and signal attenuation limit the longest trunk line using RG-58 cable to1500
feet (457 m).
Figure 5-1, LINE TAP NUMBER AND DISTANCE CHART, is used to calculate the
number of Line Tap loads that may be used at various distances from the base station.
Page 5-4
8194 Instruction Manual
Section 5: Options and Accessories
For example, if 25 Line Taps are used, their average distance from the amplifier is limited to 750
feet (228 m), using RG-58. Up to 12 Line Taps may be placed at 1500 feet (457 m) on any one
trunk line.
If longer runs are required, you may:
A. Locate the Model 8194 in the geographical center of the installation, running distribution
lines in both directions and achieving a coverage of 3000 linear feet (914 m).
FIGURE 5-1 LINE TAP NUMBER AND DISTANCE CHART - OPTION 03
B. Use a Model 8140TA Line Extender Amplifier at 1500 feet, allowing a further 1500-foot
(457 m) extension of the distribution line. The Model 8140TA counts as one Line Tap
towards the total number allowed. Use a DC-isolated 50-ohm terminator, part number
004490, at the input tee connector and at the end of the extended line section as shown in
the “Typical Interconnection Diagram”, Figure 5-2.
C. Use a Model 8140 Frequency Distribution Amplifier.
3. Each distribution line must be continuous from the base station to the DC isolated 50-ohm
load that must be used at the far end. Line taps are inserted along the distribution line by
using the supplied input tee connector. No branching or “Y” configurations may be used as
this causes impedance mismatch on the line. Anything other than a 50-ohm line impedance
may cause reflections, which can cancel the output waveform at the receiver triggering an
output fault alarm. Refer to the Figure 5-2, TYPICAL INTERCONNECTION DIAGRAM,
for an approved method of interconnection.
4. Four DC-isolated 50-ohm loads are furnished with each unit equipped with Option 03. They
may be found in the ancillary kit that is packed with each unit when it leaves the factory. If
any of these loads are lost, replacements may be purchased from Spectracom. The part
number to order is 004490. Terminators may be placed on any unused distribution output
connector to prevent loss.
8194 Instruction Manual
Page 5-5
Section 5: Options and Accessories
5. Wherever practical, permanently mount the Line Taps to a lab bench or wall nearby. This
avoids their loss or misplacement and discourages people from occasionally disconnecting
them, thus cutting off the signal to stations further down the line.
6. NEVER DIRECTLY CONNECT A DISTRIBUTION LINE TO AN INSTRUMENT; always
use a Line Tap, Multitap or VersaTapTM. Direct connection may damage the instrument or
cause an impedance mismatch on the distribution line.
Model 8194 with
Option 03, Built-In
Frequency
Distribution Amplifier
All 25 loads may be driven by a single output
or distributed among the four outputs. Last tap 1500’
maximum from 8195.
1500 feet maximum
1.0 5.0 10.0 8140MT
MHz MHz MHz (TTL)
Terminate the end of
each distribution line.
8140VT 8140VT
1.544
2.048
MHz
MHz
1500 feet maximum
Any 10-MHz line tap may drive
Model 8140 to drive an additional
25 more line tap loads.
1500 feet maximum
DC Isolated 50-ohm
terminator, P/N 004490
8140TA
Line Extender
1500 feet maximum
Each line tap output may drive
a counter or a synthesizer
FIGURE 5-2 TYPICAL INTERCONNECTION DIAGRAM
Page 5-6
8194 Instruction Manual
Section 5: Options and Accessories
5.2
OPTION 11 - RACK MOUNT SLIDES
Option 11 allows the Model 8194 to be mounted in a 19-inch rack with slide-out capabilities.
Table 5-2 lists the hardware supplied with Option 11. Verify that these items have been
received. Much of the hardware supplied with this option will not be used.
QUANTITY
DESCRIPTION
1
Right hand slide assembly
1
Left hand slide assembly
2
Adjustable rear support bracket
1
Hardware Pack containing nut plates, small rear support
brackets, and assorted hardware
1
Hardware pack containing PEM nuts and #10-32 x 1/2 truss
head screws
1
Hardware pack containing #10 KEP nuts and #10-32 x 3/8
pan head screws.
TABLE 5-2 OPTION 11 CHECKLIST
Install Option 11 as illustrated in Figure 5-3 and as described below:
1. Remove the chassis section from the right hand slide rail assembly. The right hand assembly
is designated with the letters RH after the manufacturer’s date code label.
Attach the chassis section to the Model 8194 using #10-32 screws. The locking tab must be
towards the rear of the unit.
2. Repeat Step 1 for the left chassis section.
3. Mount the right and left stationary sections into the rack using the appropriate rear support
brackets, nut plates and required hardware.
NOTE: Insert the intermediate section into the stationary section prior
to rack installation.
4. Insert the receiver into the rack assembly. Secure the Model 8194 to the rack using the front
panel mounting holes.
8194 Instruction Manual
Page 5-7
Section 5: Options and Accessories
FIGURE 5-3 SLIDES, OPTION 11
Page 5-8
8194 Instruction Manual
MODEL 8194
SECTION 6
SERVICE INFORMATION
6.0
INTRODUCTION
6.1
RECEPTION TROUBLESHOOTING
6.2
OSCILLATOR ADJUSTMENT
SERVICE INFORMATION
6.0
INTRODUCTION
This section provides information on reception troubleshooting and oscillator adjustment.
6.1
RECEPTION TROUBLESHOOTING
Please review this section prior to calling the Spectracom Customer Service Department.
If the reception problem cannot be solved following the guidelines outlined in this
section, please call for Customer Service at 585-321-5800.
6.1.1
No Reception
Cable or connector problem: Measure the antenna cable resistance to verify the integrity
of the cable and connectors. Remove the antenna cable from the rear panel of the
receiver and measure the resistance from the coax center to shield. Refer to Table 6-1 for
typical resistance values of the antenna and inline amplifier alone and when combined.
DEVICE
RESISTANCE
8225
180 ohms
8227
165 ohms
8225 and 8227
85 ohms
TABLE 6-1 TYPICAL ANTENNA CABLE RESISTANCE VALUES
Failed impulse suppressor: The Model 8226 has a high impedance when measuring
from the center conductor to ground and a low throughput resistance. A failing impulse
suppressor may be tripping prematurely. The easiest way to test the Model 8226 is to
temporarily replace it with a Type N barrel connector. If the receiver begins tracking
satellites within 20 minutes, the impulse suppressor has failed and must be replaced.
Cable length: Excessively long or improper cable type may prevent the receiver from
tracking satellites. Refer to Section 2.2 for GPS cable recommendations.
8194 Instruction Manual
Page 6-1
Section 6: Service Information______________________________________
Antenna location: The antenna must be installed outdoors and have a good view of the
sky. Refer to Section 2.1 for antenna installation guidelines.
GPS reset: In rare occasions, the GPS receiver may require a reset to set the receiver to
default values. The receiver must be placed in Test Mode to issue the GPS Reset
command. Issue the GPS Reset command, RGPS, as shown below:
Type: TM ON <ent>
The unit will respond with a message stating Test Mode has been enabled. During Test
Mode operation, the Major and Minor alarms are asserted.
Type: RGPS <ent>
After an approximate 10 second delay, the receiver responds with a reset status message.
Allow 20 minutes for the receiver to begin tracking satellites.
Receiver location: Setting the current receiver position may assist in obtaining a satellite
fix. To enter a new location place the clock in Set Mode and issue the LOC command as
follows:
Type:
Response:
SM ON <ent>
SET MODE = ON
Type:
LOC [N:S] [DD MM SS.SSS][E:W] [DD MM SSS.SSS]<ent>
where: N =
North Latitude
S=
South Latitude
D MM SS.SSS =
Latitude Degrees:Minutes:Seconds
E=
East Longitude
W=
West Longitude
DD MM SS.SSS =
Longitude Degrees:Minutes:Seconds
NOTE: The approximate location is adequate, zeros may be
used for the seconds values.
Allow 20 minutes for the receiver to begin tracking satellites.
Page 6-2
8194 Instruction Manual
_____________________________________ Section 6: Service Information
6.1.2
Low GPS Quality
Cable Length: Excessively long or improper cable type may cause low GPS quality due
to cable attenuation. Long GPS antenna lengths may require an inline amplifier. Refer to
Section 2.2 for GPS cable recommendations and Section 2.4 for inline amplifier
information.
Antenna location: The antenna must have an unobstructed overhead view of the sky
with views to the horizon. Nearby obstructions can reduce the receiver's ability to track
the maximum number of satellites available. Refer to Section 2.1 for antenna installation
guidelines.
Local interference: One reason for poor reception is harmonics from a local broadcast
interfering with the GPS L1 carrier of 1575.42 MHz. Certain television or FM radio
broadcasts, while operating within their frequency allocation, can cause GPS jamming
due to harmonics of the carrier.
The Model 8194 can be configured to operate in low GPS quality conditions by selecting
an alternate GPS qualifying algorithm. Refer to Appendix A for additional information.
8194 Instruction Manual
Page 6-3
Section 6: Service Information______________________________________
6.2
OSCILLATOR ADJUSTMENT
Over time the Model 8194 oven oscillator may require an adjustment to compensate for
crystal aging. The Model 8194 warns when this adjustment is needed by asserting an
Adjust Oscillator Alarm. This condition activates the Minor Alarm status lamp and
relay. An Adjust Oscillator Alarm is asserted when the frequency controlling D/A
converter approaches a control range limit. Typically, this alarm provides a two to three
month warning before a control range end is reached.
On rare occasions, an oscillator may experience a sudden shift in frequency, causing an
Adjust Oscillator and a Frequency Alarm. When this occurs, both Major and Minor
alarms are activated. The D/A is set to a control range end unable to correct the oscillator
frequency. Frequency error shall exceed 1 x 10-8
This section describes the oscillator adjustment procedure using a frequency counter and
an RS-232 terminal. Upon completing the adjustment procedure, the alarm lamps and
relays are cleared, and the oscillator will reacquire phase lock to the GPS reference.
The frequency counter must have a time base accuracy and measurement resolution of at
least 1 x 10-9 (0.01 Hz at 10 MHz).
A PC running terminal emulation software (HyperTerminal, ProComm Plus, etc.) can be
used as an RS-232 terminal. Configure the terminal for ANSI emulation, 9600 baud and
a character structure of 1 start, 8 data, 1 stop and no parity. Flow control is not required,
although xon/xoff is supported.
6.2.1
Adjustment Procedure
Perform the steps listed below to adjust the 10 MHz OCXO.
NOTE: The oscillator must be powered for at least 1 hour prior
to making this adjustment.
1.
Remove the top cover. Rack mounted units, unless equipped with Option 11,
Rack Mount Slides, must be removed.
2.
Connect the terminal to the Model 8195 RS-232 Comm port.
3.
Connect the frequency counter to the front panel 10-MHz output.
Page 6-4
8194 Instruction Manual
_____________________________________ Section 6: Service Information
4.
Place the Model 8194 in Test Mode by sending the TM command as follows:
Type: TM ON <ent>
Response:
TIME= 16:11:43 DATE= 2000-03-27 STATUS CHANGE <TEMP= +37.0>
COOLING FAN= OFF
ALARM RELAYS: MAJOR= ON MINOR= ON
ACTIVE ALARMS: MAJOR
IN TEST MODE
ADJUST OSCILLATOR
5.
Set the D/A control voltage to its maximum value by sending the SHI
command
Type: SHI<ent>
Response: D/A = FFFF (99%)
6.
Remove the seal screw from the ovenized oscillator. The oscillator is located
on the right side of the front panel circuit board assembly. Insert a flat-bladed
tuning tool into the access hole. Adjust the oscillator for a frequency
measurement of 10,000,002.50 ±.05 Hz.
Replace the seal screw and record the upper limit oscillator frequency.
FHI = _________________________Hz.
7.
Set the D/A control value to its minimum value by sending the SLO
command.
Type: SLO<ent>
Response:
D/A = 0000 (00%)
Record the lower limit oscillator frequency
FLO = _________________________Hz.
8.
Subtract the lower limit frequency, FLO, from the upper limit frequency, FHI,
to determine the pull range of the oscillator. This difference is entered as the
Hertz Range Value.
FHI minus FLO = HR
8194 Instruction Manual
Page 6-5
Section 6: Service Information______________________________________
9.
Enter the hertz range value by sending the HR command as shown below:
Type: HR XXX.XXX
where XXX.XXX = Hertz Range Value
Response: Hertz Range = XXX.XXX D/A = C000
9.
Return the unit to normal operation by taking it out of Test Mode.
Type: TM OFF<ent>
The oscillator adjustment procedure is now complete. Replace the top cover and reinstall
the unit. The Model 8194 will require a two to three hour period to phase lock to the
GPS reference.
Page 6-6
8194 Instruction Manual
MODEL 8194
APPENDIX A
OPERATION WITH LOW GPS QUALITY
A.0
INTRODUCTION
A.1
GPS QUALIFYING ALGORITHM SELECTION
A.2
GQA COMMAND
OPERATION WITH LOW GPS QUALITY
A.0
INTRODUCTION
The Spectracom Model 8194 is often used to provide a reference to transmitters when precise
frequency control is needed. In some installations, the GPS reception has been poor or
intermittent, preventing reliable operation of the disciplined oscillator.
One reason for poor reception is harmonics from a local broadcast interfering with the GPS L1
carrier of 1575.42 MHz. Certain television or FM radio broadcasts, while operating within their
frequency allocation, can cause GPS jamming due to harmonics of the carrier. Television
interference presents a greater challenge due to higher output power, typically 2-3 MW. Table
A-1 lists the potential problem television stations and their respective GPS harmonic.
CHANNEL
HARMONIC
66
2nd
23
3rd
10
8th
7
9th
6
18th & 19th
5
20th
TABLE A-1 TELEVISION STATIONS WITH GPS JAMMING POTENTIAL
FM radio stations, while lower in radiated power, may cause GPS jamming also. Table A-2 lists
the potential problem radio frequencies and their respective GPS harmonic.
FREQUENCY
HARMONIC
104.8 - 105.2
15th
98.3 - 98.7
16th
92.5 - 92.9
17th
87.3 - 87.7
18th
TABLE A-2 FM RADIO FREQUENCIES WITH GPS JAMMING POTENTIAL
Model 8194 Instruction Manual
Page A-1
Appendix A: Operation with Low GPS Quality _________________________________
A.1
GPS QUALIFYING ALGORITHM SELECTION
The Model 8194 is equipped with three selectable GPS qualifying algorithms. The factory
default algorithm is GPS Qualifying Algorithm GQA1. This algorithm places strict requirements
on the received GPS signal. Every second the GPS signal is qualified and receives a pass/fail
quality judgment. Under GQA1, reception is of passing quality when the receiver is tracking at
least four satellites with signal strengths >40 and a Tracking Mode of 08. This rigid qualifying
process is needed to enable the phase locking algorithm. The phase lock algorithm produces
accuracies of ±1 x 10-11 on the disciplined oscillator outputs.
In applications where GPS reception is marginal or intermittent, an alternate GPS qualifying
algorithm may be selected. GPS qualifying algorithms GQA2 and GQA3 permit operation while
tracking only a single satellite. These algorithms do not require a minimum signal strength
threshold. A satellite is qualified for use whenever its Tracking Mode is set to 08.
The number of satellites tracked and their current Tracking Model value can be seen using the
GSS command. Refer to Section 4 of this manual for a complete description of the GSS
command.
GPS Qualifying Algorithm GQA3 initially begins similar to GPS Qualifying Algorithm GQA1.
A minimum of four satellites with signal strengths greater than 40, Tracking Mode of 08 must be
tracked and establish a 3D-fix for 1 minute. At this point, the Tracking GPS lamp will turn on
and the qualifying parameters are reduced to tracking one satellite with a Tracking Mode of 08.
GPS Qualifying Algorithm GQA2 does not require an initial 3D-fix or track more than one
satellite to operate. Select GPS Qualifying Algorithm GQA2 whenever local interference
prevents the receiver from obtaining a 3D-fix. For example, select GQA2 for installations
installed in close proximity to TV channels 66 or 23 transmitters.
NOTE: Selecting GPS Qualifying Algorithm GQA2 or GQA3 changes the
oscillator-disciplining algorithm from phase locking to frequency locking. This
reduces the output accuracy from 1 x 10-11 to 1 x 10-10. This accuracy is sufficient
to meet most transmitter frequency requirements.
A.2
GQA COMMAND
To select the GPS Qualifying Algorithm, a terminal or PC running terminal emulation software
(Hyperterminal, Procomm Plus, etc.) will be needed to communicate with the RS-232 Comm
port. Configure the terminal for ANSI emulation, 9600 baud, and a data structure of 1 start, 8
data, 1 stop and no parity. Flow control is not required, though xon/xoff is supported.
The GQA selection command is aTest Mode command. Place the unit in Test Mode by sending
the following command:
Page A-2
Model 8194 Instruction Manual
Appendix A: Operation with Low GPS Quality
Type:
TM ON <ent>
The unit will respond with an acknowledgement that Test Mode is enabled. To read the current
GQA selection, issue the command as shown below:
Type:
GQA <ent>
Default Response:
GPS Qualifying Algorithm= 1
To change the GQA algorithm, issue the GQA command as follows:
Type:
GQA1 <ent>
or
GQA2 <ent>
The unit will respond with the selected algorithm.
Turn Test Mode operation off as shown below:
Type:
TM OFF <ent>
The unit shall respond with another Change in Status message.
Allow the receiver two to three hours to frequency lock the oscillator to GPS. When the
oscillator is disciplined to GPS, the front panel OSC LOCK lamp turns on and the frequency and
major alarms clear. The unit may now be placed in service.
It is recommended to periodically monitor the reception characteristics to guarantee reliable
operation. Reception quality can easily be verified using the Display Alarm Log command,
DAL. The alarm log records all changes in operational status. Total loss of reception may cause
a tracking alarm to actuate. Tracking Alarm 1 is a minor alarm and is asserted whenever the
GPS signal is lost for one minute. Tracking Alarm 2 is a major alarm, and is asserted whenever
the GPS signal is lost for 2.5 hours. Due to the potentially large number of entries contained in
this log, a page parameter "P" can be added to the command. This allows the log to be output a
page at a time with an option to continue or exit after each page. To retrieve the alarm log, issue
the DAL command as shown below:
Type:
DAL <ent>
or
DAL P <ent> Paged Output
An example of a Tracking Alarm is shown below:
TIME= 18:18:04 DATE= 1999-06-28 STATUS CHANGE <TEMP= +36.5>
COOLING FAN= OFF
ALARM RELAYS: MAJOR= OFF MINOR= ON
ACTIVE ALARMS: MINOR
TRACKING ALARM 1
Search the Alarm Log for the presence of Tracking Alarms, noting the time and date of these
occurrences. An occasional Tracking Alarm 1 is considered acceptable. The presence of
Tracking Alarm 2 represents reception problems and is not acceptable.
Model 8194 Instruction Manual
Page A-3
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