Spectracom Corporation
8194B, 8195B, 8197B
GPS Ageless Master Oscillator Instruction Manual
2-15
2.9.2 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 2.3 for GPS cable recommendations and Section 2.5 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 2.2.1 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 unit can be configured to operate in low GPS quality conditions by selecting an
alternate GPS qualifying algorithm. Refer to Appendix A for additional information.
2.10
Default Factory Configuration
Several of the unit’s outputs and operational parameters are configurable using the RS-
232 communication port and set-up DIP switches. Table 2-3 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 OR SWITCH
Antenna Cable Delay
No Delay
Command, ACD
Alarm Timeout AT1
1 Minute
Command, AT1
Alarm Timeout AT2
2.5 Hours
Command, AT2
Alarm Timeout AT3
30 Days
Command, AT3
CTCSS Tone
67.00 Hz (Option 14 & 17)
Command, CTC
Event Output
OFF
Command, EO
Signature Control
OFF
Command, SC
Set Mode
OFF
Command, SM
Test Mode
OFF
Command, TM
Time Zone Offset
No Offset
Command, TZO
10 MHz Offset
No Offset
Command, 1FO
One PPS Offset
No Offset
Command, 1PO
RS-485 Address
00
Switch selectable
RS-485 Baud Rate
9600
Switch selectable
RS-485 Termination
ON
Switch selectable
Table 2-3 Default Setting
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