Symmetricom XL-GPS, User Manual

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F119 – GPS Receiver Configuration
Once the GPS receiver is a valid time reference, it requires at least one “good current”
satellite to remain a valid time reference. If “good current” GPS satellites become temporarily
unavailable, GPS status changes to unlocked and the XL-GPS stops using the receiver as a
valid time reference.
Typically, when a “good current” satellite becomes available again, GPS status locks and the
receiver becomes a valid time reference almost immediately. Typically, the receiver it does
not need extra time to resolve its current position unless it is being used in a very
mobile/dynamic environment such as an aircraft.
If the unit is powered-cycled, the receiver repeats the complete position and leap-second
acquisition process before GPS status locks.
Note: GPS satellite visibility and signal strength affect the ability of the GPS receiver to lock
and provide valid time to the XL-GPS. Therefore, it is very important to select the
best possible antenna site and follow the recommendations in sections
“Installing the
GPS Antenna” on page 21 , and.
GPS Antenna (OK or Open)
The GPS antenna is powered by a 12-volt current from the ANTENNA connector on the rear
of the XL-GPS. If this circuit is complete (e.g., connected to an antenna) GPS Antenna
status is OK. If the circuit is incomplete (e.g., no antenna, a cable break, or a splitter) the
GPS Antenna status is Open. If circuit detects a short, the receiver opens a relay to
disconnect power from the circuit, and the GPS Antenna status is Open.
GPS Acquisition State
In Time Mode: The system has been instructed by the user that its position will remain in a
static location and has set the GPS mode to Time Mode.
See “F53 – GPS Operation Mode”
on page 79.
• Start Site Survey: The receiver is checking for changes in its saved static position
(occurs after boot).
• Survey Position: If the save static position is determined to be invalid, the receiver
begins to reestablish its current most accurate position.
• Position Hold: The receiver has determined its most accurate position, and is using
this static position to calculate its most accurate time solution.
• Start TRAIM: (for Time Receiver Autonomous Integrity Monitoring) The receiver is in
Position Hold and is monitoring the integrity of the time solution using redundant
satellite measurements in order to eliminate unreliable signal information.
• TRAIM Active: The TRAIM mode is active and working.
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