Nautel NX15, Troubleshooting Manual

Page: 20 / 274

NX25/NX15 Troubleshooting Manual Responding to alarms
Page 1-12 Issue 5.0 2016-05-06
Controller: GPS Not
Responding This alarm indicates the transmitter is configured to use a GPS
sync PWB as a frequency and phase reference, but the controller
is not receiving communication from the GPS sync PWB. The
alarm will clear when the transmitter is configured to not use the
GPS sync PWB as the frequency and phase reference, or the
controller receives communication from the GPS sync PWB.
Inspect the wiring between the GPS sync PWB and the control/
interface PWB, if applicable. If the wiring is acceptable, replace
the GPS sync PWB (see
“GPS Sync PWB replacement” on
page 1-61 ).
Controller: GPS PLL
Unlocked This alarm indicates the timing phase-lock-loop between the 1
PPS signal from the GPS and the 10 MHz reference is not locked.
This can occur due to a power failure, or because the GPS
receiver is not locked to the GPS satellites. Verify the GPS
antenna is installed and is located in a spot where it is possible to
obtain a GPS satellite lock. If the alarm persists, replace the GPS
sync PWB
(see “GPS Sync PWB replacement” on page 1-61 ).
Controller: GPS
Receiver Not
Responding This alarm occurs when the GPS receiver is not responding to
serial commands on the GPS sync PWB. When this occurs, the
GPS sync PWB's phase-lock-loop will not be locked, and the
timing signals will be free-running. Cycle (turn off, then on) the ac
power to the transmitter. If the alarm persists, replace the GPS
sync PWB (see
“GPS Sync PWB replacement” on page 1-61 ).
Controller: GPS Sync No
1-PPS The alarm occurs when the 1 PPS output from the GPS receiver is
not present. This occurs when the GPS receiver is not locked to
the GPS satellites. When the 1 PPS input is not present, the
phase-lock-loop cannot lock properly to discipline the 10 MHz
reference. Verify the GPS antenna is installed and is located in a
spot where it is possible to obtain a GPS satellite lock. If the alarm
persists, replace the GPS sync PWB (see
“GPS Sync PWB
replacement” on page 1-61 ).
Controller: GPS
Unlocked This alarm occurs when the GPS module on the GPS sync PWB
does not have a valid satellite lock. When this alarm occurs, the
phase-lock-loop is no longer running to discipline the 10 MHz
oscillator, and it is allowed to free-run at the last valid setting.
Verify the GPS antenna is installed and is located in a spot where
it is possible to obtain a GPS satellite lock. If the alarm persists,
replace the GPS sync PWB (see
“GPS Sync PWB replacement”
on page 1-61 ).
Alarm (with Prefix) Description and Troubleshooting Action