Modulator Faults - Comtech EF Data SNM-1001L Installation And Operation Manual

SNM-1001L Satellite Modem
Fault Isolation
9.1.3.2

Modulator Faults

Fault/Alarm
IF SYNTHESIZER
DATA CLOCK SYN
I CHANNEL
Q CHANNEL
AGC LEVEL
MODEM REF ACT
MODULE
CONFIGURATION
MODEM REF PLL
Possible Problem and Action
Modulator IF synthesizer fault.
This is considered a major alarm, and will turn off the modulator output.
Return the modem for repair.
Transmit data clock synthesizer fault.
This fault indicates that the internal clock VCO has not locked to the incoming
data clock, or the internal clock synthesizer has not locked to the internal
reference. This is considered a major alarm, and will turn off the modulator
output. Ensure the proper data rate has been set up and selected, and the
incoming data rate matches the modem selections.
Use interface loopback for isolating the problem. Verify the frequency of the
input data clock to be within the lock range of 100 PPM.
Activity alarm for the I channel digital filter.
This alarm is considered a major alarm, and will turn off the modulator IF
output. An alarm in this position indicates either a fault in the scrambler, or if
the scrambler is disabled, the alarm indicates a loss of incoming data. If the
fault is active with the scrambler turned off, check for input data at the
DATA I/O connector.
Activity alarm for the Q channel digital filter.
Use the I channel procedure.
Output power AGC level fault.
Indicates the level at the modulator output is not the programmed level.
Modem REF ACT fault.
Indicates incorrect EXT REF frequency input
Modulator module fault.
Typically indicates that the modulator module is missing or will not program.
Modulator/Demodulator Configuration fault.
Indicates a fault in either the Modulator or Demodulator state.
Modem REF PLL
Indicates phase lock loop is unable to lock to EXT REF.
9–5
Revision 1
MN/SNM1001L.IOM