Comtech EF Data CDM-IP 300L - Manual (Page 323)

CDM-IP 300L IP-Centric Satellite Modem Rev. 1
CD/CDMIP300L.IOM
297
10.1.6.2 M
ODULATOR
F
AULTS
Fault/Alarm Possible Problem and Action
IF SYNTHESIZER Modulator IF synthesizer fault.
This is considered a major alarm, and will turn off the modulator output.
Return the modem for repair.
DATA CLOCK SYN 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.
In the IDR type configuration, the data rate must reflect any overhead
bits that are added. In the IBS type, the internal reference is changed
to account for the IBS overhead of 16/15. A standard IDR type
configuration operating at Rev. 2 would be programmed to the input
data rate. An IDR type operating at Rev. 3 would be programmed to
reflect the 96 kbit/s of overhead. A 1544 kbit/s Rev. 3 IDR is
programmed to 1640 kbit/s. An IBS type would be programmed for the
input data rate to the channel unit. The modem accounts for the
overhead because of the change in internal reference. Use interface
loopback for isolating the problem. Verify the frequency of the input
data clock to be within the lock range of 100 PPM.
I CHANNEL 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.
Q CHANNEL Activity alarm for the Q channel digital filter.
Use the I channel procedure.
AGC LEVEL Output power AGC level fault.
Indicates the level at the modulator output is not the programmed level.
MODEM REF ACT Modem REF ACT fault.
Indicates incorrect EXT REF frequency input
MODULE Modulator module fault.
Typically indicates that the modulator module is missing or will not
program.
CONFIGURATION Modulator/Demodulator Configuration fault.
Indicates a fault in either the Modulator or Demodulator state.
MODEM REF PLL Modem REF PLL
Indicates phase lock loop is unable to lock to EXT REF.