Comtech EF Data SDM-100A - Manual (Page 63)

SDM-100A Satellite Modem Operation
Rev. 0 3–29
3.2.1.3.1 Modulator Faults
Fault/Alarm Possible Problem and Action
IF Synthesizer Modulator IF synthesizer is faulted.
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 is an indication 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.
Check to see that the proper data rate has been set up and selected. Verify
that the incoming data rate matches what has been selected in the modem.
Verify the frequency of the input data clock to be within the lock range of
100 PPM. If the inputs to the modem are all correct and the problem still
exists, replace the modem and return it for repair.
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, it indicates a loss of incoming data. If the fault is
active with the scrambler turned off, check to see that there is input data at
the DATA I/O connector. If data is present, the problem could be in the
interface section. If the fault is active with the scrambler turned on, the
problem could be in the modulator section. Return the modem for repair.
Q Channel Activity alarm for the Q channel digital filter.
Follow the same procedure as for the I channel.
AGC Level Output power automatic gain control level fault. Indicates that the level at
the modulator output is not the level that is programmed.
Replace the modem and return it for repair.
Module Modulator module fault. Typically indicates the modulator module is
missing or will not program.
This could indicate a problem in the interface between the modulator and
M&C due to modulator firmware being installed incorrectly or a pin not
making contact. Verify the modulator firmware is correctly installed. If the
problem still exists, return the modem for repair.