Comtech EF Data SDM-650B - Manual (Page 157)

SDM-650B Satellite Modem Maintenance
Rev. 6 6–13
I-CHANNL Indicates a loss of activity in the I channel of the quadrature demodulator.
Typically indicates a problem in the modulator side of the circuit. Check for
proper RF input to the demodulator. If the input to the demodulator is
correct, then the problem is in the baseband filter on the daughter card on
the demodulator, in the soft decision circuitry on the demodulator, or in the
decoder Costas processor. Replace either the demodulator card or the
decoder card to isolate the fault.
Return the failed card for repair.
Q-CHANNL Indicates a loss of activity in the Q channel of the quadrature demodulator.
Typically indicates a problem in the modulator side of the circuit. Check for
proper RF input to the demodulator. If the input to the demodulator is
correct, then the problem is in the baseband filter on the daughter card on
the demodulator, in the soft decision circuitry on the demodulator, or in the
decoder Costas processor. Replace either the demodulator card or the
decoder card to isolate the fault.
Return the failed card for repair.
DSCRAMBL Indicates loss of activity in the descrambler.
Typically indicates a loss of decoder program. Could indicate a problem in
the M&C card, or a problem in the communication between the M&C and
decoder.
BERTHRSH Indication that the preset BER threshold has been exceeded.
Setting of this alarm is done in the Utility menu. This alarm is a function of
the corrected BER reading on the front panel.
MODULE Demodulator module fault. Indicates a problem in programming the
demodulator card.
Check to see that the demodulator card and the decoder card are present
and are properly seated. If the cards are properly seated, this could indicate
a problem in the M&C card, or in the interface between the decoder card
and M&C card. Return the defective card for repair.