Demodulator Faults; Table 5-3. Demodulator Fault Information - Comtech EF Data SLM-7650 Installation And Operation Manual

SLM-7650 Satellite Modem
Maintenance
5.2.5.2

Demodulator Faults

Fault/Alarm
MODULE
CARRIER DETECT
IF SYNTHESIZER
I CHANNEL
Q CHANNEL
BER THRESHOLD

Table 5-3. Demodulator Fault Information

Demodulator section fault.
Typically indicates that the demodulator will not program.
Return the modem for repair.
Carrier detect fault.
Indicates the decoder is not locked. This is the most common fault displayed in the
modem. Any problem from the input data on the modulator end of the circuit to the
output of the decoder can cause this alarm.
First, ensure the demodulator has an IF input at the proper frequency and power level.
Ensure the demodulator data rate is properly programmed.
Refer to the fault isolation procedure for Data Clock Syn in the modulator section. Verify
the frequency of the data transmitted from the modulator is within 100 PPM.
Demodulator IF synthesizer fault.
Indicates the demodulator IF synthesizer is faulted.
Return the modem for repair.
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
processing. Return the modem for repair.
Indicates a loss of activity in the Q channel of the quadrature demodulator.
Follow the same procedure for the I channel fault.
Indicates the preset BER threshold has been exceeded.
Setting of this alarm is done in the Configuration - Demodulator menu. This is an alarm
based on the corrected BER reading on the front panel.
Possible Problem and Action
5–10
Revision 4
MN/SLM7650.IOM