ComStream CM601, Installation And Operation Manual

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Fault Handling, Troubleshooting, and Maintenance 8-5
Table 8-1 CM601 Faults
Bit Weight* Fault Type Description Possible Cause
— 0 (No faults) — — —
1 1
Tx Power
Fault
H or O Modulator transmit power
control circuit has exceeded
its dynamic range at either
the power detector or the
power control blocks
Type H – May occur during configuration changes. If
this fault occurs repeatedly during steady-state
operation, the modulator power control circuit may
be faulty, or it may be operating outside the specified
power range.
Type O – May occur if running without scrambling
(SM 0) and no data is provided.
2 2
TxIF Synth
Fault
H Modulator IF synthesizer is
out of lock May occur when the synthesizer frequency is
commanded to change. If this fault occurs during
steady-state operation, the modulator synthesizer
may be faulty, or it may be operating outside the
specified frequency range. When this fault occurs,
the modulator IF transmission is disabled.
3 4
RxIF Synth
Fault
H Demodulator IF synthesizer
is out of lock May occur when the synthesizer frequency is
commanded to change. If this fault occurs during
steady-state operation, the demodulator synthesizer
may be faulty, or it may be operating outside the
specified frequency range.
4 8
Tx Bit
Timing Fault
H or O Modulator bit time
synthesizer is not locked
Valid only when the CM601 is operating in external
or loop-timing mode.
Type H – When this fault occurs, the modulator IF
transmission is disabled unless the OM command
parameter is set to 1, in which case this fault has no
affect on the modulator transmit IF.
Type O – The TT clock that has been provided does
not match the specified transmit data rate.
5 16
Rx AGC Range
Fault
O IF input signal to the
demodulator is less than
-55 dBm or greater than
-10 dBm Typically caused by a signal that is too small due to
a rain fade or other environmental condition in the
satellite link.
6 32
Bit Time
Sync Loss
O Demodulator bit time loop
has lost lock Typically caused by excessive phase noise on the
RF upconverter or downconverter in the satellite
link, resulting in excessive clock jitter on the receive
signal into the demodulator. When this fault occurs,
the CM601 receive data output signal (RD) is
clamped high if data control is enabled.
7 64
Carr Track
Sync Loss
O Demodulator carrier tracking
loop has lost lock Typically caused by excessive phase noise on the
RF upconverter or downconverter in the satellite link
or an IF receive signal that is below the minimum
specified receive signal level for the CM601
demodulator. When this fault occurs, the CM601
receive data output signal (RD) is clamped high if
data control is enabled.
* Weight = (2
bit-1
)