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Troubleshooting
01-0870-401B 01/03 57
To clear the fault history log from a remote unit issue the FAULTLOGCLEAR
command.
Initialization Self-Test
Function
The TDR6 has several built-in-self-tests. many of these tests are performed
automatically when the unit is powered up or reset. Faults detected when the unit
is powering up are displayed as error messages on the LCD screen.
Other self-tests are performed during real-time operation as the system monitors
the transport stream. Faults detected while the unit is running are indicated by the
LEDs on the front panel.
You can also query the system on the status of faults using the Faults menu.
Troubleshooting the
QPSK Demodulator
This section provides information on troubleshooting the QPSK demodulator in a
TDR6 configured with a TDEM-6110 option module.
Input Status LED Not Illuminated
If the Status LED is not illuminated, the demodulator, decoder, or the transport
stream is not locked. This problem may be caused by:
■ Receive signal E
b
/N
0
level is to low
■ Receive signal power level is to low
■ Receive carrier offset is wrong
Receive Signal E
b
/N
0
Level
The E
b
/N
0
value in the Details menu under Input/Status displays the estimated
E
b
/N
0
level of the receive signal in units of decibels (dB).
The minimum E
b
/N
0
level required by the QPSK demodulator for flawless video
reception at each Viterbi Code Rate is listed in the following table.
An E
b
/N
0
level above the minimum DVB requirement is acceptable.
■ If the E
b
/N
0
level drops below the minimum DVB requirement, the video
reception can be interrupted or of poor quality.
■ If the E
b
/N
0
level is above the minimum DVB requirement, the TDR6 should
acquire the carrier, demodulate the signal, allow the decoder to lock the
transport stream, and provide decoded video and audio output.
For information on estimating the E
b
/N
0
level, refer to the appendix on the QPSK
demodulator.
Viterbi Code Rate And Eb/No Minimum Levels for QPSK
Demodulator
Viterbi Code Rate
Minimum E
b
/N
0
(dB)
1/2 4.5
2/3 5.0
3/4 5.5
5/6 6.0
7/8 6.4