Troubleshooting
01-0868-401B 12/02
51
Demodulator Lock and Decoding Problem
Problem:
Demodulator does not lock and decode properly
Solutions:
■
Check the decoder E
b
/N
0
level to ensure that the receive signal level is within tolerance.
■
Ensure that your antenna is correctly pointed at the satellite.
■
Verify that your LNB is oriented to match the downlink signal polarization.
■
Determine whether the IFL cable loss is excessive.
■
Ensure that all the cables are connected properly.
■
Verify that the LO frequency is set to match your LNB local oscillator frequency.
■
Verify that the RF frequency minus the local oscillator frequency matches the actual satellite
downlink frequency.
■
Verify that the data rate matches the transport data rate or transmission symbol rate of the
satellite downlink frequency.
■
Verify that the code rate matches the Viterbi code rate of the satellite downlink signal.
■
Verify that the low noise block downconverter power matches the DC voltage required by
your LNB to properly orientate to the polarity of the downlink signal.
■
Check signal using a spectrum analyzer.
■
If you have checked all of the items listed above, and your unit is still not providing flawless
video and audio, contact Tiernan Customer Service for assistance.
Front Panel Problems
Problem:
The front panel is not enabled, is in view-only mode, does not accept commands or
button pushes.
Solutions: The front panel may be in lock-out mode. Unlock the front panel.
General Performance Problems
Problem:
Low performance
Solutions:
■
Replace cable from LNB to the TDR60 RF IN port.
■
Check for ground loop potential.
■
Check the carrier offset parameter. If carrier is off by more than 1.5 Mhz from the center,
then change RF or LO parameters to reduce the carrier offset.
■
Check adjacent channel spectrum, make sure there is no adjacent channel interference
■
Ensure bit rate does not exceed maximum bit rate for a given transponder bandwidth.
■
Check signal using a spectrum analyzer.
Loss of Sync Problem
Problem:
Unable to achieve lock on the demodulator
Solutions:
■
Verify that the E
b
/N
0
level is above the minimum DVB limits.
■
If the E
b
/N
0
is sufficient, confirm that the RF frequency, local oscillator frequency, transport
or transmission symbol rate, and Viterbi code rate settings match those of the transmit
modulator.
■
Verify that the LNB Power parameter is set to allow the LNB to properly align to the
polarization of the incoming signal.
■
Check signal using a spectrum analyzer.
Problem:
Demodulator Locks Intermittently but the decoder does not lock
Solutions:
■
Confirm that the
E
b
/N
0
level is above the minimum DVB limits.
■
If the E
b
/N
0
is sufficient, confirm that the Viterbi code rate (Code Rate) is set correctly.
