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Recommended TDR signal level
The default transmit level for the TDR is 0 dBmV. Under
typical conditions this will result in the spread spectrum
signal being -40dBc relative to the return QAM channels –
significantly lower than the -25dBc level defined in the
DOCSIS specification as what is required not to affect the
return QAM CNR/SNR. As such the 0 dBmV level should be
used in most connections scenarios. Caveats to this would
be when the connection point is an amplifier with -30dB test
points instead of the more common -20dB test point –
where stronger transmit signal levels would be required.
Another case where the higher signal level might be needed
would be in sections of plant with larger than typical
numbers of passives (older architectures). The lower level -
5 or -10 dBmV settings would be recommended for end of line type situations or at
the drop when plant signal levels are minimal.
TDR run modes
Two TDR run modes are available – Continuous – where it
will continue to actively send out pulses and measure return
loss response, and Single – where only one pulse will be sent
out.
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