Cisco Explorer Series - QAM Requirements

QAM Requirements
734375 Rev H 47
QAM Requirements
QAM Forward Path Levels
The following table provides the QAM staging area RF requirements that can be
checked from Page 5 of the DHCT diagnostic screens.
Item
Modulation Rate
QAM Level
Current QAM: Level
64 QAM
-20 to +14 dBmV
256 QAM
-14 to +14 dBmV
Current QAM: S/N
64 QAM
> 27 dB*
256 QAM
> 31 dB*
* Relative to QAM power
The following table provides the QAM staging area RF requirements that can be
checked using the procedures in the NCTA Recommended Practices for Measurements
on Cable Television Systems.
Item
Modulation Rate
QAM Level
Analog/Digital Difference
at DHCT
64 QAM
6 to 10 dB down**
256 QAM
3 to 6 db down**
Amplitude Response of 6
MHz Channel
64 QAM
< 5 dB
256 QAM
< 5dB
CTB, CSO, CM
64 QAM
< -50 dB**
256 QAM
< -53 dB**
** NCTA method relative to analog
Recommended Frequencies for Improved CVT Download Performance
During the CVT download process, the DHCT scans a set of recommended
frequencies. If the DHCT does not initially find the recommended frequency, it then
searches all frequencies.
This section provides the recommended download frequencies for the following
frequency plans:
 Standard frequency (STD)
 Incrementally related carrier (IRC)
 Harmonically related carrier (HRC)