Cisco Headend System Release 2.5 User Guide
78-738186-01 Rev B
DHCT Status Reporting Utility
1-43
DHCT Transmit Level Saturation Report,
Continued
Case 1
This example illustrates a system where DHCTs transmit at levels higher than
This example illustrates a system where DHCTs transmit at levels higher than
Cisco’s recommended range of 25 to 55 dBmV.
DHCT Transmit Level Saturation Report - QPSK1
Current Tuner Input Attenuation Level: 2 (-5 to 11 dBmV)
|------------------------------------------------------------------------|
| T |
| | |
| | |
| T TT T | |
| T| ||T| TTT |T |
| || ||||T||| || |
| T TTT||T||||||||T|| |
| T T|T||||||||||||||||| |
T T TTTTTTTTTTTT|T|||||||||||||||||||| |
T-----+--------TT--T+----+---------+--------+----+----+--------+---------|
10 20 25 30 40 50 55 60 70
=================>|<==>|<==========================>|<==>|<=================
^ ^
| |
Settop Signal Core Population Settop Signal
Too Weak (25-55 dBmV) Too Strong
The midpoint of Cisco’s recommended range of 25 to 55 dBmV is about 40 dBmV.
The midpoint of the responding DHCTs depicted in the graph, and confirmed by the
data in the following chart, is about 50 dBmV—too high. Furthermore, the graph
illustrates a definite drop-off of responding DHCTs at about 55 dBmV, a clear sign
that there are additional DHCTs transmitting at levels too high to even be
recognized.
Transmit Level Breakdown
QPSK Mod Name ID Avg. Md 20db 25db 30db 50db 55db 60db
----------- --- ----- -- <----+-----+-----+-----+-----+-----+------->
QPSK1 13 50.90 52 5| 7| 27| 3549| 2250| 2421| 0
DMod: 1 49.50 50 1| 1| 11| 833| 362| 413| 0
DMod: 2 50.97 52 0| 3| 0| 774| 531| 506| 0
DMod: 3 50.20 51 1| 2| 11| 583| 357| 336| 0
DMod: 4 52.41 53 0| 1| 5| 649| 525| 725| 0
DMod: 5 50.99 51 3| 0| 0| 710| 475| 441| 0
<-----+-----+-----+-----+-----+-----+------->
QPSK Mod Name ID Avg. Md 20db 25db 30db 50db 55db 60db
----------- --- ----- -- <----+-----+-----+-----+-----+-----+------->
QPSK1 13 50.90 52 5| 7| 27| 3549| 2250| 2421| 0
DMod: 1 49.50 50 1| 1| 11| 833| 362| 413| 0
DMod: 2 50.97 52 0| 3| 0| 774| 531| 506| 0
DMod: 3 50.20 51 1| 2| 11| 583| 357| 336| 0
DMod: 4 52.41 53 0| 1| 5| 649| 525| 725| 0
DMod: 5 50.99 51 3| 0| 0| 710| 475| 441| 0
<-----+-----+-----+-----+-----+-----+------->
System operators should consider lowering the attenuation level of the QPSK
demodulators associated with this QPSK modulator. When the attenuation level is
lowered, DHCTs transmit at a lower level.