Cisco Headend System Release 2.5 Guia Do Utilizador
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DHCT Status Reporting Utility
78-738186-01 Rev B
DHCT Transmit Level Saturation Report,
Continued
Notice the Current Tuner Input Attenuation Level of 2 in the header of this graph.
This value is set at the Tuner Input Attenuator field, which is located on the
Advanced Parameters tab in the Set Up QPSK Modulator window on the DNCS. A
Current Tuner Input Attenuation Level of 2 corresponds to an attenuation level of -5
to 11 dBmV that currently exists on the network. DHCTs base the strength of their
transmitting signal on this Current Tuner Input Attenuation Level. The higher the
Current Tuner Input Attenuation Level, the stronger the transmitting signal; the
lower the Current Tuner Input Attenuation Level, the weaker the transmitting signal.
Transmit Level Analysis
The second part of the DHCT Transmit Level Saturation Report provides a chart
Transmit Level Analysis
The second part of the DHCT Transmit Level Saturation Report provides a chart
showing the detailed breakdown of the graphical data displayed in Graphical
Distribution of DHCT Transmit Levels, earlier in this section. This part of the
report contains the following data:
•
•
Total number of DHCTs assigned to the modulator and each demodulator that
transmit at each transmit level
Note: In the following example, the QPSKMOD1 modulator is configured with
Note: In the following example, the QPSKMOD1 modulator is configured with
eight demodulators.
•
The average and the median transmit level for the modulator and each demodulator
Transmit Level Breakdown
QPSK Mod Name ID Avg. Md 20db 25db 30db 50db 55db 60db
----------- --- ----- -- <-----+------+------+------+------+------+-------->
QPSKMOD1 8 41.99 42 9| 43| 219| 5865| 490| 225| 0
DMod: 1 40.98 41 2| 5| 26| 755| 46| 18| 0
DMod: 2 43.47 44 0| 0| 8| 633| 84| 42| 0
DMod: 3 39.42 40 7| 23| 64| 713| 36| 16| 0
DMod: 4 40.56 41 0| 9| 46| 718| 35| 20| 0
DMod: 5 43.51 44 0| 2| 14| 828| 94| 34| 0
DMod: 6 41.96 42 0| 3| 38| 1029| 84| 45| 0
DMod: 7 43.12 43 0| 1| 15| 853| 74| 37| 0
DMod: 8 43.33 44 0| 0| 8| 336| 37| 13| 0
<-----+------+------+------+------+------+-------->
The data confirms that the system is healthy. The average and median transmit
levels (marked Avg. and Md respectively in the heading of the chart) for the
modulator and each demodulator are reasonably close to the midpoint (40 dBmV) of
Cisco’s recommended range of 25 to 55 dBmV.
Examples of Systems Needing Recalibration
To further illustrate the value of the information contained in the DHCT Transmit
Level Saturation Report, consider these two cases. The first case, Case 1, depicts a
system where DHCTs transmit at levels higher than Cisco’s recommended range of 25
to 55 dBmV. The graph clearly shows the excessively high transmit levels.
The second case, Case 2, illustrates a more subtle example of a system needing
The second case, Case 2, illustrates a more subtle example of a system needing
recalibration. The graph looks fine but the chart depicts one demodulator
transmitting too low and another transmitting too high.