Downstream Rf Measurement In Catv Mode - Juniper G10 CMTS Hardware Manual

Downstream RF Measurement in CATV Mode

• Downstream RF Measurement in CATV Mode
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134 JUNOSg 3.0 G10 CMTS Hardware Guide
This section describes the procedure for measuring the downstream signal power from the
G10 CMTS using CATV mode on the HP8591C CATV analyzer. If your spectrum analyzer does
not support CATV mode, you can use the spectrum analyzer mode as described in
"Downstream RF Measurement in Spectrum Analyzer Mode" on page 135.
To measure the downstream signal power using CATV mode, follow this procedure:
1. Connect the spectrum analyzer to a cable within the plant that carries the downstream
signal you are measuring. The signal originates from one of the downstream ports of the
HFC Connector Module or the SIM (DS0 through DS3).
2. View (or set) the output RF power level of the specific interface to be measured. You can
view the output power by issuing the show configuration command:
user@host> show configuration interfaces cd-virtual-slot/docsis-slot/downstream-interface
cable-options downstream
...
rf-power 61;
...
In this example, the output RF power level is set to 61 dBmV. If the rf-power statement is
not included in your configuration, the output RF power level defaults to 61 dBmV.
To set the output RF power level for a downstream interface, include the rf-power
statement at the [edit interfaces cd-virtual-slot/docsis-slot/downstream-interface
cable-options downstream] hierarchy level:
rf-power rf-power;
The downstream interface power level can be from 50 dBmV through 61 dBmV.
3. Press the MODE key and set the spectrum analyzer to CABLE TV ANALYZER mode.
4. Select CHANNEL MEAS (channel measurement) and enter the desired channel number.
For example, select channel 75, which corresponds to a center frequency of 531 MHz.
5. Navigate to the third menu on the screen and select DIGITAL POWER. The spectrum
analyzer display should be similar to the display in Figure 40 on page 135.
6. Ensure that the DIGITAL CHANNEL POWER shown at the bottom of the display is
approximately equal to the configured downstream power level, minus any attenuation
between the HFC Connector Module or SIM downstream port and the point at which
your measurement is taken in the cable plant. In this example, assume the attentuation
between the CMTS and the measurement point is approximately 13 dB. Therefore, the
expected measured value should be approximately 48 dBmV.