Juniper Networks G10 CMTS manual Downstream RF Measurement in Catv Mode

Downstream RF Measurement in CATV Mode

•Downstream RF Measurement in CATV Mode

•
•	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-powerstatement 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.
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•	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.
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•	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
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	your measurement is taken in the cable plant. In this example, assume the attentuation
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	between the CMTS and the measurement point is approximately 13 dB. Therefore, the
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	expected measured value should be approximately 48 dBmV.
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134 JUNOSg 3.0 G10 CMTS Hardware Guide