Juniper Networks G10 CMTS manual Preamble

Upstream RF Measurement

•	11. Press the SGL SWP key (single sweep) repeatedly until the spectrum analyzer display is
•	similar to the display in Figure 42 on page 138. The first three graticule columns
•	represent the upstream burst transmission of a single cable modem, including the
•	preamble.
•
•	12. Press the MKR (marker) key and adjust the marker to a position on the signal that
•	represents the median power level of the signal. In Figure 42, the marker is
•	approximately positioned at a median level of 0.65 dBmV. Ensure that this power level is
•	equal to the commanded receive power level at the CMTS, plus any attenuation between
•	the CMTS and the point of measurement.
•
•	You can view the commanded receive power level by issuing the show configuration
•	command:
•	user@host> show configuration interfaces cu-virtual-slot/docsis-slot/upstream-interface
•
•	cable-options upstream
•	...
	commanded-power-level 0;
•
	...
•
•	In this example, the commanded receive power level is set to 0 dBmV. If the
•
	commanded-power-levelstatement is not included in your configuration, the
•
	commanded receive power level defaults to 0 dBmV.
•
•
•	Figure 42: Single Upstream Burst
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

138 JUNOSg 3.0 G10 CMTS Hardware Guide