Juniper Networks G10 CMTS manual Press the Span key and enter 6 MHz

Downstream RF Measurement in Spectrum Analyzer Mode

•	5. Press the SPAN key and enter 6 MHz.
•
•	6. Press the BW key and turn video averaging on by selecting VID AVG ON. The default
•	number of averages is 100. You can change the number of averages by using the
•	numeric keypad.
•
•	7. Press the MKR FCTN key (marker function) and select MK NOISE ON. This sets the
•	spectrum analyzer to read out the power bandwidth, normalized to 1 Hz. The spectrum
•	analyzer display should be similar to the display in Figure 41.
•
•	8. The power shown on the display in Figure 41—shown in the top/right and
•	middle/left—is –19.12 dBmV, at 1 Hz. In order to obtain the power in the 6 MHz
•	channel, a correction factor is required. This correction factor equals
•	10 log(ChannelBW/measurementBW). In this case, 10 log (6x10^6/1) equals 67.78 dB.
•	Therefore, the actual downstream channel power equals (-19.12 dBmV+67.78 dBmV),
•	which equals 48.66 dBmV. Ensure that this power value 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.
•
•

•Figure 41: Downstream RF Signal (Spectrum Analyzer Mode)

136 JUNOSg 3.0 G10 CMTS Hardware Guide