Cisco 7246 - uBR Router, Руководство по установке оборудования

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4-8
Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide
OL-5421-03
Chapter 4 Connecting the Cisco uBR7200 Series Router to the Cable Headend
Connecting and Configuring the Downstream
Tip •
The Vecima MA4040 displays the channel’s center frequency.
• The GI C6U displays a frequency that is 1.75 MHz below the channel’s center frequency. This value
is equivalent to the visual carrier frequency for an analog TV channel occupying the same spectrum.
Figure 4-6 Narrowcast Combiner and Output Frequency
Measuring Upconverter Phase Noise Contribution
You may use a spectrum analyzer to measure the relative aggregate phase noise contribution of the
upconverter to the RF output signal originating at your cable headend. By following the steps in this
procedure, you can determine whether or not the amount of phase noise in your RF output signal is
potentially detrimental to downstream data transmission. Perform the following steps to measure the
additive phase noise in your RF output signal.
Note Most spectrum analyzers are not designed to precisely measure phase noise.
Caution Performing the procedures in this section disconnects any active cable modems currently connected to
your Cisco uBR7200 series router.
Viewing the Downstream IF Signal
Note
Refer to the user guide that accompanied your spectrum analyzer to determine the exact steps required
to use your analyzer to perform these measurements.
50 - 595 MHz
600 - 700 MHz Narrowcast channels
1
2
3
4
5
6
3
Each segment is
a group of fiber nodes
or a region
14043
Broadcast channels
600 - 700 MHz Narrowcast channels 6
600 - 700 MHz Narrowcast channels