Measuring Upconverter Phase Noise Contribution; Viewing The Downstream If Signal - Cisco 7246 - uBR Router Hardware Installation Manual

Connecting and Configuring the Downstream
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Figure 4-6

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.
Most spectrum analyzers are not designed to precisely measure phase noise.
Note
Performing the procedures in this section disconnects any active cable modems currently connected to
Caution
your Cisco uBR7200 series router.

Viewing the Downstream IF Signal

Refer to the user guide that accompanied your spectrum analyzer to determine the exact steps required
Note
to use your analyzer to perform these measurements.
Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide
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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.
Narrowcast Combiner and Output Frequency
50 - 595 MHz Broadcast channels
600 - 700 MHz Narrowcast channels
600 - 700 MHz Narrowcast channels
600 - 700 MHz Narrowcast channels
Chapter 4 Connecting the Cisco uBR7200 Series Router to the Cable Headend
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Each segment is
a group of fiber nodes
or a region
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