Cisco Systems UBR7225VXR specifications OL-17309-02

Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend

Measuring the Upstream RF Signal

Step 1 Display a signal complete with preamble and upstream data transmission information similar to the resulting signal from Step 3 through Step 10 under the “Measuring the Upstream RF Signal Using a Spectrum Analyzer” section on page 4-22. Your spectrum analyzer should display a signal similar to the one in Figure 4-34.

Figure 4-34 Preamble Amplitude Before Resolution and Video Bandwidth Reduction

Note Figure 4-34is a display from a standard spectrum analyzer. The following figures, Figure 4-35through Figure 4-38, are taken from a vector signal analyzer. If you do not have access to a vector signal analyzer, or want to skip the following section describing its use when viewing your upstream signal, proceed to Step 3.

Step 2 (Optional) View your upstream signal using a vector signal analyzer such as the Agilent 89441A.

The advantage of displaying these signals with the vector signal analyzer is that you can view them over the time domain for a specified time interval. In addition, the vector signal analyzer enables you to measure the digital channel power of a very short duration data transmission, like the preamble of a digital signal.

a.Set up your vector signal analyzer to view both the “frequency” domain and “time” domain of your upstream signal. Your vector signal analyzer should display a pair of signals similar to those in Figure 4-35.

	Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
OL-17309-02		4-29