Cisco Systems UBR7225VXR Connecting the Cisco uBR7225VXR Router to the Cable Headend

Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend

Measuring the RF Signal at the Forward Test Point on a Laser Transmitter

Note The slight “ramp-up” at the beginning of the preamble when viewed in this mode is attributed to the time required to charge the spectrum analyzer’s detector circuit.

Figure 4-43shows a smooth and easily measured signal amplitude, providing accurate measurement of a very fast burst upstream carrier. You can compare the measurements obtained using a spectrum analyzer with those of specialized test equipment. In general, the readings from the spectrum analyzer will be within 1 to 2 dB of the (more expensive) specialized equipment. Because 1 to 2 dB is well within the calibration accuracy of spectrum analyzers, you can reliably use these procedures in the cable headend environment.

Measuring the RF Signal at the Forward Test Point on a Laser Transmitter

This section describes RF signal measurements that should be taken with a spectrum analyzer at the downstream forward test point on the fiber-optic laser transmitter.

Use the following steps to measure the downstream forward test point on the fiber-optic laser transmitter:

Step 1 Connect the spectrum analyzer to the downstream forward test point on the fiber-optic laser transmitter. Figure 4-44shows a typical measurement of the downstream forward test point.

Figure 4-44 Measuring the RF Signal at the Downstream Forward Test Point on the

Laser Transmitter

Step 2 Using the spectrum analyzer zoom feature, zoom the display on the first individual video channel. In the example in Figure 4-45, the first video channel is channel 48.

	Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
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