Measuring The Downstream Rf Signal Using Catv Mode On A Spectrum Analyzer - Cisco 7246 - uBR Router Hardware Installation Manual

Chapter 4 Connecting the Cisco uBR7200 Series Router to the Cable Headend
Any in-channel frequency response problems at the headend can impair network performance or prevent
Note
a cable modem on the HFC network from operating. The specified maximum peak-to-valley
measurement from a Cisco cable interface card is +/–1.5 dB across 5.6 MHz. At the output of the
upconverter, the maximum tilt should not exceed +/–1.5 dB across 5.6 MHz. If the tilt is greater than
+/–1.5 dB across 5.6 MHz when measured, the upconverter might not be compatible with digital QAM
signals, or the upconverter might be defective. Remember, however, that when using your spectrum
analyzer in "video averaging" mode, amplitude accuracy adjustments must also be taken into
consideration.
Step 10 Verify that your headend RF measurements meet the recommended DOCSIS parameters listed in the
tables in
headend site log
Cisco uBR7200 series router installation later in the process.
This completes the procedure to measure the downstream RF signal using the channel power option.
Proceed to the
page
Measuring the Downstream RF Signal Using CATV Mode on a
Spectrum Analyzer
The following two sections describe the methods you may use to measure the downstream RF signal
using CATV mode (digital channel power option) on a spectrum analyzer:
•
•
We recommend using as recent a model of spectrum analyzer as possible to perform the two analyses
Note
described here. You can use spectrum analyzers, such as the Agilent 8591C
http://www.home.agilent.com
outlined in this section.
Measuring the Downstream IF Signal at the Cisco uBR7200 Series Router Using CATV Mode
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.
Connect a spectrum analyzer to the downstream connector on a Cisco cable interface card installed in a
Step 1
Cisco uBR7200 series router.
Turn the power switch on the spectrum analyzer to the ON position.
Step 2
OL-5421-03
Appendix B, "RF Specifications."
(Appendix G, "Site
"Measuring the RF Signal at the Forward Test Point on a Laser Transmitter" section on
4-49.
"Measuring the Downstream IF Signal at the Cisco uBR7200 Series Router Using CATV Mode"
section on page 4-23
"Measuring the Downstream RF Signal at the Upconverter Output Using CATV Mode" section on
page 4-26
or the Tektronix 2715 (http://www.tek.com) to help you perform the tasks
Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide
Record your headend settings and measurements in your
Log"). This will assist in troubleshooting the
Measuring the Downstream RF Signal
4-23