Cisco 7246 - uBR Router, Руководство по установке оборудования

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4-6
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
Setting the European Upconverter Input Level
You must set the upconverter IF input level, according to the manufacturer’s instructions, to match the
downstream output level of your Cisco MC16E cable interface card. The Cisco MC16E features an
output rating of +40 dBmV (+/–2 dB). Refer to the
“Measuring the Downstream RF Signal” section on
page 4-16 and be sure to check the documentation that accompanied your Cisco cable interface line card
or the faceplate of the cable interface line card itself to determine its downstream output level.
Depending on the upconverter model selected (see Appendix F, “Manufacturers for Headend
Provisioning Requirements,” for manufacturers and models), you might need to add attenuation between
the cable interface line card IF output and upconverter input to achieve the recommended input level to
the upconverter.
To verify the input level, connect a spectrum analyzer to the test point on the upconverter input. If your
upconverter is equipped with a built-in meter, you do not need to connect a spectrum analyzer. The IF
input level at the test point should be 0 dBmV at 36.125 MHz.
Figure 4-4 Setting the European Upconverter Input Level
Setting the Upconverter Output Level
You must now set the upconverter output RF level according to the manufacturer’s instructions. DOCSIS
specifications permit an RF output level of +50 to +61 dBmV. Select an output level that falls within this
range that is valid for your upconverter. For example, the configuration in
Figure 4-14 shows an output
level of +55 dBmV.
Note
You should set the upconverter output to a level no greater than about +58 dBmV. This provides
headroom for test equipment calibration accuracy and measurement uncertainty, and helps to avoid
compression in the upconverter.
Tip •
The recommended output level of the General Instrument C6U is +53 to +55 dBmV.
• The recommended output level of the Vecima MA4040 is +55 to +58 dBmV at 88 to 860 MHz.
Cisco uBR7200
series routers
Downstream output
36.125 MHz IF
+40 dBmV ( 2 dB)
+
-
IF input
RF output
Upconverter
Spectrum analyzer
or meter at test point
should equal 0 dBmV
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