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Cisco uBR905 Router Hardware Installation Guide
OL-0598-01 (9/2000)
Appendix B Connector and Cable Specifications
Ethernet Connector and Cabling
For example, a 5 dB reduction in signal quality for analog downstream video might cause a slight
degradation of picture clarity, which might or might not be noticeable to a subscriber. However, a
reduction of only 1 dB in signal quality for digital data might completely disrupt service to a
Cisco uBR905 router user.
Cisco recommends that you use a headend-grade coaxial cable or a quad-shield coaxial cable with a
minimum of 60% + 40% braid and double foil insulation to connect the cable modem cards to the HFC
network. The center conductor must be straight and extend 1/8 inch (3.2 mm) beyond the end of the
connector, and the connector should be securely crimped to the cable. The following cables are
recommended:
•
RG-59—0.034 inch (0.86 mm) center conductor diameter
•
RG-59/U—0.0226 inch (0.57 mm) center conductor diameter
•
RG-6—0.041 inch (1.05 mm) center conductor diameter
Note
All three of the coaxial cables listed can be used to connect a Cisco cable modem card to
the HFC network; however, the consistent use of RG-59 cable is preferred. If you connect
an RG-59 cable to a cable modem card that was previously connected using RG-6 cable,
the difference in the center connector diameter might cause intermittent connectivity loss.
If you use different types of coaxial cable, the following problems can appear:
•
Co-channel interference—If signals at the same frequency are carried on long, parallel runs of
coaxial cable, interference can occur between the signals. Higher quality cable helps to prevent this
with better shielding. Co-channel interference is seen as hum or patterns in analog video channels
and intermittent data loss in digital channels.
•
Damage to Cisco uBR7200 series cable modem card connectors—The modem card connectors are
designed for RG-59 or RG-6 cable and connectors. Larger cables can damage the connectors.
•
High signal return loss—High quality cable and correct connectors help to ensure an optimal return
loss of 16 dB or higher.
Note
Refer to the Cisco uBR905 Cable Access Router Software Configuration Guide for
additional configuration and site requirement information related to the setup of the analog
RF signal and digital data.
Ethernet Connector and Cabling
The Cisco uBR905 router provides four RJ-45 connectors that provide the following Ethernet 10BaseT
connectivity:
•
When the router is configured for either routing or bridging mode, up to four computers or other
customer premises equipment, such as IP-capable printers, can be connected directly to the router,
one device per connector. Use straight-through cables for these connections.
•
When the router is configured for routing mode, one of the four connectors can be connected to an
Ethernet hub, which in turn connects additional computers and other Ethernet devices to the local
area network. Typically, a crossover cable connects the router’s port to the 10BaseT Ethernet port
on the hub. (However, you may be able to use a straight-through cable if the hub has an uplink port;
see the hub’s documentation for further details.)
