Installation guide

Planning and Designing RIO Cable System
890 USE 101 00 October 2006 45
Electrical Characteristics of Coaxial Media Components
Overview The following electrical characteristics must be considered when choosing the
media components for your network cable system. These characteristics determine
the maximum length of the cable system and the number of nodes permitted on the
network.
Impedance Impedance is the AC resistance of a cable or network component to a signal. All RIO
media components have a characteristic impedance of 75 Ω, with a minimum
tolerance of +/- 3 Ω. Media components that can obtain a consistent impedance as
close to 75 Ω as possible yield better performance.
Attenuation Attenuation is the amount of signal loss through media components. Cable and
other media components express attenuation in decibels (dB). Lower attenuation of
media components allows for higher signal strength and longer cable distances
throughout the cable system.
Depending on the hardware used, RIO networks are limited to a maximum
attenuation of 35 dB from the RIO head processor (or from the last fiber optic
repeater in an optical link) to any drop adapter. Although all media components have
attenuation values, the primary attenuation consideration is your coaxial cable
selection. A cable’s ability to carry a signal is mostly determined by the physical size
of the cable. A larger cable can carry a signal farther than a smaller cable. Here are
some rule-of-thumb cable loss figures:
Exact attenuation specifications for all approved cables are given in RG-6 Cable,
p. 68, RG-11 Cable, p. 69, and Semirigid Cable Connections, p. 113.
Cable Type Attenuation
1 in. semirigid 0.09 dB/100 ft @ 5 MHz
1
/
2
in. semirigid
0.14 dB/100 ft @ 5 MHz
RG-11 0.38 dB/100 ft @ 5 MHz
RG-6 0.38 dB/100 ft @ 2 MHz
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com