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Coaxial cable consists of a solid copper core surrounded by an insulator, a combination shield and ground wire, and an outer protective jacket, as pictured in Figure 1.

The primary types of coaxial cable used for networking are listed here:

• RG-58A/U    50-ohm cable used in Ethernet 10Base2 (Thinnet)


• RG-59/U    CATV cable (75 ohm)


• RG-62/U    93-ohm cable used in ARCNET and to connect IBM 3270 terminals

Coaxial cable can be cabled over longer distances (186 meters for 10Base2 Ethernet) than twisted-pair cable (about 100 meters); but because twisted-pair now offers higher data rates and is easier and cheaper to install, it is now favored over coaxial cable. The shielding on coaxial cable makes it less susceptible to interference from outside sources. Still, new categories of twisted- pair wire now allow data rates to surpass that available on coaxial cable. Coaxial cable requires termination at each end of the cable and a single ground connection. In long runs, there is a possibility that secondary grounds can form on the cable, causing noise problems and the potential for electric shock.

While coaxial cable is the traditional media for Ethernet and ARCNET networks, twisted-pair and fiber-optic cable are more common today. New structured wiring system standards call for data-grade twisted-pair cable wire that transmits at 100 Mbits/sec, ten times the speed of Ethernet coaxial cable networks. Coaxial cable is most likely a dead-end cabling scheme for large office environments, although it may occasionally be used for long backbone connections.

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