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CompTIA A+ Certification All-in-One Exam Guide

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Coax cables are rated using an RG name. There are hundreds of RG

ratings for coax, but the only two you need to know for the CompTIA A+

exam are RG-59 and RG-6. Both standards are rated by impedance, which is

measured in ohms. (Impedance is the effective resistance to the flow of an

alternating current electrical signal through a cable.) Both RG-6 and RG-59

have a 75-ohm impedance. Both of these coax cables are used by your cable

television, but RG-59 is thinner and doesn’t carry data quite as far as RG-6.

The RG rating is clearly marked on the cable.

NOTE Although it’s not in the objectives, expect to see more use of the

next step up from RG-6, called RG6QS (quad shield) coaxial cable, over the

next few years. The extra shielding reduces interference and enables stronger

internal signals, useful for pushing more data through the cable. (Think

multiple 4K television signals and you’ll be on the money about what’s

driving the upgrade.)

Coax most commonly uses two different types of connectors. A BNC

connector (see Figure 18-15) uses a quarter twist connector, and an F-type

connector uses a screw connector. BNC is uncommon, but F-type is on the

back of all cable modems and most televisions (see Figure 18-16).

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