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About Coaxial Cable [2010-11-08]

Coax consists of a center wire surrounded by insulation, which is in turn surrounded by an outer conductor of braided wire that serves as a grounded shield, enclosed in an outer jacket of insulation. The shield minimizes electrical and radio frequency interference. There may also be a layer of foil between the interior insulation and the outer conductor.

Coaxial cable is easy to work with as long as you have a few tools. Tapping into an existing coaxial line to hook up a second TV or extend a computer network is known as "splitting.” Standard tools are fine for making a couple of connections, but if you’re making a lot of them, invest in a few inexpensive specialized tools: the work will be faster and more professional. If you’re hooking up more than one additional unit, buy a splitter with three or four outputs, or terminals, instead of two. This usually yields better results than splitting the line at each device, which may weaken the signal.

Coax gets its name because its two channels run concentrically along the same axis. It is old technology that was originally designed to carry analog telephone signals at high capacity with little electronic noise. Coax is virtually weatherproof and much more durable than "twinlead" wire that is the flat wire originally used for TV antennas. Signal performance is also superior. Coax doesn’t pick up unwanted signals, and it’s not affected by contact with metal structures. And although cable installers often use special standoff supports when attaching coax to exteriors, all you need to route coax inside your house are coaxial cable clips.

The more splitters you add, or the more ports on the splitters will result is signal loss. Splitters have the loss stated on them, usually between -1 dB and -3.5dB for 2-way splitters and up to -11dB for 8-way splitters. If you have poor signal quality at the end of your last run, you may need to install an amplifier after the splitter to boost the signal strength. See the illustration below. Check you equipment to determine what the maximum allowable loss in signal strength is.