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COAXIAL (“COAX”) CABLE PRIMER: Used for television and cable modem connections since its invention in 1929, essentially unchanged. The designations RG (“Radio Grade”) and RF (“Radio Frequency”) refer to the versions of coax and their diameter and internal characteristics (i.e. amount of shielding and attenuation). In actuality, the numbers (e.g. RG-59, RG-6) have absolutely no meaning and were originally arbitrarily assigned by the military.
Today, most TV and computer modem cables are designated RG-59, although in some older buildings the previous and thinner RG-6 can be found. Since all coax is 75 ohm resistance, the primary difference between them is the gauge of the copper center wire (RG-59 is 22 AWG, while RG-6 is 18 AWG; RG-6 may be a braided core, while RG-59 is solid core; RE-59 uses a braided shield, while RG-6 may use plain aluminum). Commercial buildings may use the thicker RG-11, which can carry a signal distances greater than 200 feet and may also be “Plenum” rated, meaning it can be used inside a wall where fire safety is a concern, as it will not produce toxic gas when it burns.
Connectors can also be manufactured in varying quality, just like home theatre components, some of which are actually gold-plated. Most are referred to as “F” connectors (short, I believe for “RF”), which took the place of the older twin-lead flat antenna cable. [While it is not used very often, very small coax uses SMA (“Sub-Miniature Version A”) connectors.] Today, most connectors are compression fittings and not the earlier screw-on or crimp types. The TV and Computer connections are divided off the main incoming cable using a “tap” or a “splitter” [click HERE to learn how they work] which creates two separate coax cables, one for each signal, TV and computer cable modem.
If you are not purchasing pre-made cables, but are making your own, quality parts and perfect assembly are essential. Poorly constructed cable connections will cause signal “leak” causing distortions (known as “ingress”) such as vertical lines, horizontal dash lines or “beats” (little white random dots). These can occur from improper crimping, nicking the copper core or cutting the shield.
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