Coaxial Cable Tips, Guide and Information
What is Coaxial Cable
Coaxial or coax cable is the most common cable used for transmitting video signals. There is a solid copper core (SCC) or copper clad steel (CCS) center conductor in the coaxial cable. This conductor is surrounded by foil shield/s or/and copper braid/s that form the outer conductor and aIso shield against electromagnetic interfernce (EMI). The shield or outer conductor is encased in a PVC jacket.
All of the common “RG” designations (example: RG-6, RG-11, RG-59 etc) apply to various types of coaxial cable. Some people might think “coaxial” or “coax” means “cable with F-connections” or “antenna cable” but it is a much more general classification. Cable with two conductors and share a single common axis is a coaxial cable. All common video cable types are coaxial cables. RG stands for “Radio Guide”.
Coaxial Cable Diagram
Differences and Types of Coaxial Cable
The most common RG designations today are RG-59, RG-58, RG-11, RG-8 and RG-6.
RG-8 and RG-58 are 50 ohm coaxes, used in radio transmission or in computer networks, RG-58 being a rather smaller cable and RG-8 a larger cable. As 50 ohm cables, these two are unsuited for video work.
RG-59, RG-11 and RG-6 are all 75 ohm cable types, with RG-11 being the largest, RG-6 in between and RG-59 being the smallest. RG-6 is the most distributed and frequently used coaxial cable around. Since RG-6 is used in connecting a television set to a CATV (cable television) signal distributor, this cable is also known as the home cable. RG-6 is a successor to RG-59 cable. RG-59 and RG-6 are both very common in home a/v use, this is because their sizes are compatible with a variety of connectors. Two of them are available in many different types, with different shields, dielectrics, jackets, and center conductor materials. Most coaxial cable used for video applications have a nominal impedance of 75 ohms.
People might think cable made of plastic will last forever, but it is not true. Cable installed outdoors is subjected to bombardment of infra red (heat), ultra violet radiation, water, cold and wind (causing abrasion). All those combine to make the plastic cable go brittle and fracture. And when that happens, moisture may get inside and corrode the metal shielding, it can also run down inside and destroy whatever this cable is plugged in to. However, you can help to make it last longer by clipping the cable to prevent movement (but make sure it will not crushed by the clips), you can also paint it with a waterproof paint. Keep it away from sources of heat (patio heater, boiler vent, chimney etc) and sharp edges. Avoid placing it in areas that can trap water (gutters, troughs etc).
Solid Copper Coaxial Cable
The most expensive component in coaxial cable is the copper. Some cables are more expensive because the cable contains more copper and those contain less copper are therefore less expensive. In the last few years, the price of copper has increased dramatically and will continue to rise. Cables that contain less copper has higher resistance and therefore higher signal losses. Copper-on-copper cables are known to last longer outdoors than copper-on-aluminium cables. For most installations, copper clad steel will be suitable. But if you want the best signal possible, you can use a cable that has solid copper conductor.
Arrangement and Length of Coaxial Cable
Cable TV signals will be lowered if the existing cable is extended. The cable length is also very important, the best cable can lose a lot of signal if you do not arrange it properly. Try to make the cable as short as possible and don't leave a coil behind the TV “just in case”. Coaxial cable carries signals of very high frequency. Therefore a simple “kink” or any cable fault can affect specific frequencies without affecting others.
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