Cable TV Uses Coaxial Cable
Unlike over-the-air or satellite television, cable TV signals reach their destination on wires that physically connect the television or cable box to the cable company's broadcast equipment. For most residential and commercial applications, cable companies rely on coaxial wire to deliver their signals to the end users. Coaxial wires, often abbreviated as simply "coax," carry television signals as electrical impulses across a long, highly conductive cable (a design that gives rise to the name "Cable TV"). The central component of coax, copper, serves as a central conductor across which the video signal is relayed; this conductor may be constructed of solid copper or copper clad steel, and is typically between 14 and 22 gauge; depending on the portion of the cable TV network in which the cable is deployed. Because bare copper is susceptible to interference from a number of sources, it must be shielded by the other, outer-most coax cable components.
Dielectric Foil Insulates Coax
A bare copper or copper-steel wire, while highly effective for carrying a video signal, is too vulnerable to interference to function on its own. Instead, the center conductive component of coax is shielded by a layer of dielectric, non-conductive material usually composed of polyurethane or polyethylene and applied as a foil. The non-conductive nature of these products prevent most outside electrical sources from reaching the center conductive component, serving as a first layer of defense against interference.
Braid Further Insulates the Coax
Despite the ability of dielectric insulation to filter out a significant amount of outside interference, the insulation alone can not eliminate all electrical interference. To help further shield the center conductive component from unwanted electrical noise, coax manufacturers provide an additional layer of insulation in the form of braided wires. This second electrical barrier, known simply as "braid," typically consists of small, shielded or unshielded copper wires interwoven into a nearly solid material. The conductivity of this copper-based barrier helps not only to physically shield the center conductive component from outside noise, but employs its conductive capabilities to pick up interference and route it to the surrounding ground material. Finally, braid is an excellent source of electro-magnetic interference (EMI), adding an extra layer of protection to the video signal.
Outside Cable is Shielded or Buried
Finally, coaxial cable that must transmit video signals from the cable company facilities to the customer must be shielded from the elements as well as electrical interference. To facilitate this task, cable company employees route cables one of two ways. Outside aerial cable, the kind that hangs suspended between a series of light poles, is bundled inside a thick polymer coating designed to protect the coax from weather, temperature variations and even wildlife. Many modern cable deployments have moved away from aerial cabling, though, and instead capitalize on the natural protective properties of the Earth by burying cables deep underground. In buried cable configurations, coax cable may or may not be shielded by the same thick polymer coating found in aerial deployments, but is afforded the extra protection of being buried three to six feet under ground. With this external and natural protection and two layers of electrical insulation, coaxial cable allow cable company signals to reach their destination with little or no interference.
Tags: cable company, center conductive, center conductive component, conductive component, video signal, bare copper