coaxial cable (redirected from Co-axial cable)

coaxial cable: see cable.

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coaxial cable

 or coax

Self-shielded cable used for transmission of communications signals, such as those for television, telephone, or computer networks. A coaxial cable consists of two conductors laid concentrically along the same axis. One conducting wire is surrounded by a dielectric insulator, which is in turn surrounded by the other, outer conductor, producing an electrically shielded transmission circuit. The whole cable is wrapped in a protective plastic sheathing. The signal propagates within the dielectric insulator, while the associated current flow is restricted to adjacent surfaces of the inner and outer conductors. As a result, coaxial cable has very low radiation losses and low susceptibility to external interference.

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coaxial cable

A high-capacity cable widely used in audio, video and data applications. Commonly called "coax" (pronounced "co-axe"), coaxial cable is used for hooking up TVs to antennas, cable and digital satellite service. It is also used for cable modems and various digital interfaces such as S/PDIF.

Strong and flexible, coaxial cable contains an insulated solid or stranded wire in the center, surrounded by insulation. The insulation is wrapped with an aluminum or copper sheath, which can be a wrapped foil or a braided wire fabric. The sheath serves as the ground line and interference shield. All of this is wrapped in a plastic cover, which may have a fire-safe Teflon coating.

There Are Many Types
Often similar in appearance, there are several types of coaxial cables. Typically with impedances of 50 or 75 Ohms, cables have different outside diameters and maximum capacities for operating voltage. Cables are also rated for signal loss (attenuation in dBs per 100 feet). Coaxial cable types are designated with an RG (radio grade) prefix such as RG-6. Following are the most common coaxial cables; however, there are many more types in use.

           Impedance  Core  Layers
           Range in   Dia.   in     Typical
 Type      Ohms       (mm)  Sheath  Purpose

 RG-6        75-76    1.0   two   TV, cable, sat
 RG-6 Quad   75-76    1.0   four  TV, cable, sat

 RG-58       50-53.5  0.9   one   TV, thin Ethernet

 RG-59       73-75    0.81  one   TV, cable, S/PDIF
 RG-59 Quad  73-75    0.81  four  TV, cable, S/PDIF

Coaxial Cable

Coax uses two wires. The inner wire is the primary conductor. The ground wire is an aluminum or copper sheath that surrounds the insulation of the primary conductor and also serves as a shield against external interference.

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coaxial cable [kō′ak·sē·əl ′kā·bəl]

(electromagnetism)

A transmission line in which one conductor is centered inside and insulated from an outer metal tube that serves as the second conductor. Also known as coax; coaxial line; coaxial transmission line; concentric cable; concentric line; concentric transmission line.

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Coaxial cable

An electrical transmission line comprising an inner, central conductor surrounded by a tubular outer conductor. The two conductors are separated by an electrically insulating medium which supports the inner conductor and keeps it concentric with the outer conductor. One version of coaxial cable has periodically spaced polyethylene disks supporting the inner conductor. This coaxial is a building block of multicoaxial cables used in L-carrier systems (see illustration).

Construction of multicoaxial transmission line with twenty 0

The symmetry of the coaxial cable and the fact that the outer conductor surrounds the inner conductor make it a shielded structure. At high frequencies, signal currents concentrate near the inside surface of the outer conductor and the outer surface of the inner conductor. This is called skin effect. The depth to which currents penetrate decreases with increasing frequency. Decreased skin depth improves the cable's self-shielding and increases transmission loss. This loss (expressed in decibels per kilometer) increases approximately as the square root of frequency because of the skin effect.

Coaxial cables can carry high power without radiating significant electromagnetic energy. In other applications, coaxial cables carry very weak signals and are largely immune to interference from external electromagnetic fields.

A coaxial cable's self-shielding property is vital to successful use in broadband carrier systems, undersea cable systems, radio and TV antenna feeders, and community antenna television (CATV) applications.

Coaxial units are designed for different mechanical behavior depending upon the application. Widely used coaxials are classified as flexible or semirigid.

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(hardware)

coaxial cable - A kind of cable with a solid central conductor surrounded by insulator, in turn surrounded by a cylindrical shield woven from fine wires. It is used to carry high frequency signals such as video or radio. The shield is usually connected to electrical ground to reduce electrical interference.