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Coaxial Cable |
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coaxial cable: see cable cable, originally wire cordage of great strength or heavy metal chain used for hauling, towing, supporting the roadway of a suspension bridge, or securing a large ship to its anchor or mooring.
..... Click the link for more information. . coaxial cableor coaxSelf-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. 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 [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. 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). 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. coaxial cable coaxial cable 1.A cable consisting of two concentric conductors (an inner conductor and an outer conductor) insulated from each other by a dielectric; commonly used for the transmission of high-speed electronic data and/or video signals. 2. A single transmission cable having a concentric conductor and shielding; used for communications transmission, such as for television signals.
Coaxial Cable a cable in which the wires that constitute the circuit are two coaxial cylinders. Coaxial cables are used for transmitting electric signals over telecommunications lines, as antenna feeders for radio, electronic and television apparatus, and as connections between units of radio apparatus. The electromagnetic field of a coaxial cable is concentrated in the space between the conductors—that is, there is no external field, and thus there are virtually no radiation losses into the space surrounding the cable. The outer wire also functions as an electromagnetic screen, protecting the electric circuit from outside influences. Therefore, coaxial cables exhibit a high degree of noise immunity. Energy losses of transmitted signals are comparatively low. Coaxial communications cables are characterized by the diameter of the inner and outer wires, which are usually given in the model number—for example, KPK-5/18 (coaxial submarine cable with an inner wire 5 mm in diameter and an outer wire 18 mm in diameter). Radio-frequency cables of coaxial design are marked differently; their model numbers reflect only the inside diameter of the outer wire. D. L. SHARLE Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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