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A coaxial cable is one that consists of two conductors that share a common axis. The inner conductor is typically a straight wire, either solid or stranded and the outer conductor is typically a shield that might be braided or a foil. The point to coaxial cable is to shield the signal from interference. Open wire carries a signal better, but is subject to so many types of interference, coaxial cable is used as a solution. Coaxial cable is a trade off, the shielding protects the signal from interference, but signal loss is present.Coaxial cable is used to carry radio signals, video signals, measurement signals and data. There is always some signal radiating from coaxial cable. Hence, the outer conductor also functions as a shield to reduce coupling of the signal into adjacent wiring. More shield coverage means less radiation of energy.Coaxial cable are typically characterized with the impedance and cable loss. The length has nothing to do with a coaxial cable impedance. Characteristic impedance is determined by the size and spacing of the conductors and the type of dielectric used between them. For ordinary coaxial cable used at reasonable frequency, the characteristic impedance depends on the dimensions of the inner and outer conductors. * cctv