Radio-Frequency Cable

a cable designed for the transmission of radio and video signals. A radio-frequency cable is used as a feeder in antenna-feeder devices for radio transmitters, radio receivers, and television receivers and as a connecting cable within and between modules in radio-electronic equipment and computers.

Radio-frequency cables can be classified according to design and the arrangement of the conductors as coaxial cables, which are more widely used, and two-conductor cables. The operating wavelength range of coaxial cables is confined at the lower limit by the critical wavelength λ_cr; that is, λ > λ_cr. For this wavelength, the relationship λ_cr ≈ 0.5π (D + d) is valid, where D is the inside diameter of the outer conductor and d is the outside diameter of the inner conductor.

In the USSR, coaxial radio-frequency cables are manufactured with diameters D ranging from 0.2 to 250 mm. Radio-frequency cables with D = 0.2 mm are used to transmit signals in the centimeter-wavelength range, and cables with D = 250 mm are used to transmit signals with a frequency up to 500 megahertz and a pulsed power up to 1.25 megawatts.

In addition to the operating wavelength range, radio-frequency cables have other very important electrical parameters, which are determined mainly by the physical properties of the insulating dielectric and by the geometry of the cables. These include the characteristic impedance of the cable, the linear (distributed) capacitance, the attenuation constant, the maximum permissible power that can be transmitted, and the breakdown voltage. Markings on radio-frequency cables describe the principal properties of the cables; for example, the markings RK-75–4–11 indicate a radio-frequency coaxial cable featuring a characteristic impedance of 75 ohms and a diameter of 4 mm, with continuous polyethylene insulation.