coax

Coax, short for coaxial cable, is a type of electrical cable designed to carry high-frequency signals with reduced interference. It consists of a central conductor surrounded by a dielectric insulator, which is enclosed by a conducting shield, all within an outer jacket. The coaxial geometry confines the electric field and minimizes radiation and pickup of external noise.

Impedance is a key characteristic; common values are 50 ohms and 75 ohms, chosen to match sources and loads. Attenuation increases with frequency and length. Variants include RG-58 and RG-59 for general-purpose use, RG-6 and RG-11 for television and satellite applications, and specialty cables with foam or solid dielectrics and different shielding.

Coax is used in a wide range of applications, including antennas, terrestrial and satellite TV, cable distribution, CCTV, and data communications. Connectors such as BNC, RCA, F-type, SMA, and N-type are used to terminate coax to equipment. Coax can carry frequencies from a few kilohertz up to several gigahertz, depending on construction and connectors.

Advantages of coax include high bandwidth, relatively low loss for a given size, and effective shielding against electromagnetic interference. Limitations include signal loss over long runs, moisture ingress in outdoor installations, and stiffness or bulk in high-capacity cables; proper termination and impedance matching are essential to minimize reflections.

Coaxial cables were developed in the early 20th century and became widespread in radio, television, and data networks during the mid-to-late 20th century. Today, variants exist for specialized low-loss, high-flexibility, and high-frequency applications, and are often used alongside fiber-optic systems in modern networks.