Koaksialt

Koaksialt, or coaxial, refers to a type of electrical cable designed to carry high-frequency signals with minimized interference. The name derives from the coaxial arrangement of the inner conductor and the outer shield, which share the same axis. This structure helps confine the signal to the center conductor and shields it from external electromagnetic noise.

A typical koaksialt cable consists of four parts: a central conductive core, a dielectric insulator, an outer conducting shield (made of braided metal and/or foil), and an outer protective jacket. The core is usually copper or aluminum; dielectrics include polyethylene or PTFE. Two common impedance values are 50 ohms and 75 ohms, chosen to match the source, load, and connectors for efficient signal transmission.

Koaksialt cables function as transmission lines, with characteristic impedance and propagation speed determining how signals travel along them. They provide effective shielding thanks to the outer conductor, which minimizes crosstalk and external interference. Their losses increase with frequency and length, and performance depends on factors such as connector quality, bend radius, and shielding integrity.

Applications include distribution of radio frequency (RF) signals, television and cable TV networks, satellite uplinks, antenna feeds, and broadband internet (notably DOCSIS over coax). Variants range from flexible cables used in consumer electronics to rigid hardline variants for high-power or microwave applications. Common connector types include F-type (often for 75 ohms), BNC, N-type, and SMA.

See also transmission line, shielded cable, twisted pair, and fiber optic cable for related transmission media.