Kábelantennas

Kábelantennas are antennas in which a transmission line, typically coaxial cable or a two‑conductor feeder, forms all or part of the radiating element. This approach can be attractive when there is a convenient cable route already installed or when a conventional wire antenna would be impractical in a space-limited installation.

In a coaxial cable radiator, RF current flows on the center conductor and on the shield, generating an electromagnetic field along the length of the cable. The electrical length of the run determines resonance, with common configurations using quarter-wave or half-wave sections. End-fed arrangements place the feed at one end, while center-fed or folded variants resemble dipole-like patterns. Impedance matching or baluns are often used to present a suitable input impedance to the transmitter and to minimize feedline currents that counteract radiation.

Variants include using a two-wire feeder as a balanced radiator, where the two conductors form a dipole with the transmitter connected between them. The surrounding environment and nearby conductors strongly influence the radiation pattern, impedance, and efficiency.

Performance and practical use vary. Cable antennas can offer a compact, space-saving solution or a lower-cost option for temporary or indoor installations, but they typically exhibit lower efficiency and more variable patterns than purpose-built antennas. They require attention to impedance matching, feedline currents, and nearby conductive structures to achieve acceptable operation.

See also: transmission line antennas, dipole antennas, baluns and impedance matching.