Editing Citizens band radio (section)

==Antennas==
[[File:CB antenna.jpg|thumb|Typical center-loaded mobile CB antenna. Note the [[loading coil]], which shortens the antenna's overall length.|alt=A tall antenna with a helical coil in the middle, mounted on pickup-truck metal tool box]]

27&nbsp;MHz is a relatively long wavelength for mobile communications, and the choice of antenna has a considerable impact on the performance of a CB radio. A common mobile antenna is a quarter-wave vertical whip. This is roughly 9&nbsp;feet (2.7&nbsp;m) tall; it is mounted low on the vehicle body, and often has a spring-and-ball mount to enhance its flexibility when scraping or striking overhead objects. Where a nine-foot whip is undesirable, shorter antennas include [[loading coil]]s to make the antenna impedance the same as a physically longer antenna.  The loading coil may be on the bottom, middle, or top of the antenna, while some antennas are wound in a continuously loaded helix.

Many truckers use two co-phased antennas, mounted on their outside mirrors. Such an array is intended to enhance performance to the front and back, while reducing it to the sides (a desirable pattern for long-haul truckers). To achieve this effect, the antennas must be separated by about eight feet, only practical on large trucks. Two antennas may be installed for symmetrical appearance, with only one connected.

Another mobile antenna is the continuously loaded half-wave version. They do not require a [[ground plane]] to present a near-50&nbsp;[[ohm]] load to the radio, and are often used on fiberglass vehicles such as snowmobiles or boats. They are also useful in base stations where circumstances preclude the use of a ground-plane antenna. Handheld CBs may use either a telescoping center-loaded whip or a continuously loaded "rubber ducky" antenna.

Base CB antennas may be vertical for omnidirectional coverage, or directional "beam" antennas may be used to direct communications to a particular region. Ground-plane kits exist as mounting bases for mobile whips, and have several wire terminals or hardwired ground radials attached. These kits are designed to have a mobile whip screwed on top (a full-length, quarter-wave steel whip is preferred) and mounted on a mast. The ground radials replace the vehicle body (which is the [[Counterpoise (ground system)|counterpoise]] for a mobile whip in a typical vehicle installation).