Antennas

As 27 MHz is a relatively long wavelength for mobile communications, the choice of antenna has a considerable impact on the performance of a CB radio.

One common mobile antenna is a quarter-wave vertical whip. This is roughly nine feet (2.7 metres) tall and mounted low on the vehicle body, and often has a spring and ball mount. A common misconception is that the '102 inch' whip is the correct length for US CB frequencies; in reality, it is designed to be paired with a six-inch spring, both to bring it to the proper electrical length, and to enhance its resilience to scraping and striking overhead objects.

Where a nine-foot whip would be impractical, shorter antennas include loading coils to make the antenna electrically longer than it actually is. 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 mirrors.

Another mobile antenna is the continuously-loaded half-wave antenna. These do not necessarily require a ground plane to present a near 50 Ohm load to the radio, and are often used on fiberglass vehicles such as snowmobiles or boats. They are also ideal for base station usage where the circumstances preclude the use of an antenna that requires a ground plane to function properly.

Handheld CBs often 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 a mounting base for typical mobile whips, and have several wire terminals or hardwired ground radials attached. These kits are designed to have a mobile whip screwed on top (again, the full-length steel whip is a preferred candidate) and mounted on top of a mast. The ground radials take the place of the vehicle body, which is used as a counterpoise for the mobile whip in a typical vehicle installation.