Citizens band radio

A mobile CB radio with microphone

Citizens band radio (also known as CB radio) is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27 MHz (11 m) band. Citizens band not the same as the Amateur Radio Service ("ham" radio) which has a much longer range. In many countries, CB operation does not require a license to operate. It may be used for business or personal communications.

Like many other two-way radio services, citizens band channels are shared by many users. Only one station may transmit at a time. All other stations must listen and wait for the shared channel to be available. It is customary for stations waiting to use a shared channel to broadcast the single word "break" (or "breaker") during a lull in the conversation. This lets other people using the channel know that others are waiting. In the US, channel 19 is most often used by truckers. Channel 9 is reserved for emergencies.

History

The citizens band radio service originated in the United States as one of several personal radio services regulated by the Federal Communications Commission (FCC). These services began in 1945 to permit citizens a radio band for personal communication. In 1948, the original CB radios were designed for operation on the 460–470 MHz UHF band.^[1] There were two classes of CB radio: "A" and "B". Class B radios had simpler technical requirements, and were limited to a smaller frequency range.

Al Gross established the Citizens Radio Corporation during the late 1940s to manufacture Class B handhelds for the general public.^[2] In the 1960s it became popular with taxicab companies to communicate with their drivers.^[3] In the 1970s it became popular with truckers, who

began using it to warn other truck drivers of police speedtraps.^[3] Other drivers soon used CB radios, and the CB jargon of truckers was used in several movies.

Ten codes

When CB radios first started a series of "10 codes" were used. This was due to the early CB radios need to warm up before use.^[4] The 10 codes were used as a shortcut to longer standard messages. A few of the more often used codes are:

10-4 (ten-four) meant message received.^[4]
10-9 (ten-nine) meant please repeat your last message.^[4]
10-10 (ten-ten), transmission complete, standing by.^[4]
10-17 (ten-seventeen), urgent business.^[4]
10-20 (ten-twenty) means your location. Often shortened to "what is your 20?"^[4]
10-27 (ten-twenty seven) I am moving to channel ____.^[4]
10-200 (ten-two hundred) means police are needed at ____.^[4]

United States

Today it remains popular with truck drivers. It is used in rural areas by a wide variety of people and businesses where cellphone service is weak or unreliable. CB radios are also used by off-roaders to communicate between drivers in a group of four-wheel drive vehicles.^[5] It is used to warn drivers of various trail conditions, hazards, and delays.^[5]

Other countries

CB radio is used as a system of short-distance communications between people in many countries. Nearly all use a system of 40 channels in the 27 megahertz or 11 meter band.

Citizens Band Radio Media

Typical 1980s CB radio intended for use at a fixed location and used with outdoor antenna. "Base stations" are usually operated on household AC power but can also from a vehicle's DC power system if operated in a vehicle or from an emergency battery source. Shown with Astatic brand D-104 desk mic
Cobra 50 WX ST Handheld CB Radio
A QSL card issued by a US CB station in 1963
Image of Citizens Radio license 1972 issued by the United States Federal Communications Commission
Hand-held CB transceiver; antenna not shown
Typical center-loaded mobile CB antenna. Note the loading coil, which shortens the antenna's overall length.