Citizens' Band radio (CB) is, in the United States, a system of short distance radio communication between individuals on a selection of 40 channels within the single 27 MHz (11 meter) band. The CB radio service should not be confused with FRS, GMRS or amateur radio. CB does not (in most countries) require a license and unlike amateur radio, CB may be used for commercial communication. Similar personal radio services exist in other countries, with varying requirements for licencing and differing technical standards.
The Citizens' Band radio service in the United States was formed following a desire in 1945 by the US government that its citizens should be permitted a short-distance radio band for personal communication (e.g. radio controlled models, family communications, individual businesses). The FCC originally assigned class letters (A, B, C & D) different frequencies and their desired usage. Channels near 462 MHz in the UHF band were formerly allocated to the Citizen's Band "Class A" radio service but usage of this band varied across the USA. Class C Citizens Band service was for radio-controlled devices; no voice transmissions are permitted. It has six channels in the 27 MHz band and 50 channels just for model aircraft in the 72.0-73.0 MHz range, and 30 more channels for surface models such as cars and boats in the 75.4-76.0 MHz range. 0.75 watts is allowed on these numbered channels.
In the 1957, the FCC created the Class D Citizens Band service for family and individual business communications. The Class D used a portion of the 11-meter band that was a government band (primary allocation to US Forest service, military, etc.) and a secondary allocation from the amateur radio service. This Class D service became associated with the acronym "CB" to the general public. In the 1960s the service was popular for small trade businesses (e.g. electricians, plumbers, carpenters) and transportation services (e.g. taxi and trucking firms). "10 codes" originally used in the public service (e.g. police, fire, ambulance) and land mobile service were used for short acknowledgements. With the advancement of solid-state technology (transistors replacing tubes) in the 1970s, the weight, size and cost of the radios decreased. US truckers being at the head of the boom. Many CB clubs were formed and a special CB slang language evolved. The prominent use of CB radios in mid- and late-1970s films (see list below), television shows such as The Dukes of Hazzard (debuted 1979), and in popular novelty songs such as C.W. McCall's "Convoy" (1976) helped to establish the radios as a nationwide craze in the mid-1970s.
Originally CB did require a license and the use of a call sign but when the CB craze was at its peak, many people ignored this requirement and used made up nicknames or "handles". The use of handles instead of call signs is related to the common practice of using the radios to warn other drivers of speed traps during the time when the United States dropped the national speed limit to 55 mph (90 km/h) beginning in 1974 in response to the 1973 hike in oil prices. The FCC recommended the use of ten-codes and these were used, often in a shortened form, but also many slang terms were developed.
The low cost and simple operation of CB equipment gave access to a communications medium that was previously only available to specialists. The "boom" in CB usage in the 1970s bears several similarities to the advent of the Internet in the 1990s. The many restrictions on the authorized use of CB radio led to widespread disregard of the regulations, most notably in antenna height, distance restriction for communications, licensing and the use of call signs, and allowable transmitter power. Eventually the license requirement was dropped entirely.
The early CB radios sold for mobile use in the US had no more than 23 channels, controlled by plug-in quartz crystals. Almost all were AM only, although single sideband was also allowed. In 1977, an additional 17 channels were added for a total of 40 channels, to relieve some of the overcrowding on the original 23 channels. Channel 9 was reserved for emergency use. Channel 19 became the most popular channel, especially among truck drivers.
In 1973, various groups petitoned the FCC for an allocation of frequencies near 220 MHz for a new "Class E" Citizen's Band service. This was opposed by amateur radio organizations as well as other government agencies and commercial users who desired this allocation for their own usage. While the "Class E" initative was not successful in the 1970s, the Reagan Administration’s sponsored some of these requirements for the development of the Family Radio Service, General Mobile Radio Service and Multi-Use Radio Service. These services fulfilled a majority of the requirements (e.g. eliminate some of the interference and skip that existed on the shortwave frequencies) proposed by the petitioners in 1973. Today these radios are quiet, affordable and readily accessible.
American amateurs did lose a portion of their 220 MHz allocation in 1993 to a mobile radio service promoted by United Parcel Service for their delivery vans and the IVDS (218-219 MHz Service).
Throughout the 1970s and early 1980s a phenomenon was developing over the CB radio. Similar to the Internet chat rooms a quarter century later, the CB allowed people to get to know one another in a quasi-anonymous manner. Many movies and stories about CBers and the culture on-the-air developed.
In more recent years CB has lost much of its original appeal due to the advancement of technologies and changing values. Some of this rapid development includes: mobile phones, the Internet, Family Radio Service. The changing radio wave propagation for long-distance communications, due to the 11 year Sunspot cycle is always a factor for these frequencies. Broadband over Power Lines (BPL) initaitves advocated by EarthLink and some power companies for Internet access offer a new challenge to CB. Because power lines are not designed to prevent radiation of RF energy (no shielding like coaxial cables), BPL represents a potential significant interference source for all radio services using BPL frequency ranges - which includes the Citizens Band 27 MHz allocation.
CB is still a popular hobby in many countries though its utility as a method of communication among the general public has diminished, due to developments such as mobile phones. CB radio is still a near-universal method of communication among semi truck drivers in America and also remains very popular in rural areas with farmers and hunters, plus sometimes even acting as a sort of "party line" phone system in deep-rural areas too far in the boonies to have phone lines. Commercial drivers use CB to communicate to other truck drivers directions, traffic problems, and other things of importance. Though any channel (except Channel 9, reserved for emergency use) can be used, Channel 19 remains the most popular among truck drivers.
Legitimate, short-range use of CB radio is sometimes made difficult by uncooperative users or illegal high-power transmitters, which are capable of being heard hundreds of miles (km) away. In the United States, the vast number of users and the low financing of the regulatory body mean that the regulations are only actively enforced against the most severe interfering stations, which makes legitimate operations on the Citizen's band unreliable. Other services, such as Multi-Use Radio Service in the VHF band or FRS and GMRS in the UHF band, exist now to provide the reliable short-range communication service originally envisioned for the Citizen's Band.
The maximum legal CB power output level is four watts for AM and 12 watts (peak envelope power or "PEP") for single side band, as measured at the antenna connection on the back of the radio. More powerful external "linear" amplifiers are commonly and illegally used.
Citizens' Band radios in the United States use frequencies near 27 MHz. During periods of peak sunspot activity, even low-powered transmitters can sometimes be heard for hundreds or even thousands of miles. This "skip" activity, in which signals which bounce off the ionosphere, contributes to interference on CB frequencies. Working "skip" is illegal in the United States, since it contradicts the short-range intended use of the service, though the regulation is widely ignored.
Many radio hobbyists operate illegitimately in the so-called "free band", using either Citizens' Band equipment that has been modified for extended frequency range and higher power, or else amateur radio equipment operated outside the assigned amateur 10 meter band. Such operations are not part of the legally authorized Citizen's Band service and should not be called "CB". Out-of-band operations may interfere with licenced, public safety, commercial, or military users of these frequencies. Illegal transmitters may not meet good engineering practice for harmonic distortion or "splatter", and resulting interference to licenced radio spectrum users will often attract the attention of regulating authorities.
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