Citizens band radio

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A typical mobile citizens' band radio

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 require a license and unlike amateur radio, CB may be used for commercial communication.


The citizens' band radio service was formed following a decision in 1945 by the US government that its citizens should be permitted a short-distance radio band for personal communication. The 11-meter band was taken from the amateur radio service for the Citizen's band. But it was not until the 1970s, when technology had advanced to reduce costs, that the CB market prospered, 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 called "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 (89 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 lead 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 only 23 channels and 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.

Channels near 462 MHz in the UHF band were formerly allocated to the Citizen's Band "Class A" radio service but this band was never commonly used. In 1973 an attempt was made to allocate frequencies near 220 MHz to "Class E" Citizen's Band service but this was strongly opposed by amateur radio organizations and was never implemented, (though American hams lost much of this band in 1993 to a mobile radio service for parcel delivery vans). The intent was to eliminate some of the interference and skip that existed on the shortwave frequencies. While the extended propagation characteristics on this band was of considerable interest to radio hobbyists, interference from distant stations limited the usefulness of CB for its original purpose.

Throughout the 1970s and early 1980s a 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 been losing its appeal. This could be because of introduction of mobile phones, the Internet, Family Radio Service and the declining quality in long-distance radio wave propagation due to the 11 year Sunspot cycle.

CB radio today

CB is still a popular hobby in many countries though its utility as a method of communication among the general public has diminished recently, due to new 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, 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 attact the attention of regulating authorities.

CB usage in the United States

Typical mobile CB antenna

In the United States Citizens' band (CB) radio service is intended to be a private two-way voice communication service for use in personal and business activities of the general public. Its communications range is from one to five miles. The Citizens' band radio services are described in part 95 of the Federal Communications Commission's (FCC) and is defined as a personal radio service.


There are no age, citizenship or license requirements to operate a CB radio in the United States. You may operate on any of the authorized 40 CB channels, however channel 9 is used only for emergency communications or for traveler assistance. Usage of all channels is on a shared basis. Foreign governments and their representatives are not eligible to operate a citizens' band radio station within the United States.

You may operate your station anywhere within the United States, its territories and possessions. You may also operate your US station anywhere in the world except within the territorial limits of areas where radio services are regulated by another agency; such as the United States Department of Defense or of any foreign government.

You must use an FCC certified transmitter. No modifications are allowed to your equipment. Equipment output power is limited to 4 watts for AM transmitters and 12 watts PEP (peak envelope power) for single sideband (SSB) transmitters. There are no restrictions on size or type of antennas, except the antenna must not be more than 20 feet above the highest point of the structure it is mounted to and may not be more than 60 feet above the ground.

Channel assignments

To simplify selection of an operating frequency, Citizens' band radio is a two-way radio service that consists of 40 numbered radio frequency channels in the HF spectrum from 26.965 to 27.405 MHz, with channels generally spaced 10 kHz apart. Channel numbers are not strictly sequential with frequency.

There are unused 10 kHz assignments between channels 3/4, 7/8, 11/12, 15/16 and 19/20. These 'unused' frequencies are used by paging system transmitters and remote controlled toys such as toy boats and toy cars. These frequencies generally cannot be used by remote controlled aircraft, due to interference by CB radio in close proximity, which could crash the plane or helicopter into the ground, an object, or even a person. For this reason model aircraft can use the 72.0 to 73.0 MHz band instead, which contains 50 channels or licensed Amateur Radio operators can also use 53 to 54 MHz.

The gap between Channel 22 and Channel 23 (which is then filled by Channels 24 and 25) exists because originally CB radio ended at Channel 23. When the market grew extensively during the 1970s additional channels from 24 to 40 were added to the CB band.

This assignment of channels to frequencies has been adopted by many countries worldwide, including the U.K., although some countries have only approved the use of the first 22 channels.

The channel/frequency allocation for the 40 channels in Britain are as follows:

Channel     Frequency
Channel 01   26.965 MHz
Channel 02   26.975 MHz
Channel 03   26.985 MHz
Channel 04   27.005 MHz
Channel 05   27.015 MHz
Channel 06   27.025 MHz
Channel 07   27.035 MHz
Channel 08   27.055 MHz
Channel 09   27.065 MHz  (emergency channel)
Channel 10   27.075 MHz
Channel 11   27.085 MHz  (unofficial general calling channel)
Channel 12   27.105 MHz
Channel 13   27.115 MHz
Channel 14   27.125 MHz
Channel 15   27.135 MHz
Channel 16   27.155 MHz
Channel 17   27.165 MHz
Channel 18   27.175 MHz
Channel 19   27.185 MHz  (unofficial trucker's channel)
Channel 20   27.205 MHz
Channel 21   27.215 MHz
Channel 22   27.225 MHz
Channel 23   27.255 MHz
Channel 24   27.235 MHz
Channel 25   27.245 MHz
Channel 26   27.265 MHz
Channel 27   27.275 MHz
Channel 28   27.285 MHz
Channel 29   27.295 MHz
Channel 30   27.305 MHz
Channel 31   27.315 MHz
Channel 32   27.325 MHz
Channel 33   27.335 MHz
Channel 34   27.345 MHz
Channel 35   27.355 MHz
Channel 36   27.365 MHz
Channel 37   27.375 MHz
Channel 38   27.385 MHz  (lsb, national calling frequency)
Channel 39   27.395 MHz
Channel 40   27.405 MHz

The frequency allocation list is supplied by the FCC (Federal Communications Commission) from Part 95 - Subpart D - Rules for CB Service Citizens Band (CB) Radio Service.

Remote control

Remote control channels
3A 26.995 MHz
7A 27.045 MHz
11A 27.095 MHz
15A 27.145 MHz
19A 27.195 MHz

In addition to the voice channels, there are 5 remote control channels for use with remote controlled models such as cars, planes, boats and small toys. These channels are in the unused channel space between some of the voice channels. They get their channel name from the closest adjacent voice channel number below them. Although these channels are still available many of these devices are now controlled in the unlicensed 49 MHz band to avoid interference from nearby CB stations.

Shooting skip

Although CB radio was only intended to be a short range communications service, the frequencies on which it operates have some very interesting propagation characteristics. All frequencies in the HF spectrum (3–30 MHz) are able to be refracted by the existence of highly charged particles in the ionosphere. This bouncing of a signal off the ionosphere is called skywave propagation or "shooting skip". With the ability to shoot skip, CBers have been able to communicate thousands of miles, sometimes around the world. The ability of the ionosphere to refract signals back to work is caused by the sun and the amount of ionization possible is related to the 11-year sunspot cycle. In times of high sunspot activity the band can remain "open" to much of the world for long periods of time. In years of low sunspot activity it may not be possible to shoot skip at all.

It is recorded that, before CB radio arose, the Afrika Korps in North Africa in WWII used 27 MHz for battlefield communications, thinking that it could only be heard locally; but skip was strong at the time, and the messages were routinely monitored in Britain.


Use of import-specification FM gear, or domestic CB equipment illegally modified to operate on frequencies above ("uppers") or below ("lowers") the established citizens band is sometimes referred to as "freebanding".

Many freebanders believe frequencies located between the CB band and the amateur radio 10-meter band from 27.410 to 27.990 MHz to be quiet and under utilized.

Regulation and enforcement

Actions against violations of FCC regulations have been minimal in the past. This has often been cited as the reason for many of the problems that have plagued the Citizens' band radio service in the past.

In recent years, the FCC has had a renewed interest in taking enforcement actions against freebanding, the sale and use of illegally modified radios and linear amplifiers. Usually, the FCC will issue a request for information explaining actions found to be in violation of the commissions rules and regulations. Responding in a timely manner to such a request usually results in a "quick and painless" resolution which in most cases does not result in a fine, but merely a cease and desist order. Failure to respond to the commission's letters of inquiry will commonly result in the issuing of a $10,000 fine and in rem seizure of the equipment used, and suspension of licences in other FCC regulated services.

Many actions have been taken in recent years against the so-called freebanders operating illegally in the amateur 10-meter band. Actions have also been taken against retailers in the United States for selling linear amplifiers and non-type approved equipment in violation of the commission's rules.

Famous CBers

CB in movies

International use

Although CB was created in and for the United States, similar services exist in other countries around the world (see CB radio in the United Kingdom and Australian UHF CB-equivalent). Technical standards, power levels, and frequencies are different so North American CB equipment may not comply with European regulations, and vice versa. Often other radio services will use FM instead of AM or SSB.

A gray market trade in imported CB gear does exist in many countries. In many instances, sale or ownership of foreign-specification CB gear is not illegal, but the actual use of it is. With the FCC's minimal enforcement of its rules regarding CB radio, enthusiasts in the USA often use European FM CB gear to get away from the overcrowded AM channels. American AM gear has also been exported to Europe.

In Canada, the "General Radio Service" has the identical frequencies and modes as the United States "Citizen's band", and no special provisions are required for either Canadians or Americans using CB gear while travelling across the border.

See also

External links

  • Ursine:CB - Detailed CB radio channel plan, 10 codes, Q signals

de:CB-Funk ja:市民ラジオ no:Privatradio