Citizens' band radio

From Academic Kids

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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 have the right to 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 language evolved. The prominent use of CB radios in late 1970s films (see list below), television shows such as The Dukes of Hazzard (1979), and in popular novelty songs such as "Convoy" (1976) helped to establish the radios as a nationwide craze in the late 1970s.

Originally CB did require a license and the use of a call sign but during the CB craze of the 1970's 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). 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 1970's bears several similarities to the advent of the Internet in the 1990s. The many restrictions on the authorized use of CB lead to widespread disregard of the regulations, most notably in antenna height, distance restriction for communications, licencing 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.

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 loosing its appeal. This could be because of introduction of mobile phones, the Internet, Family Radio Service and the declining long-distance 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 popular method of communication among semi truck drivers. Commercial drivers use CB to communicate to other truck drivers directions, traffic problems, and other things of importance.

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.

Many radio hobbyists operate illegitimately in the so-called "free band", using either Citizen's 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

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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 channelized frequencies in the HF spectrum from 26.960 to 27.410 MHz. Frequencies for the channels are mostly 10 kHz apart. Channel numbers are not strictly sequential with frequency.

CB voice channels
1 26.965 MHz
2 26.975 MHz
3 26.985 MHz
4 27.005 MHz
5 27.015 MHz
6 27.025 MHz
7 27.035 MHz
8 27.055 MHz
9 27.065 MHz
10 27.075 MHz
11 27.085 MHz
12 27.105 MHz
13 27.115 MHz
14 27.125 MHz
15 27.135 MHz
16 27.155 MHz
17 27.165 MHz
18 27.175 MHz
19 27.185 MHz
20 27.205 MHz
21 27.215 MHz
22 27.225 MHz
23 27.255 MHz
24 27.235 MHz
25 27.245 MHz
26 27.265 MHz
27 27.275 MHz
28 27.285 MHz
29 27.295 MHz
30 27.305 MHz
31 27.315 MHz
32 27.325 MHz
33 27.335 MHz
34 27.345 MHz
35 27.355 MHz
36 27.365 MHz
37 27.375 MHz
38 27.385 MHz
39 27.395 MHz
40 27.405 MHz

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.


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".

Located between the CB band and the amateur radio 10-meter band from 27.410 to 27.990 MHz, many freebanders believe it to be a quiet and under utilized part of the spectrum.

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 to a lesser extent.

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


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