General Mobile Radio Service
Citizens' band radio(CB Radio)
Citizens' Band radio (CB) is, in many countries, a system of short-distance, simplex[1] radio communications between individuals on a selection of 40 channels within the 27 MHz (11 meter) band. The CB radio service should not be confused with FRS, GMRS, MURS, or amateur ("ham") radio. Similar personal radio services exist in other countries, with varying requirements for licensing and differing technical standards. In many countries, CB does not require a license and, unlike amateur radio, it may be used for business as well as personal communications.
Scope
The Citizens' Band radio service originated in the United States as one of several personal radio services regulated by the FCC. These services began in 1945 to permit citizens a short-distance radio band for personal communication (e.g., radio controlled models, family communications, individual businesses). Originally, CB was located in the 460-470 MHz UHF band. There were two classes of CB: A and B. Class B radios had simpler technical requirements but were limited to a smaller range of frequencies. Al Gross, inventor of the walkie-talkie, started Citizen's Radio Corp. in the late 1940s to merchandise Class B handhelds for the general public.[2]
The technology at the time was not advanced enough for UHF radios to be practical and affordable for the average consumer. So, in 1958,[3] the Class D CB service was opened at 27 MHz, and this is what is popularly known as CB. There were only 23 channels at the time; the first 22 were taken from what used to be an Amateur 11-meter band, while channel 23 was shared with radio-controlled devices. Some hobbyists continue to use the designation "11 meters" to refer to the Citizens' Band and adjoining frequencies.
Most of the 460-470 MHz band was reassigned for business and public safety uses, but Class A CB is the ancestor of the present General Mobile Radio Service GMRS. Class B, in the same vein, is a more distant ancestor of the Family Radio Service. The Multi-Use Radio Service is another two-way radio service, in the VHF high band. An unsuccessful petition was made in 1973 to create a Class E CB service at 220 MHz, this was opposed by amateur radio organizations[4] and others. There are several other classes of personal radio services for specialized purposes such as remote control devices.
Over time, several countries have created similar radio services. While they may be known by other names, such as General Radio Service in Canada,[5] they often use similar frequencies (26 to 28 MHz), and have similar uses, and similar issues with antennas and propagation. Licenses may or may not be required, but eligibility is generally simple.
Some countries have personal radio services in the UHF band, such as the European PMR446 and the Australian UHF CB. Like the American FRS and GMRS services, these are more properly covered in their own articles, as much of this article is specific to the antenna and propagation issues of the upper HF and lower VHF bands.
CB Frequencies Worldwide
Similar radio services exist in other countries around the world. Frequencies, power levels, and modes (such as FM, AM and SSB) may vary from country to country, and usage of foreign equipment may be illegal. However, many countries have adopted the American frequencies.
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 traveling across the border.
In Europe, the CEPT adopted the North American channel assignments, except that FM is used instead of AM. Some member countries permit additional modes and frequencies.
Before CEPT, most of the member countries used some subset of the 40 USA channels. The United Kingdom, on the other hand, originally had 40 unique 27 MHz channels, known as the 27/81 Bandplan. See CB radio in the United Kingdom. With the CEPT channels added, the UK now has 80 channels. Germany also has 40 unique channels at 26 MHz for a total of 80.
The frequencies for the 40 North American/CEPT channels are as follows. Note that for historical reasons, channels 22 to 26 are not in ascending order of frequencies:-
| Channel 01 : 26.965 MHz | Channel 11 : 27.085 MHz | Channel 21 : 27.215 MHz | Channel 31 : 27.315 MHz |
| Channel 02 : 26.975 MHz | Channel 12 : 27.105 MHz | Channel 22 : 27.225 MHz | Channel 32 : 27.325 MHz |
| Channel 03 : 26.985 MHz | Channel 13 : 27.115 MHz | Channel 23 : 27.255 MHz | Channel 33 : 27.335 MHz |
| Channel 04 : 27.005 MHz | Channel 14 : 27.125 MHz | Channel 24 : 27.235 MHz | Channel 34 : 27.345 MHz |
| Channel 05 : 27.015 MHz | Channel 15 : 27.135 MHz | Channel 25 : 27.245 MHz | Channel 35 : 27.355 MHz |
| Channel 06 : 27.025 MHz | Channel 16 : 27.155 MHz | Channel 26 : 27.265 MHz | Channel 36 : 27.365 MHz |
| Channel 07 : 27.035 MHz | Channel 17 : 27.165 MHz | Channel 27 : 27.275 MHz | Channel 37 : 27.375 MHz |
| Channel 08 : 27.055 MHz | Channel 18 : 27.175 MHz | Channel 28 : 27.285 MHz | Channel 38 : 27.385 MHz |
| Channel 09 : 27.065 MHz | Channel 19 : 27.185 MHz | Channel 29 : 27.295 MHz | Channel 39 : 27.395 MHz |
| Channel 10 : 27.075 MHz | Channel 20 : 27.205 MHz | Channel 30 : 27.305 MHz | Channel 40 : 27.405 MHz |
In the UK the requirement to have a license has been dispensed with, but all permission for the public to use the UK-specific frequencies may be withdrawn in 2010, under plans to reassign the frequencies to the Community Audio Distribution System service.[15]
In Poland (and probably some other former Warsaw Pact countries) the channels are shifted 5kHz down, so for example channel 30 is 27.300MHz, many operators add a switch that can change between the "zeroes" (the Polish channel assignment), and the "fives" (the international assignment).
Australia now has the 40 North American channels, though in the late 1970s it had an 18-channel bandplan with unique numbering.[16] On the other hand, New Zealand and Japan have unique allocations that don't correspond to any other country's.
Indonesia has the usual 40 channels at 27 MHz, plus a unique 60-channel allocation from 142.050-143.525 MHz.[17]
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 "export" radios, or possibly European FM CB gear to get away from the overcrowded AM channels. American AM gear has also been exported to Europe.
Using radios outside their intended market can be dangerous as well as illegal. For example, the British frequencies clash with a radio service used by ambulance services in Ukraine.[18]
