Citizens' band radio
Encyclopedia
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
(11 m) band. Citizens' Band is distinct from the FRS
Family Radio Service
The Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
, GMRS, MURS
Multi-Use Radio Service
In the United States, the Multi-Use Radio Service is an unlicensed two-way radio service similar to Citizens Band . Established by the U.S. Federal Communications Commission in the fall of 2000, MURS created a radio service allowing for unlicensed operation, with a power limit of 2 watts...
and amateur ("ham") radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
. In many countries CB operation does not require a license, and (unlike amateur radio) it may be used for business or personal communications. Like many other two-way radio
Two-way radio
A two-way radio is a radio that can both transmit and receive , unlike a broadcast receiver which only receives content. The term refers to a personal radio transceiver that allows the operator to have a two-way conversation with other similar radios operating on the same radio frequency...
services, Citizens' Band channels are shared by many users. Only one station may transmit at a time; other stations must listen and wait for the shared channel to be available.
A number of countries have created similar radio services, with varying technical standards and requirements for licensing. While they may be known by other names, such as the General Radio Service in Canada, they often use similar frequencies (26 to 28 MHz), have similar uses, and similar technical challenges. Although licenses may be required, eligibility is generally simple. Some countries also have personal radio services in the UHF band, such as the European PMR446
PMR446
PMR446 is a part of the UHF radio frequency range that is open without licensing for personal usage in most countries of the European Union. It has roughly the same use as FRS or GMRS in the United States and Canada. Depending on surrounding terrain range can vary from a few hundred metres to a...
and the Australian UHF CB
UHF CB
UHF CB is a class-licensed citizen's band radio service authorised by the governments of Australia and New Zealand in the UHF 477 MHz band. UHF CB provides 77 channels, including 32 channels allocated to repeater stations...
.
Origins
The Citizens' Band radio service originated in the United States as one of several personal radio services regulated by the Federal Communications CommissionFederal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
(FCC). These services began in 1945 to permit citizens a radio band for personal communication (e.g., radio-controlled model airplanes and family and business communications). In 1948, the original Class D CB Radios were designed for operation on the 460 MHz–470 MHz UHF band. 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
Alfred J. Gross
Alfred J. Gross , a.k.a. Irving J. Gross was a pioneer in mobile wireless communication. He created and patented many communications devices, specifically in relation to an early version of the walkie-talkie, Citizens' Band radio, the telephone pager and the cordless telephone...
, established the Citizen's Radio Corporation during the late 1940s to manufacture Class B handhelds for the general public.
Ultra-high frequency (UHF) radios, at the time, were neither practical nor affordable for the average consumer. In 1958 the Class D CB service was moved to 27 MHz, and this band became what is popularly known as CB. There were only 23 channels at the time; the first 22 were taken from the former amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
11-meter band, and 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. Part 95 of the Code of Federal Regulations regulated the Class D CB service, on the 27 MHz band, as of the 1970s. Most of the 460–470 MHz band was reassigned for business and public-safety use; Class A CB is the forerunner of the General Mobile Radio Service
General Mobile Radio Service
The General Mobile Radio Service is a licensed land-mobile FM UHF radio service in the United States available for short-distance two-way communication. It is intended for use by an adult individual who possesses a valid GMRS license, as well as his or her immediate family members...
(GMRS). Class B Citizens' Band is a more distant ancestor of the Family Radio Service
Family Radio Service
The Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
. The Multi-Use Radio Service
Multi-Use Radio Service
In the United States, the Multi-Use Radio Service is an unlicensed two-way radio service similar to Citizens Band . Established by the U.S. Federal Communications Commission in the fall of 2000, MURS created a radio service allowing for unlicensed operation, with a power limit of 2 watts...
is another two-way radio service in the VHF high band
Band III
Band III is the name of a radio frequency range within the very high frequency part of the electromagnetic spectrum.Band III ranges from 174 to 230 MHz, and it is primarily used for radio and television broadcasting...
. An unsuccessful petition was filed in 1973 to create a Class E CB service at 220 MHz, which was opposed by amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
organizations and others. There are several other classes of personal radio services for specialized purposes (such as remote control
Remote control
A remote control is a component of an electronics device, most commonly a television set, used for operating the television device wirelessly from a short line-of-sight distance.The remote control is usually contracted to remote...
devices).
During the 1960s, the service was popular among small businesses (e.g., electricians, plumbers, carpenters), truck drivers and radio hobbyists. By the late 1960s advances in solid-state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...
electronics allowed the weight, size, and cost of the radios to fall, giving the public access to a communications medium previously only available to specialists. CB clubs were formed; a CB slang
CB slang
CB slang is the distinctive anti-language, argot or cant which developed amongst users of citizens' band radio , especially truck drivers in the USA during the 1970s and early-1980s....
language evolved alongside 10-codes
Ten-code
Ten-codes, also known as ten signals, are code words used to represent common phrases in voice communication, particularly by law enforcement and in Citizens' Band radio transmissions....
, similar to those used in emergency service
Emergency service
Emergency services are organizations which ensure public safety and health by addressing different emergencies. Some agencies exist solely for addressing certain types of emergencies whilst others deal with ad hoc emergencies as part of their normal responsibilities...
s.
1970s popularity
After the 1973 oil crisis1973 oil crisis
The 1973 oil crisis started in October 1973, when the members of Organization of Arab Petroleum Exporting Countries or the OAPEC proclaimed an oil embargo. This was "in response to the U.S. decision to re-supply the Israeli military" during the Yom Kippur war. It lasted until March 1974. With the...
the U.S. government imposed a nationwide 55 mph speed limit
National Maximum Speed Law
The National Maximum Speed Law in the United States was a provision of the 1974 Emergency Highway Energy Conservation Act that prohibited speed limits higher than . It was drafted in response to oil price spikes and supply disruptions during the 1973 oil crisis...
, and fuel shortages and rationing were widespread. CB radio was used (especially by truckers
Truck driver
A truck driver , is a person who earns a living as the driver of a truck, usually a semi truck, box truck, or dump truck.Truck drivers provide an essential service to...
) to locate service stations with better supplies of fuel, to notify other drivers of speed traps, and to organize blockades and convoys in a 1974 strike protesting the new speed limit and other trucking regulations. The radios were crucial for independent truckers; many were paid by the mile, which meant their productivity was impacted by the 55-mph speed limit. The use of CB radios in 1970s films such as Smokey and the Bandit
Smokey and the Bandit
Smokey and the Bandit is a 1977 American film starring Burt Reynolds, Sally Field, Jackie Gleason, Jerry Reed, Pat McCormick, Paul Williams, and Mike Henry. It inspired several other trucking films, including two sequels, Smokey and the Bandit II, and Smokey and the Bandit Part 3...
(1977) and Convoy (1978), popular novelty song
Novelty song
A novelty song is a comical or nonsensical song, performed principally for its comical effect. Humorous songs, or those containing humorous elements, are not necessarily novelty songs. The term arose in Tin Pan Alley to describe one of the major divisions of popular music. The other two divisions...
s such as C.W. McCall's "Convoy
Convoy (song)
"Convoy" is a 1975 novelty song performed by C. W. McCall that became a number-one song on both the country and pop charts in the US. Written by McCall and Chip Davis, the song spent six weeks at number one on the country charts and one week at number one on the pop charts...
" (1975) and on television series such as Movin' On
Movin' On (TV series)
Movin' On is an American drama series that ran for two seasons , between 1974 and 1976. It originally appeared on the NBC television network...
(debuted 1974) and The Dukes of Hazzard
The Dukes of Hazzard
The Dukes of Hazzard is an American television series that aired on the CBS television network from 1979 to 1985.The series was inspired by the 1975 film Moonrunners, which was also created by Gy Waldron and had many identical or similar character names and concepts.- Overview :The Dukes of Hazzard...
(debuted 1979) established CB radio as a nationwide craze in the USA in the mid- to late 1970s.
Originally CB required a purchased license ($20 in the early 1970s, reduced to $4 later in the decade) and the use of a call sign; however, when the CB craze was at its peak many people ignored this requirement and invented their own nickname
Nickname
A nickname is "a usually familiar or humorous but sometimes pointed or cruel name given to a person or place, as a supposedly appropriate replacement for or addition to the proper name.", or a name similar in origin and pronunciation from the original name....
s (known as "handles"). Rules on authorized use of CB radio (along with lax enforcement) led to widespread disregard of the regulations (notably in antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
height, distance communications, licensing, call signs and transmitter power. After the FCC started receiving over one million license applications a month, the license requirement was dropped entirely.
Betty Ford
Betty Ford
Elizabeth Ann Bloomer Warren Ford , better known as Betty Ford, was First Lady of the United States from 1974 to 1977 during the presidency of her husband Gerald Ford...
, a former First Lady of the United States
First Lady of the United States
First Lady of the United States is the title of the hostess of the White House. Because this position is traditionally filled by the wife of the president of the United States, the title is most often applied to the wife of a sitting president. The current first lady is Michelle Obama.-Current:The...
, had a CB handle was "First Mama". Voice actor Mel Blanc
Mel Blanc
Melvin Jerome "Mel" Blanc was an American voice actor and comedian. Although he began his nearly six-decade-long career performing in radio commercials, Blanc is best remembered for his work with Warner Bros...
was also an active CB operator, often using "Bugs"
Bugs Bunny
Bugs Bunny is a animated character created in 1938 at Leon Schlesinger Productions, later Warner Bros. Cartoons. Bugs is an anthropomorphic gray rabbit and is famous for his flippant, insouciant personality and his portrayal as a trickster. He has primarily appeared in animated cartoons, most...
or "Daffy"
Daffy Duck
Daffy Duck is an animated cartoon character in the Warner Bros. Looney Tunes and Merrie Melodies series of cartoons, often running the gamut between being the best friend and sometimes arch-rival of Bugs Bunny...
as his handle and talking on the air in the Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
area in one of his many voice characters. He appeared in an interview (with clips having fun talking to children on his home CB radio station) in the NBC Knowledge television episode about CB radio in 1978. Similar to internet chat room
Chat room
The term chat room, or chatroom, is primarily used by mass media to describe any form of synchronous conferencing, occasionally even asynchronous conferencing...
s a quarter-century later, CB allowed people to get to know one another in a quasi-anonymous manner. As on the internet, CB radio sometimes encouraged the worst characteristics of anonymity:
Originally, there were 23 CB channels in the U.S.; the 40-channel band plan was implemented in 1977. Channel 9 was officially reserved for emergency use by the FCC in 1969. Channel 10 was originally often used for highway communications east of the Mississippi River
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
, and channel 19 west of the Mississippi; channel 19 then became the preferred highway channel in most areas, as it did not have adjacent-channel interference
Adjacent-channel interference
Adjacent-channel interference is interference caused by extraneous power from a signal in an adjacent channel. ACI may be caused by inadequate filtering , improper tuning or poor frequency control .ACI is distinguished from crosstalk.Broadcast...
problems with channel 9. Many CBers called channel 19 "the trucker's channel".
Initially, the FCC intended for CB to be the "poor man's business-band radio", and CB regulations were structured similarly to those regulating the business band
Business band
The business band is the name used by US radio users and scanner hobbyists who listen to Federal Communications Commission licensees using Industrial/Business pool frequencies...
radio service. Until 1975, only channels 9–15 and 23 could be used for "inter-station" calls (to other licensees). Channels 1–8 and 16–22 were reserved for "intra-station" communications (among units with the same license). After the inter-station/intra-station rule was dropped, channel 11 was reserved as a calling frequency (for the purpose of establishing communications); however, this was withdrawn in 1977. During this early period, many CB radios had "inter-station" channels colored on their dials, whilst the other channels were clear or normally colored (except channel 9, which was usually colored red.
It was common for a town to adopt an inter-station channel as its "home" channel. This helped prevent overcrowding on channel 11, enabling a CBer to tune a town's home channel to contact another CBer from that town instead of a making a general call on channel 11. Single-sideband
Single-sideband modulation
Single-sideband modulation or Single-sideband suppressed-carrier is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth....
(SSB) users commonly used channel 16, to avoid interference to those using AM
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
(SSB stations were authorized to use 12 watts, as opposed to 4 watts for AM stations) and to more easily locate other SSB stations. With the FCC authorization of 40 channels, SSB operation shifted to channels 36–40. Channel 36 became the unofficial SSB "calling channel" for stations seeking contacts, with the subsequent conversation moving to channels 37–40. CBers with AM-only radios were asked to not use channels 36 through 40. In return, SSB stations stayed off the remaining 35 channels so they could be used by AM stations.
21st-century use
CB has lost much of its original appeal due to development of mobile phones, the internetInternet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
and the Family Radio Service
Family Radio Service
The Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
. Changing radio propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
for long-distance communications due to the 11-year sunspot cycle is a factor at these frequencies. In addition, CB may have become a victim of its own popularity; with millions of users on a finite number of frequencies during the mid-to-late 1970s and early 1980s, channels often were noisy and communication difficult. This caused a waning of interest among hobbyists. Business users (such as tow-truck operators, plumbers and electricians) moved to the VHF business-band frequencies. The business band requires an FCC license, and usually results in an assignment to a single frequency. The advantages of fewer users sharing a frequency, greater authorized output power, clarity of FM
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
transmission, lack of interference by distant stations due to "skip", and consistent communications made the VHF frequencies an attractive alternative to the overcrowded CB channels.
Channel 9 is reserved for emergency and roadside assistance. Most east- or westbound highway travelers monitor channel 19; north- or southbound travelers monitor channel 17. CB radio is still used by truck drivers, and remains an effective means of obtaining information about road construction, accidents and police radar traps
Speed limit enforcement
Speed limit enforcement is the action taken by appropriately empowered authorities to check that road vehicles are complying with the speed limit in force on roads and highways. Methods used include roadside speed traps set up and operated by the police and automated roadside 'speed camera'...
.
Australia
Before CB was authorized in Australia, there were hand-held 27-MHz "walkie-talkies" which utilised several frequencies between the present CB channels, such as 27.240 MHz. By the mid-1970s, hobbyists were experimenting with handheld radios and unauthorized American CB radios. At that time in Australia, the 11-meter band was still used by licenced ham operators, but not yet available for CB use. A number of CB clubs had formed by this time which assigned callsigns to members, exchanged QSL cards, and lobbied for the legalization of CB. In 1977, CB was legalized with an 18-channel bandplan. In 1980, the American 40-channel band plan was adopted. From the outset the government attempted to regulate CB radio with licence fees and call-signs, but some years later abandoned this approach.The first CB club in Australia was the Charlie Brown Touring Car Club (CBTCC), which formed in Morwell, Victoria
Morwell, Victoria
-Transport:The main form of transport in Morwell is the automobile. The Princes Freeway now bypasses the town to the south while the old Princes Highway which once passed through east-west through its centre is now Princes Drive and Commercial Road. The highway connects Morwell with other...
in 1967 and consisted mainly of four-wheel drive
Four-wheel drive
Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...
enthusiasts. The club used the prefix GL (for Gippsland
Gippsland
Gippsland is a large rural region in Victoria, Australia. It begins immediately east of the suburbs of Melbourne and stretches to the New South Wales border, lying between the Great Dividing Range to the north and Bass Strait to the south...
), since "CB" could not be used. After July 1, 1977, the club changed its name to Citizens Band Two Way Communication Club (CBTCC). Other early clubs were LV (Latrobe Valley
Latrobe Valley
The Latrobe Valley is an inland geographical region and urban area of Gippsland in the state of Victoria, Australia. It is east of the City Of Melbourne and nestled between the Strzelecki Ranges to the south and the Great Dividing Range to the north – with the highest peak to the north of the...
) and WB (named after Wayne Britain). Members of these clubs are still active, and have also become amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operators.
With the introduction of UHF CB radios in 1977, many operators used both UHF and HF radios and formed groups to own and operate local FM repeaters. Members of the CBTCC formed what became known as Australian Citizens Radio Movement (ACRM) in the early 1970s; this organisation became the voice for CB radio legalisation throughout Australia. After peaking in the 1970s and early 1980s, the use of 27 MHz CB in Australia has fallen dramatically due to the introduction of 477 MHz UHF CB
UHF CB
UHF CB is a class-licensed citizen's band radio service authorised by the governments of Australia and New Zealand in the UHF 477 MHz band. UHF CB provides 77 channels, including 32 channels allocated to repeater stations...
(with FM and repeaters) and the proliferation of cheap, compact handheld UHF transceivers. Technology such as mobile telephones and the Internet have provided people with other choices for communications. The Australian government is working on changing the allocation of channels available for UHF CB Radio from 40 to 80, and doubling the number of repeater channels from 8 to 16.
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Canada
In CanadaCanada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
the General Radio Service uses the identical frequencies and modes as the United States Citizens' Band, and no special provisions are required for either Canadians or Americans using CB gear while traveling across the border. The General Radio Service was authorized in 1962. Initially, CB channels 1 through 3 remained allocated to amateur radio and channel 23 was used by paging services
Pager
A pager is a simple personal telecommunications device for short messages. A one-way numeric pager can only receive a message consisting of a few digits, typically a phone number that the user is then requested to call...
. American CB licensees were initially required to apply for a temporary license to operate in Canada. In April 1977, the service was expanded to the same 40 channels as the American service.
Indonesia
In IndonesiaIndonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, CB radios were first introduced about 1977 when some transceivers were imported illegally from Australia, Japan and the United States. The dates are hard to confirm accurately, but early use was known around large cities such as Jakarta
Jakarta
Jakarta is the capital and largest city of Indonesia. Officially known as the Special Capital Territory of Jakarta, it is located on the northwest coast of Java, has an area of , and a population of 9,580,000. Jakarta is the country's economic, cultural and political centre...
, Bandung
Bandung
Bandung is the capital of West Java province in Indonesia, and the country's third largest city, and 2nd largest metropolitan area in Indonesia, with a population of 7.4 million in 2007. Located 768 metres above sea level, approximately 140 km southeast of Jakarta, Bandung has cooler...
, Yogyakarta, Surabaya
Surabaya
Surabaya is Indonesia's second-largest city with a population of over 2.7 million , and the capital of the province of East Java...
and Medan
Medan
- Demography :The city is Indonesia's fourth most populous after Jakarta, Surabaya, and Bandung, and Indonesia's largest city outside of Java island. Much of the population lies outside its city limits, especially in Deli Serdang....
. The Indonesian government legalized CB on October 6, 1980 with a decision by the Minister of Communications, the "Ministerial Decree on the Licensing for the Operation of Inter-Citizens Radio Communication". Because many people were already using 40-channel radios prior to legalization, the American band plan (with AM and SSB) was adopted; a VHF band was added in 1994. On November 10, 1980, the Indonesian Directorate General of Posts and Telecommunications issued another decree establishing RAPI (Radio Antar Penduduk Indonesia) as the official citizens' band radio organization in Indonesia.
Malaysia
In Malaysia, Citizens' Band radios became legal when the Notification of Issuance Of Class Assignments by Communication and Multimedia Malaysia was published on 1 April 2000. Under this class assignment, CB radio is classified as a "Personal Radio Service Device". The frequency band is HF, 26.9650 MHz to 27.4050 MHz (40 channels), power output is 4 watts for AM and FM and 12 watts PEP for SSB. Channel 9 is reserved for emergencies, and channel 11 is a calling channel. On UHF 477 MHz, Citizens' Band PRS radio devices are allowed 5 watts power output on FM on 39 assigned channels spaced at 12.5-kHz intervals between 477.0125 MHz and 477.4875 MHz. Channel 9 is reserved for emergencies, and channel 11 for calling. A short-range simplexSimplex communication
Simplex communication refers to communication that occurs in one direction only. Two definitions have arisen over time: a common definition, which is used in ANSI standard and elsewhere, and an ITU-T definition...
radio communications service for recreational use is from 477.5250–477.9875 MHz FM mode with 38 channels and a power output of 500 mW. A CB (citizens' band) radio or Personal Radio Service Device under Class Assignment does not need an individual license to operate in Malaysia if it adheres to the rules of the Warta Kerajaan Malaysia, Communication and Multimedia Act 1998 (Act 588), Notification of Issuance Of Class Assignment, P.U.(B)416 Jil. 48, No. 22(e) Personal Radio Service Device, 1 November 2004.
On 1 April 2010 the MCMC (Malaysian Communications and Multimedia Commission) released a new Notification of Issuance of Class Assignment, the Communications and Multimedia Act 1998 Class Assignments No. 1 of 2010. This includes a new UHF PMR 446 MHz allocation: an eight-channel analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
Personal Mobile Radio 446 MHZ (Analog PMR446) with frequencies from 446.0025–446.09375 MHz (12.5 kHz spacing) FM with 0.5 watt power output, and 16 channels for Digital
Digital signal
A digital signal is a physical signal that is a representation of a sequence of discrete values , for example of an arbitrary bit stream, or of a digitized analog signal...
Personal Mobile Radio 446 MHz (Digital PMR 446). Frequencies for Digital PMR 446 are from 446.103125–446.196875 MHz with 6.25 kHz channel spacing
Channel spacing
Channel spacing is a term used in radio frequency planning. It describes the frequency difference between adjacent allocations in a frequency plan. Channels for mediumwave radio stations, for example are allocated in internationally-agreed steps of 9 or 10 kHz: 10 kHz in ITU Region 2 and 9 kHz...
in 4FSK mode and a power output of 0.5 watt. An unofficial citizens' band radio club in Malaysia is the "Malaysia Boleh Citizen Radio Group", known as "Mike Bravo" (Malaysia Boleh).
United Kingdom
In Great Britain, some people were illegally using American CB radios during the 1970s. The prominence of CB radio grew in Britain partly due to the popularity of novelty songs like CW McCall's "Convoy" and Laurie Lingo & The Dipsticks' "Convoy GB" in 1976 (both of which were Top 5 hits) and the film Convoy in 1978. By 1980, CB radio had become a popular pastime in Britain; as late as the summer of 1981 the British government was still saying that CB would never be legalized on 27 MHz, proposing a UHF service around 860 MHz called "Open Channel" instead. However, in November 1981 (after high-profile public demonstrations) 40 frequencies unique to the UK, known as the 27/81 Bandplan27 MHz CB27/81 Bandplan
The 27 MHz CB27/81 Bandplan is a list of the channel frequencies for UK-only FM CB radio CB radio in the United Kingdom.Unlike CB usage in the United States, and subsequently elsewhere in the world, the original UK 40 channels progress in order with 10 kHz spacing...
using FM were allocated at 27 MHz plus 20 channels on 934 MHz (934.0125 to 934.9625 MHz with 50-kHz-spacing). CB's inventor, Al Gross
Alfred J. Gross
Alfred J. Gross , a.k.a. Irving J. Gross was a pioneer in mobile wireless communication. He created and patented many communications devices, specifically in relation to an early version of the walkie-talkie, Citizens' Band radio, the telephone pager and the cordless telephone...
, made the ceremonial first legal British CB call from Trafalgar Square
Trafalgar Square
Trafalgar Square is a public space and tourist attraction in central London, England, United Kingdom. At its centre is Nelson's Column, which is guarded by four lion statues at its base. There are a number of statues and sculptures in the square, with one plinth displaying changing pieces of...
in London.
The maximum power allowable on the MPT 1320 27/81 system was 4 watts (in common with the American system), although initially radios were equipped to reduce output power by 10 dB
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
(to 0.4 watts) if the antenna was mounted more than 7 metres above ground level. The power-reduction switch is also useful in reducing TV interference
Electromagnetic interference
Electromagnetic interference is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...
. MPT 1320 also restricted antennas to a maximum length of 1.5 metres, with base loading being the only type permitted for 27 MHz operation. Over the next several years antenna regulations were relaxed, with antenna length increasing to 1.65 metres and centre- or top-loading of the main radiating element permitted. On 1 September 1987 the UK added the usual 40 frequencies (26.965–27.405 MHz) used worldwide, for a total of 80 channels at 27 MHz; antenna regulations were further relaxed, and the 934 MHz band was withdrawn in 1998.
CB radio in the UK was deregulated in December 2006 by the regulatory body Ofcom
Ofcom
Ofcom is the government-approved regulatory authority for the broadcasting and telecommunications industries in the United Kingdom. Ofcom was initially established by the Office of Communications Act 2002. It received its full authority from the Communications Act 2003...
, and CB radio in the UK is licence-free. The old MPT 1320 27/81 band will continue to be available for the foreseeable future. The rules regarding non-approved radios, modes other than FM and power levels above 4 watts still apply, despite deregulation. Persons using illegal equipment or accessories still risk prosecution, fines and/or confiscation of equipment, although this is rarely enforced. AM, SSB and amplifier use are common among enthusiasts. Packet radio
Packet radio
Packet radio is a form of packet switching technology used to transmit digital data via radio or wireless communications links. It uses the same concepts of data transmission via Datagram that are fundamental to communications via the Internet, as opposed to the older techniques used by dedicated...
is legal in the UK, although not widely used. Internet gateway stations are also beginning to appear; although illegal on 27 MHz, these units are connected to other CB stations around the world.
UK regulations differ somewhat from those in other countries; although AM/FM CB transceivers are legal (since they conform to European specifications), but the use of AM is illegal in the UK. As a result, a European CB operator cannot use AM whilst in the UK but can do so when in Ireland or on the continent. Although the use of CB radios in the UK is limited they are still popular, especially with the farming community, truckers and mini-cab services. The widely-used channel for the Young Farmers Club
National Federation of Young Farmers' Clubs
The National Federation of Young Farmers' Clubs is the largest rural youth organisation of its kind, in the United Kingdom. The Federation covers various Young Farmers' Clubs throughout England and Wales, helping support young people in agriculture and the countryside...
is channel 11. The normal calling and truckers' channel is channel 19, although many truck organisations and groups use other channels to avoid abuse. Irish truckers who travel to the UK still use 27 MHz AM, since enforcement is lax.
Frequencies worldwide
CB radio is not a worldwide, standardized radio service like amateur radio. Each country decides if it wants to authorize such a radio service from its domestic frequency authorizations, and what its standards will be; however, similar radio services exist in many countries. Frequencies, power levels and modes (such as frequency modulationFrequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
(FM), amplitude modulation
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
(AM), and single-sideband modulation
Single-sideband modulation
Single-sideband modulation or Single-sideband suppressed-carrier is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth....
(SSB), often vary from country to country; use of foreign equipment may be illegal. However, many countries have adopted American frequencies.
The European Conference of Postal and Telecommunications Administrations
European Conference of Postal and Telecommunications Administrations
The European Conference of Postal and Telecommunications Administrations was established on June 26, 1959, as a coordinating body for European state telecommunications and postal organizations...
(CEPT) adopted the North American channel assignments, except that FM is used instead of AM. Some member countries permit additional modes and frequencies; for example, Germany has 40 additional channels at 26 MHz for a total of 80. Before CEPT, most member countries used a subset of the 40 US channels.
In Poland the channels are shifted 5 kHz down; for example, channel 30 is 27.300 MHz. Many operators add a switch to change between the "zeroes" (the Polish channel assignment) and the "fives" (the international assignment).
New Zealand and Japan have unique allocations, that do not correspond to those of any other country. Indonesia has the usual 40 channels at 27 MHz, plus a unique 60-channel allocation from 142.050 MHz–143.525 MHz.
Using radios outside their intended market can be dangerous, as well as illegal as frequencies used by Citizen's Band radios from other countries may operate on frequencies close to, or used by, emergency services (For example, the Indonesian service around 142MHz operates on frequencies allocated to a Public Safety network shared with Police, Fire and EMS services in Ontario, Canada).
| Channel | Frequency Frequency Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency... |
Channel | Frequency Frequency Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency... |
Channel | Frequency Frequency Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency... |
Channel | Frequency Frequency Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency... |
|---|---|---|---|---|---|---|---|
| 1 | 26.965 MHz | 11 | 27.085 MHz | 21 | 27.215 MHz | 31 | 27.315 MHz |
| 2 | 26.975 MHz | 12 | 27.105 MHz | 22 | 27.225 MHz | 32 | 27.325 MHz |
| 3 | 26.985 MHz | 13 | 27.115 MHz | 23 | 27.255 MHz | 33 | 27.335 MHz |
| 4 | 27.005 MHz | 14 | 27.125 MHz | 24 | 27.235 MHz | 34 | 27.345 MHz |
| 5 | 27.015 MHz | 15 | 27.135 MHz | 25 | 27.245 MHz | 35 | 27.355 MHz |
| 6 | 27.025 MHz | 16 | 27.155 MHz | 26 | 27.265 MHz | 36 | 27.365 MHz |
| 7 | 27.035 MHz | 17 | 27.165 MHz | 27 | 27.275 MHz | 37 | 27.375 MHz |
| 8 | 27.055 MHz | 18 | 27.175 MHz | 28 | 27.285 MHz | 38 | 27.385 MHz |
| 9 | 27.065 MHz | 19 | 27.185 MHz | 29 | 27.295 MHz | 39 | 27.395 MHz |
| 10 | 27.075 MHz | 20 | 27.205 MHz | 30 | 27.305 MHz | 40 | 27.405 MHz |
Current use
CB was the only practical two-way radio system for the individual consumer, and served several subsets of users such as truck drivers, radio hobbyists, and those in need of short-range radio communications. While some users have moved on to other radio services, CB is still a popular hobbyHobby
A hobby is a regular activity or interest that is undertaken for pleasure, typically done during one's leisure time.- Etymology :A hobby horse is a wooden or wickerwork toy made to be ridden just like a real horse...
in many countries. The 27-MHz frequencies used by CB, which require a relatively long aerial and tend to propagate poorly indoors, discourage the use of handheld radios. Many users of handheld radios (families, hunters and hikers) have moved on to 49 MHz and the UHF Family Radio Service
Family Radio Service
The Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
; those needing a simple radio for professional use (e.g., tradesmen) have moved on to "dot-color" business radios
Business band
The business band is the name used by US radio users and scanner hobbyists who listen to Federal Communications Commission licensees using Industrial/Business pool frequencies...
.
CB is still popular among long-haul truck drivers to communicate directions, traffic problems and other relevant matters. The unofficial "travelers channel" in most of the world is channel 19; in Australia it is channel 8 (27.055 MHz) and UHF channel 40 (477.400 MHz). In Russia it is channel 15 and channel 13 in Greece, both AM. These frequencies may have evolved because tuned circuits (particularly antennas) work best in the middle of the band; the frequency for channel 19 (not channel 20) is the center of the 40-channel US band and other things being equal, signals will be transmitted and heard the farthest. Since less standardization exists in Europe, CB there is more associated with hobbyists than with truckers.
Legal (short-range) use of CB radio is sometimes impeded by users of illegal high-power transmitters, which can be heard hundreds of miles away. The other problem with short-range CB use in propagation; during long-range "skip"
Skywave
Skywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...
conditions local signals are inaudible while distant signals boom in as if they were local. In the United States, the number of users and low enforcement financing by the Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
mean that only the worst offenders are sanctioned, which makes legitimate operation on the Citizens' Band unreliable. Most offenders are not caught for interfering with other CB users; often, their self-modified equipment generates harmonic
Harmonic
A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental...
s and spurs
Spurious tone
In electronics , a spurious tone denotes a tone in an electronic circuit which interferes with a signal and is often masked underneath that signal. Spurious tones are any tones other than a fundamental tone or its harmonics...
which cause interference to services outside the Citizens' Band and to consumer equipment.
The maximum legal CB power output level in the U.S. is 4 watts for AM (unmodulated carrier; modulation can be four times the carrier power, or 16 watts PEP
Peak envelope power
Peak envelope power is the average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle at the crest of the modulation envelope, under normal operating conditions. The United States Federal Communications Commission uses PEP to set maximum power...
) and 12 watts PEP for SSB
Single-sideband modulation
Single-sideband modulation or Single-sideband suppressed-carrier is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth....
, as measured at the transmitter antenna connection. However, external linear amplifier
Linear amplifier
A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of radio-frequency power amplifier, some of which have output power measured in kilowatts, and are used in amateur radio...
s are often illegally used. During the 1970s the FCC banned the sale of linear amplifiers capable of operation from 24 to 35 MHz to discourage their use on the CB band, although the use of high-power amplifiers continued. Late in 2006, the FCC amended the regulation to exclude only 26 to 28 MHz to facilitate amateur 10-meter operation. Lax enforcement enables manufacturers of illegal linear amplifiers to openly advertise their products; many CB dealers include these amplifiers in their catalogs.
Technology
At the beginning of the CB radio service, transmitters and receivers used vacuum tubeVacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s; solid-state transmitters were not widely available until 1965, after the introduction of RF-power transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
s. Walkie-talkie
Walkie-talkie
A walkie-talkie is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola...
hand-held units became affordable with the use of transistors. Early receivers did not implement all channels of the service; channels were controlled by plug-in quartz crystals
Crystal oscillator
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency...
, with one of several operating frequencies selected by a panel control in more expensive units. Superheterodyne receivers (using one or two conversion stages) were the norm in good-quality equipment, although low-cost toy-type units used superregenerative receivers. With the earliest sets two quartz crystals were needed for transmitting and receiving on each channel, which was costly. By the mid-1960s "mixer" circuits made frequency-synthesized radios possible, which reduced cost and allowed full coverage of all 23 channels with a smaller number of crystals (typically 14). The next improvement came during the mid-1970s; crystal synthesis was replaced by PLL
Phase-locked loop
A phase-locked loop or phase lock loop is a control system that generates an output signal whose phase is related to the phase of an input "reference" signal. It is an electronic circuit consisting of a variable frequency oscillator and a phase detector...
technology using ICs, enabling 40-channel sets with only one crystal (10.240 MHz). Almost all were AM
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
-only, although there were a few single sideband sets.
Most CB radios sold in the United States have the following features:
- Automatic noise limiter or noise blanker: Reduces background noise (such as spark ignition)
- CB/WXNOAA Weather Radio All HazardsNOAA Weather Radio All Hazards is a network of radio stations broadcasting continuous weather information directly from a nearby National Weather Service office. It is operated by the NWS, an agency of the National Oceanic and Atmospheric Administration within the United States Department of...
switch: Selects weather-radio receiver - Automatic gain controlAutomatic gain controlAutomatic gain control is an adaptive system found in many electronic devices. The average output signal level is fed back to adjust the gain to an appropriate level for a range of input signal levels...
(AGC): Adjusts transmitter modulation level - PAPublic addressA public address system is an electronic amplification system with a mixer, amplifier and loudspeakers, used to reinforce a sound source, e.g., a person giving a speech, a DJ playing prerecorded music, and distributing the sound throughout a venue or building.Simple PA systems are often used in...
: Some transceivers can drive an external speaker and act as a low-power public address system, or "bullhorn". - RF gain: Adjusts the RF amplifier gain of the receiver; used to reduce received background noise, and to reduce "clipping" due to over-amplification of already-strong signals (for example, when the receiver is near the transmitter)
- NOR/9/19: Quickly tunes preset channels for calling or emergency use
- SWRStanding wave ratioIn telecommunications, standing wave ratio is the ratio of the amplitude of a partial standing wave at an antinode to the amplitude at an adjacent node , in an electrical transmission line....
: Meter used to monitor reflected power caused by mismatched antennasElectrical lengthIn telecommunications, electrical length is the length of a transmission medium or antenna element expressed as the number of wavelengths of the signal propagating in the medium....
and antenna cablesCharacteristic impedanceThe characteristic impedance or surge impedance of a uniform transmission line, usually written Z_0, is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. The SI unit of characteristic impedance is the ohm... - Volume control
Microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
choices include:
- Dynamic microphone: Uses magnetic coil and permanent magnet
- Ceramic mic: Uses a piezoelectric element; rugged, low-cost but high-impedanceElectrical impedanceElectrical impedance, or simply impedance, is the measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current circuit...
- Echo mic: Deliberately introduces distortion and echo into transmitted audio
- Electret microphoneElectret microphoneAn electret microphone is a type of condenser microphone, which eliminates the need for a polarizing power supply by using a permanently charged material....
: Uses an electrostatic method to convert sound to electrical signals - Noise-canceling microphoneNoise-canceling microphoneA noise-canceling microphone is a microphone designed to filter out ambient noise from the desired sound, especially useful in noisy environments.-Technical detail:...
: Uses two elements to reduce background noise - Power mic: An amplified microphone
Antennas
Loading coil
In electronics, a loading coil or load coil is a coil that does not provide coupling to any other circuit, but is inserted in a circuit to increase its inductance. The need was discovered by Oliver Heaviside in studying the disappointing slow speed of the Transatlantic telegraph cable...
s to make the antenna impedance the same as a physically longer antenna. The loading coil may be on the bottom, middle, or top of the antenna, while some antennas are wound in a continuously-loaded helix.
Many truckers use two co-phased antennas, mounted on their outside mirrors. Such an array is intended to enhance performance to the front and back, while reducing it to the sides (a desirable pattern for long-haul truckers). However, the efficiency of such an arrangement is only an improvement over a single antenna when the co-phased antennas are separated by approximately eight feet or more, restricting this design to use mainly on tractor-trailers and some full-size pickups and SUVs. Some operators will use only one of the two antennas; this removes both the complexity and benefit of a true co-phased array, but gives a symmetrical cosmetic appearance preferred by some truck drivers.
Another mobile antenna is the continuously-loaded half-wave antenna. These do not require a ground plane
Ground plane
In electrical engineering, a ground plane is an electrically conductive surface.-Radio antenna theory :In telecommunication, a ground plane structure or relationship exists between the antenna and another object, where the only structure of the object is a structure which permits the antenna to...
to present a near-50-ohm
Ohm
The ohm is the SI unit of electrical resistance, named after German physicist Georg Simon Ohm.- Definition :The ohm is defined as a resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere,...
load to the radio, and are often used on fiberglass vehicles such as snowmobiles or boats. They are also useful in base stations where circumstances preclude the use of a ground-plane antenna. Handheld CBs may use either a telescoping center-loaded whip or a continuously-loaded “rubber ducky” antenna.
Base CB antennas may be vertical for omnidirectional coverage, or directional "beam" antennas may be used to direct communications to a particular region. Ground-plane kits exist as mounting bases for mobile whips, and have several wire terminals or hardwired ground radials attached. These kits are designed to have a mobile whip screwed on top (a full-length steel whip is preferred) and mounted on a mast. The ground radials replace the vehicle body (which is the counterpoise
Counterpoise (ground system)
A counterpoise is a type of electrical ground that is not connected to earth. It is used in radio antenna systems when a normal earth ground cannot be used because of high soil resistance It consists of a network of wires or cables running parallel to the ground, suspended from a few centimetres...
for a mobile whip in a typical vehicle installation).
Working skip
All frequencies in the HFHigh frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
spectrum (3–30 MHz) can be refracted by charged ions in the ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
. Refracting signals off the ionosphere is called skywave
Skywave
Skywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...
propagation, and the operator is said to be "shooting skip". CB operators have communicated across thousands of miles (sometimes around the world), making initial contact on the internationally-recognized calling frequency (27.555 MHz) and then moving to another frequency. Even low-power 27 MHz signals can sometimes propagate over long distances.
The ability of the ionosphere to bounce signals back to earth is caused by solar radiation, 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. During low sunspot activity it may be impossible to use skywave at all, except during periods of sporadic electron propagation (from late spring through mid-summer). Skip contributes to noise on CB frequencies. In the United States, it is illegal to engage in (or attempt to engage in) CB communications with any station more than 250 km (155.3 mi) from an operator's location. This restriction exists to keep CB as a local (line-of-sight) radio service. The legality of shooting skip is not an issue in most other countries.
Freebanding and export radios
Operation on frequencies above or below the citizens' band (on the "uppers" or "lowers") is called "freebanding" or "outbanding". While frequencies just below the CB segment (or between the CB segment and the amateur radio 10-meter band10 meters
The 10-metre band is a portion of the shortwave radio spectrum internationally allocated to amateur radio and amateur satellite use on a primary basis. The band consists of frequencies stretching from 28000 to 29700 kHz.-History:...
seem quiet and under-utilized, they are allocated to other radio services (including government agencies) and unauthorized operation on them is illegal. Furthermore, illegal transmitters and amplifiers may not meet good engineering practice for harmonic distortion or "splatter
Spectral splatter
In radio electronics or acoustics, spectral splatter refers to spurious emissions that result from an abrupt change in the transmitted signal, usually when transmission is started or stopped....
", which may disrupt other communications and make the unapproved equipment obvious to regulators.
Freebanding is done with modified CB or amateur equipment, foreign CB radios which may offer different channels, or with radios intended for export. Legal operation in one country may be illegal in another; for example, in the UK only 80 FM channels are legal.
Unlike amateur radios with continuous frequency tuning, CBs manufactured for export are channelized. Frequency selection resembles that of modified American CBs more than any foreign frequency plan. They typically have a knob and display that reads up to channel 40, but include an extra band selector that shifts all 40 channels above or below the band and a "+10 kHz" button to reach the model control 'A' channels. These radios may have 6 or even 12 bands, establishing a set of quasi-CB channels on many unauthorized frequencies. The bands are typically lettered A through F, with the normal CB band as D.
For example, a freebander with an export radio who wants to use 27.635 MHz would choose channel 19 (27.185 MHz) and then shift the radio up one band (+ 0.450 MHz). It requires arithmetic on the part of the operator to determine the actual frequency, although more expensive radios include a frequency counter
Frequency counter
A frequency counter is an electronic instrument, or component of one, that is used for measuring frequency. Frequency is defined as the number of events of a particular sort occurring in a set period of time. Frequency counters usually measure the number of oscillations or pulses per second in a...
or a frequency display—two different components, providing an identical result. Illegal operations may unintentionally end up on frequencies very much in use. For instance, channel 19 shifted two bands up is 28.085 MHz, which is in a Morse code-only part of the 10-meter ham band. Voice transmissions in a Morse code-only segment are easily detectable by authorities. Amateur operators regard this activity as an intrusion and record, locate, and report such transmissions to the FCC for enforcement action.
Many freeband operators use amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
s modified to transmit out of band, which is illegal in some countries. Older amateur radios may require component changes; for instance, the 1970s Yaesu FT-101
Yaesu FT-101
Yaesu FT-101 is a model line of modular amateur radio transceivers, built by the Yaesu Corporation in Japan during the 1970s and 1980s. FT-101 is a set that combines a solid state transmitter, receiver and a tube final amplifier...
was modified for CB by replacing a set of crystals used to tune portions of the 10-meter band, although some variants of the FT-101 were sold with the US FCC channels standard and were capable of transmitting above and below the legal 40 channels by another 10 or more channels. On some newer radios, the modification may be as simple as disconnecting a jumper wire or a diode. Many types of amateur transceivers may be found on CB and freeband, ranging from full-coverage HF transceivers to simpler 10-meter
10 meters
The 10-metre band is a portion of the shortwave radio spectrum internationally allocated to amateur radio and amateur satellite use on a primary basis. The band consists of frequencies stretching from 28000 to 29700 kHz.-History:...
mobile radios. In the United States, the FCC bans the importation and marketing of radios it deems easily modifiable for CB; it is illegal to transmit on CB frequencies with a ham radio except in emergencies where no other method of communication is available.
A gray market trade in imported CB gear exists in many countries. In some instances, the sale or ownership of foreign-specification CB gear is not illegal but its use is. With the FCC's minimal enforcement of its CB rules, enthusiasts in the US use "export radios" or European frequency modulation
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
(FM) CB gear to escape the crowded AM channels. American AM gear has also been exported to Europe.
"Export radios" are sold in the United States as 10-meter
10 meters
The 10-metre band is a portion of the shortwave radio spectrum internationally allocated to amateur radio and amateur satellite use on a primary basis. The band consists of frequencies stretching from 28000 to 29700 kHz.-History:...
amateur transceivers. Marketing, import and sale of such radios is illegal if they are distributed as anything other than amateur-radio transceivers. It is also illegal to use these radios outside of the amateur radio bands by anyone in the US, since they are not type-certified for other radio services and usually exceed authorized power limits. The use of these radios within the amateur radio service by a licensed amateur radio operator within his/her license privileges is legal, as long as all FCC regulations for amateur radio are followed. The term "export radio" is a misnomer, since it implies that they cannot be used in the country in which they are sold and hints that the radio is legal in another country. However, the typical "export radio" has a combination of features, frequency coverage and output power which make it illegal worldwide; in reality, there is no country to which these radios may be legally exported.
See also
- Amateur radioAmateur radioAmateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
- CB slangCB slangCB slang is the distinctive anti-language, argot or cant which developed amongst users of citizens' band radio , especially truck drivers in the USA during the 1970s and early-1980s....
- Citizens Band radio in IndiaCitizens Band radio in IndiaIn India, Citizens Band is a system of short-distance radio communications between individuals on a selection of 40 channels within the 27 MHz band...
- FRSFamily Radio ServiceThe Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...
—A UHF CB system used in the USA and Canada. - GMRS
- MURSMulti-Use Radio ServiceIn the United States, the Multi-Use Radio Service is an unlicensed two-way radio service similar to Citizens Band . Established by the U.S. Federal Communications Commission in the fall of 2000, MURS created a radio service allowing for unlicensed operation, with a power limit of 2 watts...
- PMR446PMR446PMR446 is a part of the UHF radio frequency range that is open without licensing for personal usage in most countries of the European Union. It has roughly the same use as FRS or GMRS in the United States and Canada. Depending on surrounding terrain range can vary from a few hundred metres to a...
—A UHF CB system used in most European countries - Ten-codeTen-codeTen-codes, also known as ten signals, are code words used to represent common phrases in voice communication, particularly by law enforcement and in Citizens' Band radio transmissions....