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Citizens' band radio
Citizens' Band radio (CB) is, in many countries, a system of short-distance, simplex 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 commercial communication.
Additional recommended knowledge
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.
The technology at the time was not advanced enough for UHF radios to be practical and affordable for the average consumer. So, in 1958, 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.
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 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, 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.
In the 1960s, the service was popular for small trade businesses (e.g., electricians, plumbers, carpenters) and transportation services (e.g., taxi and trucking firms). "10 codes" originally used in the public service (e.g., police, fire, ambulance) and land mobile service were used for short acknowledgments. With the advancement of solid state technology (transistors replacing tubes) in the 1970s, the weight, size, and cost of the radios decreased. US truckers were 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 1970s era films (see list below) such as Smokey and the Bandit (1977) and television shows like The Dukes of Hazzard (debuted 1979) bolstered the appeal of CB radio. Moreover, popular novelty songs such as C.W. McCall's "Convoy" (1976) helped establish CB radio as a nationwide craze in America from the mid-1970s to the early 1980s.
Originally, CB did require a license and the use of a call sign, but when the CB craze was at its peak, many people ignored this requirement and used made-up nicknames or "handles". The use of handles instead of call signs is related to the common practice of using the radios to warn other drivers of speed traps during the time when the United States dropped the national speed limit to 55 mph (90 km/h) beginning in 1974 in response to the 1973 hike in oil prices. The FCC recommended the use of ten-codes and these were used, often in a shortened form, but also many slang terms were developed.
The low cost and simple operation of CB equipment gave access to a communications medium that was previously only available to specialists. The "boom" in CB usage in the 1970s and in Britain in the early 1980s bears several similarities to the advent of the Internet in the 1990s. The many restrictions on the authorized use of CB radio led to widespread disregard of the regulations, most notably in antenna height, distance restriction for communications, licensing and the use of call signs, and allowable transmitter power. Eventually, the license requirement was dropped entirely.
Originally, there were only 23 CB channels in the U.S.; 40-channel radios did not come along until 1977. Channel 9 was reserved for emergency use in 1969. Channel 10 was used for highway communications, though channel 19 later became the preferred highway channel in most areas as it did not have adjacent-channel interference problems with channel 9.
Until 1975, only channels 9-14 and 23 could be used for "interstation" calls to other licensees. Channels 1-8 and 15-22 were reserved for "intrastation" communications among units under the same license. After the interstation/intrastation rule was dropped, channel 11 was reserved as a calling frequency for the sole purpose of establishing communications; however this was withdrawn in 1977.
Until the late 1970s when synthesized radios appeared, CB radios were controlled by plug-in quartz crystals. Almost all were AM only, though there were a few single sideband sets in the early days.
Throughout the 1970s and early 1980s, a phenomenon was developing over the CB radio. Similar to the Internet chat rooms a quarter century later, the CB allowed people to get to know one another in a quasi-anonymous manner. Many movies and stories about CBers and the culture on-the-air developed.
In Britain, some people were using CB radio illegally in the 1970s, a craze which suddenly peaked in 1980, leading to legalization on 2 November 1981. However, in the summer of 1981 the British government was still saying that CB would never be legalized on 27 MHz. The government wanted a UHF frequency around 860 MHz named 'Open Channel' instead. Eventually 40 channels at 27 MHz, plus 20 channels on 934 MHz were legalized. Both allocations used frequencies unique to the UK; the 934 MHz allocation was later withdrawn in 1998. CB's inventor Al Gross made the first legal British CB call from Trafalgar Square, London.
In more recent years, CB has lost much of its original appeal due to the advancement of technologies and changing values. Some of this rapid development includes: mobile phones, the Internet, and Family Radio Service. The changing radio wave propagation for long-distance communications, due to the 11 year Sunspot cycle, is always a factor for these frequencies.
Before CB was authorized in Australia, there were 27 MHz "handphones" which are authorized on several frequencies in between the present CB channels, such as 27.240 MHz. By the mid-1970s, hobbyists were experimenting with these handheld radios, as well as with unauthorized American CB radios. At that time in Australia, the 11 meter band was still used by licensed ham operators but not yet available for CB-type 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, and later in 1980 the American 40-channel bandplan was adopted. From the outset, the Government attempted to regulate CB radio with licence fees and call-signs etc, but some years later abandoned this approach.
After peaking in the 1970s and early 1980s, the use of 27 MHz CB in Australia has fallen dramatically in the last decade. The later introduction of 477 MHz UHF CB, with FM and repeaters, and the proliferation of cheap, compact handheld UHF transceivers have been part of the reason. But other technologies such as mobile telephones, Internet chat, etc. have provided people with other choices for communications.
In Indonesia, CB radios were first introduced around 1977 when some transceivers were imported illegally from Australia, Japan and the United States. The dates are hard to confirm accurately but certainly early use was known around big cities such as Jakarta, Bandung, Yogyakarta, Surabaya and Medan.
The Indonesian Government legalized CB on October 6, 1980 through a decision of the Minister of Communications called 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 bandplan, with AM and SSB, was adopted; a VHF band was added later 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.
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:-
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.
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. 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.
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.
CB Radio today
CB was once the only practical two-way radio system for the individual consumer, and as such served several distinct types of users such as truck drivers, radio hobbyists, and those who needed a short-range radio for particular tasks. While some of these users have moved on to other radio services, CB is still a popular hobby in many countries. In America it is strongly associated with semi truck drivers and rural life.
The 27 MHz frequencies used by CBs, which require a long antenna and don't propagate well indoors, tend to discourage use of handheld radios for many applications. Many consumer users of handheld radios ( ex. family use, hunters, hikers ) have moved on to 49 MHz and then to the UHF Family Radio Service, while many who need a simple radio for professional use (ex. tradesmen ) have moved on to "dot-color" business radios.
On the other hand, CB is still popular among long-haul truck drivers to communicate directions, traffic problems, and other things of importance. This has long been the case in the United States, but less so in Europe where until recently conflicting regulations made it impossible for the same radio to be used across Europe. As a result, CB was more associated with hobbyists than truckers.
In the United States, channel 19 is the most commonly used for highway use, to the point that some radios even have a dedicated button to bring up channel 19. In some areas of the U.S., different channels are customarily used on highways running North-South versus East-West, and sometimes even for specific roads. Other channels regionally used for this purpose include 10, 17, and 21. Channel 13 is preferred in some areas for marine use and for recreational vehicles.
Several countries reserve a channel for emergency use, for example channel 9 in the United States. In CB's heyday in the 1970s, channel 9 was monitored by parties who could relay messages to the authorities, or even directly by the authorities themselves. With the popularity of cellular phones, support for Channel 9 as an emergency channel has diminished, though volunteer organizations such as REACT (Radio Emergency Associated Communications Teams), and private individuals still monitor Channel 9 in some areas.
Legitimate, short-range use of CB radio is sometimes made difficult by uncooperative users and users of illegal high-power transmitters, which are capable of being heard hundreds of miles 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.
The maximum legal CB power output level, in the U.S., is four watts for AM and 12 watts (peak envelope power or "PEP") for SSB, as measured at the antenna connection on the back of the radio. However, illegal external linear amplifiers are sometimes used. In 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, though the use of high power amplifiers by lawless operators continued. Late in 2006 the FCC amended the regulation to only exclude 26 to 28 MHz.
During periods of peak sunspot activity, even low-powered transmitters on 27 MHz can sometimes be heard for hundreds or even thousands of miles. This "skip" activity, in which signals bounce off the ionosphere, contributes to interference on CB frequencies. Working "skip" is illegal in the United States, since it contradicts the short-range intended use of the service, though the regulation is widely ignored.
Many radio hobbyists operate illegally in the so-called "free band", (which is often referred to as 11 meters, similar to how hams refer to their bands by the approximate wavelengths) using either Citizens' Band equipment that has been illegally modified for extended frequency range and higher power, or illegally modified amateur radio equipment. Such operations are not part of the legally authorized Citizen's Band service and may interfere with the legitimate users of these other frequencies, which include many government agencies. Illegal transmitters and amplifiers may not meet good engineering practice for harmonic distortion or "splatter", which will often attract the attention of regulating authorities.
CB Usage in the United Kingdom
Main article: CB radio in the United Kingdom
CB Usage in the United States
Main article: CB usage in the United States
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 earth 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.
Finally, it should be noted that under Part 95, Subpart D of the FCC rules it is illegal to engage in, or attempt to engage in communications with any station more than 250 kilometers (155.3 miles) from your location, thereby making it impossible for CB operators who wish to shoot skip to remain in compliance with FCC regulations. The intent behind this restriction is typically regarded as an effort to keep CB as an inherently local service.
Freebanding and Export Radios
Operation on "bootleg" frequencies above ("uppers") or below ("lowers") the established citizens band is referred to as "freebanding" or "outbanding". While many perceive these frequencies just below the CB band, or between the CB band and the amateur radio 10-meter band to be quiet and under-utilized, these frequencies are generally allocated to other radio services, and unauthorized operation on them is illegal.
This is done with modified CB equipment, amateur radios modified to transmit on 11 meters, foreign CB radios that may offer different channels, or with radios which are purportedly sold for export.
Unlike amateur radios which are frequency-agile, export CB's are channelized. Frequency selection on these "export radios" resembles that of modified American CB's 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, plus 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 all sorts of 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 ) and then shift the radio up one band ( + 0.450 ). The operator may have to do quite a bit of arithmetic to know which frequency he is actually operating on, though more expensive radios include a frequency counter.
Even well-meaning (but illegal) operations can end up on frequencies which are very much in use. For instance, Channel 19, 2 bands up, becomes 28.085 MHz, which is in a Morse code-only part of the 10-meter ham band. Licensed amateurs typically regard this activity as an intrusion, and have been known to record, locate, and report such transmissions.
Freeband operators also use amateur radios that have been modified to transmit out of band. While older amateur radios may require component changes; for instance, the 1970's-vintage Yaesu FT-101 was modified for CB by replacing a set of crystals used to tune portions of the 10-meter band, while on some newer radios the modification may be as simple as cutting a jumper or diode. Today many types of amateur radios can be found on CB and freeband, ranging from full-coverage HF transcievers to simpler 10-meter mobile radios. However, in the United States the FCC bans the importation and marketing of certain radios deemed too easily modifiable for the CB frequencies, and it is illegal to transmit on CB frequencies with a ham radio under normal, non-life threatening instances.
In the 2007 movie Live Free or Die Hard, John McClane seeks out The Warlock to help him find the computer hacker that no government agency can find. The Warlock's low tech back up communications system is a modified CB radio which he keeps tuned to channel 66.6, an unauthorized channel in the U.S. which corresponds to U.K. CB Channel 8(27.671 mhz).
As 27 MHz is a relatively long wavelength for mobile communications, the choice of antenna has a considerable impact on the performance of a CB radio.
One common mobile antenna is a quarter-wave vertical whip. This is roughly nine feet (2.7 metres) tall and mounted low on the vehicle body, and often has a spring and ball mount. A common misconception is that the '102 inch' whip is the correct length for US CB frequencies; in reality, it is designed to be paired with a six-inch spring, both to bring it to the proper electrical length, and to enhance its resilience to scraping and striking overhead objects.
Where a nine-foot whip would be impractical, shorter antennas include loading coils to make the antenna electrically longer than it actually is. 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 mirrors. This arrangement reduces the distortion of the wave propagation due to an unequally-shaped ground plane, lessening the effect of the truck body on the radiation pattern. In addition, when such an array is properly constructed, it enhances 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. Occasionally, operators will install co-phased antennas but only connect a feedline to one antenna - this removes both the complexity and benefit of a true co-phased array, but gives a symmetrical cosmetic appearance that some truck drivers prefer.
Another mobile antenna is the continuously-loaded half-wave antenna. These do not necessarily require a ground plane to present a near 50 ohm load to the radio, and are often used on fiberglass vehicles such as snowmobiles or boats. They are also ideal for base station usage where the circumstances preclude the use of an antenna that requires a ground plane to function properly.
Handheld CBs often 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 a mounting base for typical mobile whips, and have several wire terminals or hardwired ground radials attached. These kits are designed to have a mobile whip screwed on top (again, the full-length steel whip is a preferred candidate) and mounted on top of a mast. The ground radials take the place of the vehicle body, which is used as a counterpoise for the mobile whip in a typical vehicle installation.
CB in popular culture
CB in movies
CB radio in music
CB radio figures prominently in several country and novelty songs, mostly from the mid-1970s:
Chilton Automotive Editorial Department (1977). Chilton's CB Handbook. Radnor, PA: Chilton Book Company. ISBN 0-8019-6623-X.
Kneitel, Tom (1988). Tomcat's Big CB Handbook. Commack, NY: CRB Research Books. ISBN 0-939780-07-0.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Citizens'_band_radio". A list of authors is available in Wikipedia.|