Main article: Citizens' band radio A typical CB base station. ...

In the United States Citizens' Band (CB) radio service is intended to be a private two-way voice communication service for use in personal and business activities of the general public. Its communications range is from one to five miles (1.6 to 8 kilometres). The Citizens' Band radio services are described in part 95 of the Federal Communications Commission's (FCC) and is defined as a personal radio service. The FCCs official seal. ...

Eligibility

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

You may operate your station anywhere within the United States and its territories or possessions. You may also operate your US station anywhere in the world except within the territorial limits of areas where radio services are regulated by another agency; such as the United States Department of Defense or of any foreign government. The United States Department of Defense (DOD or DoD) is the federal department charged with coordinating and supervising all agencies and functions of the government relating directly to national security and the military. ...

You must use an FCC certified transmitter. No modifications which increase power are allowed to your equipment. Equipment output power is limited to 4 watts for AM transmitters and 12 watts PEP (peak envelope power) for single sideband (SSB) transmitters. The restrictions on size of antennas are that the antenna must not be more than 20 feet (6.1 metres) above the highest point of the structure it is mounted to and may not be more than 60 feet (18.3 metres) above the ground. 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. ...

Channel Assignments

To simplify selection of an operating frequency, the Citizens' Band radio spectrum is divided into 40 numbered radio frequency channels from 26.965 to 27.405 MHz, with channels generally spaced 10 kHz apart. Channel numbers are not strictly sequential with frequency; there are gaps for frequencies used by radio-controlled devices. It has been suggested that this article or section be merged with Radio waves. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ...

Furthermore, there is a gap between Channel 22 and Channel 23 (which was later filled by Channels 24 and 25) for historical reasons. Before CB was in existence, there was an Amateur 11-meter band from 26.96 to 27.23 MHz, and a frequency for radio-controlled devices at 27.255 MHz. The 11-meter band became CB Channels 1 to 22, and the radio control frequency was shared with Channel 23.

The frequency allocation list shown is supplied by the FCC (Federal Communications Commission) from Part 95 - Subpart D - Rules for Citizens Band (CB) Radio Service. The electromagnetic spectrum is an aspect of the physical world, like land, water, and air. ... The FCCs official seal. ...

Remote Control

There is also a Class C Citizens Band service for radio-controlled devices; no voice transmissions are permitted. It has six channels in the 27 MHz band. Five are unused 10 kHz assignments between channels 3/4, 7/8, 11/12, 15/16 and 19/20, and the sixth is shared with Channel 23. Radio control transmitters may use up to 4 watts on the first five channels and 25 watts on the last, 27.255 MHz. Some in-house paging systems, and car alarms with a paging feature, also use these frequencies, especially 27.255 where more power is permitted.

The 27 MHz Class C channels are not officially numbered. R/C enthusiasts usually designate them by color, and fly different-colored flags from the antenna to show who is on which channel. On the other hand, some CB operators illegally use these channels for voice communications, and usually refer to them by the closest voice channel below them, ex. "3A", "7A", etc.

Because of interference from CB radios, legal or otherwise, the noise level, and the limited number of channels, most "serious" hobby radio-controlled models operate on other bands. Interference is especially important for model aircraft where it presents a safety issue. 1:10 scale radio controlled car (Saab Sonett) A radio-controlled model (or RC model) is a model that is steerable with the use of radio control. ...

The Class C service has 50 channels just for model aircraft in the 72.0-73.0 MHz range, and 30 more channels for surface models such as cars and boats in the 75.4-76.0 MHz range. 0.75 watts is allowed on these numbered channels. Licensed amateur radio operators also have their own R/C channels around 50 and 53 MHz.

Part 15 and ISM Devices

Most toy R/C cars and most wireless keyboards and mice operate on the 27 MHz R/C channels, especially 27.145 MHz. But most of these devices run far less than 4 watts and do not operate under the Class C CB service. Instead, they operate under the FCC's Part 15 rules, which allow a wide variety of low powered devices to use the frequencies from 26.96 to 27.28 MHz, which covers CB Channels 1 through 27. In the U.S., Part 15 is an often-quoted section of Federal Communications Commission (FCC) rules and regulations, mainly regarding unlicensed transmissions. ...

Some other of these toys operate on the 49 MHz Part 15 channels, and often a pair of cars will be sold with one on 27.145 and one on 49.860 to avoid interference. This allows less selective, and therefore less expensive, receivers to be used than if they were using channels in the same band.

In the days when CB required a license, some low-powered or toy walkie-talkies were exempt because they operated within Part 15. However, in 1976, the FCC phased in a shift of these 100 mw^[1] devices to the 49 MHz band, with operation on the CB frequencies to cease in 1983.^[2] More recently in the 1990's, low-powered handhelds using FM voice on the 27 MHz radio-control channels were also sold to operate legally under Part 15.

Broadband over Power Lines (BPL) technology uses a wide range of HF frequencies to transmit data, including the CB frequencies. There is some potential for interference, as power lines were never specifically designed to shield radio frequencies. RF leakage from BPL is regulated under Part 15. For other uses, see Power band. ...

Another class of devices operating in the 27 MHz band are ISM (Industial, Scientific and Medical) devices regulated by the FCC's Part 18 rules. Induction welding of plastics, and some types of diathermy machines commonly operate in this range. These devices are centered around 27.12 MHz with a tolerance of ±163 kHz, that is, 26.957 to 27.283 MHz. Induction welding is a form of welding that uses electromagnetic induction to heat the workpiece. ... In the natural sciences, the term diathermy means electrically-induced heat and is commonly used for muscle relaxation. ...

Adjacent Radio Services

The Business Radio Service has several channels just above the Citizen's Band, at 27.430, 27.450, 27.470, 27.490, 27.510, and 27.530 MHz. The business band is the name used by US scanner hobbyists who listen to Federal Communications Commission licensees using Industrial/Business pool frequencies. ...

The federal government has the frequencies from 27.540 up to 28.000. Many civilian agencies use, or used to use, the frequencies 27.575 and 27.585 for low-power use. This article describes the government of the United States. ...

The 10 meter ham band runs from 28.000 to 29.700 MHz. The 10 meter amateur radio band is the highest of the High Frequency or HF bands. ...

Below the Citizen's Band, the U.S. military has the frequencies from 26.480 to 26.960.

The Civil Air Patrol has 26.620, though it now uses mostly VHF frequencies. Years ago, CAP volunteers with crystal-controlled CBs would put this frequency in their radios. Now, this frequency is all but abandoned as VHF radios are now easier to come by than crystal-controlled CBs.^[3] Civil Air Patrol seal The Civil Air Patrol (CAP) is the official civilian auxiliary of the United States Air Force (USAF). ...

Regulation and Enforcement

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

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

Todays actions of illegal CBer's are usually not cared about by the FCC. They will only go after people who disrupt important radiocommunications, or are reported by people who are having trouble with neighbors who have over-powered CB's. It usually interferes with broadcast television.

Many actions have been taken in recent years against the so-called freebanders operating illegally between 26 and 30 MHz. This segment includes military, government allocations (26 MHz - 28 MHz) not assigned to the Citizens Band service as well as the Amateur radio 10-meter band (28 - 29.7 MHz). Actions have also been taken against retailers in the United States for selling linear amplifiers and non-type approved equipment in violation of the commission's rules.

References

1. ^ These Part 15 devices are now regulated by field strength, not transmitter input power.
2. ^ Chilton Automotive Editorial Department (1977). Chilton's CB Handbook. Radnor, PA: Chilton Book Company, 20. ISBN 0-8019-6623-X. 
3. ^ CAP Frequencies

Kneitel, Tom (1988). Tomcat's Big CB Handbook. Commack, NY: CRB Research Books. ISBN 0-939780-07-0.