CB usage in the United States
In the United States, the Class D Citizens' Radio Service, or Citizens' Band ("CB"), is one of several personal radio services defined by the FCC's Part 95 rules. It is intended to be a two-way voice communication service for use in personal and business activities of the general public, and has a reliable communications range of several miles, though the range is highly dependent on type of radio, antenna and propagation. Class A and B are no longer in existence (the frequencies were folded in to the GMRS radio service), Class C is a Radio Control ("R/C") model service and is covered further down in this article.
CB Radio is most frequently used by long-haul truck drivers for everything from relaying information regarding road conditions, the location of speed traps and other travel information, to basic socializing and friendly chatter.
There are no age, citizenship, or license requirements to operate a CB radio in the United States, and the service falls under the "License by Rule" part of the FCC rules (basically, if one follows the rules one is considered licensed). Operators may use any of the authorized 40 CB channels; however, channel 9 is used only for emergency communications or for traveler assistance and the higher number channels are almost exclusively SSB modulation. Use of all channels is on a shared basis. However, foreign governments and their representatives are not eligible to use citizens' band radio within the United States.
Operation is permitted anywhere within the United States and its territories or possessions; as well as anywhere in the world except within the territorial limits of areas where radio services are regulated by a foreign government, or another U.S. agency such as the Department of Defense.
Transmitters must be FCC certified and may not be modified, including modifications to increase output power or to transmit on unauthorized frequencies. Output power is limited to 4 watts for AM transmitters and 12 watts peak envelope power for single sideband (SSB) transmitters. The antenna may not be more than 20 feet (6.1 m) above the highest point of the structure it is mounted to, or the highest point of the antenna must not be more than 60 feet (18.3 m) above the ground (47 CFR 95.408(c)) if installed in a fixed location.
AM and SSB modulation is used in the USA, some other countries have similar services in their countries that use FM.
North American/CEPT frequenciesEdit
|CB Channel||Frequency||Typical Use (US)|
|Channel 1||26.965 MHz|
|Channel 2||26.975 MHz|
|Channel 3||26.985 MHz|
|Channel 4||27.005 MHz||Often used for 4x4's/ Off-roading|
|Channel 5||27.015 MHz|
|Channel 6||27.025 MHz||Considered the Super Bowl channel|
|Channel 7||27.035 MHz|
|Channel 8||27.055 MHz|
|Channel 9||27.065 MHz||Emergency communications or traveler assistance|
|Channel 10||27.075 MHz||Often used by truckers for regional roads|
|Channel 11||27.085 MHz|
|Channel 12||27.105 MHz|
|Channel 13||27.115 MHz||Considered the Marine/RV channel|
|Channel 14||27.125 MHz||Commonly included transmit/receive crystal in many vintage walkie-talkies|
|Channel 15||27.135 MHz|
|Channel 16||27.155 MHz|
|Channel 17||27.165 MHz||Used by truckers on North/Southbound Highways on the west coast (primarily I-5)|
|Channel 18||27.175 MHz|
|Channel 19||27.185 MHz||Highway trucker channel
Notable as being the center frequency of the band.
|Channel 20||27.205 MHz|
|Channel 21||27.215 MHz|
|Channel 22||27.225 MHz|
|Channel 23||27.255 MHz|
|Channel 24||27.235 MHz|
|Channel 25||27.245 MHz|
|Channel 26||27.265 MHz|
|Channel 27||27.275 MHz|
|Channel 28||27.285 MHz|
|Channel 29||27.295 MHz|
|Channel 30||27.305 MHz||Depending on local needs, channels numbered above 30 or 35 are generally used with SSB operation.|
|Channel 31||27.315 MHz|
|Channel 32||27.325 MHz|
|Channel 33||27.335 MHz|
|Channel 34||27.345 MHz|
|Channel 35||27.355 MHz|
|Channel 36||27.365 MHz|
|Channel 37||27.375 MHz|
|Channel 38||27.385 MHz||SSB calling channel, LSB mode|
|Channel 39||27.395 MHz|
|Channel 40||27.405 MHz|
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 ("R/C") devices.
Furthermore, there is a gap between channel 22 and channel 23 (which was later filled by channels 24 and 25) for historical reasons. 27.235, 27.245 and 27.255 were assigned to Business radio use while the lower spectrum was assigned to the 11 meter amateur (ham) radio band. The 11-meter band became CB Channels 1 to 22, and the last business frequency was channel 23 and shared.
Channel 19 is the most commonly used by truck drivers on highways, to the point that some radios even have a dedicated button to bring up channel 19 instantly. In most areas of the U.S. 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 (particularly rural) areas.
Among several other services that share the CB frequencies is the Class C Citizens Band service for radio-controlled ("R/C") 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. R/C 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 the higher power is permitted.
The 27 MHz Class C channels are not officially numbered by the FCC. 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 as an alternate of the closest voice channel below them (such as 3A, as shown in the table). In CB radios whose channel selector was a multiple-gang rotary switch that presented a binary number to the tuning electronics, it was a common illegal modification to add a toggle switch (or rewire an existing switch, such as the "PA" switch that coupled the microphone to an outside speaker) to modify the low-order bit and thus gain access to the R/C channels.
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.
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 can use any amateur frequency for R/C, but those enthusiasts tend to use frequencies in their 6-meter band.
Part 15 devicesEdit
Many toy R/C cars and 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. Newer wireless keyboards and mice tend to use Bluetooth technology or frequencies in the 2.4 or 5.8 GHz region. Some R/C devices, especially quadcopters/drones, use cellular data techniques.
Some other of the R/C toys operate on the 49 MHz Part 15 channels, and often a pair of R/C 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 devices to the 49 MHz band, with operation on the CB frequencies to cease in 1983. More recently in the 1990s, 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 (3.5 through 30 MHz), which includes the CB frequencies. There is great potential for interference, as power lines were never specifically designed to shield radio frequencies. RF leakage from BPL is regulated under Part 15 and is a big problem for amateur radio operators across all frequencies that the BPL uses.
Another class of devices operating in the 27 MHz band are ISM (Industrial, 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.
Adjacent frequency bandsEdit
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 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. These frequencies are often used by illegal operators using modified CB or amateur radio equipment.
The 10 meter amateur radio (ham) band runs from 28.000 to 29.700 MHz.
Below the Citizen's Band, the U.S. military has the frequencies from 26.480 to 26.960 MHz. These frequencies are often used by illegal operators using modified CB or amateur radio equipment.
The Civil Air Patrol has 26.620 MHz, though it now uses mostly VHF frequencies. In the 1950s through the 1970s CAP volunteers with crystal-controlled CBs would put this frequency in their radios. Currently VHF military frequencies are more often used (the CAP is part of the US Air Force), as among other reasons, VHF radios are easier to acquire through military logistics than CB radios.
The US Coast Guard Auxiliary uses 27.980 MHz, it is similar to the Civil Air Patrol Frequency.
- "Citizens Band (CB) Service". Federal Communications Commission. Retrieved November 18, 2015.
Channel 9 is reserved for emergency communications or for traveler assistance.
- "TRC-235 3-Channel CB Walkie-Talkie 210-1620 Adding Crystals". support.radioshack.com. Retrieved 2015-12-21.
- Kneitel, Tom (1988). Tomcat's Big CB Handbook. Commack, NY: CRB Research Books. pp. 203–204. ISBN 0-939780-07-0.
- Chilton Automotive Editorial Department (1977). Chilton's CB Handbook. Radnor, PA: Chilton Book Company. p. 12. ISBN 0-8019-6623-X.
- "Radio Control Frequency List (with flag information)". Retrieved 18 June 2014.
- These Part 15 devices are now regulated by field strength, not transmitter input power.
- Chilton Automotive Editorial Department (1977). Chilton's CB Handbook. Radnor, PA: Chilton Book Company. p. 20. ISBN 0-8019-6623-X.
- Article 5 RR 171 Radio regulations annexed to the International Telecommunication Convention (Atlantic City, 1947) Archived July 10, 2012, at the Wayback Machine.
- Hughes, Gene; Richard Barnett (2000). Police Call, Vol. 1, 2001 edition. Los Angeles: Hollins Radio Data. pp. 277, 384–385, 387. OCLC 46316778.