Compare with amateur radio .
The Citizen's Band (CB) Radio Service, also known simply as CB, is a public, two-way personal radio service. There are several classifications of CB operation. The best-known form of CB is voice communications that became a fad in the 1970s. Mobile CB operation, especially in cars and trucks, remains popular. To a lesser extent, "CB'ers" engage in fixed operation from homes, and in portable communications using handheld transceivers.
Most CB operation takes place within a narrow band of frequencies near 27 MHz. There are 40 channels in this band. These channels are overcrowded. Congestion is worst during peaks in the 11-year sunspot cycle when the 27-MHz band supports worldwide communication known as "skip." Sunspot cycle peaks occurred in 1967-69, 1978-80, 1989-91, and 2000-2002. During the long intervals between these peaks, the normal range of operation on the 27-MHz band is rarely more than 20 miles.
Some CB operators illegally modify their equipment, or obtain illegally modified equipment, capable of higher transmitter output power and greater frequency coverage than is allowed by Federal Communications Commission (FCC) regulations. These operators use their equipment in an attempt to communicate over long distances, and/or to compete with other users of the service.ï¿½ This is called freebanding or bootlegging.
The CB Radio Service has proven useful in disaster situations, both small-scale (for example, for a stranded motorist) and large-scale (such as after a hurricane or during a flash flood). An organization of expert communicators known as the Radio Emergency Associated Communications Teams (REACT) provides communications support in emergency situations. Channel 9 (at 27.065 MHz) is monitored by members of REACT, and is recognized as the CB emergency channel in the United States.