A CB radio is a citizen’s band radio — a radio that features the 40 channels in the 27 MHz range that the US Federal Communications Commission (FCC) has set aside for unlicensed public use, whether personal or commercial. The use of CB radios is limited to areas where the FCC operates. Each radio must be certificated by the agency, a fact that is indicated by an identifying label. The CB radio range is the distance over which the radio can transmit and receive.
By FCC regulations, CB radios are limited to 4 watts of transmission power. The official FCC statement is that the average CB radio range is 1 to 5 miles (1.6 to 8 km), but the actual average range may be greater — around 3 to 6 miles (4.83 to 9.66 km), depending on several factors. Things like the terrain, the antenna size and type, the antenna mounting, and whether the antenna has been tuned can affect this distance. Using modifications known as “peak and tune” or using a high output amplifier are illegal ways that some people use to boost the average range.
Since people don't usually have a choice about their surrounding terrain, there are not many ways of controlling for this factor. A large antenna is generally more effective, however, so many radio enthusiasts choose to get a larger sized antenna, whether it is an aerial to go with a CB base radio or a mobile antenna to mount on a pickup to increase the average range they get. Antenna quality is also a factor: a low-end antenna will not have the range of a well-built model. Mounting of the antenna — whether on a vehicle or on a building — should be as high as feasible. If it can be at the roof peak or on a tower, so much the better, while on a vehicle, it should be placed at the highest secure location.
Tuning an antenna is essential for obtaining the maximum CB radio range. Tuning is done with a standing wave ratio (SWR) meter or an antenna analyzer. The purpose of tuning is to get a low SWR reading, which means that power isn’t being reflected through the feedline back into the radio, which can both damage the radio and affect the signal from being output properly. The ideal SWR ratio is 1:1, and indicates that 100% of the radio’s signal is being transmitted, so the range of the CB radio is maximized.