A citizens band linear amplifier is used to boost the power of the signal produced by a CB base station's transmitters. A boosted transmission can reach increasingly distant receivers.
A commercially available, unaltered, legal CB base station transmitter of the right model can output an AM signal of 3 to 4 watts. The maximum legal transmission in the United States is 4 watts. A linear amplifier boosts the power of the CB signal. If the signal is already transmitting at maximum legal wattage, the use of an amplifier is illegal. Sometimes amplifiers are used to boost the range of signals that are transmitted in areas of higher interference, such as more densely populated areas.