A linear HF amplifier allows the user to adjust power output, which is measured in kilowatts; tune radio frequency; and boost a weak radio signal, which is measured in decibels, before transmission. Other functions of a linear HF amplifier generally include self-cooling, automatic output reduction and bandswitching capabilities.
A linear HF amplifier is a central piece of equipment that allows an individual to broadcast over radio frequencies. In essence, the function of an amplifier is to convert electric energy into radio frequency energy, boosting a pre-existing radio frequency for broadcast. Without the functions of an amplifier, most radio frequencies available to amateur radio hobbyists would be imperceptible to the ear.
The term "linear" refers to the fact that the amplifier's input and output are equivalent. Non-linear amplifiers produce an unbalanced, less efficient input-output ratio. By using a linear amplifier, amateur radio enthusiasts can maximize a radio signal for the least amount of power. For this reason, a quality HF amplifier is coveted by radio broadcasters, ranging in price from $800 to $5,000 for amateur equipment as of 2015. However, the Federal Communications Commission closely regulates the signal strength allowed for communications, and amateur radio hobbyists must be careful to calibrate their amplifiers to broadcast within these regulations.