Learn about this topic in these articles:

In electron tube: Electron motion in a vacuum
…devices for generating or amplifying radio-frequency (RF) power.
Read More
In electron tube: Fast-wave electron tubes
…electron energy is converted to RF energy and results in amplification. Beam voltages in these devices are on the order of 100 kilovolts, and, with electron currents of about 35 amperes, steady-state power levels of 300 watts or pulsed peak power levels of 200 kilowatts can be generated at millimetre…
Read More

In television: Basic receiver circuits
…in the receiver is a radio-frequency amplifier, particularly designed for low-noise amplification. The channel-switching mechanism (tuner) of the receiver connects this amplifier to one of several individual circuits, each circuit tuned to its respective channel. The amplifier magnifies the voltages of the incoming picture and sound carriers and their side…
Read More