Signals – whether they’re for radio, TV, cell phones or any other application – are really nothing more than electrical currents. The term RF stands for radio frequency… but is applied in a couple of different ways.
In the technical sense, a radio frequency (RF) signifies rate of oscillation, which occurs anywhere from 3kHz to 300 GHz. For transmitting radio signals though, it isn’t as simple as just having an antenna and minimal equipment.
When radio signals originate, they’re generally very weak electrical currents, especially if it’s from some sort of microphone device like walkie-talkie or radio station system. These original signals are often times too weak for transmission over a long distance. Therefore, to transform this weak signal into something powerful to transmit over an antenna, an RF amplifier is used to boost the signal.
The process for transmitting signals for radio or other applications occurs in several stages in fact. In each of the stages, a signal is modified in some way to produce a desired output. Broadcast signals in fact are a collection of different “signals”, each with its own role in the final output. In the case of radio, this can include speech or music.
The RF amplifier essentially boosts each signal equally to produce a clean, linearly amplified signal which is then transferred to a system with much higher power. An RF amplifier in fact takes distortions in a radio signal and distorts them even further. Therefore, a big job of the amplifier is to ensure the signal is given maximum strength with as little distortion as possible.
Linearity, or the ability to amplify all parts of a signal by the same amount (… to ensure all signals are amplified equally), is the core element of an RF amplifier.
Within the amplification process itself, the triode – or a diode with an attached control grid – is the device primarily responsible for signal enhancement. The attached control grid regulates the electric charge flowing through the diode. By applying small voltage variations, the triode can make significant changes in the strength and behavior of the current.
In radio broadcast, information transmitted through radio frequency takes the form of speech or music and is called “modulation.” Amplitude modulation, or AM radio, is the earliest and simplest form of radio frequency modulation. It’s simple in that there’s essentially only one stage where an amplifier only has to vary the power output of an RF stage by varying the input signal.
Frequency modulation (FM) was developed in the 1930s, and while it produces a much cleaner signal, it’s a bit more complicated than AM.
Today, RF amplifiers are used in a variety of areas, including AM/FM radio, TV, radio towers, walkie-talkies and even in every cell phone and cell phone tower.
It’s safe to say that an RF amplifier constitutes a critical part of transmitting and receiving signals. Without them, radio signals would not be able to travel that far.
Think about it this way – if a DJ is speaking at the radio station and there was no way to boost the strength of the waves carrying his voice, then the only people that will be able to hear what he’s saying are ones standing in the room, or otherwise within hearing distance.