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A brief introduction to how radios work.

Summary

Often, radios can be fixed simply by looking for the sort of problems common to all electronic gadgets, with very little idea of how they actually work. But when that approach fails, it's necessary to have a basic grounding in the theory of operation in order to go deeper. That is what this Wiki page is intended to provide.

We start by looking at the basic theory of radio transmission, then go on to examine how that theory is put into practice in several different types of radio.

Basic radio theory

In theory, you might be able to connect a microphone, through a powerful amplifier, directly to a transmitting aerial. In practice that wouldn't work because (for reasons we'll come to) you'd need an aerial many miles long, and there'd be no way to transmit more than one programme at a time without them getting mixed up.

An Audio Frequency (AF) signal, such as comes out of a microphone or could be fed into a loudspeaker, consists of frequencies in the range 20Hz - 20kHz (20 - 20,000 vibrations per second). In order to transmit it, that signal has to be impressed in some way upon a much higher Radio Frequency (RF) "carrier". There are several ways of doing that, the process being known as "modulation". A radio receiver essentially has two jobs to do: firstly, selection and amplification of the modulated carrier from that station you want to listen to ("tuning", and "demodulation", or recovering and amplifying the audio signal from it.

We'll look at several methods of modulation, then explain how tuning is achieved.

External links

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