A simple radio receiver

In a radio transmitter the audio signal is combined with a wave of high frequency, called the carrier wave. This is known as modulation. Either the amplitude or the frequency may be varied. The effects of both amplitude and frequency modulation are shown in Figure 1.


In the receiver the frequency to which the aerial must be tuned is that of the carrier wave. The carrier wave must he demodulated so that the audio signal may be detected. The full circuit for a simple receiver is shown in Figure 2, the functions of the various sections being indicated.