/diy/ - Do It Yourself

>>1222831
In FM transmissions (FM as in frequency modulation, not only the VHF broadcast band) the information is transferred by modulating the _frequency_ of the carrier alone, not the amplitude of the signal. Changes in amplitude are removed by the limiter (look at the waveforms in the diagram) by simply clipping the signal. This works as long as the received signal is slightly stronger than the noise generated by the RF front end (the technical term is 'capture ratio'). In principle there is no need for the automatic gain control (AGC) found in AM receivers (AM as in amplitude modulation, not only the Medium Wave broadcast band).

>>1222861
>The AGC circuit does this.
This is a misconception. FM receivers may have such a function (called 'delayed AGC') but for totally different reasons, mainly to prevent overload of the first RF stage or to drive the field strength indicator.