The Receiver
Whether the receiver uses a traditional 'analogue' tuning dial or a modern
digital display, the principles are the same: Use an antenna to capture all
the available signals, discard the unwanted ones and recover the audio from
the one remaining signal.
But exactly how does the receiver work?
Indiana Jones...
A receiver can be thought of as a series of trapdoors and doorways (known as filters) through which the signals must pass. Unwanted signals fall through the trapdoors while the doorways allow only wanted signals through. Each successive filter has finer and finer "holes" until only one signal remains.
The first of these filters is the antenna itself and the very first circuit to which it is connected inside the receiver.