Inside the radio

An aerials receives radio waves many station on many different frequencies at same time . in order to hear a particular station a listener must tune the radio by adjusting the radio frequency filter, select a particular frequency  the selected frequency is sent to a mixer where it is combined with oscillator. The mixer and oscillator together  form a frequency changer which changes the selected RF signal  that is intermediate frequency  signal. The IF is fed into the IF amplifier and later in the demodulator. This circuit detects the slight variation in the strengthen of the signal produced by the audio frequency , which represent the original  sound. Some of the audio is fed back to the IF amplifier to provide automatic control gain  this ensures  that when tuning from a weak station to a strong one the loudness from the loudspeaker stays the same. The audio signal voltage is increased by an voltage amplifier, later the signal is fed into amplifier power  then increases the power level sufficiently to drive the loudspeaker which translate the electric signal into sound