This is the most simple fm receiver with good performances that works great even if the sensitivity is not too high. The working principle of this radio receiver may seem a little unusual. It is made of an oscillator (T2 and T3) that is synchronized with the received frequency of T1 which works as a broadband preamplifier in VHF range.
How does the fm receiver works
The oscillator is adjusted between 87 … 108 MHz with C5. Because of the synchronization, the oscillator output will have the same frequency deviation as the received signal from the fm antenna. This deviations are caused by the broadcasted audio information. The frequency modulated signal show up on P1 + R5. Low pass filter R6/C6 extracts the audio signal and then is amplifier by T4 … T6 and transmitted at the output through C9 capacitor.
FM Receiver Circuit Schematic
The coil details are presented in the fm receiver circuit diagram. The radio receiver is adjusted on different stations with the help of C5. P1 potentiometer is adjusted untill the best reception is obtained. If we attach an audio amplifier and a speaker then this frequency modulated receiver can be made very compact as a pocket radio.