Wednesday, April 6, 2022

How does the one transistor FM receiver operate?

This post may be wrong, the 1946 paper on locked in oscillator refered to on Television Engineering - Fink has not been read yet. The L, C reactance, LCR equations describing steady state ie after transient has decayed. Pehaps the most scientific method to undersatnd is taking a bouncing ball in our hands, play and examine its behaviour. The ball is a great analog computer, nature itself. We excite a system, firstly it is doing its natural it follows the forced oscillation. FOr example we clap our hand near a piano with the sutain pedal depressed, all strings vibrate excited by thisimpulse , almost delta function. On the so called locked in detector we havd to it from the transient point of view., rather than steady state. FM modulation is done by a music signal whiich is transient in nature. On the one transistor FM receiverthe received FM siugnal tries at any time to change the current through the osc L coil (part of LC). By nature inductance (analogous to mass) reacts to the change at any time and it produces an EMF (force) VOLTAGE.tHIS IS THE MUSIC SIGNAL WE GET BACK DEMODULATED. Similar to bouncing a basket ball between our hand and the floor. It has it natural osc frequency.If at any time we try to cjange that natural frequency The mass of the ball reacts (newton's 1st law), we get EMF ie force , we feel it on our hand.As we may try to descrese the frequency, same thing but force is no negative. We get our signal back, amplitude variations. Similarly to playing with a swing or a pendulum.

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