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Old 3rd Aug 2021, 1:57 pm   #1
Join Date: Feb 2021
Location: Crewe, Cheshire, UK.
Posts: 55
Default FM tuned circuits, ratio detection etc

Eh up,

I've tried researching for myself and have hit a dead end. I'm trying to learn the principles of AM/FM demodulation.

If I'm right, I believe it starts with a resonant circuit that mixes the received frequency with an oscillator to produce an IF that in turn is amplified. In AM, a detector/demodulator only allows the positive peaks to pass, which is then smoothed and amplified to the speaker.

This is the SAME in FM I believe except the frequency deviation from the main carrier frequency represents and output Voltage, so recreating the signal? All correct so far?

My only confusion is, if the variable capacitor sets up a resonant circuit for one frequency only, the carrier frequency, where is the deviation coming from fir the ratio detector to make use of?

Kind regards,

AidanCroft is offline