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[SOLVED] beat frequency oscillator question

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obrien135

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Whan I look at the BFO circuits on the internet I don't nderstand the circuit theory about how they work. Isn't a BFO just an oscillator and a mixer? Couldn't you just use an oscillator like a colpitts and feeed it into a diode balanced modulator? Wouldn't that work? I cant figure out how to design one any other way. I would like to at least understand the circuit that I use and not just copy one blindly.

George
 

You are quite correct, a BFO is just an oscillator and subject to it's output being relatively clean, you can use almost any oscillator configuration. It isn't the oscillator itself that makes the BFO, it's the fact that it beats with a fixed frequency signal, typically from the IF stages of a superhetrodyne receiver. In reality, feeding the oscillation at a point just before an AM detector turns the detector into a mixer and saves additional circuitry. High-end receivers do use balanced mixers or 'product detectors' for this task.


Brian.
 
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