Author Topic: Local Oscillator of FM Radio  (Read 1101 times)

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Offline Scr1bbl3Topic starter

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Local Oscillator of FM Radio
« on: February 22, 2021, 03:36:55 am »
Hi all,
This is the local oscillator in an FM radio I found. I understand the tank circuit, C10 and C11 function, and biasing. Does anyone know the purpose of C7 and C9? Feedback perhaps but why would you use the 9V power line for the input to output connections?
thanks, scribs
« Last Edit: February 22, 2021, 07:29:28 pm by Scr1bbl3 »
 

Offline bsfeechannel

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Offline Alex Eisenhut

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Re: Local Oscillator of FM Radio
« Reply #2 on: February 22, 2021, 03:29:01 pm »
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Offline Zero999

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Re: Local Oscillator of FM Radio
« Reply #3 on: February 22, 2021, 06:09:24 pm »
Hi all,
This is the local oscillator in an FM radio I found. I understand the tank circuit, C10 and C11 function, and biasing. Does anyone know the purpose of C7 and C9? Feedback perhaps but why would you use the 9V power line for the input to output connections?
thanks, scribs
https://app.photobucket.com/u/scr1bbl3/p/d884f174-e534-4e5b-99d0-aada2ee9cdb7
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Offline bsfeechannel

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Re: Local Oscillator of FM Radio
« Reply #4 on: February 22, 2021, 10:50:00 pm »


Now we're talking. This is a Colpitts oscillator. C9 is part of its feedback loop and C7 is decoupling the base of the transistor.
« Last Edit: February 22, 2021, 11:08:01 pm by bsfeechannel »
 


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