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The Franklin Oscillator

A project log for Yet Another MW Radio - The Audion

Another super simple medium wave radio. This time a Franklin Audion (synchronous detector).

agp.cooperagp.cooper 01/07/2017 at 03:220 Comments

The Franklin Oscillator

The Franklin oscillator is a little strange and not immediately obvious how it works:


The following helps a lot:

(source: www.radiosparks.com/images_d/Franklin Oscillator.png)

So positive feedback at parallel resonance (0 degrees phase shift).


The next image is a transistor version:

Image result for franklin oscillator

(Source: www.uploadarchief.net/files/download/franklinoscillator.gif)

Here is a rationalised (long tail pair) FET version:

Image result for franklin oscillator

(source: www.uploadarchief.net/files/download/osci.png)


Still it takes a leap of faith to get to here:

Image result for franklin oscillator

(Source: i178.photobucket.com/albums/w269/notxyl97/DL7MWNQ-Multiplier.png)

But at low voltages most of the biasing components can go!

AlanX

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