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Thursday, July 15, 2021

Mythbuster Video #5 -- More Listening on 75


  1. Nice job Bill! Looking forward to your next addition to this receiver. Forgive my ignorance but, what was the reason for halving the value of the cap in the amp? Thanks! Ted KE4NBB

    1. Thanks Ted. In the LM386, if you put a 10 uF cap between pins 1 and 8 you take the gain up to around 45 db. That is a lot. If you don't put anything there I think it is about 20 db. 5 db looks like around 30-35 db. At very high gain it can be hard to keep the amplifier stable -- it will break into oscillation and howl. So if you don't need all that gain, life is easier at lower gain levels. Bill

    2. I meant "5 uF looks like around 30-35 db."

  2. just for fun ... put the antenna after the filter and tune 75 & 20 at the same time!


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