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Cheap Shortwave transmitter homebrew

Discussion in 'Home Brew' started by T23, Jan 17, 2011.

  1. T23

    T23 Active Member

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    I built one of these but it does not seem to work?






    T23
     

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  2. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Where does the oscillator module gets it's power from? You need to power it and modulate that DC voltage with audio from the 386 amp.
     
  3. T23

    T23 Active Member

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    The oscillator gets its power from the AM output signal of the IC, the pin thats conected to the IC is the power pin of the oscilator.


    T23
     
  4. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    I have never seen something powered like that. Where did you get the idea for that? I have used those RF oscillators before as QRPppp transmitters and did manage to modulate one once but I powered it the normal way with the DC flowing thru one winding of a transformer and applied audio to the other winding. This modulated the DC supply and thus amplitude modulated the RF oscillator.
     
  5. T23

    T23 Active Member

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    I see, so that would keep the voltage the same going to the oscillator but still modulate it?


    T23
     
  6. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    No. When you superimpose an AC voltage ,such as audio, on a DC supply the voltage swings up and down in response to the audio. The AC component adds to or subtracts from the normal DC voltage. The varying voltage on the supply line is what causes the amplitude of the RF oscillator to change resulting in amplitude modulation.
     
  7. T23

    T23 Active Member

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    Ok, I see, Ill have to test this some more, I need a new lm386 though...


    T23
     

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