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Replace variable capacitor with varicap

Discussion in 'Radio and Wireless' started by michael1978, Mar 11, 2018.

  1. Audioguru

    Audioguru

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    Sep 24, 2016
    Please post a link to the webpage that has this horrible circuit.
     
  2. michael1978

    michael1978

    388
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    Mar 17, 2012
    You are right .....
     
  3. rakhmatvaris

    rakhmatvaris

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    2
    Apr 13, 2018
    Last edited: Apr 13, 2018
    michael1978 likes this.
  4. Audioguru

    Audioguru

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    Sep 24, 2016
    I see a few problems with the LM386:
     

    Attached Files:

    rakhmatvaris likes this.
  5. michael1978

    michael1978

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    Mar 17, 2012
    thanks a lot
     
  6. rakhmatvaris

    rakhmatvaris

    3
    2
    Apr 13, 2018
    Last edited: Apr 14, 2018
  7. michael1978

    michael1978

    388
    2
    Mar 17, 2012
  8. rakhmatvaris

    rakhmatvaris

    3
    2
    Apr 13, 2018
    yesterday i've tried it .... and it works
    first, I use polyvaricon first. then i just use diode varicap. I do not know why the radio sounds more detail when using varicap, that's my opinion

    test 2.jpg
    test.jpg
     
    michael1978 likes this.
  9. michael1978

    michael1978

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    Mar 17, 2012
    i gonna try also...;-)
     
  10. Audioguru

    Audioguru

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    Sep 24, 2016
    "Detail" of sounds is high frequency response. When humans are young we can hear as high as 20kHz and CD players and MP3's produce it. FM radio goes to 15kHz and sounds good. But an ordinary AM radio MUST cut the 10kHz interference beat frequency produced by adjacent stations and ordinary interference between them so its frequency response cuts frequencies above about 3kHz. A TRF radio has only a single LC tuned circuit so its frequency response is determined by the bandwidth of the tuned circuit which is affected by using a varactor to replace a mechanically variable capacitor.
     
    michael1978 likes this.
  11. aurelZ

    aurelZ

    64
    7
    Jun 10, 2019
    Back to first circuit.
    It work as is given with 500pF air variable capacitor as MW TRF receiver.
    if you wish to turn it as normal regen look into modifications.
    This circuit can work on smaller voltages using 2 AA batt - 3V.
    [​IMG]
     
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