How can I convert a homemade radio transmitter to receiver ?

Discussion in 'The Projects Forum' started by Michael George, Feb 28, 2015.

  1. Michael George

    Thread Starter Member

    Feb 8, 2015
    Hello everybody,
    I've made this FM radio transmitter and it works very well with a good quality :)
    I would like to make an FM receiver using the same idea which is common base Colpitts oscillator, and I wonder if you would mind telling me what changes should I made to this circuit to convert it to an FM receiver. I know that I can make a better receiver using LM386 or any other amplifiers, but making changes in this circuit help me understand it much better.

    niftymitter 0.23 electronics schematic.png

    I have one more question, I tried to make a change in the previous circuit and moved the trimmer capacitor to be in a position as shown in the following circuit but it doesn't work... Why the capacitor C2 of the following circuit is moved and connected to the collector as shown in the previous circuit ?
    Thanks in advance,
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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  3. DickCappels


    Aug 21, 2008
    C2 of the second circuit is not the same function as C2 of the first circuit. The two only have the designation "C2" in common and the designation is only that -how to tell one capacitor from another.

    The circuit above by Alan Yates is essentially your transmitter modified to be a regenerative receiver. The circuit was modified to turn itself off and on at high frequency -this was done be increasing the emitter resistance.

    You can read more about it on Alan's site:

    Alan's entry page:
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  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    regenerative recievers do not make good fm rewcievers. they tend to lock on to the strongest signal near where they are tuned to and have a very broad bandpass that does not allow slope detection.
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  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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