Question: Simple FM reciever????

Discussion in 'General Electronics Chat' started by samy555, Oct 15, 2012.

  1. samy555

    Thread Starter Active Member

    May 24, 2010
    116
    3
    The following is FM radio reciever circuit from:
    http://www.hqew.net/circuit-diagram/Small-FM-Radio-Circuit_8896.html

    [​IMG]

    I do not intend to implement, but Surprised by the way the two transistors T1&T2 connected.
    The tuned recieved FM signal inter the collector of T2 and out of its base to feed to the audio amplifier
    It is the first time in my life watching that stage audio feed from the base of the transistor
    Can you help me understand the work of those two transistors?
    Thank you very much
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I'm not sure, but it appears to be a regenerative design. Do other FM radios get quiet on a station when this circuit is tuned to the same station station?

    If so it is definitely regenerative. Regenerative radios work by almost, but not quite, oscillating. This ups their gain enormously.
     
  3. WBahn

    Moderator

    Mar 31, 2012
    17,788
    4,808
    I guessing here, but I would venture to say that your signal isn't coming from the base, per se, but rather from the antenna (at the junction with R1). This signal is then feeding both the audio section, via C2, and back into the RF section, via T2.
     
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