AM Radio Transmitter using a Tuner/Variable Capacitor

Discussion in 'The Projects Forum' started by don3194, Jan 17, 2016.

  1. don3194

    Thread Starter New Member

    Jan 17, 2016
    I just finished repairing an old radio from the 40s, and I was wondering if I could build an AM Transmitter using a Tuner/Variable capacitor. If not, I will just build a transmitter from a Crystal Oscillator.
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    Assuming the radio is a heterodyne or super-het design, there is a local oscillator. But you would have to add a modulation scheme, and the LO is tuned 455 kHz away from the broadcast band.

  3. don3194

    Thread Starter New Member

    Jan 17, 2016
    I am not that great in electronics, how would I figure out if it is a heterodyne or a super-heterodyne? What is the "LO" and what is a modulation scheme? I must sound stupid, but if you don't know just ask.
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    your 1940s AM set is probably valve, and will be a hetrodyne receiver, the front end tuner is mixed with a local oscillator (LO) which is usually 470Khz higher than the tuner, this produces a mixed signal of both the sum and difference, the difference is 470Khz and this is amplified and demodulated by the diode to produce an am signal.
    Last edited: Jan 18, 2016