AM Radio Transmitter using a Tuner/Variable Capacitor

Thread Starter

don3194

Joined Jan 17, 2016
2
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.
 

AnalogKid

Joined Aug 1, 2013
8,806
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.

ak
 

Thread Starter

don3194

Joined Jan 17, 2016
2
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.

ak
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.
 

Dodgydave

Joined Jun 22, 2012
9,854
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.

https://web.archive.org/web/2015010...om/circuits/mw_transmitter/mw_transmitter.htm
 
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