Circuit Diagrams for the AM Walkie-Talkie Experiments

A lot of people have asked for the circuit diagrams for this experiment, so here they are...


The Transmitter Circuit

The 7 turn link output is resonated with 47 pF to get reasonable power out, but it is still quite a feeble transmitter.


Super-regen Detector

The coil for the detector is described in the original article

AF Filter and Amplifier

Higher Q filters might be better, but these work and are very simple, using the same R and C values - which might be considered a feature.


To make a full transceiver you'll need a microphone amplifier and probably a loudspeaker amplifier although the output of the AF filter board drives a xtal earpiece just fine and small low-impedance headphones to some degree.

You'll probably want more output TX power, the design delivers about 2 mW PEP! You might consider collector modulating another RF stage driven by the xtal oscillator instead of the oscillator itself.

Design supply voltage is 9 volts.

The xtal case is grounded in the TX. Ungrounded the amplitude modulation linearity is effected - I am not completely sure why.


Parent article: AM Walkie-Talkie Experiments.