For the whole MW band, 160m and shortwave
Designed by sv3ora
I have seen quite a few AM transmitters
on the web, solid state and tube based. For this project I wanted
something that would be able to cover the whole MW band from the bottom end to the top, the 160m and
the shortware, with good audio fidelity and adequate frequency
stability, so that I can use it to broadcast music to nearby radios and
enjoy my favourite programs on them. The schematic of the transmitter I have ended up with, is shown below.
The oscillator is able to cover all frequencies from 480KHz to about 2MHz, split in two ranges, each one selected by the switch. I wanted the transmitter to be cheap and easy to be built and replicated, so I have used a 500pF varicap instead of a big and bulky variable capacitor. Frequency stability is more than adequate with the varicap in place. The oscillator output waveform is square wave, which is rich in harmonics and so it covers the whole shortwave and much more. The following amplifier stages work in class-C and the output of the transmitter is square wave as well. That way you can enjoy your favourite program at any frequency you like.
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