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With 555 timer as the carrier oscillator (500Khz LF) 4th order filtering, to minimize any nonlinearities. Basically the filtering converts the square wave to sinewave before feeding it to the second stage which is the mixer/modulator stage, which is parted by the rest of the circuit with emitter follower stages at both inputs and the output, for more stability. This is just a modulator. It doesn't have the capacity to transmitt yet. Without an antenna you'll probably have a few cm of range, at most (with a supersensitive receiver) You'd need a power amplifier and a few orders output filter to amplify it and remove any harmonics that may interfere with other stations. Since this works at the lowest end of the spectrum you can use common audio frequency techniques to amplify it. A simple class B amplifier will do, but the output must be filtered. I'll try and devise a power amplifier for this. Will post the circuit under the name ,,Short wave power amplifier''
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