A low power AM transmitter kit from AliExpress caught my interest. It was AU$30 and is crystal locked to 21MHz.
The board is good quality and went together easily.
Component values are marked on the board, which is handy because the supplied documentation is a bit different to the actual board. One ceramic capacitor and 4x 47uF electrolytic capacitors were missing but easily found in the junk box (although rather bigger than the space on the boar). There was a handful of extra small value components along for the ride.
It does work but sounds a bit rough.
Tuning the two metal tin inductor slugs increased RF voltage significantly. Fed into a non-resonant dipole and it gets out very well. This recording is at about 100m away.
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