[g4wim_tim]

I read that article with interest.

It worked on about 1GHz and used a cavity resonator with an audio diaphram as one side of the cavity, audio would phase modulate the reflected signal and be demodulated with what was effectively a direct conversion rx.

I experimented with and worked on a very similar system.

These days any high power illumination signal instantly raises attention from counter espionage types - plus you can determine exactly where the illuminating signal is coming from.

Mods - please delete this if not considered appropriate.