Léon Theremin made a device called "the thing" how can i make one and a reciver for it?

Question

http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#Espionage Wikipedia talks about it being real simple, but would an electrete mic work? would i quite litteraly attach 1/4 wavelength size wires on each side of the mic? I understand the concept just not the detals. Anybody have/willing to draw a schematic for me?

Mind you, this "the thing" has nothing to do with microwaves, it operated at 330MHz, not 2450MHz like a microwave.

The thing I like most about this "the thing" is that it is passive - so has no power source. The "power" that it uses is from the carrier wave that i need to send to it, if i understand correctly, and I can then pick up the modulated wave reflection/resonance and demodulate it. Please don't try to answer this question unless you understand electronics.

Answer 1

In the 1950's, condenser microphones were quite big clunky things with relatively high capacitance and correspondingly large variation in C with applied sound. Modern electret mikes tend to be quite small and usually incorporate a f.e.t. buffer circuit to give useful l.f. audio performance by providing a high-impedance load.

The thing presumably works by using the variation in C to vary the resonant frequency of the antenna system and hence the amount of r.f. re-radiated. The problem is going to be trying to receive a weak re-radiated signal in the presence of a necessarily strong, unmodulated incident wave on the same frequency. A tight beam on the "supply" transmitter would help, but that implies a physically large antenna aperture at u.h.f.

Answer 2

You could not make such a device by attaching wires to a microphone. Where would you attach the wires? Where would the resonant cavity come from? The Theremin device is a type of microphone itself. Unless you want to duplicate the device out of curiosity, you can achieve the same result with a wireless microphone system. You can probably find electronic project kits for such a device.

To duplicate Theremin's device you would have to build a microwave resonant cavity and you would need a microwave transmitter and receiver.