theremin antenna

[nosebone]

Hello

I'm trying to build a tremolo-circuit with a theremin-antenna to control
the speed/rate parameter. I've already found some theremin-schematics
but I haven't got yet an idea how to make that antenna control my
parameter. Does anybody know how to modify a theremin for this application?

nosebone

[ExpAnonColin]

Thanks to Transmografix for help on this idea:

Basically, you just take a very high frequency waveform generator, around 250khz, way above human hearing.  Then, you use an antenna and the grounded chassis to allow your body's capacitance to be added, in parallel, to the generator's capacitance, thus lowering the frequency.  You then take a lowpass filter with a cutoff at say, 240khz.  Since the Q is large, basically as the frequency goes down, more and more is allowed to pass through the lowpass filter.  You can then use that as a voltage source for an LED, which would then be optocoupled to a LDR, which would be used inplace of the speed knob of the tremolo.

-Colin

[Peter Snowberg]

Welcome to the forum Nosebone!

There are a bunch of ways to build the control circuits in question here and I don't do RF stuff (because I'm clueless with RF ), but you might want to check out http://www.thereminworld.com for a variety of schematics.

I think Colin's take using two seperate circuits and an LDR to join them is the way I would go.

Hey Colin.... How about a theremin oscillator with a ring modulator?   :twisted:

Take care,
-Peter