Zvex probe wah type of a wah, antenna question

[JebemMajke]

So i would like to make this type of theremin wah.



I already have this morley inductorless wah etched and the board is populated. I liked the sound and the volume of it. So that is the was i will use instead of colorsound one.

My question is about copper antenna. How big should it be? Also, can i paint it? Or even better etch something on it?

[Transmogrifox]

I made one of these a while ago.  It never made it off the breadboard except for the proximity circuit (oscillator and such).

I used a piece of copper-clad board at approximately 2.5" x 4" and screwed it to a 3/8" thick piece of acrylic (plexiglass).  The center of the plexi had a hole drilled to make space for the wire I soldered to the copper clad board.  I had drilled a hole all the way through the copper board also and tied top and bottom layers together with the connected wire -- soldered top and bottom.

To test it, I held a DMM in my hand that had a capacitance meter.  Connected one side to the wire out of the proxy sensor, and the other lead I held in my hand.  I calibrated the meter to 0 pF, then started to move my foot toward the proximity pad and noted the max capacitance when I had my shoe touching the pad.

After I knew the capacitance range of my pad, then I went back and designed my oscillator and demodulator based on that value.

Basically if you make a way to trim/tune your circuit then you will be able to adjust to a 2.5" x 4" pad, or whatever other size is convenient for you.  My pad size was based upon a scrap of board that happened to be about the right size, so I used it.

That thing was so much fun.  I need to build it again.  I still have the proximity pad, but the filter has fallen to disarray.  I think it was a state variable filter if I remember correctly.