Elektor Theremin

My first theremin was an Elektor design (3/95), very small, pitch antenna only. Simple digital oscillators with TLC555, most simple mixer with a single XNOR gate. Here is the schematic. I re-worked the original pcb and components layout for better printing and etching.
This is the second version from the same schematic (one for the road). It features a metal box, detachable antenna, adaptor for mic stand and a standard 1/4" jack with integrated on/off switch. Very reliable, though it drifts slightly with temperature and sometimes picks up RF noise.