I am building a simple theremin to demo for my physics class, and I found this schematic online that was the least complicated I could find. I built it on a pcb to minimize the capacitance of the connections, but when I connected the output ("Ausgang") to the tip of a headphone jack (to an amplifier) and the ground to the sleeve, all I get is static. I apologize for my complete lack of understanding of this circuit but I don't know where to start troubleshooting it. the "4093" logic gates are NAND gates, and the "4077" gate is a XNOR gate. I used 3 Quad two input NOR gates wired to work like 2 NANDs and a XNOR gate. for the antenna I used a 6 inch long by 3/4" OD steel pipe. The static does seem to change volume with the distance my hand is away from the pipe. I would GREATLY appreciate any help with this circuit.