Greetings everyone! I registered today but i watch the forum some time now and you guys really helped me to get some ideas and technical theory about theremins. My main goal is to make an easy to produce purely analog theremin with materials found in any electronics shop. So lets get to the topic...
My main headache now is how to go from breadboard to PCB. I have made 3 pcb's so far 2 of them weren't working at all which is pretty reasonable considering it's my first pcb design. The 3rd one i got it to work but the problem is that all my antennae sensitivity was gone, from a pretty good range i had to almost touch the antennas to get a sound and the volume antenna was even worse i had to touch it to work. So lets get to the current design
The oscillators i go with are typical colpitts ones powered by current source with lp filter at the front to avoid injection locking as much as possible. Next the outputs are buffered via jfets and mixed with a gilbert cell. After some filtering and amplification the signal is going to the VCA. The volume oscillator is going to a discriminator followed again by a jfet and then to some transistors which their purpose is to invert and scale the dc voltage feeding the VCA.
This is the current layout of the PCB
So my main question is how to avoid the failure of the previous pcb. You think it might be a circuitry disfunction or purely a matter of pcb design?