Thank you for the suggestions gents.
I removed the coax shield ground connections at the Sandwich VFO and left them at the main PCB so only one end of the coax is grounded. Unfortunately there was no change in the noise.
I also tested it both with and without an additional insulated ground wire running between the Sandwich VFO and main PCB (like the manual calls for). This didn't make any difference either.
I believe I've narrowed down the noise source to the tuning encoder. But I'm also beginning to think maybe this noise was always been present... even before I moved with the capacitors and added the coax jumpers. I suspect I've become overly fixated on it and it's really not significant.
---In CHINA_QRP@..., <larry.lovell@...> wrote :
Ground just one side of the coax. You have probably created what is called a ground loop.