Hello Mark,

I have invested some time in running the long signal leads in shielded cable and grounding it and everything I can think of to the earth ground of my 110vAC power cord. The main control board being in a plastic enclosure also now has a ground strap to the same ground. If I don't get positive results from this and other remedies offered here my last recourse is to fabricate a steel enclosure and ground it as well.

There is one construction hitch to moving the reed switches (although I agree it would be a sensible test) in that the two lead wires run down through holes in the table. I would have to fasten some type of disconnect there to make them removable. I soldered the leads to the grounded cable with the shortest possible length to reduce the chance for EMI pickup. I try to avoid many connectors for I feel each one is a potential weak point.

Later today I will have everything wired and ready to test except the adding of inductors since they are still on their way from Mouser.