XPost: sci.electronics.design   
   From: me@somewhere.invalid   
      
   John Larkin  wrote:   
      
   >On Thu, 23 Aug 2018 22:52:26 -0700 (PDT), terrypingm@gmail.com wrote:   
   >   
   >>Thanks all, mains leakage sounds the culprit. I’ll get on it today. It’s a   
   long run, with an intermediate outdooor mains socket, then a (supposedly)   
   waterproof case with the relay.   
   >>   
   >>Terry, East Grinstead, UK   
   >   
   >Maybe something underground is full of water or ants or something.   
   >Possibly the wire insulation got nicked.   
   >   
   >There are some fun instrumentation possibilities, like probing the   
   >soil at the surface and measuring/listening for AC potentials.   
   >   
   >A map of the surface potentials of some chunk of land, color coded by   
   >frequency, would be fun.   
   >   
   >We were on the roof yesterday and speculated how cool it would be if   
   >we could see RF, all the microwaves and cell phones and wifis and   
   >transmitters. That's not possible. But a surface potential map is.   
      
   To my surprise the mains cabling seemed OK, giving readings outside my   
   DMM's 200Mohm at various points.   
      
   A side issue arose has me puzzled. I found about 1V DC across a twisted   
   pair cable, disconnected at both ends, buried in several places. How   
   does that come about? Even the short section I've cut out, with gaffer   
   tape around connector blocks, has about 0.5V DC.   
      
   Terry, East Grinstead, UK   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)