Posted by Ed Holland on October 21, 2022 at 20:20:34.

I installed an invisible dog fence on our property (Even though I wasn't sure if we had invisible dogs or not). This constituted a large loop around the perimeter, supplied from a "transmitter" at the house, with a twisted pair connection from the centre to the feed point. I'd also added another smaller loop, around an ornamental garden area. This was near the path taken by the dogs, and occasionally, they had trouble negotiating it. Since they learned to stay out of the area, I disconnected this auxiliary loop But - the dogs were still getting the occasional warning beside the disconnected loop (the system warns them with a beep before giving a light shock, so they learn not to get zapped). It was then, I realised I'd actually made a giant loop antenna/transformer, with the smaller wire acting like the coupling loop. I quickly shorted the ends of the latter, and voila! no more troubles. Who says radio skills are wasted :-)

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