This weekend, I received a familiar call from my father. He was calling to request my services to help him troubleshoot issues with something electronic in his house. While I normally field calls for his PC (I haven’t been able to convince him to switch) or other household electronics, this week’s request was to help troubleshoot his invisible dog fence.
First, for those unfamiliar with invisible fences, they consist of a loop of wire, run under and/or above ground. A radio signal is sent down the wire (antenna), and if a receiver (dog collar) gets within range of the wire, they get an electric shock. The controller unit is a box that sits on the wall, with a dial which controls the transmitter power, and two LEDs which indicate power present and loop status. The system doesn’t work without having the antenna loop being continuous from end to end.
Unfortunately, PVC insulation seems to be a favorite snack of rodents, and as such, the loop is frequently damaged. The manufacturer, obviously aware of this, has designed the unit to beep in the event the loop is broken, to avoid a jail break.
After a quick online search, and a trip to the store where the unit was purchased, I still had no answers other than to uninstall the existing loop and reinstall a new loop. As the perimeter of the yard is around 300 meters, this wasn’t an ideal solution. While it did cross my mind that this was a perfect excuse to buy a TDR, I decided this would be a good time for some ingenuity.
My solution? Use a tone generator and inductive amplifier to follow the signal. When the sound stopped, I knew the problem was somewhere behind me. While my solution was not exceedingly elegant, it did work. Has anyone else had this sort of problem, and what other ideas can the group come up with?
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