Posts: 2752
Location: Mauston, Wisconsin | ToddM - 10/10/2015 11:00 AM
What are you saying Al, every time that fence finds another ground the padre gets interference on his graph? What kind of camp is that?
No, I'm saying that a electric fencer uses the ground as a return path for the pulse, if there's a weed or a insulation failure the pulses follows the earth back to the fencer itself. Even if there is no "fault path" like you peeing on the fence its still generates an electromagnetc pulse between the fence wire and earth. See the link below. Electric fencers cause all kinds of intererence, including telephone lines, internet, TV, guitar/sound systems and yes, I think quite likely sonar. The key trigger for me is the repetitive interference rate and that it becomes weaker moving away from the source.
The first step is to time the interference pulses, e.g., Padre said about every 5 seconds, but is it really 5 seconds? Not all electric fencers have the same pulse rate. This would be first instance that I know of where sonar interference seems to correlate to an electric fencer or similar device. EMI/RFI interference is a complex engineering field and one I'm very familar with as an electronics/electrical engineer.
http://www.arrl.org/electric-fence
Padre: It makes sense that a summer camp would likely have animals like "horse's" etc., so they likely have a electric fencer. It is illegal to cause radio interference. I would approach the camp owner(s) from a more benign perspective, e.g., "I'm trying to solve this mystery that only happens with my sonar on this lake." Its likely very fixable if its a electric fencer issue.
Good luck!
Al
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