Man look at that little critter fly!! I think the principles for using an AM radio are sound. I found two radios, and used them, but I couldn't quite make sense of what I was hearing. Perhaps there was a ton of localized interference. I stepped up my approach by purchasing an underground wire locator from Amazon. This gizmo sends an amplified steady signal down the perimeter wire and a separate portable device listens for the signal as I walk along the perimeter. This didn't work as easily as I'd hoped. My guess is that due to the existence of one very large perimeter wire and three intersecting shortcut-to-home wires, there's some interference/signal degradation that complicates finding the break, especially since there's normally multiple breaks due to the relatively large population of squirrels. There's got to be an easier way to find a break! I think the conclusion here is that I should just keep a bunch of loaded bird feeders to occupy their time!