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WIREFINDER 9000

Find buried cable breaks with a radio.

By Christie, Jim, John, and Terry Noe

Our dog, Maggie, loves to run around in our big yard. But how do we fence her in? Building a 500- foot fence is expensive and unsightly, so we use an “invisible fence.” This is a buried wire that runs around the edge of our yard. Maggie wears a radio collar that beeps when she gets close to the wire, or gives her a mild shock if she strays over the edge (it doesn’t hurt).

Photography by Sam Murphy

One of Maggie’s favorite sports is digging up the gophers that are endemic to our neighborhood. Unfortunately for us, the gophers have a hobby of their own, which is biting through the buried wire of our invisible fence.

How do you find a break in a 500-foot buried wire? Digging up the entire 500 feet would not be fun. You can buy commercial cable finders that will find buried wires and wire breaks, like the Armada Technologies Pro 700, but these cost from $500

to $2,000! We decided to make our own and use the money we saved for something useful, like building a big trebuchet.

Overview

Our WireFinder 9000 has 2 components: a transmitter that puts a radio signal on the buried wire, and a radio receiver. You connect the transmitter to one end of the buried wire. This causes a current to flow through the wire, which creates a radio signal that radiates from the wire. Then you can find the wire by walking around with the radio receiver.

When the receiver is close to the buried wire, the radio signal is strong and you can hear it over the receiver’s speaker. The strength drops rapidly as you move away from the cable, causing the signal to drop in volume until it becomes inaudible.

If there’s a break in your wire, the current can’t

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