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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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