In article , frank1492 wrote:
A friend has an invisible fence for her dog. The wire was apparently
severed by someone turning over soil in a rather large area adjacent
to her property.
She claims to have used a portable radio to find the break in this
system before, but she can't remember whether she was using the AM
or the FM band.

AM, tuned to a staticky place between stations.

In any event, this time she has tried a different
radio (the other one is broken) with no success.

I've observed that some radios work better for this than others. We have one
radio that's just dandy for locating breaks, and another one that isn't worth
a hoot. Don't know why.

Fresh batteries make the job a lot easier.

My question is: Can one use a radio to find a break like this? And
if so, how is it done?

Yes. Tune an AM radio between stations, and move it side-to-side across the
suspected path of the wire, just above the ground. It's best to start in a
spot where you *know* the exact location of the wire -- like where it crosses
a driveway, or a sidewalk, where you can see the saw cut that the installer
made in the concrete or asphalt. Wave the radio back and forth until you hear
a definite change in the pattern of the static -- that's what you're searching
for. Then start walking along the path of the wire, continuing to wave the
radio back and forth.

Sooner or later, you'll come to a spot where the signal fades, and eventually
disappears completely. Mark that spot.

Now go back to where you started, and in the same manner, follow the wire
around the yard in the opposite direction. Again, you'll come to a place where
the signal fades, and eventually disappears completely. Mark that spot, too.

The break is approximately half-way between the marks.

If not, is there an inexpensive device that
could be used to do it? (She doesn't want to spring for a metal
detector.)

Well, metal detectors aren't all *that* expensive... but the radio works just
fine.

I really don't need more info, but would like to know a little more
about how invisible fences work. I would assume the wire simply
acts like a transmitting antenna.

Yep, that's all it is.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.