metal dector for barbed wire fences
 

rec.radio.amateur.antenna
metal dector for barbed wire fences

Anybody here have any suggestions for possible ways to detect fence wire,
mostly 1, 2 or 3 levels of barbed wire but also some 8 inch square matrix?
Typical mounting would be on a tractor or trailer, so the detector would need
a sense of direction, ie looking outward not inward. Minimum range would be
around one foot with 4 feet probably optimum.
Typical retail metal detectors have a short range and need a metal free
environment, leaving the methods they use somewhat doubtful. Evidently, there
are detectors with seperate heads/coils and 1-5 foot ranges but, once again,
require a metal free environment.
One possible area would utilize rf antenna's, one transmiting and the other
recieving a reflection from the wire(s). A parabolic or corner reflector type
antenna maybe if not for the high frequency - two 12 inch antenna's would be
about max size and that's in the gigaherts range, which might be a problem.
Any suggestions along this line will be appreciated.

Hul

metal dector for barbed wire fences
 

If there is a free end accessible you might try feeding some rf into it
and then following along with a receiver to detect the underground
portions. This may or may not require strong attentuation at the
receiver antenna -- using a short loop or something across the input.

If there is one level. chances are you may find others underneath with
a little digging unless there are accessible ends to them whereas tracking
the RF would work just as well.

Just a wild and maybe not so crazy idea of how I'd try for a quick cheap
fix.

Irv VE6BP


"Hul Tytus" wrote in message
...
rec.radio.amateur.antenna
metal dector for barbed wire fences

Anybody here have any suggestions for possible ways to detect fence
wire,
mostly 1, 2 or 3 levels of barbed wire but also some 8 inch square matrix?
Typical mounting would be on a tractor or trailer, so the detector would
need
a sense of direction, ie looking outward not inward. Minimum range would
be
around one foot with 4 feet probably optimum.
Typical retail metal detectors have a short range and need a metal free
environment, leaving the methods they use somewhat doubtful. Evidently,
there
are detectors with seperate heads/coils and 1-5 foot ranges but, once
again,
require a metal free environment.
One possible area would utilize rf antenna's, one transmiting and the
other
recieving a reflection from the wire(s). A parabolic or corner reflector
type
antenna maybe if not for the high frequency - two 12 inch antenna's would
be
about max size and that's in the gigaherts range, which might be a
problem.
Any suggestions along this line will be appreciated.

Hul

metal dector for barbed wire fences
 

"Irv Finkleman" wrote in message
...
If there is a free end accessible you might try feeding some rf into it
and then following along with a receiver to detect the underground
portions. This may or may not require strong attentuation at the
receiver antenna -- using a short loop or something across the input.

If there is one level. chances are you may find others underneath with
a little digging unless there are accessible ends to them whereas tracking
the RF would work just as well.

Just a wild and maybe not so crazy idea of how I'd try for a quick cheap
fix.

Irv VE6BP


Good idea. RF tracking works very well for buried cables and should work
for fence wire. I used it some years ago when we were adding antennas to an
existing field and needed to know exactly where to dig only by hand. The
device is in two pieces, one of which couples RF onto a cable by induction
(from up to several feet away); the other piece is a receiver which detects
the re-radiation from the cable up to several feet away. The transmit unit
and the receive unit need to be separated about fifty feet apart or more for
this to work. Otherwise, you will get direct coupling through the air and
not via the conductor you're tracking. The receiver sensitivity was
adjustable on the one I used.

I rented our unit from a surveyors' supply house. Rent, try, buy. good
luck.

"Sal"

metal dector for barbed wire fences
 

Might be worth trying a standard electric fence generator. These put in a
pulse of a few 10,s of kv( as far as I know)
Probably pick it up as a 'click" on a standard AM/FM reciever. These blokes
could maybe suggest a better antenna. Just make sure you if you need a leak
you dont use the fence post!!!!!.
"Sal M. O'Nella" wrote in message
...

"Irv Finkleman" wrote in message
...
If there is a free end accessible you might try feeding some rf into it
and then following along with a receiver to detect the underground
portions. This may or may not require strong attentuation at the
receiver antenna -- using a short loop or something across the input.

If there is one level. chances are you may find others underneath with
a little digging unless there are accessible ends to them whereas
tracking
the RF would work just as well.

Just a wild and maybe not so crazy idea of how I'd try for a quick cheap
fix.

Irv VE6BP


Good idea. RF tracking works very well for buried cables and should work
for fence wire. I used it some years ago when we were adding antennas to
an existing field and needed to know exactly where to dig only by hand.
The device is in two pieces, one of which couples RF onto a cable by
induction (from up to several feet away); the other piece is a receiver
which detects the re-radiation from the cable up to several feet away.
The transmit unit and the receive unit need to be separated about fifty
feet apart or more for this to work. Otherwise, you will get direct
coupling through the air and not via the conductor you're tracking. The
receiver sensitivity was adjustable on the one I used.

I rented our unit from a surveyors' supply house. Rent, try, buy. good
luck.

"Sal"