Electric fences & emi

I was at a civil war relic spot a couple of weeks ago & the field I was in was surrounded by electric fences. It made my detector almost unusable. I heard every pulse of the fence even at low gain & discrimination turned up. I found nothing deeper than four inches deep. I know there were relics there because of the location. Any one know how to get around these fences? Over the years that I've been detecting some I could hunt almost next to them others impossible to hunt. I know you guys have a bunch of experience so I'm all ears. Thanks Tim

Try a CZ there. If that does not work.......... you'll be hard-pressed to find something that will.

NASA-Tom Wrote:
-------------------------------------------------------
> Try a CZ there. If that does not work..........
> you'll be hard-pressed to find something that
> will.


Used my cz-3d at an old fishfry grounds back in 09 around an electric fence and it done the same thing. Even at a distance of 60ft. or better it still done this.

A few ideas:
SOME time, they will be turned off. Maybe for maintenance work, new posts, relocating them, etc. Try and get advance warning of such work.

They may get flat batteries eventually, and this fact may go undiscovered for days/weeks. If you keep checking, you may get an opportunity.

Detect after heavy rainfall. The water everywhere seems to partially 'short out' the wire to ground, taking the sting out of it's pulses.

The fence may have a fault. I've encountered a 'haphazard' installation, and in one spot an audible tick could be heard. Closer inspection showed a visible spark jumping across an incorrecty made joint in the 'rope'. I think there must also have been a short somewhere, or the spark would not jump.... This spark likely put out most of the interference.

Ask if it could be intentionally turned off at any suitable time. Eg. if it's keeping in horses, are they ever taken away at weekends for competitions etc?

When I was field testing the Tesoro OutLaw, I was in a situation like that. I was hunting a field that had given up 3 ringers to a group hunt several years ago. The field was pretty clean until I came upon the electric fence. I had the 12X10" DD coil mounted to the OutLaw and I would get a false at the ends of my swing. I noticed I could work close to the fence if I dug the repeatable signals, found some old hollow based bullets that way. Kinda noisy but I just worked for the repeatable signals.

Tom I have several CZ's & will try them at this location buddy. Over look the obvious. Vthanks Tim

I was using my G2 if that makes any difference.

Yes..... there should be a fairly large difference between G2 vs CZ ....... in reference to EMI.

Cool thanks for helping me out. Tim

I would ask if they could turn it off for a few hours. The cattle would already be trained to not lean on the fence by now. Horses don't usually go through anything unless spooked.
Corey

Have no knowledge of electric fences but hunting a new school built over an old park my Explorer went bonkers when the security lights came on at dusk....Simply used the noise cancel feature and unit ran smooth....Wouldn't this work with an electric fence as well?

Had a reason to search for "electric fence" and found this thread.

Hunted a site for CW today that was heavily worked years ago (by numerous others) and I just recently gained access. It is surrounded with electric fence and even in the center of the 15 acre parcel, the Deus steadily went "thump...thump...thump" with the pulsing of the fence controller. The right hand side of the horseshoe display would darken by just less than half, then just more than half, then almost completely darken. The VDI would jump between mid 20s and 60s and several points in between. I tried all 4 frequencies and shifted frequency both negatively and positively at each frequency with no improvement. Reducing sensitivity lessened the thumping somewhat but the depth loss was so much at the 40 sensitivity setting, that I just left it at 90 and hunted for targets between thumps. No CW found but several non-ferrous targets (50s to 80s) were dug at up to 8 or 9 inches.
When I returned to the car, I tried the F75SE. It, too, had the "thump...thump...thump" interference, but when I turned the sensitivity down to 40 or 45, the thumping mostly went away, and air tests on a mini ball still registered at 8 or 9 inches. Interestingly, the thumping was considerably more severe in all metal mode than in discriminate.

My thoughts, too, were to try the location after a rain to see if that makes a difference, and to ask the owner if perhaps I can turn the controller off while I am detecting there. But, with the F75SE, I do believe I will be able to mitigate the fence pulsing enough so that it is not a problem. Not pertinent to this discussion, but the much larger problem with this property at the moment is how thick the woods portion is with downed trees and limbs and how thick and high the sedge grass is in the fields.

Pleasant Garden, NC
AT Max, Nokta Impact, MX Sport, Nokta FORS Relic, GPX 4800, Infinium, Racer, Deus, F75SE, Nautilus DMC II (order of acquisition, last to first)

Does an archeologist argue with a plow? A bureaucrat with a bulldozer?

Hi Wayne. Hunting after a rain may help, but only a little. After a rain the voltage/amperage on the electric fence may be reduced somewhat. But if the fence was constructed using a ground rod return system (most common) you will still be 'grounded' and therefore part of the electric fence array if you are standing in the ground field holding your detector. 

We have over five miles of 12.5 ga. electric fence on our property; since I built nearly all of it myself I am quite familiar with both construction and operation. Neither of my detectors (Deus or CZ 3D) will operate properly anywhere near my fence. Both pickup and register each electrical pulse through the system, the Deus more so than the CZ. The only thing I know that works is to turn off the system.

I hope this helps,
Duke 

Just to clarify my comments about detecting after rain: the fence system I have problems with uses a ground spike return. The wire (stainless steel wire woven in with polyester rope) is supported with plastic eyelets, screwed into wooden posts. After heavy rain, the posts and eyelets are saturated, allowing the wire to discharge to ground slightly at every post. The ground itself should also be a better conductor, too. It certainly seems to lose some of it's "bite" when wet.

Edit for further clarification: "bite" means electrical interference generation, as seen by a metal detector.



Edited 1 time(s). Last edit at 10/24/2014 04:10PM by Pimento.

Actually it gains a bit of "BITE" after a decent rain.

When I use to go fishing I needed to cross an electric fence with all my gear.
Backpack slung over shoulder, fishing rods leaned up a post,... I attempted to drop the wire so I could step over it,...

I used a rain drenched branch of a tree standing nearby the fence,... thinking wood is a great isolator.

Talk about a shocking education in conductance!!

HH
Johnb

Hi Pimento. You are correct; some fences due to construction materials and methods will 'leak' amperage via multiple small shorts through cracked and worn insulators. These leaks are often amplified dramatically after a hard rain. Your advice to Wayne was correct, he should try to hunt the site after a hard rain. If however the fence was constructed properly with high quality insulators and connectors the ampere / voltage loss will be minimal even after a soaking rain. 
Duke

its the buried residential electric/radio dog fences that give me grief. if the new f75 can negate that im a buyer.