NEL 5" Sharp Unstable Over Rain Soaked Ground?

[lloyd0161]

I am running a Gold Bug Pro but should be same with F19. Strange behavior of my 5" NEL Sharp coil over freshly rain soaked ground. If the coil is swiped on wet grass it becomes chattery as heck and unstable with constant falsing all over the place. If the coil is kept an inch or so above the wet grass it worked better but still unstable. If the conditions are dry it works fine. Over the same wet grass the 5 x 10 and 11" coils work fine. Anyone else had the same experience? This was very frustrating. I tried manually ground balancing with no success.

 

[mudpuppy]

I get that kind of thing with the F70 running the 11"dd in those conditions if the top few inches of dirt/sand/grass are wet/frost, and underneath dirt/sand is dry...gotta drop sens and maybe go neg on the thresh to tighten up the pings and lose the false...
Just a theory, the layering effect of dampness changes the dirt GB parameters...one layer is more conductive than the other instead of being all the same? Maybe somebody that knows for sure will pipe up..
Mud

 

[Mike Hillis]

Coil falsing on wet grass is typically a sign of poor shielding in the coil. Or a shielding failure.

HH
Mike

 

[Hightone]

There is less resistance in a wet environment than a dry one. Water/moisture is conductive. The detector field is more sensitive to signals because of this. Usually, acknowledging the increased sensitivity, and using the sensitivity control on the detector effectively, will place the detector in a more stable state. If you are running as hot as the detector can go, wet ground increases that sensitivity even further, usually beyond the detectors engineered stability state.

 

[jim tn]

It doesn't sound right to me. I have had two Sharpshooters and used them in the water and wet grass often with no falsing. Wet grass doesn't bother any of my other coils either. HH jim tn

 

[lloyd0161]

Maybe something is not right with the coil; crud

 

[jim tn]

If so, they will take care of it. HH jim tn

 

[Hightone]

Mine was only a suggestion from past experiences and my understanding of electrical engineering.

 

[lloyd0161]

Mine was only a suggestion from past experiences and my understanding of electrical engineering.

All information is good. The coil worked fine today without the fresh rain soaking. So maybe the coil is too sensitive with wet ground. I will need to wait for our next rain and play around a bit with ground balance and sensitivity. Maybe there is nothing wrong with my coil. Maybe just the conditions. The larger coils are maybe more suited to wet conditions in my soil. This little 5" coil will barely pick up a freshly buried quarter at 6" and with correct ID when the ground is just moist. Just a whisper of a signal but impressive. Of course other small shallow targets give the same response so it is a crap shoot. Maybe I will get a second Sharp as back-up and compare.

 

[amberjack]

super sensitive coils, my mate is always telling the sharpshooter on the etrac gives him a bit of a hard time at night in the dew soaked grass, I had one on the etrac 12 x 13 couldn't get near the wet salt sand with it, I have a sharp on the F19 and yep night wet grass it can get a bit excited and chatty, so super sensitive and there is a price to pay for that F19 and the sharp wet night grass seems to be more sensitive to EMI but not always or everywhere.

so no probably nothing wrong with the coil they are just super sensitive do you see pluses in the dry ?

AJ

 

[Mike Hillis]

Loyld,

The shielding is bad on the coil. Coils should not false in wet grass. If your coil falses in wet grass you have a bad coil. Bad shielding also means more EMI effects, and you don't always hear EMI effects as chatter. Sometimes things just go quiet and you lose performance without even being aware of it.

You need to get your coil replaced.

HH
Mike

 

[Hightone]

Yes. A good possibility if the moisture is causing it from an external source. Metal detectors use a Faraday Cage technology to form a Faraday shield. Shielding is only effective when stray signals can be deposited to earth ground. Metal detectors can only send those stray signals if the coil is close to the ground through it's field. Unsealed properly, and moisture defeats the Faraday shield.

FARADAY SHIELD - A continuous metal foil wrapping around search coil windings used to reduce electrostatic interference caused by contact with wet vegetation on the search coil housing exterior.

I suggested the sensitivity route first (internal solution) since it's easiest and I didn't know all the factors (detector, soil, settings).

 

[mudpuppy]

So I've been running a faulty coil for 5yrs? No wonder I cant nothing but shallow clad or go above 70 sens! Thanks Mike!
I will have to live with it I suppose, warrantees well expired and I have gotten used to it by now...maybe I'll try running full power just to see if it was me or the coil, probably me...I cant take a lot of chatter, I get enough of that on the phone and at home........
Mud

 

[Mike Hillis]

Mud,
If your coil has always falsed in the wet grass, then yes, you could have been running a badly shielded coil all these years. Or maybe just scared the crap out of it with a hacksaw

HH
Mike

 

[mudpuppy]

Ha!
"Accessory For Sale" One slightly modified 11"dd to good home, mature, trim, light and balanced, freshly refurbished ears, documented in field performer...sensitive, likes walks on the beach and moderate conversation..recently divorced, no baggage or games, likes to be employed daily in the dirt by mature F series swinger."...
Mud

 

[lloyd0161]

I'll have to check when I bought the coil. I got it from "Serious Metal Detecting" which is about 45 minutes from where I live. I'll have to stop by there this weekend. Thanks for all the advise.

 

[shadowulf]

Not to discount what Mike H says, but my 5x10 had falsing issues right from the box.
After turning down the sens and adjusting the thresh, it finally settled down.
My area tends to GB out between 88-96, with moderate to high alkylinity. And wet ground usually requires alot of tweeking to get the F70 down to huntable.

That being said, its possible that the shieldind was bad from the factory.
Being you are so close to the retailer, have them check. I
'm considering a tune up by Fisher, even though they have said it sounds normal to them.

 

[amberjack]

if it works fine in dry grass then its fine its just a nel coil doing its thing.

AJ