High VDIs (+80 or higher)...could it EVER be iron or mineralization?

[Hawkeye P]

Was hunting an old place last night and struck a rather high signal. The VDI jumped back and forth a little on each swing, but never dropped below +80 or so. Most passes, it hit +94 every time. I was sure there was something good down there. Depth showed solid at 6" so I started digging. And digging, and digging, and digging. I ended up digging about 12" down and enlarging the hole to about 6" diameter before I gave up. The whole time, the same signal was still there, supposedly in the dead center of the hole. I did find a rusty nail, but it was off to the side of the hole and definitely was not affecting the readings. My pinpointer could find nothing in the hole (except the nail).

I understand that copper wire, pipes, and etc. can be detected down to 18" or so if they're large enough (personal experience). However, USUALLY the signal from such a large item would get stronger as the dirt was cleared away. I've experienced the same thing from any large non-iron target - the more dirt you clear away, the stronger the signal. I'd imagine the same would hold true for a jar full of coins.

I know there is a lot of iron junk in the ground at this place, so I was wondering...would an iron target, or maybe high mineralization, ever produce a high, repeatable VDI (+80 or higher)? I didn't notice anything close to the high-VDI target when I swept the area in all-metal mode. That signal is still bothering me, because I can't understand why a relatively solid, repeatable, high-VDI signal would be so hard to find. I'm seriously considering heading back out with a shovel and digging till I can't dig no more.

 

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[Tin Nugget]

Normally when that happens to me I end up digging to china just to find a large pipe. Large iron can confuse the detector as well although with a few swings in different directions it will normally give itself up as iron.

 

[Hawkeye P]

Normally when that happens to me I end up digging to china just to find a large pipe. Large iron can confuse the detector as well although with a few swings in different directions it will normally give itself up as iron.

OK, so I haven't gotten the chance to dig up what frustrated me earlier, but I did hit another target that gave me the same problem. So I got out the big spade and dug a BIG hole, and ended up finding a rusty nail, not even a very big one. For some reason, this nail was giving off a jittery +94 reading until it came out of the ground. The VDI was jumpy, but none of the passes showed iron until it came out of the ground. I wonder if the much-discussed "halo effect" can actually affect VDI readings that much? It's really strange.

I've decided that if I'm in an area where there are no pipes or wires, I'm going to dig those questionable signals, even if I have to break out the spade. I can't stand the idea of leaving something good in the ground once I've found it!

 

[niffler]

Hawkeye, I like your attitude! Niffler

 

[ivan salis]

dissolved aluminum foil will do that

as will a highly dissolved nail -- the "rusting" has a odd electrical feild effect --that can cause false readings at times esp at depth.

 

[Sky Pilot]

I must say these are all very EXECELLENT responses posted here!!

I might also add that without exception, every White's with a digital VDI display that I have ever owned has been "eccentric" in this regard!
You may wish to disable the Auto Trac option, as very trashy areas tend to muddle it's performance.
Lowering your sensitivity will reduce responses, but they will be more reliable.

Hope this helps!! Normally I would add that "The best descriminator is a shovel", but you've nailed that one!!

Warmest regards, Richard

 

[Chug And Red]

Although my detector does not have the vdi!! i have found large items that scream silver, that are large items, Bolts, spikes, Etc form WW 2 docks that were torn down here some time they start as copper and change the further i dig!!!!! i have found bolts 3 feet long up to 2 feet deep if i feel like digging at the time when the signal it bouncing around !!!

 

[Capt. Destructo]

Howdy Hawkeye,

This has happened to me also. Again today, so I took notes. **disclaimer- as a new boot to detecting, I could be wrong, constructive criticism is encouraged.** So I had a solid hit at +77 both ways, pinpointed at 1.5". Cut a plug, ran it over the coil, nada. Having trouble with my program and pinpointing so I carved out the upper right, nada again. Signal still strong and reading .05" now, switch to all metal mode and check the surrounding area for an anomaly sucking or boosting my signal. Nothing very significant. Long story short, with my entire coil in the hole at 6" Still getting +77 at .05", tired of pussyfooting around took the tru temper #2 to it. @ 8" there was a 20d rusty nail, once removed my signal dropped to +66, @ 12" there was a stove or pipe fitting 6" in diameter and 1.5 tall dead center of the hole. Why the + VDI? I have read when the XLT reads a signal it measures the phase @ 4 angles, one being +180 degrees, ever dropped a sign in algebra class? I am assuming that at the bottom of the hole with no opposite movement there is no signal to discredit or average against it. Usually in all metal mode when a signal is held will fluctuate and go to the negative side if it is ferrous. Not this time, out of the hole -66 and a big fat grunt, in the hole with the nail DING! +77 Go figgure. Glad I wasn't at the park, someone would have freaked at the size of the hole, in the end, it patched in nicely. Stoked to hear that you went back and dug your signal. If you don't look, you'll never find anything, HH

Capt Destructo

 

[Hawkeye P]

So, the best way i have found to save digging is to try to judge the size by the pinpointing size and dropoff...

After a while, you will be able to tell a coin sized target from a larger one by the pinpointing characteristic.
[/quote]

I'm starting to get the hang of that again. I used to be pretty good at it with my Classic III, but 2 years of being out of the game and starting fresh with a new detector can make anyone feel like a rookie! "Coin size" objects are pretty easy (especially when they're actually coins, lol), but I've found that the M6 is a pretty sensitive machine, and a .22 shell casing sometimes screams like a half dollar. In general, though, you're right - practice helps a lot!

Thanks for all the input, everyone. Crazy stuff!

 

[McKinney_5900]

So, the best way i have found to save digging is to try to judge the size by the pinpointing size and dropoff...

After a while, you will be able to tell a coin sized target from a larger one by the pinpointing characteristic.

I'm starting to get the hang of that again. I used to be pretty good at it with my Classic III, but 2 years of being out of the game and starting fresh with a new detector can make anyone feel like a rookie! "Coin size" objects are pretty easy (especially when they're actually coins, lol), but I've found that the M6 is a pretty sensitive machine, and a .22 shell casing sometimes screams like a half dollar. In general, though, you're right - practice helps a lot!

Thanks for all the input, everyone. Crazy stuff!
[/quote]

What if it was a clay pot of coins though. You have to consider that, or at least I do! Just looking for coin sized objects like it takes the BIG prizes out of the hunt, and that is much of the reason I like to detect. It's not all, but it will always be in my mind to look for a cache.