Poor depth/ID in test bed problem.

[midotron]

So I decided to try making a test bed with some standard clad coins that I found detecting. They all had a little corrosion, which I know can make ID a little harder.

I started with 6 inches or less. A quarter (5"), dime (3"), zinc and copper pennies (3") and a nickel (4").

I was surprised that both my Minelab Quattro (10.5 and 4.5x7 coils) and Fisher F22 did not give a clear and consistent id on the Quarter. The signals were jumpy depending on direction. They do much better in air tests with around 11" and 9" respectively.

They really had trouble with the nickel with it barely registering on the F22. The Zinc penny seemed to only show up as iron on both machines. The dime was a more consistent but not as strong as I would expect at the depth.

I was able to crank sensitivity up fairly high on both machines before EMI became an issue (powerlines), but I am wondering if soil is the issue? I am in Indiana and the soil is dark and damp currently.

Anyone have any idea why depth seems so limited in the test garden?

Cheers,

Mike

 

[medicchief]

Could be the soil, also the coin corrosion wasn't leeched into the surrounding soil either (as might be found originally). Might get you some top soil from your local home store, check it for metal and use it in your test holes. Power Lines certainly don't help a max test. Just guessing....

 

[Big Treble]

Silver coins or clad!

 

[midotron]

All clad except a 1970s penny.

 

[medicchief]

Silver coins or clad!

Appears to be all clad....?

 

[midotron]

Come to think the copper penny was an ok signal.

 

[halfstep]

Dig a normal size hole about 6" deep and loosen up the dirt. Then run a magnet around in the hole thru the loosened dirt and see how much stuff sticks to the magnet. That stuff that sticks to the magnet is what will kill the depth of a detector. You can put the magnet inside of a zip-lock before using it so the magnet stays clean.

 

[tinsmith]

A test garden must sit a long time before its useful. Right now you're better off testing your machines in real infield tests. Here's why.--
"The "halo effect" theory holds that buried metal objects have an ionization "halo" that increases their apparent size to a metal detector searchcoil. This makes the objects detectable at greater depth. In other words, according to this theory, long-buried metal objects have something you cannot duplicate with a recently-created test garden. ". And in other words, the coins need a lot of time for the metals to leach/contaminate The surrounding soil. Hope this helps.

 

[Big Treble]

Try digging up your coin, hot gluing it to a piece of yard stick, ruler or other thin and firm material, and slide it into the side of the hole.

Many minelabs dont shoot well through disturbed ground. This will allow you to detect through the undisturbed dirt.

If of course the coin is dry and dirt is dry it will have an impact. But check it several days after the rain and see what happens.

 

[maxxkatt]

another mistake made is not clearing the area of other metal objects especially iron. put your detector in all metal mode and swing over the area and remove all metalic objects.

 

[midotron]

Thanks for all the ideas. The soil does seem to be pretty trashy in the yard and it is much denser than undisturbed soil I find at the park. I will try another test garden at some point, but now it is snowing. I did get out today and find an 18" round file and the soil was super loose compared to the yard.

 

[IDXMonster]

As others have already alluded to....it sounds like a “dirt” problem. The Quattro should be SPANKING all those signals for sure. Keep us posted on this please!

 

[KOB]

I'm not a dirt hunter but would think this is a good learning experience. Tinker with all sorts of settings. If you can master this on your test garden , it should be a cakewalk out at the park.

 

[midotron]

Today after digging a lot of trash and one shotgun shell in the park I tried the test garden again with the Quattro. All but the zinc were giving better signals even with the coil several inches above. I guess the damp soil has already leached some minerals from the coins and strengthened their singal. I will go try with the F22 now.

 

[midotron]

The F22 is doing a little better with the garden as well, especially with the nickel. It would barely register anything, but now I can hold it 4" above the ground and get a good lock.

 

[Big Treble]

Today after digging a lot of trash and one shotgun shell in the park I tried the test garden again with the Quattro. All but the zinc were giving better signals even with the coil several inches above. I guess the damp soil has already leached some minerals from the coins and strengthened their singal. I will go try with the F22 now.

Just my opinion, but i believe the Silver halo theory is not due to corrosion, but simply a non porous flat disc holding moisture from passing. This moisture is what enhances the signal.

The iron halo was due to rusty iron that corrodes and lifts flakes to enhance the signal. Silver may corrode but i don't believe it happens to the poimt that it actually enhances a signal. Ive certainly never seen the silver halo in the groumg like rusty iron halo.

Just my opinion.