Coin garden question

[kraykepler]

Hi,
I just planted a coin/bullet garden. The coins/bullets were at 6, 8, and 10 inches; when I went to see how my various machines and coils would react, The problem is that I got a lot of iron and hot rock signals. The sounds were coming through, but not the ID's or VDI's. Is this because the targets are too "fresh" and haven't developed the halo effect? If so, about how long should I expect to wait before I get realistic readings? The one good thing is that it's given me a new perspective on listening for the different sounds.

 

[maria8forever]

Hi,
I just planted a coin/bullet garden. The coins/bullets were at 6, 8, and 10 inches; when I went to see how my various machines and coils would react, The problem is that I got a lot of iron and hot rock signals. The sounds were coming through, but not the ID's or VDI's. Is this because the targets are too "fresh" and haven't developed the halo effect? If so, about how long should I expect to wait before I get realistic readings? The one good thing is that it's given me a new perspective on listening for the different sounds.

It just sounds like to me Kraykepler that maybe you are running the sensitivity to high.Or you could be near a power line or other electrical interference.You can get electrical interference from being to close to a house,which you can help also by cutting down on your sensitivity.A lot of detectors will pop and crackle when trash is under the coil,this is normal.Well someone here will help you figure it out,keep trying you will figure it out!.good luck .Chuck.

 

[John-Edmonton]

It took about 6-7 years before I started getting a better hit on them. Some people give them a saline (salt water) soaking to speed up the process.

Here's mine;

 

[Monte]

When it comes to metal detecting and metal detector performance, I am a rather practical sort of guy. My #1 goal whenever I turn on a metal detector, any time or any place, is to learn something new or refresh something I've learned in the past. And "the past" dates back to the spring of '65 when I built my first "metal/mineral locator.' Detectors and coils have progressed a lot through the years, to be sure, but the variables that can exist haven't changed. That is, trash is still a problem; target masking is always going to happen; not all coins and positioned 'flat-to-the-coil'; there are limits on detection depth; from reading various forums and "stories" I find that hobbyists continue to either mis-judge target depth, or they rely on the numeric read-out (often wrong), or they stretch the facts a bit. Other things are constant, such as mineralization can be a factor, and the variables still apply as well, such as the condition of the mineralized ground such as porous or hard-packed, low-mineral to challenging minerals, very dry or damp or wet or well soaked to target depth, etc., etc.

There are many statements used on these forums that are actually over-hyped, or mis-described. One errant topic is regarding "halo effect" and another is the misstated description regarding the "shape" of a generated (transmitted) electromagnetic field ('V' or "cone) of a concentric coil. Naturally, I can only demonstrate some of my beliefs/findings in a personal display, but like everyone else I will just add my thoughts even though they might differ from others. Take them for what they are worth ... free.

I just planted a coin/bullet garden.

I've come to prefer a natural "test garden" ... the real world. There are just so many variables that it is not easy to design a testing area that will represent the many conditions we are likely to encounter afield. All that a test garden might attempt to duplicate is one of two things:

A.. Under ideal conditions, what performance we can expect fro our detector/coil combination based upon settings used. In other words, how deep might we expect to find a particular coin, IF the coin is laying 'flat' to the coil, and IF it is in uniform ground that lacks any masking trash, and IF we use a proper sweep speed and approach, and still get a desirable audio response AND a "proper" visual Target ID and/or numeric read-out.

B.. What is the deepest we might find a particular target and get a reasonable "Dig Me" audio hit w/o supporting lock-on visual information.

Generally, I only consider planting a test scenario once I have spent enough time with a particular detector or two and have learned what I might expect them to do afield. Then I can try to duplicate that performance so that I can use it to compare what I know works against other makes and models I want to evaluate. And then it's only done when I don't have the time to do side-by-side comparisons in the field on naturally located targets.

The coins/bullets were at 6, 8, and 10 inches; when I went to see how my various machines and coils would react,

Unless you are searching in unbelievably non-to-very low mineralized conditions, those depths are too deep to get a 'proper' TID/numeric read-out with most detectors, and even too deep to anticipate a good audio response.

Additionally, you probably buried the coins laying 'flat' to the surface whereas I have no clue how you might position an assortment of bullets. Bullets can be found laying "on their side," or "nose up', or "base up," or on an angled position. Unless you have planted an undamaged round ball, you're going to have the potential for differing results based upon the bullet's position. We find them at differing angles, even though many/most might be more-or-less on their side. You would need an assortment of bullet types, sizes, and shapes with samples of each specimen buried at a variety of positions to duplicate potential field results.

Likewise, you would need a few specimens of the same coin buried in different positions and various depths to get a feel for what the detector might reasonably do when taken afield.

Most modern detectors, in most "average" ground conditions, can reasonably be expected to respond to coin targets down to about 4" and give a rather consistent audio and visual ID response. Honest-to-gosh DEEPER coins will be in the over 4" range, and DEEP for most detectors, in reality, will be the 6", 7" and 8" deep coin targets. Can they be found deeper? Certainly, if everything is ideal and in your favor, but that's seldom the case.

The problem is that I got a lot of iron and hot rock signals.

What sort of responses did you get from this area before you disturbed the ground to plant the test plot? Did you search it in a true 'zero' discriminate setting as well as a true All Metal mode and clean out all trash? Did you adjust for a proper ground balance before cleaning the area?

You didn't mention what make or model detector you were using or which coil was affixed on the working end. You can get 'Iron' or 'Hot Rock' signals from iron and hot rocks, naturally, but also from some disturbed ground itself because the small spot of ground that was disturbed will react different from the undisturbed, compacted ground around it when you sweep the coil. Also, when targets are planted too deep, you might get that low-end Iron or high-end Hot Rock reading due to a combination of disturbed ground and a target that's just too deep to provide sufficient signal to properly process. Thus, an improper visual display.

The sounds were coming through, but not the ID's or VDI's.

Likely due to reasons I stated. Too deep and or caused by spotty ground disturbance.

Is this because the targets are too "fresh" and haven't developed the halo effect?

Forget about a 'halo' effect. It's because the test samples are planted too deep in disturbed ground. If they were at a reasonably 'average' TID depth of perhaps 4"-5" they might still not register correctly due to the blend of undisturbed and disturbed ground covered on the sweep of the coil. A lot depends upon the ground mineralization, ground balance setting, and sweep speed.

As for the halo effect, the most likely type of target to have any significant "halo effect' might be iron. Iron will easily rust away and deteriorate with sufficient breakdown and leaching into adjacent ground such that there will be an ample amount to have a minimal effect on the detector's generated electromagnetic field. Gold is a very noble metal and it doesn't break down. A silver coin will leach off a very minimal amount of surface metal and what little it might develop about the coin will reach its maximum after about a year in the ground once it comes to rest in compacted ground so it doesn't move ... and if there is sufficient chemical makeup to cause some minute amount of surface decay. Copper might breakdown a tiny bit more, but it the long run, there still will not be any detectable "halo" because it would also take moisture, not just surface, but basically saturated H[sub]2[/sub]O to the coin's depth such that the water would assist any possible electrical conductivity of minute (very minute) particles that might have leached from the subject target.

Then, more than any "halo" effect you are gaining the benefit (usually) of having the wetted ground matrix to help enhance the target signal. Keep in mind, however, that hunting during the "wet season' can be both advantageous as well as disadvantageous because while it might help in the detection of desired targets, it will do more to enhance the response (and masking effects) of decaying iron junk, and it can also alter the ground mineralization factor the detector deals with.

If so, about how long should I expect to wait before I get realistic readings?

A LONG time, unless you make sure the area is clean and reposition the targets to depths from about 4"-6". Or you can leave them then and wait until you have had sufficient time pass for moisture to saturate the area and the disturbed ground to compact and stabilize to a condition similar to all the surrounding matrix. You might try watering it on a regular basis, well, and walk over it a good deal to help compact it.

In the meantime, just go hunting and find out how your detector/coil will respond to targets you FIND and then determine when the PLANTED targets start to respond about the same. Then you'll know how long they will take to give a similar response.

The one good thing is that it's given me a new perspective on listening for the different sounds.

Yep, the #1 thing you want to listen for is a good or reasonable 'iffy' audio response, then investigate. Don't always rely on a nice-and-proper visual TID info because you're not always going to get it.

Happy Hunting, and I'm still curious what detector model and coil you're using.

Monte

 

[kraykepler]

Hi Monte,
Great information, as always, on the test garden. Thanks very much.
I'm testing an M6 and MXT with the 5.3, 10DD and 6 inch coils. This is in an area that is clean but which has produced musket balls (no coins), and when found, they gave VDI's in the 40's and 50's. I am 100 yards from any houses or EMI.
I GB'ed both machines and ran them in the same modes: very little disc., and full gain.
I buried Minnie balls on their side, and the very dry soil could be considered mineralized (N. Va.). I've been digging for 10 years and have about 50 and 25 hours on the MXT and M6, so I feel I know the machines somewhat well, at least well enough to be confused with the readings I got.
Your suggestion that I re-plant at shallower depths and angles is a good one. Perhaps I'm expecting too much from reading the posts from people digging dimes at 10 inches and wondering why I'm not.
You should consider writing a "MDing for Dummies" book. I'd love a copy.

 

[marcomo]

I find that hobbyists continue to either mis-judge target depth, or they rely on the numeric read-out (often wrong), or they stretch the facts a bit.
Monte

So Monte, does this mean you're skeptical about the Ohio guy who found a penny at 16" with his Explorer?

Or the other fellow who said his Cen-Tech pinpointer would pinpoint a coin at 5-6 inches?

Yet another said his F-5 wasn't a very deep machine at all, it was only finding coins down to 10 inches.

All kidding aside, another excellent and informative post from our Guru of the Northwest.

I'm certainly not saying depth is insignificant but, speaking for myself, I know how easy it is for someone new to the hobby to think "what am I doing wrong" or "I need a deeper detector" when reading about those really deep finds.

The truth is I could count the coins I've found at 7" or more on my hands and toes, and have several of my toes left over. My deepest coin at 9" somehow feels better now. Thank you, Monte!

But then again, I'm sure guys were exaggerating "inches" long before the metal detector was invented...