→ Search coils are not 'perfect.' I own DD's and Concentrics from a 4" Concentric, 4.7X5.2 'OOR' and 5" DD. a 6" and 6½" and 7" Concentric toa 5X9½ DD that I keep mounted, as assigned, for full-time use on the different makes and models. I have larger-size extra coils at-the-ready in my Accessory Coil Tote as well. Why? Because none are 'perfect' for all applications

→ Metal Detectors are not 'perfect.' I own 13 detectors comprised of 9 different models and none are 'perfect' but each one has its own strengths and weaknesses to provide versatility.

→ Desired targets are not always of a 'perfect' alloy mix or location depth or orientation to the search coil or sweep direction.

→ Types of masking trash do not fit a 'perfect' category.

→ Keepers-and-Trash can be oriented close or far apart and at different orientations and depths such that nothing is going to be 'perfect.'


All we can do is be alert for any types of new and different challenges that suggest a new-to-us challenge that we can learn from. Duplicate the new challenge for future testing with any detector we own or might consider, and especially try to check the new challenge on-site once encountered just to compare the results using other detectors we have on-hand before it is disturbed.

Quote
glabelle
Everyone is familiar with Monte’s nail board test. It was configured after a real-life coin-nail configuration that Monte stumbled upon in a ghost town. While it may be a good comparison test for various detector’s ability to separate a coin (in the same plane) in the presence of nails, I don’t think it represents a real life scenerio.

It is a good 'comparison test' for any and all detectors not just a select few or 'various' detectors. If it is a Discriminating detector, it should be tried on this test. There is a possible 8 hits using a left and right sweep over 4 market routes. My Nokta FORS CoRe and FORS relic w/5" DD, a White's Classic w/6½" Concentric, and my Tesoro Bandido II microMAX and Silver Sabre microMAX w/6" Concentric will all get 8-out-of-8 hits.

A Teknetics T2+ w/5" DD and White's MXT All-Pro or MX-7 w/6½" Concentric generally hit 7-out-of-8 times. But a Fisher F44 w/5" DD or 7" Concentric, Teknetics Omega 8000 using he same coils as the F44, won't even get 4-out-of 8 hits. That tells me something about their ability to hit good targets in dense iron nail trash, and this was and is a 'real life' scenario. It is exactly the same nails and orientation as I encountered in real life.

And coins being on the surface isn't all that unusual, either. I have encountered and 'eye balled' Indian Head, Wheat-Back and memorial Cents on-the surface of old towns, encampments, mining sites, stage stops and other old-use places. Also Shield and 'V' Nickels, Seated Liberty Dimes and Quarters from 1853, 1857, 1858, 1877 and others, a 2¢ and 3¢ piece, and sometimes I could see discarded iron trash nearby, but most often encountered unseeable ferrous and non-ferrous junk very close to the exposed old coins.

ANY in-thee-field encounter is a valuable encounter that helps us learn the strong and weak performance of different detectors and coils.

Here's another of those mystery situations of unseen iron junk. I was doing some tests in my living room, knowing there are nails, screws and who knows what under the carpet in the floor. I was simply listening to the audio response from several detectors I own or have/had for sale, so I grabbed a modern clad dime from my pocket and dropped it on the carpet. I the got my Fisher F44, I have two of them, with the 5" DD coil, and the other sports the 7" Concentric coil. I was listening to the Volume adjustment for the Artifact and Custom modes. I could hear the low-tone for iron in the floor under the carpet.

From where I stood I could sweep over the Dime from left-to-right and then right-to-left and clearly heard the audio response from both directions. I tried the other with the 7" Concentric coil and heard a good, clean response from each direction. I compared the audio response then with the ferrous range rejected, from both directions. 10¢ coin visible, and unknown ferrous trash at least 1½" or more below the coin and carpet and padding.

I also tried it with a modified White's Classic ID w/6½" Concentric coil, White's XLT w/6½" Concentric coil, Nokta FORS CoRe w/'OOR' DD and 5X9½ DD, Nokta FORS Relic w/5" DD and 5X9½ DD, Nokta-Makro Anfibio Multi w/5" DD and 7" Concentric, Makro Racer 2 w/5" DD and 7" Concentric, Teknetics T2+ w/5" DD and Omega 8000 w/4" Concentric, 5" DD and 7" Concentric, and a Tesoro Bandido II microMAX and Silver Sabre microMAX w/6" Concentric coil on each of these models and a Silver microMAX w/8" Concentric standard coil, and in each and every test, all of these detectors easily produced a clean, clear audio response from both directions.

However, standing in the exact same position each time with all of the detectors, and sweeping left-to-right across the dime then right-to-left following the same routes, the White's MXT All-Pro and my MX-7, each with own their 6½" Concentric coil, would ONLY give a good response sweeping from left-to-right. Neither of them would hit when swept from the right-to-left direction !!

A real-life test with a coin in plain sight and the different and unknown size and orientation of ferrous junk 1½" to 2" below the good target.

The rejection level used by the Discriminate setting can also make a significant difference, even when the desired target is laying on top of the ground and the problem trash is deeper and out-of-sight. My good friend, David S., and I were hunting my all-time favorite ghost town of "Twin Flats" in 1990 after the new Tesoro Bandido was introduced. Dave was using his Tesoro Toltec 100 and operating at minimum Disc. That model used the earlier designed Disc. level which I often describe as D-90 or D-100. My new Bandido was using the newly introduced ED-120 Disc. circuitry which allowed a lower rejection level providing more acceptance of the very small lower-conductivity range for thin, small gold jewelry.

I was also operating at the minimum Disc. level which is how I always hunt with a Tesoro Disc. model. As I worked in the open spaces in and around the sagebrush, I spotted a round, circular-shaped object on top of the ground. It was a Nickel and I got a good hit, but just a little 'ragged' or 'dirty-sounding.' As if I was just accepting the lower-conductive Nickel, but close to rejecting the Nickel. If I recall it was an 1868, and as I swept the coil around the coin and out away from the coin, I couldn't hear another target close around it, but could tell there was a larger-size target almost directly under the coin by using the Threshold-based All Metal mode.

I gently increased my Disc. level and it only took a slight adjustment to reduce the acceptance range close to duplicating the earlier low-end Disc. setting. I called David over and told him I had a good example of why I felt he ought to get a newer Bandido w/ED-120 Disc. acceptance. His Toltec 100 was at the minimum Disc. level and he could eyeball the old Shield Nickel, but could not get any hit at all with a direct sweep across that old Nickel coin.

I picked up my Shield Nickel, then slowly worked my way down to find the offending iron debris. At about 8" to 9" directly under the spot the Nickel was, I recovered a partially corroded/eaten-up RR spike. Just enough to defeat the performance of one detector with a higher low-end Disc. setting but not enough to keep me from detecting it with my improved lower-end circuitry design. A viewable coin on the surface and a deeper, larger-size iron junk object below it. Still, a valuable test scenario for several detectors to compare performance on.

Once again, a realistic, valuable, and genuine 'test' we can learn from, Nothing is 'perfect.'

Quote
glabelle
In my last Nevada ghost town outing, I gridded an area and pulled all the nails out. I found an iron bar 4” deep. This says something to me. Items in ghost towns can be buried in the soil, and not necessarily right on top of the ground.

True. Coins, Trade Tokens and Trash can be dropped, tossed or intentionally buried anywhere, and in the decades that have passed they might or might not have been displaced or covered, or even exposed due to deposition of sand, dirt, grass, weeds, leaves, etc. or from being stepped on, erosion, or the effects of wind and rain.

The good magnets you are using should help clean up a lot of the clingable iron debris and help a lot with target detection during your search.

Quote
glabelle
Thinking about it some more, I concluded that many coins may have been dropped when the town was in full swing. They could have sunk some, during rains and being stepped on, or covered up by who knows what. Then when the town was raised and looted, all the nails ended up over the top of previous items.

They could have been exposed, or covered due to erosion or displacement, but they don't 'sink.' And, as you noted, that was prior to a town's demise and structures either being torn down or, worse yet, burning down and leaving a lot of nails and other messy iron debris on-site.

Quote
glabelle
So, I ran a little test to see how well a detector could separate a coin in Monte’s configuration, and what I think is a more realistic scenerio.

They are ALL 'realistic', however the more common encounter is with both iron nails and lost coins, etc. being out-of-sight at unknown depths or orientations.

Quote
glabelle
First, Monte’s standard test.
Detectors used: White’s Classic III (8” concentric) and Equinox 800 (6” DD). Target: 1857 Indian Head.
Classic III can detect a coin at position #1, 6 ways. The “2” line is not consistent either swing direction.
Equinox (Park 2) nailed it (so to speak) in all 8 directions – and noticeably at greater depth. No real surprise.

But a Classic III, ID or IDX Pro would generally hit 8-out-of-8 using a 4½" or 6½" Concentric coil. The 8" diameter is more of a struggle. Coil size, alone, can alter a detector's performance.

Quote
glabelle
Then, I placed the coin only 1” below the nail board. Voila. Nada, nothing, from either detector in any direction. Lesson learned about real world masking.

Yes, there are a number of conditions we can encounter. I do a lot of testing to find the strengths and weaknesses of the detectors I like to use to know which are best for different applications.

Quote
glabelle
This article was written by Tom Dankowski many years ago. One quote:
"What is hard to believe (and priceless education) is the fact that NONE of these targets were detectable in just 2 inches of dirt depth…… on the bed sheet……….. UNTIL the mask was removed. EACH one of these targets were/are detectable to ranges of 11 inches – 12 inches in the air….. or in clean dirt."

Might have been true with THAT test using THOSE detectors and THOSE settings and THOSE search coils at THAT time. A different make and model detector, and different search coils, and different Discrimination settings, and using different search coil sweep speeds can make a difference to some degree.

And you might have one coin at 2" under the bed sheet, but the particular trash targets on top might have the orientation changed, or the distance off-center from the coin changed, or even the particular size, shape and alloy mix of the coin can make a remarkable difference. His 'test' isn't always a duplication of what we might encounter afield, either. It is only one example of what can potentially happen.

Quote
glabelle
So I decided to construct a magnet “broom” that would pull all the trash up to unmask the goodies. I built 2 “sweepers” with VERY powerful neodymium magnets. These are not your ordinary magnets and are not cheap ($50 each) – but hey, if you are willing to spend $200 on a coil, why not something that will allow them to work?

I’ll put these to the test in Nevada. See pics of "sweeps'.

And with all this discussion you bring out, the better examples of how to defeat some of the iron debris challenges we face are:

1st.. Recognize that ferrous debris can usually be a terrible, offensive challenge to successfully search a site.

2nd.. We need to use the best detector and coil possible ... however ...

3rd.. Do whatever it takes to remove a lot of the masking trash prior to using a metal detector. This will certainly work in our favor, and your get-serious magnet rakes should definitely help in that respect.

Looking forward to the amount of ferrous scrap you'll be able to clean out of some areas on the 11th WTHO to Nevada ghost towns on June 13th thru 16th. Those tools might not be cheap, but they can be very well worth the investment when put to work.

Monte

"Your EYES ... the only 100% accurate form of Discrimination!"
Stinkwater Wells Trading Post
Metal Detector Evaluations and Product Reviews monte@ahrps.org ... or ... monte@stinkwaterwells.com 503-481-8147Regular-Use Outfit: Nokta / Makro: FORS CoRe, FORS Relic, Racer 2 and Simplex+Tesoro: Bandido II µMAX and Silver Sabre µMAX .. XP: ORXSpecialty-Use Outfit: Fisher: F-44 .. White's: XLT and modified IDX ProKiller B's 'Hornet' -- Detector Pro Grey Ghost XPNote: Detectors are listed alphabetically by Brand. Models are chosen based on search site conditions.*** All working well today to make memories for tomorrow. ***