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Monte's Nail Board Test Questions


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Prompted by one of Abenson's recent posts (including link and discussions on Monte's site) I decided to BYO and do some testing myself.  Here's my build:

100_0421.thumb.JPG.6f521cfa19a3cecd941f9cf8b151b995.JPG

Template on the left.  That came from Monte's .pdf.  I'm pretty sure my printer got the scale correct.  I will point out that 20d nails (the big ones) have a length tolerance of +/- 3/32" (+/- 2.4 mm) and Monte's appear to be on the low tolerance end with mine on the high end, but hopefully that doesn't matter much if at all.  My board is 1/2" plywood and the two coin recesses have USA small cent diameter.  Nails are epoxied in place, slightly (~1 mm) recessed.

I've read Monte's document 3 times and still have some questions/uncertainties which have led to this post.  My first question probably has an obvious answer given that (from his document) he created this test based upon an actual ghost town site discovery with these locations of nails and an Indian Head Penny at coin location #1 (center).  My question is:  how close to the board are you supposed to swing the coil?

I took the board outside for my first test -- no coins at all to get a baseline.  Minelab Equinox 800, 11" coil, EMI canceled, ground balanced, Park 1 custom 5 tones, Recovery Speed = 5, Iron Bias F2 = 0, sensitivity/gain = 17, no discrimination (i.e. no channels notched out).  Swinging as close to the board as I could get I heard non-ferrous signals from one or two directions.  I could 'cheat' and look at digital TID's, but from what I've read this is supposed to be an audio only test.  So how do I proceed and determine (once I put a coin on the board) if I'm hearing the coin or the falsing nail signals?  I don't think simply creating a threshold to eliminate the nail falsing is a reasonable solution in this case (as you would do for an analog detector such as an early Tesoro, from what I understand).  I could be wrong on that, of course.  Again, I didn't look at the digital TID, but my lowest channel (including ferrous) ends at +5 and it was above that.

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17 minutes ago, GB_Amateur said:

My question is:  how close to the board are you supposed to swing the coil?

As close as is required to get the best result from each detector. There is no requirement they be swung at the same height or speed.

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5 minutes ago, phrunt said:

I've never understood the reason for these tests

The nail board test tries to create a standard at least. It provides a data point for consideration. People put too much faith in it, however, and I would never consider any detector to be good or bad based solely on this test. Which is easily gamed in videos, by the way. People like them though, and it’s all in good fun. Certainly helps keep forum threads going! :smile:

 

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To further Steve's point, 2D separation is also only one aspect that provides a benchmark on separation performance.  3D testing is probably more representative of real life (when do you see all the targets/trash lined up on the exact same plane in the ground) but there really are no standardized test setups like Monte's board to provide standard benchmark results for comparison.  Because of the myriad of performance, equipment (e.g., the coil used), target, and environmental variables in play, a given detector may perform well on a 2D test and do terrible on a 3D test or vice versa.  EL NINO77 pointed that fact out in this post.

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1 hour ago, phrunt said:

I consider a junky area a bit of junk every 2 or so steps while swinging.

Simon, you are so sheltered!  😁  Two trash hits on every step (compared to your one trash hit for every two steps) would be sparse distribution in some parks where I hunt (especially the one I've been going to pretty much exclusively during 2020) and that is tame compared to a lot of sites.  You need to come detect around old miners' camps, for example.  Some people even hunt old trash dumps -- now that takes some serious patience!

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The test is actually almost the opposite of a depth test. Detectors with very fast recovery speeds in a 2D test probably are not set up to punch very deep. The emphasis is separation of adjacent surface targets, and ground may or may not be involved at all (board on ground, or on box above ground). Ground effects can affect the results. And people love putting in their own nails or coins. I prefer some rusted nails as I never detect where people spill clean, new nails.

My board in simply Monte's test printed out and on cardboard, with tie strap loops holding the nails.

I don't use this much, as I prefer head to head field testing*. But it comes in handy at times for a quick coil comparison, or to see if I can duplicate results seen online if they seem suspicious.

monte-nail-board-test-herschbach.jpg

 

*I take two (or more) detectors into the field. I use detector A to locate a target in the ground and note the responses. I then check the target with detector B and note any differences in target response. I recover the target after attempting to predict what it is.

I then find a target with detector B and check it with detector A, once again noting signal differences. I repeat this over and over, alternating detectors each time, one as the "finder", and one as the "checker". I am looking especially for weak targets that one detector can get and the other will not. Something that defines a difference in the machines. If you do this a lot, you will find most modern detectors will do just as well on the vast majority of targets. It's actually difficult often to get a clean decision between two machines based purely on how they are doing on "found targets". Often it boils down to one detector simply sounding and feeling better than the other, and that is so subjective two operators might come to opposite conclusions in that regard.

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One of the basic rules when testing in the original "Monte performance Nailboard Test" .... is to set the detector discrimination correctly so that a false signal from the nails is eliminated before the main test ... as best as possible ...

With Equinox, you can use the Ironbias setting to such an extent ... that you are satisfied with the quality results of the nail discrimination .... used in this Nailboard test, or use the detector sensitivity adjustment to better correct this effect ... from all sweeping directions. coil above this test ...

The prescribed height of the spool sweeping above the Nailboard test is 2-3 inches ..... for correct results in this test ..

A test coin is also standardized and it is an Indian head cent ....

One advice ..
Since  detector Equinox uses coil 11" as a standard coil ... the increase in recovery speed will be very effective on the final test result.

Another important setting for Equinox is the Iron Bias setting ...
you will see for yourself to what extent the test results can change when you use too high Iron Bias settings ...

Finally, after the tests of Equinox on various multifrequency programs, I try to test how I work individual 1F frequencies 5,10,15,20a and 40 khz .. in this separation test .... I think you will be surprised ... how to be able to change the separation properties of equinox according to the used 1F frequency.

 

 Mr. Monte's test .. is a test that is sufficiently standardized ... and this means that the results of these tests can be reliably shared accurately and sufficiently compared between users around the world of detectors ..

IMG_20200514_203756.jpg

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45 minutes ago, EL NINO77 said:

A test coin is also standardized and it is an Indian head cent ....

Good to know.  I've actually found several, but for you detectorists outside the USA it's extra effort, not that they cost much (prior to shipping, anyway).  There seems to be enough difference in the compositions (based upon TID/VDI measurements) that substitituting a late 95% copper USA small cent isn't quite the same.  Standards are standards!

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2 hours ago, EL NINO77 said:

Mr. Monte's test .. is a test that is sufficiently standardized ... and this means that the results of these tests can be reliably shared accurately and sufficiently compared between users around the world of detectors ..

IMG_20200514_203756.jpg

Like I found out it's only standardized if you have an actual board Monte builds which you can purchase from him. The board I printed is way harder than his board. When you watch my tests on my board it's a head to head comparison.  You can't duplicate the same results I get. That's why there was so much controversy over my Apex test. Because on Montes board the Apex does much better than on my board, same with the Vanquish.

I don't think anybody is really out to skew the results in favor of one detector over the other, at least I'm not. The thing you have to remember is that many variables come into play that you or another person might not be able to duplicate. That's why I always put up one detector against another on the nail board test. Then it shows how each one does against the other. At that point it's a fair comparison it's not like I put one detector on a harder test than the other just so I can say one is better than the other.

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