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Quite honestly, the NBPT shocks a lot of people!

November 12, 2015 05:20AM avatar
For 21½ years now I have used the Nail Board Performance Test in seminars, at club meetings & outings, helping customers when I was a detector dealer, working with people on get-togethers, such as the 'Welcome-to-Hunt Outings' we hold each year, or just anyone at any time I feel they need a little help (visually) learning the best ways to handle dense iron nail challenges, selecting the best search coil type and search coil size, making the most efficient Discrimination settings, and learning the pros and cons of search coil sweep technique to handle really challenging iron infested sites.

The NBPT is a representation of many similar old site encounters I have had for over 46 years of ghost town and old-site hunting, and it is based on an actual, in-the-field encounter on Memorial Day Weekend in the ghost town of Frisco, Utah in '94. I can guarantee you it was an education for several people there when I encountered it, and continues to 'educate' people all the time.

Comically, for me, is how so many of the top-dollar detectors on the market, promoted for Coin Hunting and Relic Hunting, totally FAIL to pass the NBPT or sometimes only do very marginally, getting only periodic hits on random sweeps with very controlled sweep speeds. I am not telling anyone using such makes and models that they are a bad detector, they just are not fit for some of the really nasty challenges I encounter at so many of the old sites I hunt. Relic Hunting tools they just aren't, but they might satisfy some operators for urban Coin Hunting tasks.

At first I was leery of the test on the Ace with the sniper coil, as it was done with the 150 which DOESN'T have the relics mode and I felt it was unfair.
The Garrett Ace 150 and Ace 250, and many older Bounty Hunters, White's Prizm series and the renamed Coinmaster and Coinmaster Pro models, and a lot of the competition out there, have a delayed response and not a good quick-response and fast-recovery which is part of what is needed to handle heavily iron littered conditions.

I know of many "quick-response" detectors promoted for close-condition coins or for working in "relics" that also can't do well on the NBPT, but even though they might have a quick-response and fast-recovery for accepted targets, such as a row of coins placed within only a few inches of each other, they don't do well when called upon to Discriminate (reject) the Iron Nails. Their circuitry designed might be quick, at times, but not all that efficient when also processing rejected targets to recover from that and then respond to a desired non-ferrous target close by.

So I construct my own and even in the relics mode the Ace only gave an occasional blip.
The results are not surprising to me.

By the way, I have seen people print out copies of the NBPT and sometimes they are not to scale. I have also seen them use little, thin brad nails like you would use to put a piece of wall paneling into a 2X2 or something. It is important to use the exact NBPT measurement and proper-size nails in order to get the right iron rejection and also deal with the influence of the larger-size ferrous nails.

It's time for a plug: smiling smiley ...

I still have about 40 Nail Board Performance Test 'kits' on-hand, and they are $20 each, hand-delivered, or $25 ea. if mailed in the lower 48 US states.

These are all made to the exact size and measurement of the original encounter with the four Iron Nails and 1800's Indian Head cent in the ghost town of Frisco, Utah.

But the shocker came when I decided to test my antique?: Royal Sabre which is by default in the bottlecap mode at it's lowest disc level.
Yes, the Royal Sabre is one of the early Tesoro models, but the Tesoro engineered circuitry (a Big 'Thank You' to what Jack Gifford brought us), especially on the second phase of their detector model progression, has been the standard since the summer of '83 by which I compare any make or any model, and any coil size or type, for handling the NBPT.

The Royal Sabre, like the Inca, Silver Sabre & Silver Sabre Plus, Golden Sabre & Golden Sabre Plus, early Cutlass models and the 'original' Eldorado, Toltec 100 and Toltec 80, all had the more limited lower-end adjustment of Discrimination range. At the minimum setting, it was a bit above iron reject and even was rejecting some Thin to Modest-Sized Foils in the lower non-ferrous conductivity range. That was a problem for avid Coin & Jewelry Hunters because at the minimum Disc. setting it was rejecting thin gold chains, gold studs and tiny, thin gold rings and other similar gold jewelry and low conductors.

But still, they are able to handle the NBPT better than most of the competition on the market today, or even back in the "antique era" as you describe. Bottle caps would still respond, as they do on most motion-based Discriminating detectors, but if encountered with a too brisk sweep speed, they could be 'classified' as probably iron and rejected, but that's part of what I refer to as "Quick-Out" and, like "EPR," is a search technique to help classify probable ferrous targets that I have been instructing since around 1980/81.

When I referenced the "second phase" of the Discriminate circuitry progression, I am referring to models since the 'original' Bandido in 1990 that introduced the ED-120 Discrimination (Jack's descriptive term). The 'ED' means Enhanced or Expanded Discrimination, on the lower-end, so that at the minimum Disc. setting it will 'accept' the upper 120° of the phase. In 'simple' terms, that means that at the 'minimum' setting it is just slightly above iron nail rejection yet allowing the detection (acceptance) of thin gold chains and similar lower-conductive, non-ferrous targets. This design is a killer in very iron littered conditions.

You'll find this second-phase or progression on models like the 'original' Bandido, Silver Sabre II, Bandido II, Toltec II, Pantera, Golden Sabre II, Cutlass II and a few other models. Note that in my personal arsenal I list a Bandido II which is my most grabbed, most used Tesoro. I keep the 6" Concentric coil mounted to it full-time for the trashier sites I hunt (that's the one Tesoro named 5.75).

It and the other models in this group handle iron nail conditions a bit 'quieter' or 'cleaner' than future models, what I refer to as the third-phase, which include the micro-housed models such as the Sidewinder µMAX, Silver Sabre µMAX, Bandido II µMAX and others with the ED-120 Disc., but also with the newer "Low-Noise/High-Gain" circuitry that can give them a little better depth and louder response to mid-depth and deeper targets than most second-phase models.

It passed!!! And with ease!!!
Very expected, and that's some of what surprises many people, especially newcomers who have invested several hundred to over two-thousand dollars for detectors and small accessory coils that ... well, just fail in dense iron like this.

Guess what I used the rest of the day?
Almost forgot-the regular coil was bad on my Royal Sabre and it was done with the 5.75" coil.
Glad to hear you have the very good 6" Concentric coil, but sorry to hear about the 'stock' 8" donut coil. Those early, thin, white-colored 8" coils were my favorites for more open areas as they were lighter and generally worked better than the newer brown 8" coils.

Another thing I don't see mentioned, the nbt gives a great idea of the correct sweep speed for best results.
Make it to one of my seminars, an outing, or just come across me when I grab a Nail Board and I can assure you I always point out the need to be alert to the limitations and/or requirements for search coil selection and search coil sweep speed on this test. I point it out for two reasons. One is to show how limited some models are, requiring a more controlled, very slow sweep speed, and also how forgiving most Tesoro's can be, like the models I use. You can sweep them a little faster than any of the competition I have compared them with and still get 8-out-of-8 hits. thumbs up

Best of success with your 'antique' Royal Sabre and hunting challenging iron nail infested sites.


"Your EYES ... the only 100% accurate form of Discrimination!"

Stinkwater Wells
Trading Post

Metal Detector Evaluations and Product Reviews
'How-To' help for Coin & Jewelry Hunting, Relic Hunting and Useful Techniques.

My Regular-Use Detector Team are various models from: Makro, Nokta, Tesoro and White's
Pinpointers: Using Nokta and Makro and Uniprobe Pointers.
Headphones: Using Killer B's 'Hornet' and White's Pro Star and Detector Pro's Uniprobe ... All w/'tank style' ear cups.
Recovery Tools: Using White's Ground Hawg Shovel and DigMaster digging tools.
Note: Detectors are listed alphabetically by Brand. Models are chosen as desired based on search site conditions.
Other models on-hand for 'Specialty Use.'
Additional search coils. mounted on spare lower-rods, are on-hand in my Accessory Coil Tote.

*** All working well today to make memories for tomorrow. ***

monte@stinkwaterwells.com .. or .. monte@ahrps.org
(503) 481-8147
Subject Author Views Posted

Nail board test shocked me......

slingshot 894 November 08, 2015 03:08PM

Quite honestly, the NBPT shocks a lot of people!

Monte 924 November 12, 2015 05:20AM

My findings with the older vintage Tesoros

Hombre 691 November 08, 2015 09:28PM

Re: My findings with the older vintage Tesoros

supertraq 555 January 06, 2016 06:26PM

Re: My findings with the older vintage Tesoros

slingshot 628 November 09, 2015 06:48AM

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