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D.... The next major advancement: VLF-Disc. and Motion-Discrimination.

May 09, 2021 09:22AM avatar
Like our first VLF Ground Balanced detectors engineered by George Payne when at White's Electronics in '74, let's move on to his next noteworthy design achievement in '77 / '78 when he was a design engineer at Bounty Hunter. That next detector design was the Red Baron and the new creation was VLF-Discrimination. What is VLF-Disc? It just means it is operating in the Very-Low Frequency range AND also provided variable Discrimination. In some ways detecting got easier because now, with the VLF Ground Cancelling adjustment, it helped eliminate false signals from the ground, could get a little better depth, and with Discrimination it could reject some of the problem trash.

Naturally we have to expect some negative things as well. In this case, the new VLF-Disc. circuitry design required ample search coil sweep speed in order to get a complete signal, process and take out the ground signal, to pass along the target signal. The 'ample sweep speed' was better described as a very-fast or very-brisk search coil sweep. It almost seemed like a golf club swing, it was so fast ... but it worked. At least it worked reasonably well for searching a beach or a wide-open grassy park or other places that didn't include a lot of dense, closely-positioned unwanted trash, especially Iron-based debris. It was terrible in dense weeds and brush, or highly littered places, and struggled more to handle Iron.

At the introduction, George Payne added another new term to the industry that, fortunately, didn't stick. That was S.P.D. which stood for Synchronous Phase Discrimination. A technical way to describe what was required and going on with the required fast search coil sweep to process signals. I'm glad most manufacturers simply used VLF-Disc. to describe this search technique, and because it required a continuous coil sweep we soon called it 'motion-based Discrimination'.

Also, because it required more filters to handle the processing, it was referred to as a "4-Filter" design even though it wasn't exactly 4 different filters. It was just a loose, so-called description of the fast-sweep motion-based Discriminators. In the next five years most major manufacturers adopted a similar 4-filter VLF-Disc. design and this new detector type did succeed in getting a lot of people active in detecting since they had fewer false-signals (ground mineral related) to deal with and, for some, it added a little 'fun' as well. Over the next decade, by the latter '80s, they had improved the design somewhat in order to slow the required sweep speed from very brisk to more of a moderate-to-fast sweep requirement.

In 1982 Fisher introduced the 1260-X which was a David Johnson circuitry design that was welcomed by many because it was our first slow-motion VLF-Disc. detector. It employed what they termed 'Double Derivative' circuitry. Translated to normal detector-speak, that means 2-Filter, and it stared a new and growing trend in the industry. Most of the so-called 4-Filter type detectors at the time were still a very brisk-sweep design and had a long 'ring-time' from a target response. That is, when the coil is swept over a target at that fast rate, the audio response 'rings-on' for a bit of time while the search coil was well past the located target. That meant you could hunt more open areas and get a good audio 'hit' from a target, but the search coil was often gong over nearby objects when it hadn't recovered from the 'ring-time' to be able to respond to them.

The new 2-Filter detector was a slow-motion operation with a quick-response and fast-recovery. In other words, you could sweep the coil more comfortably, not have a long 'ring-time', hear a located target 'quickly' and be able to hunt in trashier areas and find closer-positioned targets because it recovered 'fast'. Very good for urban Coin & Jewelry Hunters due to being more comfortable to use, and also working better in trashier locations, such as tot-lots, around popular picnic sites, etc. The Fisher design did have a weakness, as I mentioned in an earlier post, and that was its poor ability to deal with bothersome Iron Nails and a lot of other ferrous discards. That meant the serious Relic Hunters liked the 2-Filter concept, but they work more ferrous-littered sites and needed better Iron discrimination.

We got that in July of 1983 from Tesoro Electronics with Jack Gifford's 2-Filter design in the Inca. For ME, that introduction made a significant change it the detectors and coils I used, and completely changed my direction in detecting to 85% Relic Hunting. Ghost Towns and all sorts of long-ago places that had ample local and transient activity. I maintained some detectors in my outfit to complement the Inca, but it immediately replaced most of the other regular-use units, plus I became a Tesoro Dealer.

Since that time, now 38 years later, I have always kept at least two of my all-time favorite Tesoro models in my Detector Outfit, making sure at least one is part of my Daily Travel Team that stays in my vehicle. They were a slow-motion detector with quick-response and fast-recovery, and they have done a very commendable job of handling the very heavily iron-littered sites I have most enjoyed hunting. I have, since the latter '80s, had some other brand detectors that featured visual Target ID and some with audio Tone ID, but they were simply models to 'complement' what the Tesoro's have provided me. At least until the most recent year or so.

With the arrival of both the 4-Filter and 2-Filter types of detector design, most of the other offerings,started to fall in interest.. If you've been following these posts you'll recall I mentioned 1983 brought us two new concepts. One was the Tesoro entry with slow-motion and silent-search performance and better Iron Discrimination. The other was the 'new' original Teknetics and George Payne's designs for the 'CoinComputer' series, especially the upper-end that brought us visual Target ID. Two new and very notable advances in metal detector design, as well as some added features and adjustments with the upper-end Teknetics models.

Other manufacturers soon followed their lead and started making their own detectors with visual Target ID, and most also incorporated audio Tone ID after George did that with the CoinCompter models. Of course the Coin Hunting Hobbyists took to the new TID modes right away, but they also brought a higher MSRP to the market, especially for back then. The Tesoro line, and those who tried to produce a competitive model, occupied the lower-priced end of the market, and that was also something Coin & Jewelry Hunting Hobbyists found favor with. It all depended on where you hunted and how active you were ... or how much you were willing to spend.

When I worked or Compass Electronics in the latter '80s I did keep two of their models on-hand ... but I used them very seldom because they didn't work as well as my Tesoro's in most old sites I hunted. Now, keep in mind that all manufacturers were working to stay alive in this industry, and that was partly because it was hitting a peak from '83 to about '87 or so. Most budget brands were quickly folding up. An amazing number of little guys who just couldn't compete. By '91 we also saw the original Teknetics, who had purchased Bounty Hunter, get bought out and soon Compass Electronics was done.

Before Compass died they did bring out one new model in late '87 and '88 called the Scanner series. It was a John Earle design and it, also, contributed some beneficial circuitry design that we can appreciate more in this past two decades. John's design was called 'Vari-Filter' and to best describe it, in John's words, it was essentially a 3-Filter type concept. (Now remember, we have used the terms 4-Filer, 2-Filter and now 3-Filter to best describe a motion-based 'concept' of filtering out ground signals to pass along good target signals.) Sadly, because Compass Electronics was at the end-of-the-line, that new analog circuitry design came to an end ... for a while ... when production ended ±1990 / '91. What was the 'Vari-Filter' or '3-Filter' benefits? We could search with a little faster sweep speed, like the the 4-Filter models but without the long 'ring-time'. But they also worked like the 2-Filter detectors that allowed us to use a slow-and-methodical sweep speed and enjoy the quick-response and fast-recovery more like the good 2-Filter units.

My favorite models that featured visual TID & Tone ID were products of the '90s. The White's XLT, and later the 6000 Pro XL / XL Pro. Nothing during that era caught my attention until White's hired David Johnson to help with a couple of models, and one of those was the original MXT. Extra features? No. Fancy adjustment features? No. Performance? Yes. The MXT was based on the 3-Filter circuitry design which was a very good move. Into the early 20-teens, like ± 10 years ago, White's did enhance the MXT with Carl Morland's handiwork to make the MXT Pro, and that was my favorite White's general-purpose detector, until January of 2015. It is still one of the better models White's made while they were still in business.

And now we move into the future, better known as: Today and the Modern Era of Digital Circuitry Designs.

I am going to include most middle-line to upper-end models in this group that have come along from 2000 to the present. This will include the following:

• F-75
• F-70
• Gold Bug Pro
• F-19
• F-44

• AT Pro
• AT Gold
• AT Max
• Apex

• Equinox 800
• Equinox 600
• Vanquish 540 / 540 Pro Pack
• Vanquish 440

Nokta / Makro:
• FORS Relic
• Racer
• Racer 2
• Impact
• Kruzer series
• Anfibio series
• Simplex +

• T2 series
• Patriot
• Omega
• G2
• G2+

• V3i
• VX-3
• MXT Pro
• M-6
• MX-5
• MX-7

• Deus

Yes, I might have ,missed one here-or-there, but this is a good-size list, and there are several on that list that I consider passable for hunting in dense Iron Nails or other ferrous-contaminates sites. As I said, 'several' but that is far from a majority number. I use my Nail Board Performance Test as my #1 make-or-break 'test' of any new detector I handle, with any coils available, to see which of these 'modern' digital-circuitry detectors can compare with a very proven performer in tough Relic Hunting conditions ... my good old analog Tesoro Bandido II µMAX. To be very honest, most of them don't come close.

Most readers know about my NBPT, but for those who don't, here is a brief description:

Memorial Day Weekend, 1994
Location: Frisco, Utah, long-deserted and wll hunted ghost town.

On my way to Prescott AZ to give a one week class on Recreational Metal Detecting at the college, I stopped to join my friends as a couple of clubs had their annual get-together there. I was also evaluating a newer detector in a Relic Hunting atmosphere, knowing it probably wouldn't do well from some testing I'd done, plus working some urban renovation work with scattered Iron Nails.

When I worked my way onto the top of the former 'school hill' I was confronted with one of the densest scattering of Iron Nails I'd seen in quite a while. Just what I wanted. I looked down and around to find a relatively clean spot to Ground Balance and, right there in front of me a couple of feet away, was a round disk surrounded by 4 Iron Nails of different sizes and orientations. I lightly brushed the dust to reveal an 188? Indian Head Cent. An ideal 'test' example, and better still, it was a natural, in-the-field encounter comparable to other similar finds I've made through the years.

I tested this layout without disturbing anything. I used the new detector I was evaluating and another I had for comparison. I called three guys up who had their top-end White's 6000 D and Di Pro series models using a couple of different size coils, and none of them could get more than one target response sweeping the 8 marked directions. Based on how I confronted this coin loss with Nails, I marked 4 lines in the dirt to sweep the coil's center across the Nails and Indian Head. There were 4 'lines' that crossed E-W and N-S, plus the 2 diagonal lines. That's 4 sweep routes, and moving from left-to-right and then right-to-left, a possible 8 good-target hits. They only got 1-out-of-8, and the new detector I had from Discovery Electronics got 1-hit and kind of 'ticked' on a second direction, so it was also just 1-out-of-8 possible hits, and that was using a small coil, too.

To show the three White's users why I, and my good friends who thrived in ghost towns, used our simple, non-display, analog Tesoro's w/7" Concentric coils, I called my friend Debbie up who was using her 'original' Silver Sabre. She not only got 8-out-of-8 good hits with its 7" coil, but could walk around it and continually sweep any direction and produce good hits. I had a notebook along to keep track of results and could save the exact coin-and-nails layout by pressing down with a sheet of paper for their imprints. I then recovered those very same Iron Nails and Indian Head Cent and from that I made a duplicate layout ... my Nail Board Performance Test.

Yes, all the targets are on the same plane, but that's how they were when I encountered them, and honestly that's how many of the old coins I have found have been oriented for decades of hunting such places. On, or close to, the same plane. But I am certainly not going to say that's how they are always going to be found. I've found coins that were shallower than Nails or other ferrous debris, and I have found old coins that were deeper than some nearby ferrous debris. A 3-Dimensional orientation is going to present some different sets of challenges and will often be the reason we still have a lot of good targets out there to be found. Because coins were not findable due to partial good-target masking, or they were completely masked.

When I evaluate ANY make or model detector I always try to use the smallest coil they offer for it because, generally, smaller coils can work in and around dense debris and brush much better,. I also do some 'air-testing' and use several test samples to learn what their:

Discriminate adjustment range allows

visual display

audio response

recovery speed ... for a non-ferrous target

where desired non-ferrous targets read-out on the VDI display

where common ferrous-based trash (Bottle Caps, washers, Nails, etc.) read-out is on the VDI display

if possible also learn just what each control does and doesn't do, and their functional range of adjustment

It doesn't matter if you own and use a really old detector, a fairly older model, a newer unit or a detector made in the last five or six years. Each of them will have some strong / good points and each will have some weak / bad points and for best success using them, and to take on different types of hunting conditions, put in the time to learn them well.. Never fall into the rut of thinking that only one detector model will excel at "doing-it-all.' Some are very, very useful, but they still have a weak point.

They might lack a desired search mode for some applications or they might not have an adjustment function you would like, but they can end up providing ample performance to take on some really nasty old-site challenges. But to do so, it will require five things: [1] Good-potential Site selection; [2] a Detector that performs well in ferrous debris; [3] a Search Coil that complements the Detector's ability; [4] the best Control settings; and [5] the Detector Operator's knowledge and ability to use the best Search Techniques to help find and classify likely Iron.

And [5] includes sweeping a site slowly-and-methodically, passing over the same sweep-route 2 or 3 times, ample over-lapping, and a good dose of patience. Often I have seen people venture out to try their hand at Relic Hunting and the experience is enough to change their mind and stick to all the common city related locations.

For those who have followed these presentations of what we had, how they worked, and what brought us to where we are with the modern digital detectors we have today, you can see that while we improved in the way of adjustments, features and performance, we also had to learn the trade-offs in doing so. Also, do some testing as well as on-site hunting and learn what YOUR limitations are. What you expect in the way of performance to take on Iron Nails and other challenging junk.

For example, on my NBPT there are a possible 8 good hits. My general cut-of for 'pass / fail' in general is a detector & coil have to score at least 6-out-of-8 to 'Pass' the test. However, my personal requirement for any detector & coil for dedicated Relic Hunting sites is they must give me at least 7-out-of-8 or the full 8-out-of-8 to be loaded in my vehicle for such an adventure. I do have a few other 'tests' I do, also based on in-the-field encounters, to help me know the strength and weaknesses and behavior of my detector / coil selections for those troubling sites.

What we have to look at now is what ferrous litter is going to do to challenge us and our detector's performance and see if there's any way to be able to tackle that type of unwanted debris.


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

Stinkwater Wells Trading Post
Metal Detector Evaluations and Product Reviews
I'm now located in Clyde, Texas
monte@ahrps.org ... or ... monte@stinkwaterwells.com
Detector Outfit: A selection of my favorite makes and models, with the best coils mounted for the tasks I'll take on.
Apex .. FORS CoRe .. FORS Relic .. Impact .. Inca .. Bandido II µMAX .. Silver Sabre µMAX .. MX-5
Pinpointers: Pulse-Dive Pointer and AT Pro-Pointer .. Headphones: 'Hornet' & 'Wasp' .. MS-3 Z-Lynk
*** All working well today to make memories for tomorrow. ***

Edited 1 time(s). Last edit at 05/14/2021 12:39PM by Monte.
Subject Author Views Posted

Now we are going to take a stroll out of the urban trash.

Monte 293 May 06, 2021 10:46AM

F.. We have now arrived at Iron Nails and Rusty Tin ... What to Use and What to Do?confused smiley

Monte 109 May 14, 2021 02:37AM

E.. Problem Common Trash; so-called 'False Signals'; Useful Search Techniques.

Monte 128 May 11, 2021 06:26AM

D.... The next major advancement: VLF-Disc. and Motion-Discrimination.

Monte 109 May 09, 2021 09:22AM

C.. And then came the Discriminators, and VLF's and VLF/TR-Disc.

Monte 85 May 07, 2021 06:27PM

B.. Just what was a "Metal / Mineral Locator" I spoke about?

Monte 93 May 07, 2021 10:03AM

A.. First, let's follow the path that leads us into various Iron / Ferrous debris.

Monte 162 May 07, 2021 05:08AM

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