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

May 07, 2021 05:08AM avatar
I was fortunate to get started back when it was a lot easier to 'classify' Iron or Ferrous trash from Non-Ferrous. Much easier because the detectors we used, and the search coils that worked better, were really the norm. And looking back to those days from the latter '60s and on thru the '70s and into the erly '80s, just like today, we hd two groups of metal detector users. The 'Hobbyists', who wanted to have a unit to turn on, sweep over an area and find whatever gave a good 'Beep,' just to have fun, and the other group. Those were the Avid Detectorists.

Like the Hobbyists, they also wanted to get out detecting and find good stuff, and they did. But they were in a different class of enthusiasts because they didn't only want to find whatever the detector responded to ... they wanted to learn and know WHY. They put in more time to learn the basics of what made a detector work, and why they could or couldn't get good performance on various targets out there. They made it a point to learn each control on their detector(s) so they could properly adjust the Tuner, Ground Balance (once that came along) and also learn how the Discrimination adjustments worked. By that I mean what good points and bad points there were to using too much Discrimination.

The savvy individuals learn that Iron Nails and other ferrous (magnetic) discards had a different effect on the EMF (Electro-Magnetic Field) and even better, the savvy Detectorist also learned, by proper example or diagram, what the EMF looks like on a side-view of a search coil, wheres today, I read all sorts of incorrect information with an errant description of what the working EMF resembles.

We also had a few benefits in our favor, such as:

► Most of us used a conventional TR, and the better models were great at separating or classifying ferrous from non-ferrous. (Note: Early in that period we had BFO's and they also were good at ferrous / non-ferrous audio classification.)

► Then TR-Discriminators which let us learn some were a bit better than others based upon the lower-end limits of accepted targets.

► Next came the VLF / TR-Disc. models which gave us the ability to search without a serious coil-height issue in the GB VLF mode, but we still had good ferrous / non-ferrous target classification.

There were other things that helped provide better audio classification, such as:

Those detectors used analog circuitry.

When we 'progressed' to Metal Locators only and not Metal / Mineral Locators with broad Tuning ability, they still 'classified' targets well, and could hit non-ferrous coins in (as in under) a small cluster of Iron Nails

Although we had Double-D coils from Compass Electronics in '71 and a few other manufacturers followed, we learned that Discriminators worked better with a Coplaner or Concentric coil design.

Ferrous object rejection just was not a major issue until '78 or later after we got our first 'motion-based' Discriminator (VLF-Disc. aka Ground Balance Disc.) which were the so-called 4-Filter or very fast-sweep detectors. That's when we started to encounter more ferrous-object challenges with some man-made junk like the crown-type Bottle Caps as well as round washers and other typical ferrous debris to include ... Tin. Especially the broken-off and scattered Rusty Tin shards from decaying cans and similar discards. Those can be a bigger problem because you might encounter an area with a lot of small shards of Rusty Tin that are in various sizes and shapes rather than a more uniform and consistent-size object.

The fast-sweep motion-based detectors had more challenges confronting Nails and other Iron junk. Then in '82 we started to see some changes, and in '83 both improvements in performance, but also a new design concept that was destined to create additional problems. In 1982 Fisher introduced their 1260-X which was our first 2-Filter (aka 'Double-Derivative) detector. The Fisher circuitry design gave us slow-motion sweep with quick target-response. Much more pleasant to hunt with compared to the 4-Filter type fast-motion models, many of which had a long 'ring-time' before re-set, and a delayed response.

The problem was that it did a terrible job of trying to handle common Iron targets, specifically the most frequently encountered ... Iron Nails. Then in '83, a long thirty-eight years ago, we had both Good and Bad new detector offerings show up. The 'good' was when Tesoro introduced their first popular 2-Filter model in July which was the Inca. Like the Fisher 1260-X, it gave us the comfortable slow-motion sweep as well as the quick-response and fast-recovery for working trashier places. Better still, it did a superior job when it came to Discriminating a lot of common Iron Nails and other ferrous discards. That was what opened the door for me and many others when it came to Relic Hunting the older sites where that type of trash is encountered.

Then there was the 'bad' and that came from the new up-start company, the 'original' Teknetics with their new 'CoinComputer' series. Those were 4-Filter designs that also required a very brisk sweep-speed, and that alone made them bad choices for hunting in dense Iron debris at old-use locations, especially when most of them also had a lot of weeds and stiff brush to deal with. But that wasn't the bigger problem because all the other 4-Filter type models from other makers also depended upon a faster sweep-speed. The bigger problem was that it was the introduction of visual Target ID. And shortly after we got George Payne's visual TID he also incorporated audio Tone ID based on the conductivity range of the visual Target ID.

That was very good news for so many urban Coin Hunters because it helped them identify likely desired Coin targets (remember, we are talking about US Coins as here is where 'Recreational Metal Detecting' really got its start) which meant they spent less time recovering unwanted trash targets. In more of the wide-open public parks and schools or similar areas, it did add a little 'fun' to the hunt, and for many it increased their good-target recoveries.

The bad news for Coin Hunters is that it still wasn't always going to be accurate in a lot of modern trash because coins-and-trash that were too close would result in a 'blended' response of the different conductivity levels which meant the visual and audio Target ID was not going to be a spot-on correct Coin read-out. So there might have been a good target there, but the partial-masking of the undesired and too-close discarded trash meant the Hobbyist ignored the not-so-good signal and kept on searching.

Almost all other detector manufacturers started to incorporate visual Target ID, as well as some sort of audible Tone ID, to their upper-end models and soon their full line of detectors. The bulk of the folks who enjoyed recreational metal detecting were the typical Coin & Jewelry Hunters ... the 'average' Hobbyists, who soon started to put more and more trust if their detectors to produce an accurate Target ID / Tone ID response, and when they didn't, those targets were left behind.

Those were the city folks hunting city sites where most of the 'trash' they dealt with was non-ferrous. But remember, we have taken a stroll out of the city limits and entered the world most Relic Hunters confront on a routine bases, and those are the ones that are very contaminated by Iron Nails, other ferrous debris and Rusty Tin. Just the nature of how this junk effects a detector's EMF is going to be a challenge, especially when we try to rely on any visual or audio report of what they encounter that is out-of-sight.

Translated: Due to the more difficult affects of Iron on the EMF there is going to be more errant results when we relate to the Visual and Audio target response, and the more errant the results are, the more good-target making is going to affect what we decide to recover afield. To compound some of the problems is that in more recent years we have seen other trends in this industry, such as:

Almost all detectors made feature a numeric VDI read-out and Audio Tone TID report.

Most detectors also come standard with a bigger-size search coil.

Most of the coil designs are Double-D rather than Concentric.

Most detectors made today or in recent years, are based on a Digital circuitry concept. Analog, as we knew it, is gone. (Unless we also add a good analog-based detector to our outfit.)


Follow along as we touch more on Iron, Detectors, and 'How to work Iron Infested Sites'.

"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 .. Bandido II µMAX .. Silver Sabre µMAX
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*** All working well today to make memories for tomorrow. ***

Edited 1 time(s). Last edit at 05/07/2021 06:25PM by Monte.
Subject Author Views Posted

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

Monte 287 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 105 May 14, 2021 02:37AM

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

Monte 123 May 11, 2021 06:26AM

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

Monte 102 May 09, 2021 09:22AM

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

Monte 80 May 07, 2021 06:27PM

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

Monte 90 May 07, 2021 10:03AM

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

Monte 160 May 07, 2021 05:08AM

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