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Fringe Area Detection


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I got my first metal detector in 1986.  It was a White's Coin Master 6000 DI Pro.  I bought it because I live near the beach and a friend of mine had a friend who was selling them.  I didn't know much about detectors and I used it on the beach in the dry sand only for about 3 years before life happened and I put it away.  I didn't get another detector until 2010 and it was a ML 5000.  Now that I had it I had to start learning about the desert and more about metal detectors.

One of the first things that I 'noticed' about a detector is that you don't have to be directly over a target to hear it.  You get a sense for a target by coming close.  You get a bigger sense for an aluminum can than you do a quarter for instance.  I've searched and searched over the years for a way to describe this near to target sense which is much greater in the 5000 (PI) and the 7000  (ZVT) than with the Coin Master (VLF).

Today I was reading an email from Kellyco who is the company that services most Minelabs in the United States.  They also sell most other detectors and give advice to their customers.  The email that I received led me to a reprint of an article: How Metal Detectors Work Reprinted with permission from Modern Metal Detectors.  The full article is here: https://www.kellycodetectors.com/catalog/how-metal-detectors-work#more

In that article it uses the term Fringe Area Detection and that gave definition to what I had been trying to describe for years.  I had tried to say a coil is like a Nerf ball with many targets off the search area and you are drawn to a target like a moth to a flame.  As it turns out this is just 'fringe area detection' which lets us push our detectors to much greater finds.  I think you will see how many times we have discussed this part of metal detecting without using this term.  The fringe area on my 7000 is larger than the illustration shown.  Here is what the article says about fringe area detection:

 

 

Fringe Area Detection

Fringe area detection is a phenomenon of detection, the understanding of which will result in your being able to discover metal targets to the maximum depth capability of any instrument. The detection pattern for a coin may extend, say, one foot below the search coil. The detection pattern for a small jar of coins may extend, perhaps, two feet below the search coil as illustrated in the drawing on the facing page. Within the area of the detection pattern, an unmistakable detector signal is produced.

Electromagnetic Field Strengh

This illustration shows the location and approximate proportional size of the fringe detection area in which faint target signals from around the outer edges of a normal detection pattern can be heard.

What about outside the detection pattern? Does detection take place? Yes, but the signals are too weak to be discerned by the operator except in the fringe area around the outer edges of the detection pattern as shown in the drawing above. A good set of headphones is a must, if you desire to hear fringe area signals. The next more important thing, is training in the art of discerning the faint whispers of sound that occur in the fringe area. Skill in fringe area detection can be developed with practice, training, concentration and faith in your ability. Develop fringe area detection ability to a fine art and you are on your way to some great discoveries that many detector operators will miss. The ability to hear fringe area signals results in greatly improved metal detection efficiency and success.

 

Mitchel

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Paying attention to that area-of-influence (fringe area) will increase your take...

My Garrett deepseeker had a coil that made identifying ferrous or non ferrous fairly sure proof. The fringe area for ferrous was well beyond the edge of the coil and usually the non-ferrous was at the edge and strongest in the center...

fred

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A few years ago I got a 63 grammer with fringe area detection. I`ve never thought of it as fringe area detection, I`ve always thought of it as the coils throw out heaps of energy sideways. There was nothing particularly clever about me finding this piece, I definitely heard it way before the coil went over it. cheers Dave

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On 7/22/2017 at 9:07 AM, mn90403 said:

A good set of headphones is a must, if you desire to hear fringe area signals. The next more important thing, is training in the art of discerning the faint whispers of sound that occur in the fringe area. Skill in fringe area detection can be developed with practice, training, concentration and faith in your ability.

Yikes! I have been saying this identical thing, in my Klunker kind of way, for a long time.  Now that it is published by a reputable source maybe detector/prospectors will pay a little better attention to what they are listening to. Listening is always more important than hearing.

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The quote is from Modern Metal Detectors by Charles Garrett, first printing 1985. So Charlie heard about your advice and put his seal of approval on it quite some time ago Norm.

Garrett's original books are quite good, before the marketers took over and replaced all the real detecting photos (often black and white and often picturing competing brands in a friendly manner) with posed color photos with models. Prettier maybe but the nitty gritty realness of Charlie's first efforts was lost. I still have a like new first printing copy of Modern Metal Detectors on my bookshelf because of its clear concise text and excellent illustrations. The old version of the book is white - the new "marketers version" is green.

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Ah no, just got rid of all my headphones and enjoying the wireless speaker thingo, no more soggy tropical ears and you lot are advocating a back to the future thingo. Speak up what did you say............ a MN brand of headphones

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I think the reference to headphones 'back in the day' was based upon the audio provided with the metal detector which was just a built in speaker.  There were not many external speakers sold with the units.

JP's booster and some others like Doc's allowed many to go 'headphone-less' and still hear the subtle signals because the speakers were closer to the ears.  The same can be said for the new wireless speakers like the WM10 and WM12 which can be mounted on a harness or a cap very close to the ears.

I like the description of fringe area detection because it describes the phenomenon (repeatable) which is the reaction of a partial response of a coil/detector combo.

The most confusing part will be to make a distinction between this and 'peripheral area detection' which is an instruction we are given to find gold that is still left.  Sometimes we would call that searching the fringe areas! (Look around the fringes of the patch for more gold.)

Mitchel

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5 hours ago, Norvic said:

Ah no, just got rid of all my headphones and enjoying the wireless speaker thingo, no more soggy tropical ears and you lot are advocating a back to the future thingo. Speak up what did you say............ a MN brand of headphones

Ah yes, new pads for my headphones. No more snow on my earlobes and freezing wind blowing in my right ear and out my left.

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