concentric coils

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Bibelot
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concentric coils

Post by Bibelot » Tue Apr 30, 2019 4:16 am

Is anyone using the concentric coils ? I picked up a 9" concentric coil, really like it, don't think I'll ever leave home without it. I have been using it set up on the MMK along with taking the Anfibio with the stock 11 double D coil but need to source the money for a 7" concentric for my racer/racer 2 machines. The 9" concentric has good depth, I'm finding targets that were missed with the double D coil.


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Re: concentric coils

Post by fred » Tue Apr 30, 2019 4:43 am

Bibelot wrote:
Tue Apr 30, 2019 4:16 am
Is anyone using the concentric coils ? I picked up a 9" concentric coil, really like it, don't think I'll ever leave home without it. I have been using it set up on the MMK along with taking the Anfibio with the stock 11 double D coil but need to source the money for a 7" concentric for my racer/racer 2 machines. The 9" concentric has good depth, I'm finding targets that were missed with the double D coil.

Whatever the detector each size and type of coil generally has it's own strong points. Concentric coils tend to go deeper than double D ones, however, the maximum depth is over a narrower area in the middle of the coil. To cover the ground properly you need to overlap the swings far more than with the double D. ::g
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Re: concentric coils

Post by Bors » Tue Apr 30, 2019 7:43 am

I would agree with all Fred said on this subject here`s a bit of info second paragraph down I pulled in to indicate the differences to the newer detectorists reading this..
Also I find ,Concentric Coils don`t seem to handle bad Ground mineralisation as good as DD coils do. The concentric coils are good working in amongst the Iron for their tight downward pointing conical shaped detection pattern.
I do like the 10" DD for the solid DD design, better for working in stubble or other locations where an open coil might hang up on corn stalks getting snagged persistently .
The concentric I like if just for being better behaved. The DD is the better coil for bad ground. But also Concentrics do well on milder ground.

The pictures show the detection fields of the two coils, the concentric and DD coils. The lines show the search field penetration of the two different metal detector coils. From the picture you can see why as was said why the DD coil can separate better than the concentric or mono loop coil. One of the bad things about the DD coils is sometimes bottle caps are harder to tell from good targets. With a little practice and keen ear to the audio one can tell the tell tale signs of a cap. Usually falsing at the tip or heel of the coil is a great indicator. I personally LOVE the DD coil. I feel the advantages of depth and separation greatly outweigh the negatives of digging a few screw caps. I also will prefer a smaller coil over a bigger coil in most situations. Yes bigger coils get more depth but the main trouble I see is not the depth it is the target mashing of trashy areas. I have found more good targets with the stock coil or smaller coils.

Everyone wants to get that extra advantage with their metal detector. One of the ways to get extra out of your machine is to get a situation specific detector coil. When you have the right metal detector coil for the right job your good detecting finds can go drastically up. You wouldn't want to use racing slicks on a mud course at the track. Same applies to metal detectors. Now what kinda coil is right for me? Smaller coils are usually more sensitive and get better separation. Bigger coils get better depth but can mask close targets. Each metal detecting situation is different and certain coils have advantages different places. Most of the time the stock coil will give you the best results for that specific metal detector. Metal Detector manufacturers spend many hours trying to get the best all around coil for that detector. Right now the two main coils are the (DD) and the concentric or also named (mono loop) coil. The concentric coil puts out a cone-shaped field (shaped like an icecream cone), the DD field is more like the "knife blade" of the concentric (shaped like an I).As said before The DD coil separates much better ,and gets a more even depth, especially in mineralized ground.

DD and Concentric coils.
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Last edited by Bors on Tue Apr 30, 2019 3:47 pm, edited 2 times in total.

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Re: concentric coils

Post by Saffron » Tue Apr 30, 2019 2:25 pm

Bors wrote:
Tue Apr 30, 2019 7:43 am

<big cut >
Everyone wants to get that extra advantage with their metal detector. One of the ways to get extra out of your machine is to get a situation specific detector coil. When you have the right metal detector coil for the right job your good detecting finds can go drastically up. You wouldn't want to use racing slicks on a mud course at the track. Same applies to metal detectors. Now what kinda coil is right for me? Smaller coils are usually more sensitive and get better separation. Bigger coils get better depth but can mask close targets. Each metal detecting situation is different and certain coils have advantages different places. Most of the time the stock coil will give you the best results for that specific metal detector. Metal Detector manufacturers spend many hours trying to get the best all around coil for that detector.

<cut>
I so wish people realise this, newbies especially. We frequently see posts along the lines of "Will I find more with a bigger coil?" the answer is "possibly yes, IF you are on clean ground and most targets are deep" .... but if the ground is full of trash and you only have 6 inches of soil ontop of rock then the answer would be "probably not, and possibly even less good items".

All coils have advantages and weaknesses. The default coil supplied with the machine is probably the best allrounder. But in some circumstances a bigger coil would be better, while in others a smaller coil would be better.

This site rates the different aspects of the various Nel coils ability, and would also be a guide to other makes of the same coil sizes.
http://nel-coils.com/index.php/en/

By giving a rating it shows the strengths of each coil and how by having a selection of coils you can swap them around to maximise you chances of making good finds for each search location.


Slightly off subject but another frequent question is "If I upgrade my detector will I find more", sometimes getting additional coils rather than a new detecor would be a better option (and possibly cheaper).

Evan

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Re: concentric coils

Post by Koala » Tue Apr 30, 2019 8:20 pm

whoever fist started the blade vs cone
Its not over simplified
Its total rubbish.

I have build loads of coils both DD and concentric. I have checked the detection zone by looking at the output of the fist opamp with an oscilloscope

But its fairly easy to check if your detector has a true no motion. Put a piece of card a few inches above the DD and push a coin from the outside to the middle

if you can't be bothered it will trace a circle thats slightly squashed east and west direction and slightly off centre towards the receiver side of the coil

same with concentric it will be close to a circle but if you raise the card you will see its nothing like the cone point in the diagrams.

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Re: concentric coils

Post by Bibelot » Tue Apr 30, 2019 9:08 pm

coil pattern.jpg

Thank you for the replies. The soil here is usually very mild,probably why I prefer the concentric to the Double D.
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Re: concentric coils

Post by Jacza » Fri May 10, 2019 5:17 pm

I like the 9' concentric coil on the MMK. The target id seems to be more stable and it looks like the performance is better on small and low conductive targets. Last week I found a golden locket with it on a hunted out site. Due to the smaller receiver coil it is not as much affected by EMI. The only negative sides: more overlapping and more false iron, but this is tolerable.

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Re: concentric coils

Post by Bors » Sat May 11, 2019 8:02 am

Bottom line is I`m thinking it doesn`t really matter about what's portrayed by the Detecting pattern diagrams because people "normally", don`t say they buy a coil for tech bumf stated about either DD or Concentric nowadays. I`d say the majority of people go by the recommendation of other detectorists,and they then try it to see if it suits them or not. Some like the Concentric, for the reasons Concentric gives, others prefer DD for its particular offerings and it`s common knowledge of both pluses or minuses so people go by what seems appropriate to their need from a recommendation or from trying and liking.
I think if you asked many newer detectorists what each Coils method of working was in as far as detecting pattern s concerned many wouldn`t have a clue. And I`d also say lots of newbies buy a detector today without a clue as to what type of coils on their detector and are baffled by DD and concentric when asked what type of coil is on their detector.
Personally, I have my own little way where now I use the Nox with DD, and the Tesoro Bandido with Concentric for using as and when required for a particular requirement place, and it works for me that way. I could, of course, use a DD on the Bandido but prefer the Concentric stock coil in trashy ground detecting

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Re: concentric coils

Post by Koala » Sat May 11, 2019 10:48 am

seem nobody except me is willing to test this for themselves.

Found this written by the lead designer of the T2

DD.jpg
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Re: concentric coils

Post by Bors » Sat May 11, 2019 3:04 pm

Koala wrote:
Sat May 11, 2019 10:48 am
seem nobody except me is willing to test this for themselves.

Found this written by the lead designer of the T2


DD.jpg
I can`t see anyone being that bothered to be honest doing any test Koala , as I said in my previous post I don`t think its that important. :D
One either likes one coil or the other (or both)and if you don`t like a coil ,you get shut of the one that you don`t like or isn`t up to the job in your own view.

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Re: concentric coils

Post by Saffron » Sun May 12, 2019 1:27 am

When I look at buying a coil I will have a specific requirement in mind, it could be any of the following (or maybe others but these are the most likely 3)
1) Extra depth
2) Increased ground coverage.
3) Improved sensitivity for small targets in trash

I will then read the various reviews and ask anybody I know that uses a coil that I am considering what they think.

What I will NOT think about is "Is it a DD on concentric?". It could be that to meet my requirements one type is superior to the other, but this will have been shown by the reviews and feedback from other detectorists not because the type of coil was my first concern.

Evan

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Re: concentric coils

Post by Bors » Sun May 12, 2019 8:43 am

Saffron wrote:
Sun May 12, 2019 1:27 am
When I look at buying a coil I will have a specific requirement in mind, it could be any of the following (or maybe others but these are the most likely 3)
1) Extra depth
2) Increased ground coverage.
3) Improved sensitivity for small targets in trash

I will then read the various reviews and ask anybody I know that uses a coil that I am considering what they think.

What I will NOT think about is "Is it a DD on concentric?". It could be that to meet my requirements one type is superior to the other, but this will have been shown by the reviews and feedback from other detectorists not because the type of coil was my first concern.

Evan
I think that sums up precisely what I`m getting at.
Truthfully speaking Throughout my detecting years I`ve never favored Concentric coils after the introduction of the DD. Because of No choice, I had Concentric on early CScopes and a Fisher 1265x and I knew nothing of any other type of coil really till the DD did eventually arrive. Even from those early days, DD became the preferred coil to use by many detectorists and the detecting Magazines pushed the trend even more. Concentric was still used by some detectorists but not as much as DD. I liked DD better ,because of their qualities over the concentric lacking.
So the Illustrated Pattern of detection by each coil be it DD or Concentric, has never really swayed me in any way. It's just it was portrayed by the Detecting companies and was generally accepted as being right, but I don`t think people based their choice of the coil by those marketing illustrations alone.

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Re: concentric coils

Post by Bibelot » Wed May 15, 2019 12:17 am

You cannot expect a Double D coil to hit an old silver coin sitting down the barrel of an old square nail. There are reasons one choses to use one type or size of coil vs another.... they weren't just designed for merely sales profit.
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Re: concentric coils

Post by Jacza » Tue May 21, 2019 4:13 pm

Which coil to prefer depends on the search situation. For testing a new open field and for an iron infested ground I would still prefer a DD coil, but in other situations like coin hunting on a hot spot or militaria search in the forest a concentric coil can be better.

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