Double D Coil vs Concentric

[CoilFisher]

Anyone really notice a great difference in these vs the old concentric. Is it all just hype?

 

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[Treasure_Hunter]

My question is, Has anyone scientifically prov-en information showing the "fields" that come off of any coil, I've seen Eric Foster, Prospector Al and several others discuse but no one can measure this type of data from what I have read......... Plus would not the Matrix of the soil/sand affect this from one location to the next?

WOT in Action, deep target? 18/19 inch's possibly, no problem with pinpointing...............

http://www.youtube.com/watch?v=xInLPXijE70

Same here OBN, I have no problem at all locating with my WOT or my SEF Butterfly coils....

 

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[M Scott @ FTP]

Jason, The concentric delivers all its transmit power through one coil set while the DD delivers 1/2 its power through each of two coil sets. That's why the concentric goes deeper. My concentric picks up at the extreme edges of the coil which means that picture is wrong because it only shows signal at the center hole. The picture is BS. Try any detector with a concentric and prove this to yourself, if that is possible. My detector will pick up a large object at 2' which tells me that little cone is BS. My comments are based on actual usage over many years not just wild mutterings pulled from the air. Frank

Frank is right-the picture is complete BS created by detector companies marketing departments. Far too many people believe the imaginary detector field because they saw it in a manufacturers catalog.....

Here are some facts from detector designer David J whom has also stated the drawings are BS;

http://www.fisherlab.com/hobby/davejohnson/searchcoils essay revised.htm

DD better depth in bad soil and concentrics are cheaper to manufacture-lots more infor if you read all his essays on the web site.

Mike

That article doesn't say anything about "pictures" being BS or anything close to it.

Geez people, are some of you REALLY that dense?!

The transmit coil puts off signal.
the metal object radiates back its own signal from the transmitted energy
the recieving coil picks up the energy
the detector compares the differences and tell you what it thinks is down there.

Now, WAKE UP! A metal object above, below, or beside a coil will still recieve and re-radiate a signal
the picture that some you are complaining about isn't a fully discriptive picture, it's a representation of DETECTION AREA for small targets, under the coil, where you will typically be seeing them.
Oh, and Frankn... if the detector wasn't seeing differences in radiated frequency, it would never detect anything. No returned signal will ever be stronger than the field from the transmit coil, therefore if it is only seeing ONE frequency, it is blind.

I'm done trying to explain such a simple concept to such dense people.

Dave has stated on other forums that the drawings of coil detection fields are not accurate and we have discussed it at length on other forums.
The link provided some accurate information on DD and concentric coils written by DJ. His information is always accurate and he has dispelled the myth in depth on another forum.

 

[M Scott @ FTP]

Frank is right-the picture is complete BS created by detector companies marketing departments. Far too many people believe the imaginary detector field because they saw it in a manufacturers catalog.....

Here are some facts from detector designer David J whom has also stated the drawings are BS;

http://www.fisherlab.com/hobby/davejohnson/searchcoils essay revised.htm

DD better depth in bad soil and concentrics are cheaper to manufacture-lots more infor if you read all his essays on the web site.

Mike

Mike you better go back and read your reference, no where in it AT ALL does he say they are BS, in fact he praises them...

"The advantages of the DD are greater depth in mineralized soil, a broad sweep pattern, and narrower target response. Its primary disadvantages from a user's point of view are multiple responses on shallow targets and poor discrimination of flat iron objects. Designing and manufacturing them is more difficult because their lack of radial symmetry makes them prone to drift which the design and the manufacturing process must minimize. Manufacturing cost is higher because the coils cannot be wound on high-speed winding equipment."

I have been using large DD coils for over 4 years, they simply rock..... I have found .06 of a gram gold rings with them, the depth is fantasitc, the foot print makes cover areas so much easier, I am have absolutely no problem pinpointing with them, or recovering multiple targets under the 15 inch footprint most of mine have......

Sorry for not being clear-Dave has on other forums dispelled the myth of the supposed detection field emmited by different style coils-I prefer DD for most of my hunting and think both coils are valuable tools. The link I provided was just some written info from DJ regarding the different styles. My main point is that the drawings are false and DJ whom knows more about how detectors work than just about anyone has agreed(on other forums) that they are not accurate.

 

[Treasure_Hunter]

Sorry, I still disagree, I started with concentric coils and have been using DD coils for over 4 years now, I have seen the advantage they have over concentric coils......

 

[gleaner1]

Sorry, I still disagree, I started with concentric coils and have been using DD coils for over 4 years now, I have seen the advantage they have over concentric coils......

Is the advantage the heavier weight, or the lack of depth? T-Hunter, the masses need to know.

 

[Treasure_Hunter]

Sorry, I still disagree, I started with concentric coils and have been using DD coils for over 4 years now, I have seen the advantage they have over concentric coils......

Is the advantage the heavier weight, or the lack of depth? T-Hunter, the masses need to know.

Hummmm, maybe that is the problem, some of the "masses" have too much mass, I'm 63 and the weight is no problem for me at all, is it too heavy for you? Maybe you might want to think about joining a gym if the weight is a problem .... . I get 15 plus inches out of both my WOT and my SEF Butterfly coils, maybe it's just too deep for you....

I hunt in the water in the surf with both my WOT and my SEF 12x15" coils and I have no problems doing so, but then again I'm only 63 so it's easy for me....Hell, I even swing the SEF Butterfly 15x18" coil on my Sovereign GT if I'm not going in the water.....

 

[gleaner1]

Okay, but I still do not understand how the huge dd you use in the salt surf is better than the 8" concentric I use in the ancient amusement park in the woods. Your insults not withstanding.

 

[Treasure_Hunter]

Okay, but I still do not understand how the huge dd you use in the salt surf is better than the 8" concentric I use in the ancient amusement park in the woods. Your insults not withstanding.

Gleamer, it wasn't meant as an insult it was a joke which is why I used the " ".... Weight is not an issue....As far as the 15 inch, my DD coils gives twice the footprint, you do not have to overlap like you do with a concentric coil and it gives more than twice the depth of an 8' concentric coil.... I have hunted city and couty parks with it and I have no problem at all with pinpointing with them nor with multiple targets under the coil, I pinpoint each target and recover it till there is nothing there.

 

[gleaner1]

Okay, but I still do not understand how the huge dd you use in the salt surf is better than the 8" concentric I use in the ancient amusement park in the woods. Your insults not withstanding.

Gleamer, it wasn't meant as an insult it was a joke which is why I used the " ".... Weight is not an issue....As far as the 15 inch, my DD coils gives twice the footprint, you do not have to overlap like you do with a concentric coil and it gives more than twice the depth of an 8' concentric coil.... I have hunted city and couty parks with it and I have no problem at all with pinpointing with them nor with multiple targets under the coil, I pinpoint each target and recover it till there is nothing there.

Oooooh I told you folks that this is a good topic. Its really deep and profoundly whatever. Its great!

 

[gleaner1]

I had a Double D elliptical concentric coil once. Once.

 

[U.K. Brian]

Easy answer to all this is to do as I suggested when the subject first came up and do some tests. You can either use a buried coin or even better a test peg with the top just sticking out of the ground so you know exactly where the target is in relation to the coil or even better have several of the same coins at different depths.
Tests are easy if using a non motion mode.
Truth is the oft used diagram is a load of rubbish because coil designs of both main types do vary so much.

I have lots of detectors and more coils and anyone can try them on my in ground test bed any time. Concentrics tend to be deeper and nicer to use. Double D's pick up less ground effect (though if you use a really large DD then you could be picking up more mineralisation than with a small concentric).

Pity no one bothers to look back to the time when Fieldmaster put the first DD on a motion detector (the Searchman). All the other manufacturers were so quick to point out the problems with DD's.

 

[CoilFisher]

Well, I can tell you thus far the only real difference I can perceive from a 11" Double D Ellliptical coil v\s an 8" concentric is that I can scan a larger area quicker, and it tends to find things out near the edges that the concentric might not because of the shape of the coil. So the only thing I have gained from it is covering more area quicker. Actually, pinpointing with it is the same as my concentric now. I just look to where the lower shaft meets the coil and that is dead center. Depth is about the same.

Thx for all your info everyone!

 

[Jason in Enid]

It is also better in mineralization because it sees less percentage of soil at any given time.

 

[gleaner1]

It is also better in mineralization because it sees less percentage of soil at any given time.

Jason, how can any particular coil that sees a lesser percentage of the soil be better? By logic, that coil would therefore see less percentage of targets. How can a shallow coil be better? Replace your most beloved big dd with a concentric, slow down and re-discover tectin. This does not apply to 100% of detectorists in 100% of soils. It's a case by case situation. I get best results with concentrics, they are hot on deep crap in my mild loam and I'm not in a hurry. For others, its all dd. It's a never ending discussion.

 

[earthmansurfer]

It is also better in mineralization because it sees less percentage of soil at any given time.

Jason, how can any particular coil that sees a lesser percentage of the soil be better? By logic, that coil would therefore see less percentage of targets. How can a shallow coil be better? Replace your most beloved big dd with a concentric, slow down and re-discover tectin. This does not apply to 100% of detectorists in 100% of soils. It's a case by case situation. I get best results with concentrics, they are hot on deep crap in my mild loam and I'm not in a hurry. For others, its all dd. It's a never ending discussion.

It's inherent to the design of a DD to see a slice of the soil where the two D coils meet. The "effective" area is smaller than the effective area of a concentric so that is why concentrics have problems in minerals. It is easy to test this. Yeah, the drawings are not spot on. But the basic idea is that the field of detection is different. So, that lesser percentage is deceiving as it is a slice. Imagine this - a 6X10 Dd coil has a narrow but long (10") field below it. It is like a few inch wide knife cutting through the ground. You can effectively scan more of the ground. A 6" concentric (that would be the equivalent) would have a much wider field at a shallow and moderate depth, it picks up too many targets and that could cause masking if the ground is too contaminated. It's width and height is the same, a DD's has a very narrow width.

I need to play with the concentric more to be able to say more, but it is pretty much a given that DD's are great in mineralized ground and concentrics don't work in highly mineralized ground (but do work in moderately mineralized ground.) DD's are often EMI magnets, concentrics are not. When the iron is heavy smaller DD's seem to do better than concentrics but when the iron is moderate concentrics might see "under" the iron in a sense where as DD coils see between the iron (narrow detection field). If you an imagine a concentrics field does taper down as it gets deeper this is probably why it can sometimes see under iron. But a DD coil has a much much narrower field to begin with and in addition to that it tapers down (so there is not much room to see under.) That is hard to describe. The best thing to do is get a similar sized coil (DD and concentric) and hunt with both equally. You'll see a difference after a short while imo. (And it will be different for other people with other conditions.)

EMS

 

[bigscoop]

The best coil is the one you're most comfortable using and have the most confidence in. In my mind, this is how you determine what is the best coil for you and your machine.

 

[Jerry-Wi]

I understand the differences and the advantage and disadvantages of both the concentric and DD coils. I have both and use both. For large open areas that are not littered with trash I prefer the large concentric. For very trashy area where target separation becomes important, I use the DD.

Jerry

 

[Keppy]

Sorry, I still disagree, I started with concentric coils and have been using DD coils for over 4 years now, I have seen the advantage they have over concentric coils......

TH .. The reason you have no problem pin pointing is you spend most of your time in the water or on a sandy beach...........................

 

[Treasure_Hunter]

Sorry, I still disagree, I started with concentric coils and have been using DD coils for over 4 years now, I have seen the advantage they have over concentric coils......

TH .. The reason you have no problem pin pointing is you spend most of your time in the water or on a sandy beach...........................

Keppy my friend, while it is true I love hunting beaches more than land, but I have hunted many, many county and city parks using my Sov GT and a WOT coil..... I can pinpoint a quater or dime with it.......

 

[Frankn]

Check out the Deep seeking metal detector post if you want to see something that will go very deep and still pick up small nuggets. I posted a video on it also. frank