Will a Larger Coil Cover MORE Area?

Terry Soloman

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I just read another response to a newbie saying that a 12" coil will allow the new hobbyist to cover more area faster than he can with an 8" coil.

I completely agree that a larger coil can give more depth, but the argument that you can cover "more" ground with a larger coil, "faster" than you can with a smaller coil is suspect to me at best.

How much more area are you really going to cover with an 12" coil, than with an 8" coil in an hour? None? Two-square feet? When you look at the signal transmission cones of the two coils, you see a noticable difference in depth, buy very little difference in coverage area.

In my experience hunting with 20" coils for deep gold, you actually move a lot SLOWER than you would while swinging with a 12" coil looking for 3" - 11" new drops.

Now, I am talking about concentric coils and I do realize that there are "wide sweep" coils like Tesoro's "Clean Sweep," but these DD coils max out around 7" in depth. Great for covering a beach or park for new drops, but only at moderate depths.

Talk to me..
 
Man....I use a 5.3 in trashy areas and a 12" in regular spots. Each swing of the 12" is equal to just over 200% of the swing arc of the 5.3".

In clean, open areas I can swing the 12" fast enough that I can just walk slow. With the 5.3" its more of a broken shuffle.
 
The old timers with the excals know in some cases depending on mineralization,an 8" excal can go deeper than a 10" excal.Can't remember the figures? But the 10" sees so many more gallons of sand than an 8".So the cone on the 8" actually penetrated deeper and with a more precise cone than a 10",which was more live a v than a u.
 
I have no doubt the larger coil covers more ground, personally I can move twice the speed in a big open field with the lager coil without having a fear of missing anything... :yes:

coils.jpg
 
I have no doubt the larger coil covers more ground, personally I can move twice the speed in a big open field with the lager coil without having a fear of missing anything... :yes:

coils.jpg

Yeah but infest the ground with iron and pulltabs and try to find a quarter.I ran 3 coils over the same area with the same machine from largest to smallest.The bigger coils confused the machine.The smaller coil you could watch the numbers and pick out a quarter signal.The larger coils never saw a quarter at all.
 
Wot where did u get that layout of the coils and such very interesting if its accuarte.
 
I just read another response to a newbie saying that a 12" coil will allow the new hobbyist to cover more area faster than he can with an 8" coil.

I completely agree that a larger coil can give more depth, but the argument that you can cover "more" ground with a larger coil, "faster" than you can with a smaller coil is suspect to me at best.

How much more area are you really going to cover with an 12" coil, than with an 8" coil in an hour? None? Two-square feet? When you look at the signal transmission cones of the two coils, you see a noticable difference in depth, buy very little difference in coverage area.

In my experience hunting with 20" coils for deep gold, you actually move a lot SLOWER than you would while swinging with a 12" coil looking for 3" - 11" new drops.

Now, I am talking about concentric coils and I do realize that there are "wide sweep" coils like Tesoro's "Clean Sweep," but these DD coils max out around 7" in depth. Great for covering a beach or park for new drops, but only at moderate depths.

Talk to me..


You are spot on the money Terry.
An example is a 14.5" all terrain round DD. It has a "depth centre", for want of a better word, of 4" dead centre of the coil. A 12" has around 3", an 8" around 2", give or take-Maths isn't my strong point, so please don't anyone take the figures to be excact.

Now, if a 12" coil has finished a sweep, the next sweep should no further forward than 3". A 1" difference in "Coverage" to the 8".
Worth the extra cost for the difference in depth, sure, but it really shows Coverage for what it is, a complete myth.

The only way to achieve true extra Coverage is by running a larger coil when looking for near-surface targets, and I know of no-one who would waste time doing that.

Regardless of coil size, anyone who has been detecting with a swing a couple of inches more forward than the last will not detect a good area to their true advantage.

The size of a coil for extra depth, on both VLF's and PI's, petters out around the 15" mark, any coil larger than that really only gets better Coverage, and we all know what Coverage is now, don't we?
 
I'm no Einstein. But....I do know my 10" coil vs the 8" seems to cover the same areas I had detected previously with the 8" a lot faster. And deeper.
Maybe its just my mindset.:grin: But that's half the battle right there isn't it?
 
A DD coil does not scan like that though. It does not narrow to a cone. Its 11" swipe is the same at 1" as it is at 12"

http://metaldetectingforum.com/attachment.php?attachmentid=84071&stc=1&d=1296652700

Sorry broevol, but it does act like a cone, much in the same way a concentric or mono does. The DD's do not detect the same at say, 1" a couple of inches back from the front or rear of the coil as they do at depth.
The so called Blade of a DD, is only noticable from the front on look, not the side view. From the side, as in the pic, the look the same as concentrics, minus the tip of the cone.
 
It is not the fault of detectorists that the misunderstanding came about regarding DD coils. Early on in the piece, a few on the manufacturers released drawings of how a DD behaves. Minelab started it, then a couple others followed suit.
 
Wot where did u get that layout of the coils and such very interesting if its accuarte.


Hi Indian. I quickly drew them this morning. Not very pretty or precise, unlike my fellow Dyslexic DaVinci. And I apologise for the large size pics.

How I know of the layout, would probably be due to more than 30 years detecting, owning 60 odd units and 100 odd coils, and the testing and daily use of what I currently run.
 
I'm in no way smart, or trying to be a smart alec. I'm afraid I have a very limited education and do not have the least idea of how even Electricity works.

But I do know detectors and how the behave in the ground. My type and level of dyslexia let's me see from sound. I guess that's why I love detecting.
 
Yeah but infest the ground with iron and pulltabs and try to find a quarter.I ran 3 coils over the same area with the same machine from largest to smallest.The bigger coils confused the machine.The smaller coil you could watch the numbers and pick out a quarter signal.The larger coils never saw a quarter at all.

99% of my sites are pulltab & iron infested & I find quarters just fine with the big coil... Maybe its just your machine... :D
 
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