Minelab Explorer Classroom Forum

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Lets Talk Double D's...
Posted by: seahunter34
Date: December 17, 2011 12:27PM
Double D coils. I grasp the DD concept where there is more of a narrow windshield wiper blade field running down the center. But that is not entirely so, because my DD Coil still sees targets to a degree everywhere under the coil and not just along the center strip. There are several styles of DD coils. Some are round or rounder, while others more elliptical. Here's what I want to know. Given 2 DD coils of the same length- say 12 inches down the center strip, but one is round and the other elliptical (narrower), what are the in field performance differences?

Would they both go the same depth? Would the round coil cover more ground? That would mean the round would be more prone to target masking and ground minerals? I ask because NEL makes 2 Explorer coils. One is 12.5X8.5 and the other a rounder 12X13. What would be the difference in the field?

Re: Lets Talk Double D's...
Posted by: dewcon4414
Date: December 17, 2011 03:58PM
Interesting questions .... something you may have to ask Tom Dankowski. I agree you do deal with HALO and get a response NEAR and AWAY from the receive coil. You really notice it in Ferr.... listen to the tones as you get close to a target and watch the digital screen. They change more drastically as items are averaged for TID and tone. Ive used my concentric coil by slightly turning it on edge which can give you a little separation. So to me the narrower the field the better the separation and like you said more target masking just by the amount of soil being processed. As the amount of soil is increased id be surprised if you dont loose some depth on a wider coil.


Re: Lets Talk Double D's...
Posted by: BJ in Okla.
Date: December 21, 2011 06:35PM
I read a post a while back, by someone that works for Whites,,,,,
He said that a 6" x 10" dd was equal to a 6" coil in depth and that a 10" round dd coil would be deeper....


Re: Lets Talk Double D's...
Posted by: BJ in Okla.
Date: December 21, 2011 06:48PM
I have read in some metal detecting books , they talk about Halo's,, and made some posts about Halo's.
Dave J. and Tom D. and some others said there was no such thing as a Halo...
You might do a search on Tom's forum.

Re: Lets Talk Double D's...
Posted by: Rob (IL)
Date: December 21, 2011 07:41PM
That's the way it was explained to me when I was talking to a Whites engineer. I don't have a picture right now but the field is actually more like looking a a ship hull from the front or rear.

"Everyone has an opinion, but mine is free":devil:
"You might very well think that; I couldn't possibly comment..."

Thanks Rob..........:cheers:N/T
Posted by: BJ in Okla.
Date: December 21, 2011 08:32PM

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Re: Lets Talk Double D's...
Posted by: BHMACK
Date: December 27, 2011 10:04AM
I find the DD Minelab Pro coil to have a detection area like this....



Re: Lets Talk Double D's...
Posted by: The Magician
Date: April 27, 2013 07:55PM
I don't know about the oblong type DD's like the SEFs, (though that design makes sense), but the pointy DDs like the joey coil or the platypus, I think that shape is restrictive and does affect performance. I prefer round DDs.

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