When does the coil type (DD, concentric, etc.) really matter?

[OregonMike]

Hi,

There's DD coils, concentric coils, SEF "butterfly" coils, oval-shaped coils. When does it really matter? How would someone know without actually field testing a coil whether it would be a good choice in his own area?

Here's what I have experienced in my own area, which is in the Willamette Valley of western Oregon:

Last year, I buried a Merc dime in my back yard, about 5 inches down. I know planted coins aren't the same as those dropped years ago, but it's the only way I can get a constant with which to compare all the coils.

The DD will find the planted Merc, but it takes a number of sweeps and is not reliable. If I didn't know there was a silver dime there, I would miss it often.
The 5.3 concentric will find it, sometimes, but usually not without a number of passes. However, once it's found, it locks on very nicely.
The 9.5 concentric finds it and it hits hard. I can walk around the yard detecting with my eyes closed (not to be recommended) and the two aforementioned coils will not always find the dime, but the 9.5 finds it every time.

I have also noticed that in the current ground conditions (dry and hard ground) the DD coil found the dime more quickly and more often when the ground filter was set at 5.0, but that the 9.5 concentric was better at 7.5.

I haven't tried an SEF "butterfly" coil or an oval coil, but a buddy of mine had an SEF for a while (with a Minelab) and chose to give it up, saying he wasn't getting any better results from it than the coil that came with the detector.

I also realize that the smaller the coil, the better the separation but there's usually less depth, so that's a reason to try one or the other. However, returning to the title question of this post, when does the coil type (not size) really matter?

Thanks in advance for any responses,

Mike

 

[burlbark]

I have found the dd have had better separation but dont catch targets as nicely as the concentric coils

. I do need to try a butterfly coil just to satisfy my desire.

 

[Larry (IL)]

Much depends on your ground, the DD and SEF coils seem to do a better job the more mineralized the ground is. Just the opposite for the conicals. You are correct though that the best way to see what coil works best for you in your ground and hunting style is to try one.

 

[Rob (IL)]

And the best coil is the one that works for you. Rob

 

[OregonMike]

Thanks for the responses. I have insisted on using the DD coil a lot, believing that since that's the one White's chose to sell with the detector, it was probably the "right" one to use. The engineers I've talked to seem to think so, and my sales guy does, too. However, my own experience is that I'm getting better results with the 9.5 concentric. Maybe it's because that's what I had on my previous detector and I'm more used to it. Who knows? Anyway, my last hunt was in parking strips in an older neighborhood, and although no silver showed up, the wheat cents tended to hit really hard, so I think that at least for a while, I'll stick to the 9.5 and see what happens. Once I get over some silver I will probably have a better idea whether there's really any difference or not.

Thanks again,

Mike