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Concentric coil coverage question

J

jpiii

New member
Hi Gents,
I have the 10x5 HF coil and I'm considering the purchase of a second coil for my X-Terra. I am curious about the effective coverage area of a concentric coil. Page 3 of the X-Terra manual shows a depiction of the sensing area from the outside edges of a concentric coil, yet I have seen other illustrations that show the sensing area as the inside receiving coil or winding. Either way, I'm leaning toward the 9" MF concentric.

Thanks in advance for your advices!
John
 
Choice of coil should include concerns for the mineralization in the areas you hunt. If you live in an area with low to moderate mineralization, then the 9-inch concentric should provide more depth than the elliptical. At least all of them I've owned have done so in my neck of the woods. When I hunt with a DD coil, I overlap my swaths by 1/3. With the concentrics, I make an effort to overlay the swaths by 1/2. Although the concentric does "narrow down" the detection field (around the entire circumference) proportionally to depth, don't be mislead into thinking that the DD coil won't do the same thing on the tip and heel of the coil. Its a bit like splitting hairs when you ask about whether the sensing area is at the outside of the transmit windings or at the inside of the receive windings. Actually, it is somewhat of a combination of both. The transmit windings send the electromagnetic signal to the target, which in turn sends back eddy currents from the electronic signals it produces in return. So depending on how deep the target is, its conductivity, size, shape and the effects of the soil matrix, the target signal could be narrow or wide. JMHO HH Randy


Concentric coil field of detection
[attachment 211139 concentriccoilpattern.jpg]



DD coil field of detection
[attachment 211140 DDsearchcoilpattern.jpg]
 
The 9" MF concentric is my coil of choice in most situations.

Most versatile IMHO.

Good Hunting

Denny
 
Sorry for the late reply, and thank you very much for the clarification. I was thinking that the increased overlap was for the smaller primary reception coil in the center, and wasn't thinking about the cone shaped detection field overall. This helps a lot, and based on some of the other posts I am thinking that the 3khz coil might be an excellent choice for coin and relic shooting in this area of Alaska with mild to moderate soil but I'm still on the fence about the overall utlility between the MF and LF. For me, researching and reading about everyone's experience with the two is part of the fun!
 
The concentric coil was also an issue for me. I'm looking at the 705 and at the AT Pro, with a DD. I'm in western Pennsylvania most of the year, but get to the Jersey shore in the summer. I'm leaning to the AT Pro. I'd be interested in some insight from those who have the 705. Two people I know here have 705s, but they only search here.
 
IF your from western PA, I'd go the 10.5" DD HF coil. Believe it would be the best for the beach too. My MF concentric coil just gathers dust anymore, but probably would split time with my two DD's if it were a LF concentric.
 
Thanks for the advice. I was looking at the Garrett AT Pro as an upgrade, but came into a few extra bucks and the Minelab 705 was interesting, but it doesn't come with a DD coil. That was my concern. I think I'll save the $130 difference and buy beer.
 
I believe the 705 does come with a DD HF coil, If i'm not mistaken. It's the gold package I believe.
 
The XT-70 does come with a 5x10" DD HF coil in the gold package. Just for the record here are some of the DD coils available for the XT-705 which can be bought separately for it: 6" DD HF coil. 5x10" DD HF coil, 10" DD MF coil, 10" DD HF coil, 15" DD MF coil. I'm believe there are others available for it too.
 
Will the DD coil make this any better than the AT Pro? I'm not running around any gold fields, but I do spend a couple weeks at the Jersey Shore every summer. Most of my time is in western PA. Would this "gold" package be of any real use?
 
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