12x10 DD quandry

[Mr B]

I have a tesoro outlaw and mojave. My 8 concentric coil will air test 9 inches on nickles with both machines. However when I install the 12x10 DD coil I can only get about 7 inches on an air test. It just seems to me that I should at least get close to what my concentric coil gets. Can a coil be tuned without adjusting the detector also? I usually stick to smaller coils and I'm happy with my depth on my concentric coils , but when I do use the DD I don't want to be penalized depth plus swinging a heavy coil. Any ideas?

 

[Nauti]

Concentric coils tend to be slightly deeper than dd coils and as you go bigger with any style coil you start to loose a little sensitivity to smaller items.

 

[Monte]

I have a tesoro outlaw and mojave. My 8 concentric coil will air test 9 inches on nickles with both machines. However when I install the 12x10 DD coil I can only get about 7 inches on an air test. It just seems to me that I should at least get close to what my concentric coil gets.

As Neil stated, generally you will find that a Concentric coil and Double-D coil of the same/similar size will show an edge in depth-of-detection for the Concentric design. Also, as a general rule, as the search coil size increases it provide a bit better depth on larger-size objects while loosing responsive performance on smaller-size objects.

Can a coil be tuned without adjusting the detector also?

Yes, search coils are tuned to provide proper performance within the specs determined by the detector manufacturer. Other than that, the 'tuning' or 'calibration' is governed by the detector's Ground Balance setting. If the Mojave is switched to the best functional setting with the 2-position toggle switch, and the Outlaw manually adjusted for a peak-performance GB setting inn the Discriminate mode, then you'll be getting all the performance possible from the search coil that's mounted.

I usually stick to smaller coils and I'm happy with my depth on my concentric coils , but when I do use the DD I don't want to be penalized depth plus swinging a heavy coil. Any ideas?

I almost always use a smaller-than-stock search coil, and have been doing so since early '72. I've followed that decision to provide more comfort with a lighter and better-balanced set-up; to be able to work in and around and under brush and building rubble and closer to metal structures; and naturally to handle the trashier sites I generally find myself hunting.

On my Nokta FORS CoRe and FORS Relic, I can only use their 4.7X5.2 and 5" Double-D coils because the manufacturer doesn't make a Concentric design for these devices. I also use their mid-sized 5X9½ open-frame DD coils. The rest of my Regular-Use Detector Team, my Makro Racer 2, White's XLT, modified Classic ID and MX-7, and Tesoro Vaquero, Bandido II and Mojave, I keep smaller-than-stock Concentric coils mounted for all of my day-to-day detecting needs, and only the Mojave has a 'standard' Concentric mounted in the 7".

I have some of these model's standard-size coil on a lower rod in my Accessory Coil Tote in case I need or want them, and some I didn't even care to keep around since I seldom use a standard coil. I only have one model that has an over-size search coil in the A.C.T. for the seldom-use need for one. I have owned and tried both the 10X12 Concentric and D-D coils for Tesoro's, but never cared for them and have no use for their demonstrated performance.

Question: You stated: "... when I do use the DD I don't want to be penalized depth plus swinging a heavy coil." This made me wonder what types of sites you search; and what reason you would have to opt for the DD design coil; and why an over-size and heavier-feeling search coil?

Monte

 

[Mr B]

I generally use the 5 3/4 inch the 7 in or the 8 in concentric. If I am in hot ground I have found the 7 inch widescan works great. I'm not a fan of large coils and I don't use them that much but I guess I was more curious about the performance. Thanks to all for your replies.

 

[Stoof-tabsallday]

Small correction Monte. The relic can use a concentric the fors gold + has the 5.5x10 solid concentric. And it runs really well

 

[Monte]

The 5½x10 Concentric is available for the Relic / Gold Plus, and I was one of the earliest users of that coil on the Relic having put it to work with all the other coils available with the prototype to become the Relic and then with my production models. It is a terrific performing mid-sized coil on the Relic, too, but I think my concentration at the time was on the smallest-sized coils. Those that would be in the 5½" to 7" diameter Concentric size.

I know that I talked that coil nup quite a bit and many Relic users couldn't find it at the big-shot dealer outfit in Florida. The so-called 'Distributor' and even right now they still don't show that on their website. Only the 5½X10 Double-D coil.

Still too bad they didn't make the round 7" Concentric for the CoRe and Relic like they made for the Impact, Racer 2 and Kruzer models.

 

[Stoof-tabsallday]

Yeah I was one that couldn't find it either Monte.
I ended up ordering from Turkish dealer.
Low and behold 2 weeks later not only was it in stock in Florida but they even listed it as a gold+/relic coil.
Go figure. I bugged them for almost a year about that coil. Guess I should have waited a bit longer.
I was surprised that it made it from Turkey in the same time it would have taken to get from a dealer in the states. But I would gladly order from any dealer stateside, especially sponsor dealers here. But when our "distributor" doesn't have it, no dealers have it.