Heres a video I made showing the increased performance of a great coil design

I hunt in a lot of mineral and DD's are a must...but as the art of coil design advance's...even older DD's are becoming less desirable...here's a perfect example of night and day difference between 2 coil's....

I am using the MXT-PRO for the demo...A great bad ground machine....

The first coil is the White's DD 6x10 elliptical
The second coil is the 8x6 S.E.F. coil......

Now so far the only machines to see through the brick have been the AT-PRO and the MXT equipped with the S.E.F. series...and ironically they are very similar designed coil's...

the Fisher/Tek Bi-Axial get close but not quite ...


I will let the video show the performance gain's of a High performance coil....

[www.youtube.com]


Keith

Very nice video, I always questioned the quality of these after-market coils, made in Bulgaria (SEF) and Ukraine (Neil) and still do, but you can't argue with results such as these. Some love them, others don't think they offer any improvement compared to manufacturer coils, and I think that might depend on the machine you use them with, some work better with some machines, or some manufacturer coils are just not as good, just don't know. Too many variables. But it's good to see clear tests like these to finally get to the bottom of things and get some answers! Well done Keith!

Nice video, Keith. I've been thinking of getting an 8x6 for my Explorer...

Steve

I watched your video.........quite enlightning. Then I did some research on the SEF coils for the Teknetics T2. To make a long story short, they make them for the T2. But a SEF post, with a response by Dave Johnson (head engineer) at First Texas, stated the only coils that work on the T2 are those that are factory made. So, does it really work or doesn't it?
Has anyone used a SEF on a T2?

i have seen reviews reporting that the sef coils on the t2 did not work as well as the stock coil.
every review i have seen for sef coils used on excaliburs report the sef coils are quite a bit better than a stock coil.
thats about all i know.

Keith...interesting video, well done. Your point is well taken where a target is influenced by a 'hotrock'. The SEF coil responds much better, and the red clay brick is acting just as you described....a 'hotrock'.

Now let's look at this a bit differently and now presume the brick represents the soil minerals in a given area. Checking both coils again but ground balancing to the brick, how does the nickel respond in each case? Thanks...

Jim.

Correct............and Grnd Balancing to the brick would (much closer) represent real-world red clay Georgia (or Tenn, Va).
HOWEVER.............as is...............the test is still interesting.

Here is a review of a large SEF coil for the T2 if anyone is interested.

[www.garysdetecting.co.uk]

Hi Tom...yes I agree it is interesting regarding the SEF and brick / hotrock result...but I'd like to know why. It might be interesting to see where the ground phase reads with each coil ground balanced over the brick or over any substrate. That maybe grasping at straws....to wonder if the SEF coils GB was lower than that produced using the Eclipse DD....yet it is information I'd like to see if Keith can do so...

Jim.



Edited 1 time(s). Last edit at 05/30/2011 05:22AM by HumblePie.

Jim,

I have (somewhat) reconsidered my thoughts IRT this matter. It may not be wise to Grnd Bal a detector to a 'hot rock'.........and leave the primary dirt matrix uncorrected (improper Grnd Bal); yet...............in this case.........that red clay brick is very similar to certain types of soils that Keith is exposed to.....on a regular basis.

Keith did indeed Grnd Bal to a matrix of some sort (underneath the concrete floor)...........and utilized the red brick as hot-rock representation; ........... a fairly realistic scenario. An area............say: 4-feet by 4-feet.... of those same red-clay bricks..........with the nickel underneath one of the bricks...(near the center of the 4' x 4' area) would afford a better representation....via....allowing Grnd Bal to the bricks....then sweeping the coil over the low-conductor (good/correct choice) nickel.

Yes.........knowing the Grnd Bal number for (underneath the concrete floor).......................and also knowing the Grnd Bal number for the red bricks....would be more indicative of resultant.

Keith...........................Do you feel like moving a ton of bricks!!!!!?

sometimes one would jump to 76 or 74 but it was with either coil but they were for the most part staying at 75.....there's no re-bar in the floor( I wish there was for the floor is starting to crack!!!) It a dug basement no back fill just red clay below it...

the brick balances at 88......


Now if I balance to the brick the eclipse response does improve when testing but it's still say 70% iron I.D. and 30% foil(5-6 on the I.D.)......the S.E.F. coil completely goes 100% high tone with less fluctuating I.D. although reading a bit high at 30.....

The main purpose was to show when all setting's are equal which coil out does the other....in this one scenario....

The coil design of the S.E.F. is well thought out in the mineral handling aspect for sure.....I know they deal with a lot of terra-cotta ( fired clay) over sea's on the roman site's and this may be were they tested and designed it to exceed???

The S.E.F. design is ahead of the older design De-Tech offered/offer's...for sure in mineral handling....

The design is not a gimmick I am almost positive of this the Symmetrical Electromagnetic Field is of a blunt design on the front and back and I wonder if this gives better see-through??? the At-PRO offer's a similar design and it works equally/better on the test......Go to the other coil offering's for the AT and it will not see the Nickle under the brick....Put the Blunt Tip DD stock coil back on and the target is back without an ounce of strain to get it........

Garrett is on to something also...and it's all in coil design....the AT would be just another rehash for the most part but the coil up's the ante...

I hope for better coil design's to come from manufacturer's in the future.....De-Tech or whoever...I honestly believe the design team at De-tech are on to something....You can tell when a design has been researched and there design holds merit .....They are serious about coil building...

I have had the older De-tech simple DD design and the newer S.E.F. and they are advancing in technology and Q.C.



Just my thought's

Keith

Very interesting test/report Keith.----For anybody that is interested in this coil (8X6 SEF)---I see that Kellyco put them on sale the other day ($129.95 delivered).---I think that's about thirty bucks off regular price.-----------Del

Keith..........good write-up......and solid/founded opinion.

Keith good read

Hi Tom…yes I agree with you about balancing over hotrocks by and large…but that was not my reason for wanting the GB numbers on the brick. I was curious to see how the GB readouts compared between coils, and second…to see how the Eclipse performed after ground balancing over the brick. In fact I duplicated the test on a red brick here with the Eclipse DD / MXT with the same result.

That aside…Keith’s latest results indicate some other factor is at play with this coil…and Keith may very well have pinpointed the reason for its superior performance. It would be interesting to get a comment from a design engineer on the matter but I am inclined to Keith’s view. I think he's nailed it down.

Thanks very much Keith for taking some extra time to respond to my questions. I’ll bet dimes to doughnuts that very few of us would have anticipated the SEF’s superior “hotrock performance” without you pointing it out to us. It’s an intriguing result that leads me to think that an SEF coil may offer a real advantage for us rockhunters if the sensitivity to small stuff is on a reasonable par with the Eclipse DD. Excellent presentation that has taught me something new…thanks again.

Jim.

for any insight the test may of gave you.....

That's the great thing about the forum we all benefit from each other.....


And if I may add the 6x8 is very sensitive to the small item's maybe better than the eclipse...

One scenario that comes to mind is the .22 hull.....the woods are full of them ....even more so than the shot gun hull.....But in bad ground I dig very few of them...They airtest at 6-8 on the i.d with either coil....

Using the eclipse 6x10 they read zero in the mineral dirt higher or close to 6-8 in more neutral dirt.....
Using the 6x8 S.E.F. They read 6-8 in the same mineralized dirt the eclipse read's them at zero.....and I actually find the .22 short's that the eclipse calls iron....

The 6x8 can has a natural ability to neutralize mineral ......

Was waiting for some one to catch it but I will point it out here.....
In the video notice when I ground grab the eclipse how loud the ground mineral is almost to and overload.....that's at the stock G.B setting after turning it on.....
Well notice how much milder the ground sounds on the 6x8 when I do the grab ? It too is at the stock ground balance setting....

both machine's are set at sens 9....

the 6x8 can see less ground mineral than the eclipse for some reason??

they both get the blowback from the ground but the 6x8 is less intense.....

Don't think it's a weaker magnetic field it is deeper than the eclipse by inches.....

it's all in the coil design I believe.....


Thanks

Keith

that is a very good price on the coil for sure....

the coil is the type coil you will use 90% of the time on a machine...perfect size most application's....

Wish more people would get them and test them ....

there not gimmick's....

Enough people give some feedback and maybe we will see further advancement's...

Keith

Hey Keith --

Thanks much. I have wanted a small coil for my Explorer SE Pro, and had narrowed it down to a few, including the SEF 6x8. Your posts here convinced me -- I have a 6x8 SEF on the way! I'm thinking it may spend a good bit of time attached to my machine...

Steve

I have an 8x6 sef that is on truck for delivery today for my Safari I have had for only 2 weeks. Im hunting an area that has 6" of top soil that was added to site over the years and underneath is a clay base. Lots of finds have been had at the layer. I will be testing it this week but the heat is going to be a concern as to when. Lots of trash also as it is an old apartment site that has been torn down to foundations. I will be using auto, low trash, all metal with a very slow swing. I hunt with a guy that uses an E-Trac with the 8x6sef. and gets grt depth and ID. Consistanly getting coins mixed with nails. Grt seperation and price led me to purchase. Plus the 8"FBS is the heavest coil for size Ive seen.

I wonder how SEF coils............for different brand detectors...............perform. Will they produce the same resultant on other detectors...as they do with the Whites.

I can speculate the footprint......but truly wonder what the electromagnetic footprint presents. (There's a few other factors involved also).

Keith...thankyou for the follow-up information. Your comment below...

"Using the eclipse 6x10 they read zero in the mineral dirt higher or close to 6-8 in more neutral dirt.....
Using the 6x8 S.E.F. They read 6-8 in the same mineralized dirt the eclipse read's them at zero.....and I actually find the .22 short's that the eclipse calls iron...."

Yep, I've often experienced the same thing on spent blasting caps in mining areas, and that's using either the Eclipse DD or the 12" concentric coils. You'd get a perfectly good signal but see the ID all over the map but mostly in iron territory. With our minerals I wasn't too surprised, but were I hunting gold it tells me to dig everything 'cause discrimination does not work in those conditions on that size target. The SEF coil appears to be an answer to that issue to some extent...

Your comment below...

"Was waiting for some one to catch it but I will point it out here.....
In the video notice when I ground grab the eclipse how loud the ground mineral is almost to and overload.....that's at the stock G.B setting after turning it on.....
Well notice how much milder the ground sounds on the 6x8 when I do the grab ? It too is at the stock ground balance setting...."

Well you're right...I did not notice until I replayed the video...and there is no mistake either...a definite difference in mineral pick-up.

Have you tried this test with a larger SEF coil? Looking at Kellyco I see they offer several larger sizes too. To accommodate the larger silver ore hunting up here in Ontario I would prefer to go with at least a 10"X 12" SEF. I doubt the results would be much if any different, but would like to hear from anyone who has or can run a similar test with a larger SEF coil.

Keith your tests may directly result in a real improvement to prospecting silver at least with the MXT. This has been a most interesting presentation and discussion. Thankyou...

Jim.

PS: Almost forgot to comment on Tom's post. It would be a good thing to learn what if any difference an SEF coil would make to an F75 in a similar test...



Edited 1 time(s). Last edit at 06/01/2011 05:46AM by HumblePie.

Keith

Is the SEF coil you bought, the same brand as being sold by Kellyco?

Jim

The very first thought I had when I read Keith's post is, this should be great for prospectors.

Would a SEF coil get the same results on a PI detector?

Great thread Keith!

I see they are expanding there offering's ...for many models know....even have them for the Tesoro line......Would like to see what one would do on a Tejon.....


Keith

similar and has more depth to boot.....The 10x12 really gets down deep....while still retaining good sens to smaller target's....

the 12x15 will probably be my next purchase.....for the open area's since the 8x6 does so good as an all rounder main staple coil....the 12x15 will be for the truly deep target's...

not sure why but the 15x18 cost like 3 times more???? must be some special tooling involved and that's just a crazy big size.....


Thanks for the reply....

Keith

I believe they are the sole importer here in the state's///I may be wrong???

Not sure what the performance gains would be on a P.I.??

thanks

Keith

Thanks Keith for the additional information on the larger SEF coil. I guess we all look for any advantage to give us an edge, and your results surely indicate these coils make a significant difference to target response and ID. As to coil size I don't believe I'd want to swing 15"X 18" for long, but the next smaller size might work out OK...depending on the terrain.

Turtleman...because VLF and PI units deal with minerals differently I can't possibly speculate about design. Perhaps others could do so, but I imagine this is a question best put to the manufacturer's engineering staff.

Thanks very much Keith for all your assistance.

Jim.

That was a very interesting test Keith. Thanks for taking the time to make that video. Since the At Pro is also able to see through the brick I cannot help but wonder if we will see an SEF coil for the At Pro.

Jerry

If there are some positive attributes (and negative performance) from a aftermarket product............it would behoove of a detector Mfr to "take note"..........learn how to capture/incorporate the 'positives'...........and learn from the 'negatives'.....for their very own product(s)........so as to continuously improve their product...and future products. (((Especially if the envelope has been pushed to 'perceived' limits...of their product))).