Coil choice - Shallow Ground

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Coil choice - Shallow Ground Empty Coil choice - Shallow Ground

Post  Rob.B on Thu Dec 08, 2011 7:19 pm

Hi...

I'm planning to go to an area tomorrow with what I consider shallow ground (Starts at ground level, hard red clay type dirt which comes out in hard clumps when dug).

Question:-
Should I use a smaller coil for stronger signal, or the larger?

I understand a larger coil will cover more ground & provide a lesser signal.

I would really like to be looking for a good sized nugget as I have an older machine, not the newer which picks up grains.

I'm wondering how far down is good gold (Understanding some mines are 2K down), but as a detectorist, do you thing a 10" coil will be OK in ground which starts at the top?

Thank you for any feedback

Rob
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Post  Inhere on Fri Dec 09, 2011 1:25 am

G'day Rob.B. If you are still around Maryborough and using a SD2000 I would use
10" Elip DD or maybe mono on the shallow ground and an 18"-20" DD on the deep ground.

Some of the grounds pretty noisy around that way. Wink
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Post  Rob.B on Fri Dec 09, 2011 6:30 am

Tat's the area,,,, Thank you
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Post  Guest on Fri Dec 09, 2011 7:38 am

Rob.B wrote:Hi...

I'm planning to go to an area tomorrow with what I consider shallow ground (Starts at ground level, hard red clay type dirt which comes out in hard clumps when dug).

Question:-
Should I use a smaller coil for stronger signal, or the larger?

I understand a larger coil will cover more ground & provide a lesser signal.

I would really like to be looking for a good sized nugget as I have an older machine, not the newer which picks up grains.

I'm wondering how far down is good gold (Understanding some mines are 2K down), but as a detectorist, do you thing a 10" coil will be OK in ground which starts at the top?

Thank you for any feedback

Rob


Gday Rob

The term "shallow ground" best describes areas where the surface soil is relatively thin over the cap rock, usually these places are easily recognised by either having being scraped, or areas that have had dry blowing done on them, and also where the vegetation is low and stunted looking or covered mainly in low grasses, examples of this is where you can see the vegetation is particularly thin, say on a hillside, these are areas of interest as it can often mean a reef structure very close to the surface.

"Deep ground" best describes areas that have a heavy surface soil, deep and loamy, often areas washing down towards a creek will have deep pockets of overburden, also the vegetation will be larger, bigger trees need deep ground for their roots, you will often see lines of trees following a creek line, creek lines are forms of faults so the ground has opened up enough through the bedrock to allow the roots to get deep enough and support the trees.


Selecting your coil correctly can make the difference between getting gold or not getting gold, so your first observation would be to assess the ground that you want to detect, some areas can have both shallow and deep ground in close proximity, this is why it important to carry a selection of coils with you, a quick walk around before firing up your machine is the way to do that.

Small coils are usually used for small shallow gold pieces, shallow being down to about 10 inches or so, most of the small pieces found would problably fall into this sort of depth catagory when you are working shallow ground, small pieces can also be at considerable depth as well of course but you wont be able to detect those with your small or large coil unless the surface overburden is removed by a machine for instance.

A small coils will give a far sharper response to a small piece of gold than a big coil, also it will be more sensitive to specimen type gold nuggets as well, the advantages to a small coil are that you can get a small coil closer to the ground surface so as to get better ground penetration, in areas that are covered in rubble or where you need to get in between the clumps of vegetation say like in spinifex country, also they are better for doing an initial search of tailings from workings or old scrapings, and for working creeks looking for small pieces trapped in crevices.

The downside of a small coil is that you dont get good ground coverage on open ground, it will have a limited depth capability, and because its easier to swing and use, you can easily fall into the trap of keeping it on your machine even when the ground gets deep and you need to get a bigger coil on.

Large coils are used for the main purposes of ground coverage and depth, by large I am talking about any coil over say 14", the only advantage a large coil will give you on shallow ground is ground coverage, if the gold is small and shallow you may find some of it but you will definately miss a lot more, if you are seeking large gold at depth then you should be working deep ground with large coils, while a small coil can and will detect a large deep piece under some circumstances you really have to be lucky to have placed the coil right on top of the target to have heard it, with a large coil even if you sweep reasonably close to it you will get some kind of response.

The downside of using a large coil is you wont get as much sensitivity to small pieces unless they are relatively close to the surface, using it on shallow ground looking for small pieces will be less rewarding than using your small coil and also more tiring, but for deep ground and say patch hunting where you will be covering all types of ground a big coil the way to go.

For the most part meduim sized coils are more productive if you are working about all different sorts of areas, coils in the 11" to 14" range, either round or eliptical depending on your preference, seem to be the best sizes for a general purpose coil, small enough to give a reasonable response to small shallow bits but at the same time capable of reasonable ground coverage, and producing a pull you up signal on a deep piece as well if you happen to pass over it.

Its all about understanding the ground type and then selecting the right tool for the job.

cheers

stayyerAU






Last edited by stayyerAU on Fri Dec 09, 2011 7:48 am; edited 1 time in total (Reason for editing : spelling correction)

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Post  Wombat on Fri Dec 09, 2011 8:05 am

StayyerAU you explained that very well mate as I'm about to work an area that will have all those conditions of ground cover you mentioned. I'm planning to use a Nugget Finder 14"x 9" Mono eliptical (Gray spider) on the 5000. This area I have never worked before.

Wombat


Last edited by Wombat on Fri Dec 09, 2011 1:03 pm; edited 1 time in total

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Post  Guest on Fri Dec 09, 2011 10:59 am

Wombat wrote:StayyerAU you explained that very well mate as I'm about to work an area that will have all those conditions of ground cover you mentioned. I'm planning to use a Nugget Finder 14"x 9" eliptical (Gray spider) on the 5000. This area I have never worked before.

Wombat


Gday Wombat

The Nuggetfinder 14x9 advantage coil was very well suited to the 4500 so I would assume that it would work just as well on the 5000, its a very sensitive coil and excellent for small bits, and also very good for finding specimen nuggets, and a good shape for poking about under bushes, I have seen some nice pieces found at depth with one as well, if its a new area to you spend a bit of the time getting in close around the bases of trees and under shrubs, they are usually the most neglected spots in any area, and usually the most productive spots in worked areas.

cheers

stayyerAU


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Post  Guest on Fri Dec 09, 2011 12:04 pm

I wonder what others have found with using their beloved smaller non Minelab coils Monos from their 4000 and 4500 on their new 5000.
My personal experience is that what worked well on those previous Minelabs are perhaps too sensitive on the already sensitive 5000...I have found more interference/noisy signals/instability in noisy ground using my Coiltec Mono 14 x 9 and my 16" round Mono than using my Commander 11" standard Mono and the larger 15 x 12" on my 5000. Last weekend my detecting mate tried using his trusty NF 10 x 7 <or thereabouts> on his new 5000 and he was also disappointed to find he could not get it stable <in Tarnagulla>. Previously his NF coil on his 4500 were unbeatable combinations both in the Triangle and in W.A...and he found much gold....
I really do subscribe to the theory that when it comes to the 5000 with smaller coils you cant beat the Minelab Commanders on the 5000. I dont even get the other non Minelab out now..just the Mono Commanders 8" round,11" round and the 15 x 12" elliptical <even though its a heavy brute in relation to its size>
What are other 5000 users finding....?..I guess to each his own,but none of us wants to minimise our chances of hearing weak signals with any instability..the 11" Mono is like shatting in bed..nothing else compares IMO...Hoo Roo

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Post  Beer Beeper on Fri Dec 09, 2011 1:32 pm

For a go-to all-around general purpose medium sized coil and you want a bit more depth than the 11 round & 9x14 sizes, then instead use the Commander 12x15 mono--NF 11x17(both equivalent to about a 13 round ) & 14 round, CT 12x18(equivalent to about a 14 round and I hope this will be the next Blitz one).

Going to the 16 round and 12x24(equivalent to about a 16 round) sizes are pushing it to lose some sensitivity on about (minus)-.5 gram bits, but some more depth on larger nuggets. Also JP uses the 18 round and seems to get some very small gold with it by driving it right.


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Post  Rob.B on Sat Dec 10, 2011 2:22 pm

Thanks Stayer,,,, I usually stuff the 10" into the back pack.....Good explination of ground.

Thank you
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Post  jibhorsegully on Mon Apr 29, 2013 11:46 am

The best coil for this situation in my experience is the 14 in coiltek dd or mono.This coil will give you good ground coverage and pings the smaller stuff and the larger bits in shallow to mid depth.It is a consistently quiet coil and an excellent inbetween size coil.
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