Author Topic: Big Coil talk  (Read 934 times)

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Peter

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Big Coil talk
« on: May 04, 2017, 09:24 am »
I thought it might be a change if I mentioned  briefly  about Big coils , rather than a specific make coil , for those new to the hobby or those who might not have delved into what a coils shape and size actually does when its used instead of the stock coil and are considering getting ,that game changing "Big coil"  it might be helpful to consider what exactly their about to get if they`ve decided its gonna be a  " Big One." .

There are many different sizes of coils available and each one may fine tune your hunting ,but only if you get the correct size. Larger coils can go deeper than smaller coils but only on larger targets. When using a large coil, its possible you may lose sensitivity to small targets. A large coil is also more susceptible to masking. Masking happens in the discriminate mode when a good target and junk target are both under the coil at the same time. If the targets are close enough together, the bad target will be discriminated out, and at the same time, the detector will not be able to pick up the good target. Masking is very common in junky park land or kids playgrounds and around houses.
Smaller coils will concentrate the signal and make the detector more sensitive to the little targets. Unfortunately, smaller coils tend to lose depth when compared to the larger  ones. Being that these coils don‘t have as wide a search pattern, they are also less likely to mask targets in trashy hunting situations.
Knowing where you are going to search and what you are hunting for goes a long way in choosing the right coil for the job. A larger coil is used to hunt in a clean area and/or for targets that may tend to be deeper. A small coil will help to find the smaller targets such as small thin hammered coins or fine jewelry. Small coils can also be used to hunt for coins & jewelry in extremely trashy sites.
The length and width of the coil affects different aspects of its performance. The length of the coil (toe-to-heel) affects your coverage area, while the width (side-to-side) affects the depth.
 With large coils,often people over estimate the coils ability  they put on, thinking "if I put this much bigger coil on ,I`m going to go a foot deeper".
 Ah yes! if only !! 
I`ve put bigger coils on various detectors in the past and been very disappointed in the results  . Of course there will always be those among`st us who will love to say different and tell you outrageous stories how they put their 15" coil on ,and were pulling the hammered out by the hand full since applying the large coil. Well, that often helps convince themselves ,as well as others that it it must be possible ,but in reality it never seems to happen quite as definite as that. The conditions have to be right before a Large coil can achieve its potential goal.
  So,choosing the right coil and choosing it for the right reasons is a VERY important job. Its no use buying a "certain" coil just because Joe Bloggs 250 miles away bought one and loves it. His ground might be much different to your Ground and what suites him might be a nightmare to you to use.
So before buying a bigger coil  , make sure your buying it for the right reason especially if your ground is highly mineralised or full of junky targets ,a much bigger coil will be a liability and NOT an asset,because the amount of detected mineralization with a large coil has negative effect on detector's performance: the larger the coil, the more mineralization it "catches " and  this disables a metal detector in terms of deep ground penetration.
 Another thing people don`t take into consideration especially the "older" detectorists often ,is the bigger the coil the more often the heavier it goes. AND this often ofsets the balance when swinging the coil.  You might think on first swinging a detector with a large coil it hasn`t made that much difference, but its not the first 20 minutes that it becomes apparent, its AFTER that it starts to take effect. You soon find your arm begins to ache or get uncomfortable as your swinging and this is because of the out of balance effect of the larger and heavier coil kicking in.
 Well after these few points its not all bad. There are without doubt pluses for adding that bigger coil as long as you`ve got the right one for the job. 
As I said before don`t expect by fitting that bigger coil to be having to go out and but a bigger spade. Very often ,In REALITY  you might get a couple of inches more for your outlay ,and of course on the positive side , that couple of inches can mean the difference between detecting ,or not detecting that coin,but it has to be mentioned ,don`t expect too much  more in regards to the depth , because you inevitably will be disappointed at how much you lashed out for the privilege of using that new big coil only to find it never lived up to what others told you you were going to get and what you actually got ,after all it wasn`t their money that bought it was it,and the last thing thats never wanted to be thought about is how much that BIG coil actually cost and what you got in return for your outlay.?.

Keith67

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Re: Big Coil talk
« Reply #1 on: May 04, 2017, 11:03 am »
Wise words Peter.  It's amazing how many people tell newbie Ace 250 owners to buy a Nel Tornado but nobody asks the person where they search !  I like the Nel on my 400i and it has it's place, but there are times and places where it really struggles and the stock coil is a far better choice.  A nice article mate, and full of good information.
Flirt with the dirt, beep, dig, dance....

GP27

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Re: Big Coil talk
« Reply #2 on: May 04, 2017, 06:08 pm »
Thanks Peter, a very informative read didn't realise it was the coil width that done the depth, cheers mate

needlegun

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Re: Big Coil talk
« Reply #3 on: May 05, 2017, 04:17 am »
Width over lenght .
Now where have i heard that before?