Post By U.K. Brian
Post By Gary Drayton
May 28, 2012, 11:33 PM
Is a larger coil always deeper on a VLF?
I know this probably cannot be answered in absolute terms and will depend a lot on target size. Let us just say we have two Excals. One is fitted with a 10 inch coil and the other is fitted with a WOT. We are trying to detect a nickle. A plain old nickle. Will the WOT always be deeper on a target this size? Or will beach mineralization sometimes create enough background "noise" so to speak, that the smaller coil will actually be able to penetrate deeper?
And how about a target the size of a half-reale? Will the small size of a coin of this type make using a smaller coil preferrable? What about the effect of mineralization on this size target?
I am wondering about this issue both in wet sand and in shallow water.
How about my next trip to the Treasure Coast? Would I be ahead using an Excal with a WOT or one fitted with a 10?
May 28, 2012 11:33 PM
May 29, 2012, 01:23 AM
It can be answered for any detector if you know the detector and the coil being used. Whatever the detector type (VLF/BBS/FBS/Pulse etc) there's a certain ability to ignore ground minerals. For best performance on standard coin/ring sized items you have to be able to balance out the ground (and remember the G.B. control doesn't do away with ground affect it just makes it easier to hear the target but the effect is still cutting performance).
Some detectors even when correctly ground balanced still can't cope with the degree of negative soil mineralisation or positive wet sand so the only choice is to drop coil size or change from concentric to DD so that the amount of active coil area is reduced so there's less ground effect as you have pointed out.
Then throw in a pince of good coil design as some coils can be more effective than others even though they are of the same size.
Finally add target masking for high rubbish areas where small coils and detectors with faster recovery speeds cope far better.
Unfortunately though we know the WOT coil loses less sensitivity than older large coil designs there's no way anyone can know the rubbish contamination or mineralisation state of the area you will be working so you have to be prepared to use a range of coil sizes. Not to easy with the Excaliber or any of the other hardwired detectors unless you modify them. For in the water I would go for the 10" for ease of use as much as anything. Out of the water I always say save some money and get a Sovereign or non waterproof CZ and gain the advantage of being able to suit coil to site. Money saved can go towards a second or third coil and there's further savings to be had in the future when repair or tune up is needed which is going to be far cheaper with a standard type detector.
I've a good range of hammered silver/copper/bronze coins from the Treasure Coast and I doubt if I detect there for more than a few weeks every ten years. Unfortunately many are as daft as brushes when it comes to finds. Only last month one of the people from this forum said he didn't want small gold finds from the beach. But if he can't find small, which could have a very large diamond in it, then he's not going to be finding the collectable stuff thats also valuable and much more interesting.
May 29, 2012, 06:25 AM
Having done many test with nickels on my local beaches with various machines and different coil sizes, including the WOT, I can tell you the answer is "no", the larger coil is not "always" deeper. And as already pointed out, sensitivity to smaller targets is sacrificed. On the other hand, day in and day out on the beaches I "jewelry" hunt, which are largely blue collar beaches, the WOT greatly outperforms the smaller coils on the ring sized targets I'm pursuing so it is my personal day to day coil of choice for these reasons. Obviously, the larger coil isn't always the best choice which is why I opt for connectors so I can maintain the ability to switch my coils out, which I do when I'm in some of the river areas I hunt searching for older relics and other items of interest.
"The key to finding gold is finding places where it can be accessed."
May 29, 2012, 06:36 AM
Yes Sov GT
One third jewelry of the World are under sand so far
May 29, 2012, 06:37 AM
Great advice Brian, I have found the odd trinket or two on the Treasure Coast and can also agree with Brian that you would be much better off buying a Sovereign GT or CTX3030 and be able to swap search coils at will. The beach or sand conditions dictate what size search coil is best and in my opinion depth is quite over rated on Florida beaches. The majority of small silver reales on Treasure Coast beaches and modern gold rings on Florida tourist beaches are no more than a few inches deep.
May 29, 2012, 06:58 AM
I believe the ability to adjust the sensitivity between the large and small coils also comes into play which was hit on. EMI, Minerals or trash may reduce depth on a much large coil and not affect one a bit smaller. Which basically increases its depth over the larger coil. It allows for a more effective foot print. Some people using the WOT on the Xcal say they can only run the sensitivity up to 4 or you over power the coil. Mine in the water on my local beaches can run 7 or 8 sensitivity with the 10 inch coil. Gary ive not been at this as long as you so i can only say the rings i find on the beach, like you said arent 15 inches deep..... or is the detector just loosing sensitivity to them? Also, how do you like FBS on the 3030 over the Sov?
May 29, 2012, 07:34 AM
I used the Whites DF for a couple of years and got rid of it because although I found many large platinum and gold bands with it, I saw a marked drop off in the ladies rings with stones which tend to be the expensive finds. The final year of my DF experiment I hardly used it at all because I went back to my Excalibur full time and immediately got my mojo back with the thin bands with stones and still got good depth out in the deeper water with the Excalibur. I find large and small rings both deep and shallow with the Excalibur. In my opinion a lot of wether a beach hunter finds deep and shallow targets has to do with their metal detecting technique especially sweep speed and search coil control. To answer your question on the CTX3030 I will continue to use my Excalibur, Sovereign GT and CTX3030, I look at owning the CTX3030 as having another great choice of machine for beach and water hunting with a great range of user and search coil options. You can do things with the Excalibur that you cannot do with the Sovereign GT, you can do things with the CTX3030 you cannot do with the Excalibur or Sovereign GT. Owning and using all three allows me to cover all likely beach and shallow water hunting scenarios.
Originally Posted by dewcon4414
May 29, 2012, 08:00 AM
Thanks for all the great information, guys. I hadn't really thought about the fact that the CTX was the only fully waterproof multi-frequency with interchangeable coils, at least to my knowledge. It just seems to me that this is ALMOST, lol, a good enough reason to spring for one. Trying to keep two older Excals waterproof and in the field has become a real headache.
Originally Posted by Gary Drayton
Last edited by hobbit; May 29, 2012 at 08:50 AM.
May 29, 2012, 10:21 AM
i get 2 inches better depth with my big coil in air tests so id think that would apply to the ground ...i dont use it though its super heavy and it kills my shoulder after 40 mins
May 29, 2012, 11:17 AM
*************** WHAT YOU DO WITH THE FINDS YOU DIG UP IS YOUR BUSINESS AND NO ONE ELSES, IGNORE ANYONE ON A SOAPBOX TRYING TO PREACH OTHERWISE! **************
I only hunt with the large coils at the beach, I use a WOT and the SEF 12x15" butterfly coils on my 2 excals and I use a WOT or the SEF 15x18" butterfly coil on my Sov GT.... Is a 15 inch DD coil deeper than the standard 10 inch dd or concentric, yes, would a 15in DD be deaper than a 15 inch concentric, no, but it would cover a lot more area since you lose coverage on the concentric coil as the signal goes down........Is a WOT or SEF 12x15" coil deeper than a 10" concentric yes, by a great deal......
As far as weight, I always use a harness when I beach hunt, I connect the bungie to my camelback that I wear for water, for me the harness is a no brainer, it supports most of the weight of the coil, I can let go of it while in the water if I need to and it hangs right by my side.... I can hunt for 8-12 hours with no problem if I use the harness....
People say the large coils are not as sensitive, I found a .06 of a gram 14 k gold ring every bit of 10-12 inches deep with the WOT coil.
Last edited by Treasure_Hunter; May 29, 2012 at 11:21 AM.
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May 29, 2012, 11:54 AM
I think Gary nailed it on the head when he made mention of user sweep speed & coil control. Larger coils are simply too difficult for a lot of hunters to master because every little flaw is magnified greatly, which tends to get too frustrating/irritating for most. This sweep speed/coil control obviously also has a great deal to do with how high a sensitivity setting the user is able to apply as well. Also, the mode of operation will also have an effect on depth. Personally, I use coil connectors so I can switch coils out pretty quickly if needed/required and I have never had an issue with them leaking, etc., (yet!) however, they do require constant maintenance and care in order to maintain any level of trust in them.
"The key to finding gold is finding places where it can be accessed."
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