Coils and questions about depth

kentuckycornelius

Jr. Member
May 14, 2021
20
36
Detector(s) used
Minelab Equinox 800
Primary Interest:
Metal Detecting
I have a question about coils and the 'nox 800. I've seen a couple of YouTube channels proclaim that a 6 inch coil can go as deep as the stock coil, especially in trashy conditions or mineralized soil. Their statements go something to the effect that: 1. The VLF waves sent out by the main processor go as deep no matter what size coil you have on, 2. too much masking occurs in the trashy soil, and 3. the processor gets overwhelmed in the mineralized soil. Since the smaller coil has a smaller diameter field, you can avoid a lot of the trash effect, and also since it has a smaller field, the amount of information the processor has to handle in mineralized soil is more manageable.
I have 3 different size coils and I tend to agree with the trash statement to a degree. I have went over an area previously hunted with a 14x9 coil and found a number of wheats and Indian Head pennies. However, I haven't found any higher conductive silver coins. It's my opinion that the larger coils find the higher conductive items even in trashy soil, but since pennies ring up lower they can be masked easier. I'm not sure about the mineralization part though. My ground balancing rarely goes above 50 so I don't think I've had soil that is mineralized enough to test this theory.
In my test garden I can find all the coins buried with any one of my coils, 6 inch coil included. I've got pre- and post-82 pennies, nickels, dimes, and quarters buried flat and at angles about 7-9 inches deep. None of the coins, buttons, small buckles, etc. has been deeper than 10 - 12 inches deep "in the wild", I have found bottle caps at least a foot down (on a beach, dry sand, ground balanced about 0) and whole pop cans at least a foot down at some parks (large size and high conductivity makes them stand out at a greater depth).
So what are your thoughts and experiences? Do your large coils pick up the high conductors even in trashy conditions? What about the theory of the processor in the Noxs getting "overwhelmed" and missing targets? Is the statement about VLF waves correct? Does each coil send them as deep? I don't have enough physics or math to know the answer about wave behavior and transmitters other than the low frequencies tend not to get dispersed as easily and as such can find deeper targets.
 

cudamark

Gold Member
Mar 16, 2011
11,639
10,593
San Diego
🏆 Honorable Mentions:
3
Detector(s) used
Equinox 800, Fisher Impulse AQ, E-Trac, 3 Excal 1000's, White's GM3 V-sat. White's TM808, VibraProbe, 15" NEL Attack, 5X10 Joey, Steath 920ix and 720i, TRX, etc....
Primary Interest:
All Treasure Hunting
With just my layman's viewpoint....I find the bigger the coil, the deeper target I can find. With the Nox coils, I don't find masking as big of an problem as I've had with other detectors. I think some of it is the faster processor and the ability to adjust that speed. I tend to run the speed up and swing slower in trashy areas and can still find high conductors in the trash. It's kind of a balancing act playing recovery speed against swing speed depending on the degree of trash and the depth of the good targets. I rarely use the 6" coil. I mostly use it in the absolutely trashiest areas, like around a picnic table, fire ring, etc. I also like it when I need to get right next to playground equipment and fence posts.
 

Bart@Big Boys Hobbies

Supporting Vendor
Supporting Vendor
Jul 24, 2005
4,144
906
Moore Oklahoma
Detector(s) used
Call for your Treasurenet special discount! Be sure to mention Tnet when you call!
Primary Interest:
Metal Detecting
With just my layman's viewpoint....I find the bigger the coil, the deeper target I can find. With the Nox coils, I don't find masking as big of an problem as I've had with other detectors. I think some of it is the faster processor and the ability to adjust that speed. I tend to run the speed up and swing slower in trashy areas and can still find high conductors in the trash. It's kind of a balancing act playing recovery speed against swing speed depending on the degree of trash and the depth of the good targets. I rarely use the 6" coil. I mostly use it in the absolutely trashiest areas, like around a picnic table, fire ring, etc. I also like it when I need to get right next to playground equipment and fence posts.
Great post. I try to run my recovery speed on the slower side. Turning it up you lose a bit of depth and good targets don't hit quite as hard.
 

CPT_GhostLight

Greenie
Jul 21, 2021
12
22
Colorado
Detector(s) used
Minelab Equinox 800, Vanquish 540, & ProFind 35, Whites Prizm 6T, Fisher Gold Bug 2 & F-Pulse
Primary Interest:
All Treasure Hunting
In the simplest terms, detector depth capability is directly related to the conditions of the medium it is trying to penetrate. This is why "air tests" show much deeper capabilities than soil. With only air between the coil and a target, there is nothing to affect the transmitted and received signals. It's way different when there is soil or sand between the coil and target.

Blanket statements like "VLF waves sent out by the main processor go as deep no matter what size coil" are not correct. With DD coils, the center strip of the coil where the two loops overlap is where the strongest field is created. The larger the DD coil, the larger the loop overlap, and the stronger the created field, so the deeper the penetration. However when dealing with soil any metals, salts, chemicals, trash, and humidity levels will affect the VLF waves emitted by the coil. So the more impurities and pollutants in the soil, the less depth you will be able to detect. Electromagnetic interference (EMI) will also impede depth. Anything that can block, scatter, or affect VLF waves in any way will reduce depth.

So yes the statement "masking occurs in the trashy soil" is basically correct because masking is caused by anything that distorts or blocks the signal return of a good target.

The statement "the processor gets overwhelmed in the mineralized soil" is basically inaccurate. Mineralization is just naturally occuring metallic oxides, like iron particles, that also affect VLF waves the same way other pollutants do. The processor is amazingly fast and capable, but you can overload the input using too much sensitivity in noisy ground.

The great thing about the Equinox is the Sensitivity, Noise Cancel, Iron Bias, and Revocery Speed were all developed to deal with these kinds of things. It sounds like you understand alot of the concepts of the Nox, but it might be a good idea to read through the manual a few times. There is some great information in there and also in books by Andy Sabisch and Clive james Clynick which will help immensely too. Youtube videos are great, but the thing to remember is everybody has different ground and ground conditions where they are, so what works for one place is not necessarily good for another place.

But even though the larger Equinox coils will detect deeper than the smaller ones, the difference is really only an inch or two between them. Depending on soil conditions, the 15" coil will go about 1-2" deeper than the 11", the 11" and the 10x5" get almost the same depth, and the 6" goes about 1 inch shallower than the 11". But again, this all depends on soils conditions and detector settings.
 

cudamark

Gold Member
Mar 16, 2011
11,639
10,593
San Diego
🏆 Honorable Mentions:
3
Detector(s) used
Equinox 800, Fisher Impulse AQ, E-Trac, 3 Excal 1000's, White's GM3 V-sat. White's TM808, VibraProbe, 15" NEL Attack, 5X10 Joey, Steath 920ix and 720i, TRX, etc....
Primary Interest:
All Treasure Hunting
In my experience with Minelab detectors, Most of them do not air test well. With the Sov, Explorer, Etrac, CTX, and to a lesser extent the Equinox, I get better depth in a ground test than an air test....for whatever reason. As for the depth of the different coils, I find a much greater range of depth between the 6", 11", and the 12X15" than you have, but, as mentioned, we may have totally different ground/hunting conditions. There can be as much as 10" of difference between my 6" and the 15" coil in most of my sites.
 

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