Change Of Coils Changes Bottle Cap Tone Break

[kac]

I have 2 coils on my Tejon. 8x9 conentric I use in high trash areas and parks (same thing) and a 10x12 i use for woods and fields.

I got lazy and left the widescan on and hit a local park and came across bottle cap after bottle cap and could not find a good tone break to cut them out without losing too much range.

I saved a couple and tucked them in my back yard 6" down and did a quick test. I set my 2nd discrim for break on the widescan and the primary for the concentric  and there is a huge jump between them.  Both discrim match up on other items such as coins and rings, pull tabs.

Note that both coils actually ground balance the same and the widescan can pick up the tiniest pieces of lead and foil. I have found lead pellets from a pellet gun 4-6" down with it. I can also place a cast iron hammer head half over a dime and still hear just the dime though broken signal It's there. So I am really stumped on the bottle caps. Maybe someone here knows why.

[kac]

Has anyone been able to figure out why my concentric coil can snub out a steel cap so low which is perfect in trashy parks yet on the DD on both the same machine or my ATP they tone break is so much higher? Is it a DD quirk?

I noticed that DD's struggle much more with iron around an object especially if it is parallel to the target ie dime and nail with Tx and Rx cross over lined up.

[Goldpick]

I did read a while back on a comment from Tom on Dankowski about how the electromagnetic field on a concentric is much broader and less focused than that experienced on a more focused/narrow field on a DD coil.  That might possibly go some way to highlighting to iron caps and pushing the TID value higher on a DD whereas the concentric may be less prone to doing so.  Just an observation on my part, not sure whether it is entirely correct.

[Noah (FL)]

Tesoro discrimination just works best with a concentric coil. Not sure why that is but it just is. I always struggle with steel bottle caps when I use my cleansweep.  Usually to get them to discriminate out witha DD coil you will be well into foil zone and will be passing little gold jewelry.  For trashy park hunting it’s just a trade off of wanting extra coverage vs not digging caps??????

[kac]

As you see I have disc one that trims out bottle caps at the foil line with the concentric. Disc 2 is where the same cap trims out with the dd coil. I don't know if a dd has narrower magnetic field than my concentric as the concentric on the 8x9 Tesoro is really small when compared to a Whites or Garretts. Scan field is similar to the width of the ATP being 8 1/2" wide dd and depth are pretty similar between the 2 machines.

Interesting the clean sweep has similar break as other dd's

Other iron break same spot between machines and coils as well as other metals.

Anyone have a concentric of any size and can say where bottle caps trim out? Curious on other machines and concentric sizes.

As far as trashy areas I do swap back to that concentric and it has plenty of depth for a park. I will give give up the coverage when hitting fields of caps as that concentric I can literally pick out a dime completely surrounded by old iron nails and not hear the iron. Something I found DD's will struggle with as they depend on the angle you approach the targets.

[EL NINO77]

I will make a similar comparison between the Tesoro Mojave detector on a 7 "" Precizion "concentric coil and a 6X8" DD SEF coil. "

[Steve Herschbach]

On 10/28/2019 at 11:38 AM, kac said:

Has anyone been able to figure out why my concentric coil can snub out a steel cap so low which is perfect in trashy parks yet on the DD on both the same machine or my ATP they tone break is so much higher? Is it a DD quirk?

It’s a very well known difference in concentric versus DD which is why old timers seek out machines that can employ concentric coils.

Coil Basics by Carl Moreland

About Search Coils by Dave Johnson

Search Coil Field Shape by Dave Johnson

From the second article above “The advantages of the DD are greater depth in mineralized soil, a broad sweep pattern, and narrower target response.  Its primary disadvantages from a user's point of view are multiple responses on shallow targets and poor discrimination of flat iron objects.” Emphasis added.

[kac]

Nice read, so I'm not crazy! Might explain why I and another guy with a Whites with a concentric are doing really well in some trashy areas and others are struggling. I never realized this issue until I got the 10x12 dd on my Tejon and ran into trash in an area I could skip through silently and pick out the good stuff.

Thanks

[Magic12]

Kac

 

am Experiencing the Same

Thing with a Vista X

To discriminate Bottlecaps

i have to go as high as 90% of discrimination 

so high that even a us quarter gets discriminated

 

Unfortunately there is no Concentric coil

am sure ill do much better 

 

 

My Question is 

is the concentric coil also better to discriminate 

big alumimun and pull tabs 

does the concentric pushes the pull tab more to the bottom 

or it just affects the iron