My Cibola Disc Testing

[Obsessive]

Some days I think Ive got this thing figured out, some days I don't....

I purchased my Cibola new just a few months ago and, while Ive done several air tests, I'd like to think that each time they become more in depth.

Its not uncommon for me to find screw caps at 6" or 8"'s down. But I do find it interesting that often I'll hit a layer at a similar depth across an area that will consistently give up coins (and trash) from (seemingly) the same decade... all 70's, all 80's, all 90's, etc. Maybe I'm over thinking this, but I swear I'm starting to see a pattern in the layers of earth I'm digging through and think this is telling me about the rejuvenation history of that particular lot. Meanwhile, I hope I'm getting better at this; I keep thumbing that disc knob and making better guesses at whats going to come out of the ground.

The other day I was hanging out with a friend who has a larger selection of old and new gold jewelry than I have available, so I decided to chart my air test results and thought I'd share.

All items were tested with the sensitivity at around 7 and the threshold at about 1 o'clock (a good audible hum while holding the AM button). The only knob changed was the disc setting.

I also experimented with the coins on edge and flat, but those results are not included here. I will say though that I was surprised when the Kennedy Half Dollar while on edge did not register consistently across the coil, if at all. I will likely do more in-depth testing with this on edge vs flat variable in the future.

On this chart green is a good solid signal. Orange is where things break up. Red is no tone.

I'm a bit disconcerted that the lower conductive targets phased out in the Iron zone or below, particularly since most of the areas Ive been hunting are very trashy due to years of fill over fill.

Does changing coils in anyway affect the discrimination capabilities? I'm guessing not, but thought Id ask.

Anyway, here it is... Your feedback is welcome and please let me know if you have any suggestions as to how I may improve on this testing.

 

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[Terry Soloman]

Nice chart. You are putting more hours in on the headphones, digging hundreds of targets. You are beginning to speak the Cibola's language. Now it's time to get the 11" x 8" widescan coil, and see what you've been missing. It will have to be tuned to your machine at the factory, so give Rusty a call!

 

[digger27]

I'm a bit disconcerted that the lower conductive targets phased out in the Iron zone or below, particularly since most of the areas Ive been hunting are very trashy due to years of fill over fill.

Does changing coils in anyway affect the discrimination capabilities? I'm guessing not, but thought Id ask.

Everything looks completely normal to me, the reason why you are concerned about the lower gold conductors coming in low is because you have a lack of knowledge about physics and how things actually work in this world and how it affects our tools...and us and our perceptions.

Gold can come in anywhere from iron up into low zinc on big class rings and even higher if the piece is large or very high karat gold.
$20 gold coins for instance.

In the ground many things can affect the signals we get on targets like gold rings including soil types, position in the ground, other metals in the vicinity and more.
On top of that there is something else that is happening in regards to a few specific types of targets and I am referring to most chains of all kinds mangled jewelry and especially open or broken rings.
There is something called Eddy currents you should be aware of, the actual definition is...

"Eddy currents (also called Foucault currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor, due to Faraday's law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field."

What this means is when we scan a chain, an open ring or an odd shaped piece of jewelry the return signals we get are not going to be the same on a different shaped target like coins...it is going to be different, lower and also the depth we can pick them up is also going to be affected.
This is not just on gold either, this will be on all metals including silver.
Many new hunters assume all silver objects will come in high like coins and are surprised when some don't.
Several years ago I asked about this and why chains came in so low and an engineer on another forum gave me this answer...

"It's the physics. The magnetic field generated by the Eddy currents induced by the transmit coil on the targets are very small in the case of a chain. Basically, because of the contact resistance between each link is relatively high, the Eddy currents are each confined to a single link in the chain. So, each small link in effect becomes a target. Because each link is small, it can't generate a large field for the receive coil to detect. Also, the links are pointing in somewhat different directions, so their individual magnetic fields don't readily add up to a larger field which would make for easier detection.
For the above reasons, chains are hard to detect. What usually "give them away" is an attached medal, or a sturdily built clasp."

When it comes to broken rings the same thing happens...signals will be lower and in unsuspected areas and maybe at less depths than the same target would be if complete.
This is not exactly correct but it helps when I think of it this way...targets that are broken and open the loop is energized but the return signals to are coil are not the same as if the loop was closed...it is missing some of that signal because it "leaked out" and so comes in lower and sometimes a bit less solid and more choppy.

Once I learned this I went on to find a lot more chains and odd signal jewelry in my career because I now knew that these type of targets are out there and I should be aware, assume nothing, plus a few more targets I found over the years helped drive home this point.

I have yet to find a silver chain much higher than nickel except this one, most come in at foil and even the thickest silver chain I ever found which was a men's Figaro bracelet came in as a dead on zinc cent signal.
Luckily I was digging all zincs at the time and you should have seen how shocked I was when this thick shiny thing was in the hole instead of the zinc cent I was expecting to find.




This is another bracelet, a solid silver band with a heart.
In the ground when I got the signal it was open and came in as another zincoln signal, out of the ground after I closed it and retested it changed into a high quarter signal instead.




Here is one of my favorite ring finds ever, a small but very thick silver Harley Davidson silver ring.
In the ground it was bent in the middle into a figure 8 shape and had to be sitting in the dirt with the edge up, essentially it was seen by my detector as two large links in a small piece of broken chain and acted like another zincoln...and a bit bouncy one at that.
After straightening it out I tested it again and now it returned to a more normal signal between a dime and a quarter from all angles.




Your detector and test results are completely normal and will act like this no matter what kind, size or type coil you have mounted...it is doing exactly what it is supposed to be doing and behaving in ways that are governed by the one thing we can't change in this world, the laws of physics.
Basically you just have to be aware of the physics in all this and understand how things actually work in our hobby and once you do you maybe you will dig a few of the more odd signals you come across out there...and hopefully have some very pleasant surprises as I have had out in the field if you do.

Here is an excellent vid that illustrates that point about open and broken rings.

 

[Vern2]

Digger, that was verrrry interesting.

 

[digger27]

Digger, that was verrrry interesting.

Just putting some helpful information out there.
Since I asked that question about chains I went on to find all of these that are silver plus many more silver chains, junk chains and several broken rings.
The thick rope chain on top of the pic is almost an ounce of silver, was mostly balled up and still only came in as a nickel.
In this hobby, as with most things in life, the more you know....

 

[eyemustdigtreasure]

Nice chart! I'll try it with my trusty Cibola some time.
Anyway, sounds like you are on the right track, but continue to test and dig,,,,
but HEAR what you are digging, too....
Example: staainless steel scraps sound sharp, snappy/LOUD...! Not frendly at all...!
Lead and gold, even brass sounds sweeter, SOFTER....real FRIENDLY...~!
Even silver sounds great! Even larger coins.
So, always, compare what you hear, to what the discrim dial tells you.
Tip: After locating your target, with your Tesoro, press and hold the pinpoint/all-metal Button down, as you lower the coil from coil-height, towards your target,
The sound will get louder and louder, until it shrieks...! That distance remaining, is the DEPTH to your target.
I hope I helped, but maybe didn't ....

 

[nagant]

great thread, I'm so rusty at detecting. Good days and bad, just need more swing time.