On my mind -- Random Thoughts

Regardless of Mfr...... I keep running into a laws-of-physics commonality (and a marketing mindset)..... whereby....... any VLF coil that is larger than....say.... about 11"............. just simply does not produce more depth on coin-sized targets. Anything larger than 11" or 12"........ and the performance bell-curve....... especially in regards to depth........ swings over to the other side. I know I have brought this up multiple times in the past decade; yet, the occurrence continues to repeat.......and at a higher rate. Even Pimento has alluded to this. The 'wishful thinking' mindset is circumvented with a reality-check....... every time.

However; I do applaud the Mfr's for 'trying' to ascertain greater depths.

So it seems Minelab is peddling the 11" stock coils for a " good reason".

And on their older models they were 10.5" coils.


Sounds like these bigger coils are an aftermarketer's " target area" for sales/ profit.

I've never liked bigger coils. Now I know why.

Good info Tom, as always......

I like the 13-15 range for Big brass though!!

13 is about right for baseball size stuff..

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

NASA-Tom --

Interesting post; funny, I just alluded to this observation of yours, in the FGP thread, where I noted your finding that the larger FGP coil did not achieve greater depth "in the dirt."

You DID say in your FGP write-up that the larger coil DID achieve more "depth," in air testing, but that additional depth was not ascertained in the real world (in the dirt). I conclude that the issue is one where the "volume of mineralized dirt being seen" by the larger coils becomes so great, that it offsets any possible depth performance gains, such that 11" is roughly the sweet spot (at least, for smaller "coin-sized" targets)? Would this be a correct conclusion, as to the "why" of this?

I have a 13" Ultimate coil for my Explorer, and I LOVE that coil. What I will say, though, is that what I feel it really does well, is that it seems to make moderate depth targets report more strongly/confidently. Thus, it's easier to pick out the 7" and 8" coins, as they report more "solidly." In addition, it's a very light coil for its size, and seems to be a very "tight" coil from the perspective that it separates quite well for its size. However, I will say that while that I do get some "psychological gain" using the coil, since it does such a good a job with the moderate depth targets, I CANNOT say that I've dug a coin any deeper than the deepest ones I've dug with the 11" stock coil. Same depth? Yes. Deeper? No. The limit seems to be just shy of 10" on a dime, in my dirt, with EITHER coil.

Steve



Edited 1 time(s). Last edit at 12/30/2015 03:53AM by steveg.

Steve,

Your assumption about 'mineralization' limiting the overall depth performance is correct. This is a large contributor for the: "Large Coil Syndrome".

And....... yes. There certainly is (a large portion of) 'perceived' depth gain when you have a large coil installed......whereby, the 'within-detectable-range' targets will sound louder/easier/more-intelligible. But.............. this is also to say: "Why" it is so important to increase depth of any unit....... even by simply/only a few tenths of an inch on a coin. For example: Let's say that I have a detector sent to me for calibration. Before calibration,.,.,.,, the unit achieves 11.7" of depth (in real-world dirt) on a clad dime. In my calibration process...... I manage to push the unit 0.3" deeper on a clad dime (in real dirt). Three-tenths of an inch does not sound like much............ hardly even worth the effort. But...................now....................... when hunting in the real world.....in real conditions.......... you find a coin at 10" or 11" depth. It will (now) sound much louder, more positive/certain, more repeatable, audibly report with forceful authority; subsequently making it substantially more likely to be found/dug. This is also to say...... the fringe-depth targets will now report with substantially better resolution. The deeper targets will now be easier cherry-pickers/piece-of-cake targets.

earthmansurfer alludes to exactly this phenomenon. His first detector was real-world capable of detecting coins to 8". Second detector was capable of detecting coins to 9". Third detector capabilities is 10". With just slightly more depth capabilities with each subsequent new unit............. a whole new world opens up. Not only does greater depths open up a whole new uncharted world............... it also exposes older/more valuable finds. This makes for a doubly positive outcome/resultant.

What if a 8" coil views about 1 gallon of dirt. And a 15" coil views about 30 gallons of dirt. Do we (probably unsuspectingly) have a 30-times greater chance of having tiny rust flakes..... small bird shot...... tiny pieces of hot-rocks....... etc.............................. to inhibit the detection of a intended target? Then what if we introduce mineralization.

Summation: A large coil 'can' add more depth.... but only up to a certain (physics limited) size coil.

NASA-Tom,

Thanks for the follow-up post. Confirms some of what I thought about the "why" part of the "large coil syndrome," and also confirms what I've noticed with the 13" coil in terms of clearer, more confident reporting of targets that are within detectable range.

Good stuff, thank you sir!

Steve

I use 15" a NEL Attack coil on my G2 for relic hunting. It's the best setup that I've ever used. Very deep can hunt in iron great ground coverage to boot. I have a cz3d 1021 that's deep but certain size nails confuse it but deep. I love it & will never get rid of it. It's just the new FT higher frequency machines with a large after market coil kicks but where I hunt.

Digger70pa Wrote:
-------------------------------------------------------
> I use 15" a NEL Attack coil on my G2 for relic
> hunting. It's the best setup that I've ever used.
> Very deep can hunt in iron great ground coverage
> to boot. I have a cz3d 1021 that's deep but
> certain size nails confuse it but deep. I love it
> & will never get rid of it. It's just the new FT
> higher frequency machines with a large after
> market coil kicks but where I hunt.


How does this setup do on coins? I think it's a given that most " relics" will be larger than coins...

I think another component is moisture. My G2 in wet soil performs better overall...the larger ultimate coil seems to hold the depth better in drier soil in late summer than the stock. In the wet soil I am more likely to leave the lighter stock coil on because I get clearer signals and can pinpoint easier on the deep targets

Doess a double D coil "see" the same amountont of dirt as a concentric, it seem like a DD would see less

DD coils do indeed see less soil; yet, at a higher 'focused energy' rate.

Due to the nature of my employment/work (exploration/discovery/invention)........... has prompted a thought:

I long for the day whereby detecting a 13" deep penny is merely 'childs-play' ........ (not even a challenge)....... due to evolution/revolution of technological advancements. It will happen someday. . . . . . and we will look back in history....and 'reminisce' about those days gone past..... when we were so restricted..... and could only see a small amount of "inches" in the ground.

Tom,
I think you're right. I probably won't be around to see the 13" penny detector, but the thought of having to dig that deep for one doesn't thrill me. I'd rather dream of taking one of our latest detectors back to about 1960. I used to slay the silver in CA, in the 70's with an old White's TR Goldmaster but the silver was only down about 3 to 4". Now everything has had another 45 years to sink deeper. Good thing about living in AZ, everything is pretty near the surface. Here, we only have to worry about 13" nuggets.

If................. in the mid-1970's................ your silver coins were 3" - 4" deep.,.,.,.,.,.,.,.,., wonder how deep they were in the mid-1980's. How about the mid-1990's!!!!

Most of the places I hunt........ I could easily dig large holes......... and pose no public eye-sore issues.

I have found the larger coils hit harder and deeper on coins on edge . Also remember when 6" on a penny in disc mode was exceptional so perhaps the easy 13" penny is not to far out/off.

At the right site those larger coils will outproduce the stock coils because of the much greater square footage covered in any given time frame .

I am now having thoughts of:

If more depth is to be ascertained in the detection of buried metals............... a "format" change is in need.

Tom, do you think we will get to the point where some type of in-ground imaging is possible in a conventional detector type chasis? Thinking about some of the ways Google can identify objects from images/shapes you could possibly have software that would report on coin shaped objects.

Tom,
The issue isn't depth of detection. Though that is what is stated all the time. You really want increased depth of ferrous/non-ferrous identification.

There are plenty of VLF units that go really deep. But the depth is obtain by an all metal mode that can't get a strong enough signal to perfrom a phase shift id to determine ferrous vs non ferrous.

Be more clear...you want greater identification depth. To get that requires some way of making the deeper coin size targets appear either 1) larger, or 2) larger.

Think about how this works. Magnetic fields creating eddy currents causing magnetic fields which are disturbing magnetic fields within a three dimensional matrix of dirt full of impurities. We are basically shining a flashlight into the ground looking for a reflection that is brighter than the ground reflection. The only way to Id at deeper depths will be to make the deeper targets bigger. The only way to make the deeper targets big enough to generate id is to get the generater of the primary magnetic field closer to the targets.

Figure out a way to turn your transmit" coil into a ground probe to generate the magnetic waves closer to the deeper items, thereby generating stronger magnetic responses in them, so that your surface, pole mounted, 'receive' loop can pick them up and identify them. You do this all the time when you dig a hole and poke your search loop in it.

Or...why can't your transmit loop be hola hoop size, something you lay on the ground and you detect inside it with your normal size, pole mounted receive loop?

Or ...What would happen if you walked around with a 2' two box transmit coil and a 8" pole mounted recieve coil?

As you said...format change.

HH
Mike

Mike Hillis Wrote:
-------------------------------------------------------
> Or...why can't your transmit loop be hola hoop
> size, something you lay on the ground and you
> detect inside it with your normal size, pole
> mounted receive loop?

This has been done.

deadlift = Yes, but we are (technologically) not there yet.

Mike = Not sure I understand your logic. To make objects appear larger (for greater eddy current generation) .... via shoving probes into the ground is not practical. ... And to use a huge coil is also impractical (on many fronts). There needs to be an efficiency/practicality factor employed.

This thread is one I could probably get in over my head in, but anyway here goes.

I used a F75 unit quite a bit, and have an aqaintance who has used one probably far more than I.

I heave heard the following when using the detector and my acquaintance has commented he has as well.

On deeper targets using the F75.

Some of the deeper targets indeed ID as iron bit give a more " borderline" tone-- and many times these targets turn out to be deep nonferrous.

So my question is, could a detector be engineered ( realizing accuracy would not be ideal) to indeed compensate or use some added values to indeed get these more fringe depth targets to report more fully as nonferrous--- especially in the tone dept, and yes TID would be nice too.

Like an added simulation of sorts- not whole so detector could maybe error less so on deeper nonferrous.

It seems when the non- ideal tone is heard on some of the deeper nonferrous--- the detector is in fact sensing something.

This set of values ( added simulation) used would be both fooling the detector of sorts, but by the same token helping it as well.

And if such could be done-- would be user selective.

I mean I understand folks want more depth on nonferrous targets,,, but would it be safe to assume if this indeed happens -- it will be the TONE arena that occurs first--- not TID



Edited 2 time(s). Last edit at 01/15/2016 07:23PM by tnsharpshooter.

The old treasure barons when Iin two tones wouldgive a different tone on targets deeper than I.d.could Identify..


It wouldn't lie to you..


it told you it didnt know..

right post lol..


Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

Keith Southern Wrote:
-------------------------------------------------------
> The old treasure barons when Iin two tones
> wouldgive a different tone on targets deeper than
> I.d.could Identify..
>
>
> It wouldn't lie to you..
>
>
> it told you it didnt know..
>
> right post lol..
>
>
> Keith

So there was a third tone in two tone?

The issue is still that a target response has to be strong enough to process it. There comes a point where the target response itself is too small to do anything with other than to say I'm here even in mineral free dirt. The target response has to be made stronger at the target level. And there is nothing efficient about hunting tiny target signals. It is concentrated work in a small area that requires stone cold stability and tons of patience when the target itself responds like the way stars twinkle, or a light breeze blows by your ear, if your detector is even sensitive enough to even report that small. I have even had my pulse interfere with hearing tiny target signals.

There have been great strides made in removing ground effect and EMI effect to get more of, and cleaner, target signal to process. But there is still a limit imposed by target size that has to be overcome to get greater ID depth. And that can only be overcome by increasing the apparent size of the object itself.

The worst thing about this whole discussion is that any attempts to increase the apparent target size also increases the apparent size of all the impurities in the medium the target resides in.

Maybe someday someone reading this whole discusson will have an aha moment.

HH
Mike

It made a stacatto sound..

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

Need a true disc with ID PI machine I guess .

I wonder sometimes.

FBS technology--- it doesn't incorporate true all metal.

Is there a reason why???

WHAT IF:

A format-change emerged whereby................. IB/TR/VLF/PI were relegated...... with subsequent replacement via sonic density-imaging or ultrasonagraphic target resonance imaging or, or, or .... etc............ some form of (never previously thought of) technology shift. Yes, items like glass may/would resonate (now); yet, differentiable via frequency resonance ID abilities. ,,,,,,,, And a plethora of other variables (with discerning abilities) ......... were to exist. Mineralization issues may/would go away. (And yes, a host of other 'challenges' may/would emerge)...... yet, open a new revolutionary pathway for evolutionary progress.

50% of the solution to a problem is: "Identifying the problem". I can identify the problem (((and hold myself partially accountable; yet, still searching))) and quest/seek for answer(s).

As I get older.......... and realize my body is running out of time (surreal negated immortality onset) ............... the desire for greater achievements (especially greater depths......... and subsequent greater discoveries) is immeasurably overwhelming. I NEVER want to say: THERE ARE DREAMS I'LL NEVER LIVE TO SEE.

I get it. Perform an ultra sound on a 12" deep dime.

I just hope when I do it turns out to be twins or even triplets. Lol

Seriously I think battery technology may indeed eventually open up another form of technology that can be applied to metal detecting.

And this new technology may indeed be discovered accidentally --- actually could be a by product of another technological discovery.


[physics.wm.edu]



Edited 1 time(s). Last edit at 01/16/2016 06:44AM by tnsharpshooter.

This is nearly exactly what my notion/inference is. And......... this is only ONE example/possibility for future detection....... yet, may pose the 'answer'.

With current-day technology.........we are making leaps/strides in the electromagnetic understanding of ferrous/iron......... and are starting to unmask at a more rapid rate (so I think!). ((( It's all 'perception-based' ))).
But...... we have been at the 12" capabilities on coins (in clean dirt) for the past 1/4-Century. It 'might' be time to "rethink" approach methodology.