On my mind -- Random Thoughts

Tom...…… there's a few detectors that can do this. Problem is...…… the detector 'sees' a composite signal (nails with coin)……. and (rightfully-so) registers/reports the composite as: 'something slightly above the conductivity of nail(s)'. . . . . . . . usually in the foil range. On non-ID units..... this is not very evident. Without a VDI (or meter of some sort)….... it is hard to tell what the unit 'thinks' the composite signal is.
Another problem is: When a coin & nails combo gives a 'detection ID'...…… it will report as a 'high-coin' (high-tone) "false"...……….. leading the operator to believe that the unit is actually ID'ing ""coin"". . . . . . . . . . . when...……….. in actuality...………….. it is a high-tone "false". A solo bent square-nail can report as a high-tone 'false'.
A third problem is: lift the nails (that are touching the coin)…… just a few tenths of an inch above the coin...…… and now the detector will much more readily report a ID of "iron". This test presents more validity...……...as...………. real-world conditions present just exactly this type of 3-dimentional target separation condition.
I have never liked testing a detector on a coin with nails combo...…. whereby..... the coin and nails are on the same plane/altitude. Even worse: when the nails are touching the coin.

Andrew...….. I'm going to attempt to answer your questions #2 & #3.

Inventing.... is one of the most difficult/challenging feats to perform. You must have a "vision".
You must have a "dream".
In order to begin...…… you must have the end in mind.
Not afraid of inhibiting factors; yet/rather, look upon them as a exciting challenge. Creating something that does not exist yet...….. is a: Epiphany...…. and is almost (but not quite) impossible. Everything you have learned...… creates muscle-memory mindset...… of which: must be 'shattered'.... so as to 'clear' your entire lifes-worth of mental programming (and everything you believe/solidified)...….,,,,,,,,,...……,,,,,,,,,,...…….. in order to 'vision' something that contrasts against your lifelong 'everything' mindset. Fortitude to forge forward...….. goes against every grain of your primal compositional makeup. "Comfort-Zone" is your own incarcerating inhibitor.

In life...…. in all of my exposure...…… I have learned to focus on the strengths/positives...….. applying the 80/20 rule: 80% on the strengths. . . . 20% on the weaknesses. Minelab has strengths. Tarsacci, Nokta/Makro, Fisher has strengths. They are NOT the same strengths. It is within this (confines) delta/difference...… that Epiphany(s) can birth. In my collaborative efforts with these companies...…. it makes it even easier for me to have MUCH greater 'vision'..... for future 'launch'. . . . . . . than would (otherwise) be possible. . . . . . . due to a more broad, multiple-angles approach exposure...….. allowing me to 'see' differently. Teamwork is one thing. Multi-teamwork is yet another plateau.

(((Out of time. Much more to go))).

NASA-Tom Wrote:
-------------------------------------------------------
> Tom...…… there's a few detectors that can do this.
> Problem is...…… the detector 'sees' a composite si
> gnal (nails with coin)……. and (rightfully-so) regi
> sters/reports the composite as: 'something slightl
> y above the conductivity of nail(s)'. . . . . . .
> . usually in the foil range. On non-ID units.....
> this is not very evident. Without a VDI (or meter
> of some sort)….... it is hard to tell what the uni
> t 'thinks' the composite signal is.
> Another problem is: When a coin & nails combo give
> s a 'detection ID'...…… it will report as a 'high-
> coin' (high-tone) "false"...……….. leading the oper
> ator to believe that the unit is actually ID'ing "
> "coin"". . . . . . . . . . . when...……….. in actua
> lity...………….. it is a high-tone "false". A solo b
> ent square-nail can report as a high-tone 'false'.
> A third problem is: lift the nails (that are touch
> ing the coin)…… just a few tenths of an inch above
> the coin...…… and now the detector will much more
> readily report a ID of "iron". This test present
> s more validity...……...as...………. real-world condit
> ions present just exactly this type of 3-dimention
> al target separation condition.
> I have never liked testing a detector on a coin wi
> th nails combo...…. whereby..... the coin and nail
> s are on the same plane/altitude. Even worse: when
> the nails are touching the coin.


Nasa-Tom : Did you have a chance to use a 77b ? They do not false on bent nails. And if/when there is a space between the nail to-the-coin (as opposed to "touching" the coin) didn't make a difference. The "trick" worked whether or not there is a space between the nail to the coin, or not.

I showed this to a sales rep. at Fisher Co, back when they were still in Los Banos. Showed it to him right there in their parking lot. He was blown away. He thought they had a machine that could perform the same stunt (I forget which one). He walked back inside the building, and came back out with a machine. But try as he did, he could not tell when a coin was under a nail-or-two, versus the nails solo.

I was asking him if such an ability could be brought back to the present age, in a modern package. He promised me he would pass this information along to their engineers for some feedback. That was the last I ever heard from him. Despite leaving several messages, in the months that followed, asking " What is the progress on my question ?"

Tom...….. I've never owned one; yet, I have had one in my test-garden..... many, many years ago. I clearly recall the owner placing a couple of rusty/bent nails on top of a copper wheat penny...…. and the 77B would report the non-ferrous coin. Then...…. I swept the coil of a Fisher 1266X over the same combo target...…. and could also detect the coin with the 1266X. At that time...… we did not suspend/raise the nails above the coin. He was more 'stunned' by the depth performance of the 1266X...….. and ……… that is where we placed much 'focus' on.

NASA-Tom Wrote:
-------------------------------------------------------
> ... the 1266X...…..
>

Yes, the 1266x was super deep. It can air test 1.5 ft. on a quarter with ease, for instance. But in actual hunt conditions, that machine was horrible squirrelly. If anything, it was prone to getting false positives on deep nails, as I recall. I do not recall that it could see through small iron to get a coin.

oh well.

Tom_in_CA Wrote:
>
> Nasa-Tom : Did you have a chance to use a 77b ?
> They do not false on bent nails. And if/when the
> re is a space between the nail to-the-coin (as opp
> osed to "touching" the coin) didn't make a differe
> nce. The "trick" worked whether or not there is
> a space between the nail to the coin, or not.
>
> I showed this to a sales rep. at Fisher Co, back w
> hen they were still in Los Banos. Showed it to h
> im right there in their parking lot. He was blown
> away. He thought they had a machine that could p
> erform the same stunt (I forget which one). He wa
> lked back inside the building, and came back out w
> ith a machine. But try as he did, he could not t
> ell when a coin was under a nail-or-two, versus th
> e nails solo.
>
> I was asking him if such an ability could be brou
> ght back to the present age, in a modern package.
> He promised me he would pass this information alon
> g to their engineers for some feedback. That was
> the last I ever heard from him. Despite leaving
> several messages, in the months that followed, ask
> ing " What is the progress on my question ?"

The Compass 77b has an operating frequency of 100kHz. I am not aware of a modern machine with an operating frequency quite that high.

(((But...….. we're looking into this (100Khz)...….again))).

Isn't the 100khz operating frequency why the older TR machines ignore/see through nails that way?

coinhunterseth Wrote:
-------------------------------------------------------
> Isn't the 100khz operating frequency why the older
> TR machines ignore/see through nails that way?

Yes. The 66TR, for example, could do the trick too. However, for some reason, the 77b was just smoother, deeper, or whatever.

Andrew...….. I cannot believe it is taking me this long....to answer your three questions.
"What direction do you feel they should be going in?" and "What does the future hold for us?"
Here goes another incremental attempt/installment..... to answer these last two questions:

Today's current technology metal detectors look at two primary aspects of intel. This is how far (or short) we have come. First; a metal detector 'detects metal'. Secondly; more recently....we have been able to look specifically at 'phase-shift' of the detected object.....and tell the conductivity of the metal (to include ferrous and non-ferrous)….. and generate a target-ID based off of the angle of the phase-shift. I might add: Accuracy has been (rather stunningly) accurate. In the 1960's...…. this would have merely 'been a dream'. Now......it is a reality...…. even to the point of separating out ferrous phase-shift...…. and conductive phase-shift. In the 1960's...….. we would have called this "Impossible".

We are ready to see a third dimension added to the (above two) intel gathering abilities....of current technology. We are ready to see the next "impossible" ….added to the next generation/batch of metal detectors. That being: 'density' of the detected target...…. via the signature-to-hull-emitter-correlation of the target. It can be seen on a O-Scope...… the delta between the signature of a wad of chewing gum foil...…...and...…. say a bullet/coin/ring. One returned signal will look mushy (from the wad of chewing gum foil). The other returned signal from the hull of the detected object (coin/bullet/ring)... will look very distinct/clear/smooth trace on a O-Scope. This is 'captured data'...… that could (now) be employed to substantial intel/benefit/attribute(s).
I bring this third dimension up because...… I know it is within the "do'able" abilities of today's capabilities/mindset...….. if we continue (((should we choose))) to stay incarcerated within the confines of magnetic/electromagnetic VLF IB foray. This would be the continuation of (what I call): minute' incremental evolutionary advancement(s).

We will see better audio presentation. Mfr's…. should-be-going/are-going.... further in this direction. (((Multi-tone ID..... and in raw-data fashion no-less..... equals wonderful human-interface intel conveyance))).
Yes...… I am curious to see if FTP can "mass production" a 7uS coil.
We 'should' see ""special"" coils evolving. (((Inductive Balanced dual-field/quad-field.....analyzed through comparator))).
Ironic to see the 100Khz subject … brought up.... again.
We are seeing better mineralization handling. And there's more to come. There's some serious 'thunk-time' going into this.
There's some (so-called: "impossible") PI revolutionary-status...… that should (and is) being fruitioned.

There are a few very innovative 'brains' out there. Minelab is exceptionally forward-thinking. . . . . and with continuous positive lock-on mini-milestones..... collective advancements. Nokta/Makro is the most burning-passion/aggressive entity....to date. FTP...… whilst in their innovative/inventive phase (again)..... is riding on a razors-edge (in many regards)….. one being the AQ/Impulse. If ever fully mobilized.... Dimitar could sweep the entire industry. I've already seen/witnessed (proven) some (of many) conceptual notions...… and in functioning hardware capacity...….and not: merely 'words-on-paper'. XP is feverishly attempting to tackle/conquer the carpets-of-nails dilemma.

A lot more to be said. Out of time...….. again!

Tom-Thanks for all your answers so far. It has given me a lot to go over in my mind.

I wondered myself if FTP was going to be able to mass produce a 7uS coil.

The XP Deus 81 KHz elliptical coil in carpet of nails is awesome, I've pulled some good stuff that other machine simply will not see.

In the near future I will be getting a Tarsacci again, I was really fascinated with it while I had my first one. It could/can be a great relic hunter once you understand it.

There's some (so-called: "impossible") PI revolutionary-status...… that should (and is) being fruitioned.

Thats an interesting statement. Why are PIs still very hands on? I mean they seem to have a lot of potential...... but still rely heavily on the user and his ability. We know there is depth and sensitivity to be had. I believe thou the more they process a signal even with a PI they will loose depth. Also.... why do most of us rely MORE on the tones than say the digital read out? Dont the tones just reflect the digit...... or is it happening so fast we get a tone NOT reflected in the digit? Density..... awww something ive asked you about Tom.

John & Pimento have triggered (reminded) a thought of mine. I've had intent of posting this about 12-years ago...…. yet, other priorities prevailed.

I have discussed this before..... in 'how to mitigate EMI' most appropriately; yet, did not discuss some of the physics behind the principle. I 'touched' on the subject of Vertical Polarization and Horizontal Polarization of energy.
Nearly 30 years ago...… I noticed the phenomenon ...with a CZ platform. Recently (a few months ago) I incurred THE most pronounced/accentuated delta/differential example...… to date. I was "old coin" hunting with proto MUU-2 EQX..... testing a spectrum of different settings.....(((and wondering if I had gone terribly wrong with MUU-2 intent))). I am in a open field..... far behind a old school. Far away from any structure(s). EMI was somewhere between medium.....and medium-low. I was in Park Mode-1...… and the highest I could run Sens was '18'.... and that was after properly mitigating EMI. Certain events prompted me to perform a battery of tests.
Results:

1. With metal detector sitting on the ground...… and coil vertical...….. I could air-test a clad dime..... to approx. 7".
2. With metal detector sitting on the ground...... and coil horizontal..... I could air-test a clad dime..... to approx. 8.5".
3. With metal detector suspended about 3-feet above the ground..... and coil horizontal..... I could air-test a clad dime..... to approx. 8.5".
4. With metal detector suspended about 3-feet above the gorund..... and coil vertical......... I could air-test a clad dime..... to approx. 7".
5. With the clad dime buried at 7" deep in Florida low-mineral dirt.... I could barely detect the 7" deep dime.
Returning home for an immediate trip into my test-garden.
6. With metal detector sitting on the ground...... and coil vertical....... I could air-test a clad dime..... to approx. 11".
7. With metal detector sitting on the ground...... and coil horizontal... I could air-test a clad dime..... to approx. 11".
8. With the clad dime buried at 11" deep in Florida low-mineral dirt (my test-garden).... I could barely detect the clad dime..... to approx. 11".

What stands out the most (to me) is: With Sens on '18'...... I could air-test a dime to 7" in the real world. . . . . . and to 11" in my test-garden. This is with all settings exactly the same. This is the largest ""difference"" experience that I have ever encountered. What an eye-opener. EMI...... especially: silent EMI...... is killing us. UNSUSPECTINGLY. (((You don't know...... what you don't know))).

If the Engineering Controls methodology to rid EMI is: "Noise Cancel" channels........... we have grossly errored.
Noise Cancel channels is complete incorrect methodology to mitigate EMI. There are MUCH better Engineering Controls that can be put in place ... to rid EMI. For about 2 Decades..... I have expressed this .... to several corporate entities. (((Wait/watch who comes through))).

I have mild soil too, but have noticed the opposite of your results. Unknowingly I built a test garden in an area the EMI is generated from somewhere and happened to pickup the source on my CB radio that is also ham radio. I have weird tonal high pitched tonal bell sound (pinging) come across it but move away 150 yards and it disappears. So in the test garden I'm not getting the depth I get in the field.
So test garden is not used anymore for now. I'm putting in a house and they are putting in a new up to date transformer and I'm wondering if that is the solution to my EMI. We don't realize all the pinging going on around us and unshielded electrical currents, welcome to the modern mans world.

What about painting the coil with some of that EMI shielding paint?

NASA-Tom --

Until one of the manufacturers "comes through" with the better-engineered approach to mitigating EMI/silent EMI, is the "proper" method for mitigating EMI the one I believe you described elsewhere, i.e. "air testing" a coin, at your detecting site on a given day, while running the machine through the various noise-cancel channels, and selecting the channel that offers the greatest air-test distance?

Thanks,

Steve

The problem is that EMI is like ground minerals. You can cancel the ground's response but you can't cancel the ground mineral's strength. In the same manner you can cancel the EMI response (noise canceling frequency shifting) but that doesn't cancel the strength of the EMI.

HH
Mike

Mike,

I get what you are saying about the ground response -- and that makes complete sense. But, if that's true with EMI as well (and I am not saying it's not), then what I said above (which is what I understood that NASA-Tom suggests for "EMI mitigation") wouldn't seem to make sense. In other words, if EMI is only being "quieted," through a "noise cancel," but it still is having the same negative effect on detector performance, then I'm not sure why there would be greater depth acquired on a coin (greater air-test distance) on some noise-cancel channels as compared to others, while running through the "manual noise cancel" process I mentioned above.

It would SEEM to me (again, I could be wrong), that by slightly altering the frequency of a transmission (i.e. a "noise cancel"), that you at least theoretically could sufficiently "move" that frequency "away from" the frequency of a background source that was "interfering," and thus that background source -- now at a slightly different frequency from your transmission -- might yield less destructive interference...

It SEEMS to be a different scenario, to me -- that which exists between ground balancing, and noise cancelling. When ground balancing, you are of course not changing the transmit frequency, but just "compensating for" the detector's response to the ground matrix. BUT -- instead of "ground balancing," actually switching transmit frequency CAN allow you to achieve better performance, reducing the negative effects (attenuation) of the ground mineral, right?

And so, for a very similar reason as to why one detector frequency might be less affected by ground mineral at a particular site, than another frequency, aren't there instances where a machine at 5 kHz encounters less destructive interference EMI (or more) than when running at 40 kHz? And therefore, isn't it possible that a machine running at 5 kHz might encounter less (or more) interference than when running at, say, 5.125 kHz (i.e. a different noise-cancel channel) -- thus, not merely "quieting" the audible effects of EMI, but actually reducing the destructive interference thereof?

Steve



Edited 3 time(s). Last edit at 11/19/2019 08:11PM by steveg.

Steve, In my opinion you are thinking in the right direction... The stronger the EMI, the more degrees of separation required to not be affected by it.

HH
Mike

Mike,

Yes, what you say there, I THINK, is the crux of the issue, i.e. is the amount of "offset" that you get by choosing a different noise-cancel channel to not only reduce the audible effects of the EMI, but also the actual interference or degradation of performance that results...

I would love to better understand the answer to that question, and also what the "other engineering options" there are to combat EMI, that NASA-Tom mentions...

Steve

The simple way to combat EMI is to transmit a stronger TX signal. Then the wanted signals from the target ( and the ground of course) wil be stronger, but the EMI will remain the same, as the receive side of the detector is unchanged. Massive changes are not necessary, simply doubling the coil voltage would be pretty effective, and not hard to achieve. Power draw from the battery would increase modestly, but that's acceptable, and can be dealt with.
I believe ther are some circumstances where this isn't productive .. certain grounds don't care for it, but I am not skilled in this area.
Some of Georgi's earlier Nexus machines transmitted a very strong signal, and it's reported they are EMI immune.

Lots of different types of EMI and my detectors have responded in different ways than the obvious chatter......for example...with a F44 and a Xterra 70....some EMI will mute the audio....kind of like muting a trumpet. The audio is there but muted. You move into it and the mute is on, you move out of it and the mute is off. On the Explorer series there were places where the audio changed by an half octave and went flat or got squirrely. You could still detect but the audio was weird.

What I'm getting at is that is more than a one size fits all solution.

HH
Mike

WVcm = As long as you do not bury electrical power cables underground..... that supply your abode.

ghound = Coils do have shield paint.

steveg = Yes. That is still the best methodology for mitigating EMI...… is to span through the Noise Cancel channels whilst air-testing a coin..... on-site.

Mike Hillis = If you've ever had the stereo in your car on (say) 105.1...… and you are close to a transmitter (another radio station) that is transmitting on a very adjacent channel (say 105.3) you will hear the interference. BUT...… if you tune to 105.9.... that is far enough away from the 105.3 emitting problem. . . . and your EMI is gone..... at no cost to 105.9 performance.

Pimento = Absolutely spot-on! If you increase X-mit power...… and accordingly reduce Rcv Sensitivity...… you have effectively mitigated most EMI! Look at the old analog detectors. There has been TOO much emphasis placed upon reducing X-mit power..... so as to save/elongate battery life! (Which is severely inhibiting).

Ok... unlike the explorers which have 11channels or even a Sov both allegedly can shift thru what appears to be many more harmonic choices. Does the Nox only have the ones listed....or does each product the ability to shift slightly? Doubling the coil output.... how would that go with the FCC regulations?

Dew...…. The EQX has 19 Noise Cancel channels...…. which are very slight shift in Operating Freq(s).
We are well within the Xmit power guidelines. There's plenty of headspace for increasing transmit power.

Tom ..... what i was trying to say is the Nox has 5 distinct freqs for the 800..... while the FBS was allegedly able to take advantage of 100 freqs. With more freqs wouldnt it be better at noise canceling.... or does that have nothing to do with it? More power to the coil wouldnt it require even better filters, more batteries (making it heavier), and dont some machine have a limiter to the coil to ensure a steady flow of battery use?

voltage limiter circuits control power flow from the battery to the controller. The controller sets the power going to the coil.

The "100" frequencies of the FBS have been proven to be about 95% harmonics received from 2 or 3 actual transmitted frequencies.

The multi-frequencies used by the MI-Q could be more of a liability in EMI because you have more range where you can pick it up.

======================================================

You can see my videos here: [www.youtube.com]
My blog is here: [thesilverfiend.com]

======================================================

> The "100" frequencies of the FBS have been proven
> to be about 95% harmonics received from 2 or 3 act
> ual transmitted frequencies.

I *think* that I've read that they use 2 frequencies, approximately 2.5 khz and 25 khz. It's been a while since I read about them, but I think I saw that in a post made by Geotech (Carl Moreland?) somewhere.

The Explorers use 11 channels with varying freq's in between. You can cycle through to get the quietest channel/freq, but I have not found a way to mitigate EMI with those machines.

I think the E-Trac and CTX x-mitt at 3.125 kHz for the low freq and at the 8th harmonic or 25.0kHz for the high freq. There are other harmonics but they aren't sampled, just those two. I think the noise cancel shifts the nominal freq off Channel 6 up/down a small amount. It looks to adjust 2.224% per channel up or down. The total available variation appears to be 5.560 kHz on the high freq and 0.695 kHz range on the low freq, which isn't much difference and wouldn't likely affect performance. It's perhaps enough to avoid EMI or reduce its effects.

Something like this:

..............High (kHz)...Low (kHz)
1................22.220......2.778
2................22.776......2.847
3................23.332......2.917
4................23.888......2.986
5................24.444......3.056
6................25.000......3.125 (Default)
7................25.556......3.195
8................26.112......3.264
9................26.668......3.334
10..............27.224......3.403
11..............27.780......3.473


-Johnnyanglo