Why do VLF's units detect deeper in moist ground????

IMO, if the detector air tests poorly - due to the algorithm not being able to adequately subtract the mineral signal (because there is no ground to balance to) then the in-ground testing could exceed the air test, as the sensitivity would be ineffectively set by an incorrect ground setting in the air. The CTX/E-Trac doesn't ground balance in the normal sense, and has been found to do better in the soil matrix than the air, at least on occasion.

The rule that a properly setup detector will detect further in the air than in the ground still holds true. But an improperly setup detector could, at times, detect further in the ground than in the air.

Nexus Wrote:
-------------------------------------------------------
> Fletch88 Wrote:
> --------------------------------------------------
> -----
> > So reading all of this brings to question, can
> > it's be found deeper in the ground than in air
> > test. I think yes, but have read just the
> opposite
> > in posts from engineers etc.
>
> The common consensus is no to your question.
>
> However.
>
> If any detector will detect deeper in the ground
> than in air will have to be in relation to some
> kind of a constant. In this case the constant will
> be the ground it self. Only after a proper ground
> balance is made on any particular site comparative
> measurements will have any meaning. Comparison
> between in ground and in air detection range would
> have meaning only if the ground interference is
> taken out of the equation, meaning the detector
> have no further problems with ground after the
> ground balance is made.
>
> I was one of the most fears supporters of the idea
> that VLF detectors can not detect deeper (or at
> least better) in the ground than they ever could
> in air. Our best ever results in some conditions
> were air to ground same measurements, but never
> better in the ground.
> The new Nexus Standard MP change that. The
> measured average signal detection in ground with
> the MP is 12-14% better than in air, BUT ONLY
> AFTER THE GROUND BALANCE IS DONE.
>
> In absolute values VLF detectors will always be
> more sensitive in air than in ground, simply
> because their sensitivity in air can be boosted
> almost indefinitely and for detection in ground
> that same sensitivity will have to reduced
> dramatically for proper functionality.
>
> So if one chooses to compare the absolute values
> then the answer is no.
>
> But if one chooses the values in the real working
> environment then the answer is yes.

Gerogi from Nexus has for years told Minelab owners that it was impossible for any detector to air test poorly and then detect deeper in the ground, physics wouldnt allow it he said well now he claims his firms new detector defies physics and indeed you can get a detector to go deeper in the ground than in the air what a turn around Georgi

jimmyjiver Wrote:
-------------------------------------------------------
> ATTENTION::::ATTENTION::::NEWSFLASH::::The laws of
> physics cease to exist for Nexus...."The new Nexus
> Standard MP change that. The measured average
> signal detection in ground with the MP is 12-14%
> better than in air, BUT ONLY AFTER THE GROUND
> BALANCE IS DONE."......"This is
> phenomenally,astronomically greatness in it's
> rarest form"......says JJ from Tom Dankowski's
> renown forum, (as reported by the Boston
> Globe).....Shame on me for thinking you had a
> hidden agenda all this time....LoL....JJ
>
>


> PS: Me got to get me one of them
> magical,miracle,meticulous machines.

I have no hidden agenda, but a clear and honest business proposal to anyone who is interested in a new and a good product. There will be demo videos produced soon enough to show everything.
The laws of physics apply in this case as they apply in all other cases. For one to know what is possible one have to gain understanding of what is happening in reality.

Ridicule will not help you to gain knowledge.

PI detectors for example are all showing better results in ground than in air tests, no exception, period. The same search conditions apply for VLF, because all targets are in the same soil.

u2robert Wrote:
-------------------------------------------------------
> I'm no rocket scientist or a nuclear physicist
> like some of you guy, but here my take on the
> ground verses air test it's like this if I shoot
> my 1911 45 across an open field that round will
> travel about 850- 900 FPS until it runs out of
> energy which will be about a mile and then fall to
> the ground, now if I take that same 1911 45 and
> point it at the ground and shoot it, it will
> travel about 12" into the ground why because of
> the resistance from the ground same with the radio
> signals from my coil, resistance will keep the
> coil from detecting deeper in the ground than in
> the air. and that's all I have to say about that.

Radio signals are not used in metal detectors. Electro-magnetic waves on which all VLF are based do not cease in ground. The example is inaccurate.

sanjuro Wrote:
-------------------------------------------------------

>
> Gerogi from Nexus has for years told Minelab
> owners that it was impossible for any detector to
> air test poorly and then detect deeper in the
> ground, physics wouldnt allow it he said well now
> he claims his firms new detector defies physics
> and indeed you can get a detector to go deeper in
> the ground than in the air what a turn around
> Georgi

Yes I did say so and as far as Minelab VLF's are concern I stand by it. I own CTX3030 and this detector never gets in ground tests near what it can show in air. But all GPX are the exact opposite. They all go deeper in ground than in air, because they use the ground's ferro-magnetic properties to do so. It is exactly what Nexus Standard MP does, probably not to the same extend as PI.

The problem with air tests it can be affected by unheard outside interference. I also agree MLs do not like air gabs in the soil.... so between the metal BLEEDING creating a larger target and filling in these soil gaps you may well see and increase in depth.... depending on the target.

Dew

On the Golden Olde website, Norman (I think I have his name right) wrote about his test garden and his detectors. When the ground was wet, one detector would bang on his test targets, but as it dried up, it would eventually not respond to them. However, he reported on another machine that liked the ground dry, and it would hit on his test targets better in dry ground than when the ground was moist. I'll have to go back and re-read the article to see what the detector names were as I recall the brand/models at the moment.

I believe him. While single frequency VLF's have a lot of things in common, I think that the the design intention has to be taken into consideration. It would be a misnomer to say that all VLF's detect better in moist ground than dry, or to discount the ability to use ground mineralization as a target amplifier. Remarkable things have been taking place in regards to the ground signal and how to use it.

HH
Mike

Nexus Wrote:
-------------------------------------------------------
> u2robert Wrote:
> --------------------------------------------------
> -----
> > I'm no rocket scientist or a nuclear physicist
> > like some of you guy, but here my take on the
> > ground verses air test it's like this if I
> shoot
> > my 1911 45 across an open field that round will
> > travel about 850- 900 FPS until it runs out of
> > energy which will be about a mile and then fall
> to
> > the ground, now if I take that same 1911 45 and
> > point it at the ground and shoot it, it will
> > travel about 12" into the ground why because of
> > the resistance from the ground same with the
> radio
> > signals from my coil, resistance will keep the
> > coil from detecting deeper in the ground than
> in
> > the air. and that's all I have to say about
> that.
>
> Radio signals are not used in metal detectors.
> Electro-magnetic waves on which all VLF are based
> do not cease in ground. The example is inaccurate.


Radio signals/Electro-Magnetic waves, you know what I meant, it does not change the fact that the Electro-Magnetic waves will still be stifled from the resistance from the ground, giving you a better air test than actual ground test, ground balanced or not

I was going to say what Nexus already said about the Minelab GPX machines. This is something I wanted to show in a video when I get the chance. I haven't put my GP to the air test ruler yet, but if I were to take a good guess, I bet it air tests a quarter at only 10 inches. But in the ground...you better be prepared to dig 15+ inches for the same quarter if its in the ground. The GPX machines are more stable than the older GPs and therefore can be ran a little hotter too...they have better timings in them and can go even deeper in the ground. In Virginia I was digging Civil War bullets 15 to 18 inches all day long that sounded like they should have only been 6 or 8 inches by the signal they gave. And on top of that, it really doesn't matter if it is fresh buried or been in the ground a while...it will still pounce on it that deep. Some VLF machines don't like disturbed ground and just wont hit a freshly buried target that well. The GP and GPX machines don't seem to matter, as long as they have soil to balance to.

Hi Nexus,,,hey I'm kinda curious why Kellyco and others have flat turned you down in the U.S.????....Is it possible that you are making claims that are false????....Now we really are getting off topic, you are now bringing in pulse detectors into the equation, to try and justify your point even more....I also see your new miracle machine debuts in February,is this some early promotional tactics?.....Below is an outlandish claim you made how your new VLF machine outperforms a PI machine....I also included a comment from Dave Johnson and you?,,,somewhere I read that George Payne and Bruce Candy? basically said the same thing Dave said....In closing I do however think your new machine looks nice and is very well laid out....Performance ?....The jury's still out on that one....LoL....JJ

PS: I'm not trying to put down anyone here I'm just trying to get more facts and answers.....If it's on the Internet it has to be true....LoL...



#1....Dave Johnson says..... "A properly done “air test” provides an indication of a machine’s potential to “go deep” on buried coins. Because of interference from magnetic iron minerals in the ground, actual detection depth will usually be much less than what’s achieved in “air test”




#2....I asked Georgi (Nexus designer) Can machines that don't air test well, go deeper in the soil.

He said No absolute Crap !! this is scientifically impossible if a machine air tests badly it will detect badly in the soil despite of what you read on metal detecting forums and some manufacturers literature.
However some machines that air test better can loose a higher percentage of depth in the soil around 30% depending on what type of search coil is used.




#3....LC: Pulse Induction technology is on the market since years but seems it is just at the beginning of its evolution. Some major companies are presently working to give PI a true discrimination, lower energy requirements and better ground balancing. Do Nexus is effectively interested in this kind of Time Domain technology?

GC: The new Nexus Standard MP have actually matched and in some cases have exceeded the PI performance in most mineral conditions apart from concentrated black sand and heavily magnetite saturated soils.

MP also exceeds the discrimination ability of any PI detector and it exhibits much faster recovery speed, needed for use in iron infested areas.

In normal soil conditions, PI has never match in performance level our resonant tuned Nexus detectors, especially equipped with the big Ultima search coils.

jimmyjiver Wrote:
-------------------------------------------------------
> Hi Nexus,,,hey I'm kinda curious why Kellyco and
> others have flat turned you down in the
> U.S.????....

As a rule we don't run after Kellico or anyone else in the US or anywhere else for this matter.
We deal only with companies that are seriously interested in our products and come to by their own decision.

Is it possible that you are making
> claims that are false????...

NO. But let me tell you what is possible. The fact that you really do not know what you are talking about.

.Now we really are
> getting off topic, you are now bringing in pulse
> detectors into the equation, to try and justify
> your point even more...

I dont justify anything. I test everything. I am an engineer not a lawyer.

..Below is an
> outlandish claim you made how your new VLF machine
> outperforms a PI machine...

In normal and light soil definitely yes. PI gains more depth only in mineralized conditions. VLF have better discrimination and faster recovery in all cases.

> PS: I'm not trying to put down anyone here I'm
> just trying to get more facts and answers.....If
> it's on the Internet it has to be true....LoL...

But you just did. Your attitude is quite slanderous, childish and insulting. And based on what?
>
> #1....Dave Johnson says..... "A properly done
> “air test” provides an indication of a
> machine’s potential to “go deep” on buried
> coins. Because of interference from magnetic iron
> minerals in the ground, actual detection depth
> will usually be much less than what’s achieved
> in “air test”
>
> This is only if the ground balance is not included in the calculation. In absolute value every VLF detector will be much more sensitive in air than in ground, but this is not how detectors work in real life. They work on soil unless you can find coins flying in air somewhere. Please read my previous post and try to think about this.

In the soil there is interference not only from magnetic Iron minerals, but also a lot of organic compounds, salts, air gaps etc. In fact we have established in our late development and research that magnetic properties of the ground benefit the detection by concentrating and extending the search field of any search coil.
>
>
> #2....I asked Georgi (Nexus designer) Can machines
> that don't air test well, go deeper in the soil.
>
> He said No absolute Crap !! this is scientifically
> impossible if a machine air tests badly it will
> detect badly in the soil despite of what you read
> on metal detecting forums and some manufacturers
> literature.
> However some machines that air test better can
> loose a higher percentage of depth in the soil
> around 30% depending on what type of search coil
> is used.

This comment is about 7-8 years old. In those days there was no VLF technology capable to do better. Now there is. We call it a Super Dumping Technology and we have included it in the MP.
Five centuries ago the Earth was considered flat and centre of the Universe. That also changed.
Some thing needs to be seen before they are understood.

>
> #3....LC: Pulse Induction technology is on the
> market since years but seems it is just at the
> beginning of its evolution. Some major companies
> are presently working to give PI a true
> discrimination, lower energy requirements and
> better ground balancing. Do Nexus is effectively
> interested in this kind of Time Domain
> technology?
>
> GC: The new Nexus Standard MP have actually
> matched and in some cases have exceeded the PI
> performance in most mineral conditions apart from
> concentrated black sand and heavily magnetite
> saturated soils.
>
> MP also exceeds the discrimination ability of any
> PI detector and it exhibits much faster recovery
> speed, needed for use in iron infested areas.
>
> In normal soil conditions, PI has never match in
> performance level our resonant tuned Nexus
> detectors, especially equipped with the big Ultima
> search coils.


These are the facts.

If you have any further questions I'll be happy to answer as best as I can.

u2robert Wrote:

>
>
> Radio signals/Electro-Magnetic waves, you know
> what I meant, it does not change the fact that the
> Electro-Magnetic waves will still be stifled from
> the resistance from the ground, giving you a
> better air test than actual ground test, ground
> balanced or not

Electro-magnetic waves do not loose intensity in the ground.
The loss of depth in most VLF detectors is a direct result of a disturbed balance between the RX and TX caused by the soil proximity.

One should compare test results in real search conditions where everything counts. There are no targets to find in the air, therefore there is no point comparing over amplified air sensitivity to suppressed ground condition adjustments.

Comparative tests have real value only when the detector is tuned to work on the soil.

The real sensitivity of any detector is a proportion between ground mineral interference and target signal strength.

Hi,,,,You are way to funny....LoL....I'm going to be brief here because I'm kinda laughing myself into a frenzy....I have completed my mission for the day so have a nice day and I will let you have fun all by your lonesome....I'm done with this topic....JJ

NEXUS.....NO. But let me tell you what is possible. The fact that you really do not know what you are talking about.

JJ.. reply....LoL...You are right I'm only a Genius in certain areas....In this case I think I ruffled your feathers enough you might fly away on me..LoL..



NEXUS.... "As a rule we don't run after Kellico or anyone else in the US or anywhere else for this matter. (LoL where are you selling them at then?) We deal only with companies that are seriously interested in our products and come to by their own decision.


NEXUS reply earlier...."You will get a lot of use of the MP as long as you stay away from the parks that are full of pull tabs unless you would not mind digging them out. I do not think we will have a dealer network in the US soon. Every attempt so far was a failure. Last year we send test samples to Kellico at their request and never heard from them again. They would not bother to even return the samples worth 3000 Euros.
As uncomfortable as it may seem folks from the US will have to buy directly from us. Shipping is free."

[www.dankowskidetectors.com]



PS: Hope I did not hurt your feelings that was not my intent

Hi Nexus,
I'm sorry but I have never looked at your units before, but your talk about your use of ground minerals caught my eye as not many post about this or are aware of what is taking place with ground signal usage today.

Reading your adverts, the Standard MP operates in All Metal (where most VLF's get their best depths in mineralized ground) yet you are also providing ferrous / non-ferrous identification. Are you providing this ferrous/non-ferrous discrimination in a true non-motion all metal mode? And does it provide this ferrous / non-ferrous discrimination to full depth of detection?

HH
Mike

Nexus,you want a u.s. dealer? Send one to Tom or Keith...if its what you say,you will get plenty of advertising and someone will pick you up. Ray

Yes send one to Keith and Tom, they are the acid test!

Mike Hillis Wrote:
-------------------------------------------------------
> Hi Nexus,
> I'm sorry but I have never looked at your units
> before, but your talk about your use of ground
> minerals caught my eye as not many post about this
> or are aware of what is taking place with ground
> signal usage today.
>
> Reading your adverts, the Standard MP operates in
> All Metal (where most VLF's get their best depths
> in mineralized ground) yet you are also providing
> ferrous / non-ferrous identification. Are you
> providing this ferrous/non-ferrous discrimination
> in a true non-motion all metal mode? And does it
> provide this ferrous / non-ferrous discrimination
> to full depth of detection?
>
> HH
> Mike

It would be more fare if we do not discuss Nexus in this tread any further. The tread was not initiated for advertising Nexus or any other detector and it is not polite to high jack it.
Please refer to our web site contact page and I'll give you all answers there.
Alternatively you could open a new tread concerning Nexus.
Thank you for your attention.

jimmyjiver Wrote:

> NEXUS.... "As a rule we don't run after Kellico or
> anyone else in the US or anywhere else for this
> matter. (LoL where are you selling them at then?)
> We deal only with companies that are seriously
> interested in our products and come to by their
> own decision.
>
>
> NEXUS reply earlier...."You will get a lot of use
> of the MP as long as you stay away from the parks
> that are full of pull tabs unless you would not
> mind digging them out. I do not think we will
> have a dealer network in the US soon. Every
> attempt so far was a failure. Last year we send
> test samples to Kellico at their request and never
> heard from them again. They would not bother to
> even return the samples worth 3000 Euros.
> As uncomfortable as it may seem folks from the US
> will have to buy directly from us. Shipping is
> free."
>
> [www.dankowskidetectors.com]
> .php?2,70029,70180#msg-70180
>
>
>
> PS: Hope I did not hurt your feelings that was not
> my intent

It does not say anywhere that we attempted anything in the US. Just the opposite.
US dealers want to dictate terms to the rest of the world, but that's not going to happen.



Edited 1 time(s). Last edit at 01/28/2015 07:50AM by Nexus.

So you choose to ignore my statement Nexus,and now you dont want to talk about Nexus. ok...good luck.

deathray Wrote:
-------------------------------------------------------
> So you choose to ignore my statement Nexus,and now
> you dont want to talk about Nexus. ok...good luck.

I am sorry if you feel this way. I didn't mean to ignore anyone here. As I said the tread was not originally intended for Nexus and I am simply trying to be polite.
I was seriously disappointed from Kellico and their ignorant behavior.
They have contacted us back in 2007. I denied them dealership because they wanted to enforce their sale policy over ours.
Last year they came to Bulgaria asking for an audience. We had a 2 hours talks with a lot of promises from their side. Then they have received samples from us. And then came the silence. No responsibility of any kind.
I am really not trying to be rude, but we do not wish to deal with this kind of mentality.

Even though I started this thread, my question was answered. Y'all feel free (within Forum boundaries) to chat in this thread. I'm heading over to the Nexus site to see what they got.

Nexus Wrote:
-------------------------------------------------------
> u2robert Wrote:
>
> >
> >
> > Radio signals/Electro-Magnetic waves, you know
> > what I meant, it does not change the fact that
> the
> > Electro-Magnetic waves will still be stifled
> from
> > the resistance from the ground, giving you a
> > better air test than actual ground test, ground
> > balanced or not
>
> Electro-magnetic waves do not loose intensity in
> the ground.
> The loss of depth in most VLF detectors is a
> direct result of a disturbed balance between the
> RX and TX caused by the soil proximity.
>
> One should compare test results in real search
> conditions where everything counts. There are no
> targets to find in the air, therefore there is no
> point comparing over amplified air sensitivity to
> suppressed ground condition adjustments.
>
> Comparative tests have real value only when the
> detector is tuned to work on the soil.
>
> The real sensitivity of any detector is a
> proportion between ground mineral interference and
> target signal strength.

All right, all ready

Electro-magnetic waves do not loose intensity in the ground.

It's been written that a circular coil's two-way field strength drops (ignoring soil) at the sixth of the distance from the coil: 1 / [(R2 + D2)1/2]3 , where R = Coil Radius, D = Distance to target.
One-way field strength follows cube-rule: 2x(Tx windings)x(Tx current)x(coil radius)^2 / [(coil radius)^2+(target depth)^2]3/2

A target at 6 cm deep would produce a signal 1/729th as strong (decrease in intensity) as that at 2 cm deep.
A target at 10 cm deep would produce a signal 1/15,625th as strong (decrease in intensity) as that at 2 cm deep.

Soil resistivity and moisture attenuate signal both directions (from pimary & returning secondary field); about 0.1 decibel signal loss per foot soil tranversed at 10kHz

Signal strength decrease with depth. Most detector operators would have noticed that the target signal strength is highly dependent upon the distance of the target from the coil.This is because the magnetic field decreases very quickly with increasing distance between the transmit coil and the target ; so too does the magnetic field decrease very quickly with increasing distance from the target to the receive coil. Suppose the transmit and receive coil are one and the same, as in a mono-loop. Suppose the target is directly on the central axis of the coil. If the coil radius is a, and the target distance from the coil z, then the field at the target is H=2nIa 2 /(a 2 +z 2 ) 3/2 where I is the transmit current and n the number of transmit coil windings (and thus receive too, as this is a mono-loop wound coil). Assuming that the target is small, the signal from the target back to the coil is similarly detected in proportion to 2na 2 /(a 2 +z 2 ) 3/2 .Thus the there-and-back signal is proportional to 1/(a 2 +z 2 ) 3 .background interference is sferics, mains and very occasionally, radars etc. To determine the source of interference, change the orientation of the plane of the coil from horizontal to vertical. If the interference increases dramatically, the source may be sferics. Alternatively, check with a figure “8” receive coil or the “cancel” mode; if the interference is unaffected, then the source may well be from static (or radars etc), but if the interference ceases with the figure “8” coil or cancel mode, its source is not from static, but
magnetic fields.............JJ

All I can say is, "Where do I get my diploma?"

Johnnyanglo Wrote:
-------------------------------------------------------
> Electro-magnetic waves do not loose intensity in
> the ground.
>
> It's been written that a circular coil's two-way
> field strength drops (ignoring soil) at the sixth
> of the distance from the coil: 1 / [(R2 + D2)1/2]3
> , where R = Coil Radius, D = Distance to target.
> One-way field strength follows cube-rule: 2x(Tx
> windings)x(Tx current)x(coil radius)^2 / [(coil
> radius)^2+(target depth)^2]3/2
>
> A target at 6 cm deep would produce a signal
> 1/729th as strong (decrease in intensity) as that
> at 2 cm deep.
> A target at 10 cm deep would produce a signal
> 1/15,625th as strong (decrease in intensity) as
> that at 2 cm deep.
>
> Soil resistivity and moisture attenuate signal
> both directions (from pimary & returning secondary
> field); about 0.1 decibel signal loss per foot
> soil tranversed at 10kHz

I do realize my statement was not clear to begin with.

You are talking about sensitivity of a metal detector to targets in the soil. I am talking about electro-magnetic waves and their natural distribution, not concerning detection of metals with VLF at all. Those are two different things.
The fact that metal detectors loose sensitivity to targets in the ground have nothing in common with distribution of electro-magnetic waves. How well a detector can measure a target response is a different matter from how well electro-magnetic waves will distribute trough the soil.

The other fact that the intensity of a TX signal transmitted by a circular loop decreases naturally also have nothing to do with loss of transmitted signal strength in the ground, because it decreases by the same laws in the air to.

Use as an example PI technology.
With PI signal strength in the ground is actually higher than in air, always. And the more mineralized or magnetic the soil gets the deeper PI goes.

I am aware of all principal calculations described in various books, but they concern mostly Induction Balance and its reaction to soil, not the actual distribution of transmitted signals trough the soil.



Edited 1 time(s). Last edit at 01/30/2015 08:07AM by Nexus.

Nexus is correct when he says the "inverse 6th" guide is not relevant. What you are debating is the difference in the signal between "in air" and "in ground". It's tempting to say that the ground absorbs some of the strength of the coil & target. It will, but over a 2 foot (60cm) return path, it's barely noticeable. [cavers use VLF to communicate underground, it does pass through rock reasonably well]. It's also plausible to say that the microscopic iron content of the ground will distort the shape of the magnetic field, eg. making it 'fatter but shallower' - that would give reduced depth. But it might make it 'narrower and deeper', I really don't know. Some good scientific measurements may shed light on this, as might a computer simulation.
The inverse 6th guide does have some relevance, here, as it shows the "small change in depth" for "large change in signal". So for example, if your ground did in some way cause a 20% drop in signal, that would be equivalent to a 3% drop in depth (eg. 0.3" at 10").