Air Tests for PI/VLF machines

I am trying to understand the technology of metal detectors and my current interest is depth. I have been reading up on air tests for PI/VLF MDs and how accurate or inaccurate they are. I see where people say they are meaningless because their machine is deeper in ground and then I see quotes around web by experts like Eric Foster saying that an air test should be as deep as any in ground test. So what is correct?

If I am understanding air tests correctly then an air test is as deep as a detector will hit that specific item, like a dime. If there was the so called halo effect, then it could go deeper but in general the ground test cannot be deeper than the air test. And when comparing two machines that halo effect shouldnt matter because if one air tests better it would detect that halo better. In fact, the ground test can only be less because of mineralization. This is where a VLF will start to drop depth but a PI will handle that better so the PI should be able to better maintain their 'air test' depths better than a VLF which will drop depth as ground gets more mineralized. Is this correct? And if this is correct, wouldn't a PI and VLF be very similar in performance in ground with very little mineralization? Thus for example the beaches I hunt in the US east coast where there is very little mineralization a vlf and pi should be very close in performance. Its would not be until I get in the water where I need to turn down my sensitivity on my vlf that I start to notice that difference in PI depth. Is this correct or am I not understanding this correctly?

I know nothing about PI detectors, but you are spot on about the VLFs (single frequency units anyway). In minerally inert soil that is "sterile" a single frequency VLF will theoretically detect an object in the ground as deep as in the air. Add some minerals or other metallic objects and the depth usually decreases in ground (except in the case of the iron halo effect you mentioned under certain circumstances).

I've never used a multifrequency VLF such as some of the Minelabs either, but I've seen many that say they will detect deeper in the ground than they air test under the right circumstances.

In my opinion air tests are anything but useless, at least for single frequency VLFs (again, my knowledge of multifrequency VLFs and PIs is lacking). They can let you know if something on your unit isn't performing properly or if you're in a in a high EMI environment and need to shift frequencies if you have that capability.



Edited 2 time(s). Last edit at 05/14/2016 06:58PM by DFinTX.

DFinTX Wrote:
-------------------------------------------------------

> I've never used a multifrequency VLF such as some
> of the Minelabs either, but I've read plenty that
> says they will detect further in the ground than
> they air test under the right circumstances.

I have heard this too but it doesn't make sense to me. Can anyone explain this or is it just marketing? I don't see how or why it would be the case.

Air tests are not useless - but if you think they tell you much about performance in bad ground of one machine relative to another, good luck with that.

Machines as a rule do not gain depth in the ground. There are however machines that lose far less depth when used in real conditions than other machines. A basic PI air tests poorly against a hot VLF. However, in real bad ground the VLF may lose half its depth, the PI only 10%. Those are not quotable figures, just an illustration about what I am trying to convey.

Multi frequency is a bit similar to PI in that regard.

The only real thing that matters in most metal detecting is how well a detector cancels the ground, unless you have very mild ground. Air tests cannot reveal how well a detector handles the ground. It is like air testing machines to see which one works best in salt water. What's the point?

Now, if you want to see what a detector can't do, air tests are great. I do not expect my detectors to perform better in ground than in air. Air is the 100% best case scenario in nearly all scenarios.

Steve Herschbach Wrote:
-------------------------------------------------------
> Air tests are not useless - but if you think they
> tell you much about performance in bad ground of
> one machine relative to another, good luck with
> that.
>
> Machines as a rule do not gain depth in the
> ground. There are however machines that lose far
> less depth when used in real conditions than other
> machines. A basic PI air tests poorly against a
> hot VLF. However, in real bad ground the VLF may
> lose half its depth, the PI only 10%. Those are
> not quotable figures, just an illustration about
> what I am trying to convey.
>
> Multi frequency is a bit similar to PI in that
> regard.
>
> The only real thing that matters in most metal
> detecting is how well a detector cancels the
> ground, unless you have very mild ground. Air
> tests cannot reveal how well a detector handles
> the ground. It is like air testing machines to see
> which one works best in salt water. What's the
> point?
>
> Now, if you want to see what a detector can't do,
> air tests are great. I do not expect my detectors
> to perform better in ground than in air. Air is
> the 100% best case scenario in nearly all
> scenarios.


This is exactly what I thought. Thank you.

P.I.s in general should airtest as deep as they can go in Most soil's...

Some clay's Like I have causes weird things to happen to a P.,I. signal..

BUT also a P.I. I have found that say may only hear a dime at 11 inches in airtest but will hear 13 inch buried dime it usually because there's some EMI present in the air...the Pulse coils can pick up alot of NOISE and you not even hear it when the coil is not grounded..but drop coil to the soil and the EMI is lessened and depth can seem deeper than the air..But check the dime say in another spot in the air and it ,may airtest 14 inches and will also hear the 14 inch dime...

But a P.I. should airtest in optimum emi environs as deep as it can go and possible deeper...Some soils like I said can still cause a P.I. to be reduced..RED Clays are one but the still are better at punch than a VLF in red clay..

Keith

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



Edited 1 time(s). Last edit at 05/14/2016 08:37PM by Keith Southern.

Quote:"I've read plenty that say [multi-freq Minelabs] will detect further in the ground than they air test under the right circumstances. // I have heard this too but it doesn't make sense to me. Can anyone explain this?"
It's simply because they air-test poorly. I understand it's to do with their 'automatic ground balance' behaviour, which misbehaves when there's no ground to measure, thus setting up the machine in a compromised way. Put them above real ground, they do what they were designed to do.
I've no idea if it's actually possible to trick a BBS machine into giving a good airtest, eg. by having the machine stationary above real dirt, and sweeping the target above the coil.



Edited 1 time(s). Last edit at 05/14/2016 08:07PM by Pimento.

Hi,,,,Minelab use to have on their web site that a machine can't go deeper in the ground than it's air test....For some reason that page disappeared....I think when a rumor got started about Minelab's not air testing good but going deeper in the ground is when that page went bye-bye....I do believe that they lose a lesser amount than most machines do....A metal detector won't go deeper in the ground than it air tests.....JJ

Well, there is a common case where a detector will indeed go deeper in the ground than it air tests...
...and it's because most people air test in their house/kitchen where the EMI is sky-high, then hunt in an area where there is very low EMI.

The silent EMI around a house...and even of the ignition noise of vehicles driving by...can adversely affect any detector.

You'll notice this tendency (to be affected by EMI) quite obviously if you crank up the gain on a TDI while near 'civilization'.

mike

[www.fisherlab.com]

PI's are susceptible to all sorts of EMI, some which can last a second or two or that is ever changing.
On my PI I have a 15 turn frequency control which you can adjust the khz in micro amounts to combat EMI.
Like the motorcyle's engine EMI emitted. Amazing how much EMI is out there that passes right thru your brain.
We now live in a very noisy environment that is manmade added to the naturally occurring EMI, sun, solar flares etc.

DeepTech Vista X with 3 search coils.
Works for me

Mike in CO Wrote:
-------------------------------------------------------
> Well, there is a common case where a detector will
> indeed go deeper in the ground than it air
> tests...
> ...and it's because most people air test in their
> house/kitchen where the EMI is sky-high, then hunt
> in an area where there is very low EMI. ...

Agreed! And if they don't air test in the house, they do it in the back yard,
usually not far from power lines. Lots of EMI problems there, especially
in big cities.

So air tests without EMI would be good and yes doing an air test in a house is a terrible idea just due to metal all over the place in walls and such. A yard can work well if there is no EMI.

I actually have a very high end EMI detector that I had to purchase several years back when we were building a house a few hundred yards from a cell phone tower and I needed to make sure the waves were not coming near the property. It turned out they were and we didn't buy but I still have the detector. The detector cost just as much as the service so I said forget hiring someone and bought it myself. I actually use it in my house to place beds and stuff so that we are near the least amount of it. Even in a room with wifi you can avoid it but you need to know exactly where the signal is beaming. I have found that certain frequencies can go through my walls and certain will not. Its a pretty cool detector. Obviously its strong near computers, TVs, sockets, etc but then it will randomly beam through your house at points. The biggest things I have found that cause it are flat screens and microwaves. When the microwave is on it produces dangerous levels like 10 ft out. The TV is around a 2-3 ft halo.

Hi,,,,Specifics Bob (from the movie Phenomenon) I don't know why people are trying to complicate the question ever further by adding the EMI factor.....Okay, with all things being equal (EMI etc.) a detector will not go deeper in the ground than it air tests at.....A PI & VLF detector that air tests equally will probably share equal in ground test too, under low ground mineralization conditions....The PI detector will win over the VLF detector when the ground mineralization increases....I won't go into the debatable halo issue........JJ

"I don't know why people are trying to complicate the question ever further by adding the EMI factor"
Because it's relevant. If you want to do a proper comparison, do both the air-test and the ground-test in the same location, at the same time.
Just to complicate things further (hehe) EMI can increase depths (mainly in air-tests). Say your machine has a threshold, and if the target strength is above that, it beeps. Add some mild EMI, and the (EMI + target) signal can further exceed the detectors' threshold, in a broken fashion. This allows you to get a signal from a weaker target.

And just for fun: In my opinion, pinpointers go further in-ground, because the ground gives a signal, hence (target + ground) will be a stronger signal than target alone. Not always useful, though, as strong ground, like wet salt beach, will cause the pointer to trigger without any target at all.



Edited 1 time(s). Last edit at 05/15/2016 09:29PM by Pimento.

Hi Pimento,,,,Hey it took you long enough to get on here and dispute my latest opinion.....You always come out when I post an answer and try to dispute what I said.....I was just sitting here waiting for you to say something,,I actually told my wife that you would when I made my reply....First off the poster never mentioned EMI.....So now you are saying that EMI is a welcomed intrusion while someone is out detecting..LoL..."Because it's relevant. If you want to do a proper comparison, do both the air-test and the ground-test in the same location, at the same time."...........I did say this ..........Okay, with all things being equal (EMI etc.) a detector will not go deeper in the ground than it air tests at.....I'm saving the best for last because I never lay all my cards on the table at once....I could actually dispute a lot of things said and back them up with facts not fiction,but I don't....I just sit here and grin..... JJ

Pimento Wrote:
-------------------------------------------------------
> Quote:"I've read plenty that say will detect
> further in the ground than they air test under the
> right circumstances. // I have heard this too
> but it doesn't make sense to me. Can anyone
> explain this?"
> It's simply because they air-test poorly. I
> understand it's to do with their 'automatic ground
> balance' behaviour, which misbehaves when there's
> no ground to measure, thus setting up the machine
> in a compromised way. Put them above real ground,
> they do what they were designed to do.
> I've no idea if it's actually possible to trick a
> BBS machine into giving a good airtest, eg. by
> having the machine stationary above real dirt, and
> sweeping the target above the coil.

I would assume that an automatic ground balance machine would air test the same as ground with no mineralization, right? On my CZ21, when I am at my beaches with low mineralization I can set my ground balance or 1 or 10 but it has no effect on depth because there is hardly any mineralization...similar to an air test. So ground balance shouldn't affect the depth unless the machine has problems detecting in ground with low mineralization. I dont see how ground would make a difference since the machine should know its low mineralization vs high not air vs ground.

Quote
pimento
If you want to do a proper comparison, do both the air-test and the ground-test in the same location, at the same time.

For in the ground depth, yes because mineralization and ground type can play a big factor. But an air test should produce an average depth for each machine regardless of location. Obviously if the person is doing it in their house or something they may get some funky results but overall and air test in one state should be the same as one in another assuming there isnt some type of obvious interference. Of course things like settings and hot vs cold machine will play a difference but there should be an average. I believe NASA Tom has stated some of the CZ3D average air tests depths that one should have.



Edited 2 time(s). Last edit at 05/15/2016 05:22PM by adamBomb.

Just for fun, and because it dawned on me that I had never really air tested my GPX, I took it out to see what it could do in the air. I have used these things for a long time now and know what they are capable of in bad ground, including red clay. I have more hours on pulse machines in the last 6 or so years than I have on VLF machines. Anyway I was not disappointed in the air test numbers, as those are pretty much the same as what we see in the ground with the GPX.

Using the stock 11 inch coil and simple Normal timing, everything else at factory presets. I did a noise cancel and tested a Quarter, Dime, Nickel, Copper penny, and a .58 minie ball.

Quarter - 17 inches
Nickel - 19 inches
Dime - 15 inches
Penny - 15 inches
Minie - 15.5 inches

In the ground there is not much deviation or loss from that, vs the VLF machines that may air test close or better to those numbers.

JJ: I've never felt EMI a welcome intrusion in real-dirt hunting, I feel this is because my machine doesn't have a lack of sensitivity to targets, it lacks the ability to discriminate correctly on weak targets (they get called 'iron'). So a small depth gain by adding 'just the right amount of EMI' is unlikely to result in more weak targets correctly identified. It's hard to judge, I admit, as you can't turn the EMI on/off to see the difference. This 'calling weak targets iron' effect doesn't happen in an air-test, discrimination seems to work well out to the limit of the machine.
Adam: I think you're correct about single-freq machines, the ground-balance setting seems to have little obvious effect on airtest results. The BBS in essence uses two frequencies (3.125 KHz / 25 KHz) and then does some math to work out what's ground and what's target. The math uses such science as: Knowing how the ground behaves at 3 KHz allows you to calculate how it behaves at 25 KHz. And vice-versa. So if you measure ground response at both the freqs, you can in effect subtract one from the other, and almost eliminate what's 'ground' and leave what's 'target'. If there isn't real ground present, with real fluctuations (that you would get while sweeping), this math may not deliver what is expected.
My earlier idea of doing an airtest above dirt is flawed, as (presumably) you would fix the search-coil in place, and thus there would be no fluctuations in the ground signal.
[ this method is used for testing PI machines, though - I think Eric Foster has recommended it.]



Edited 1 time(s). Last edit at 05/15/2016 10:29PM by Pimento.

Hi,,,,You will see an obvious affect on a Garrett AT Pro when shifting the ground balance settings, especially between high & low conductor objects as far as depth goes in an air test....Tesoro actually gives instructions in their manual for the ground balance settings when doing an air test, there's more etc....Below is some food for thought that you can chew on....

Dave Johnson says..... "A properly done “air test” provides an indication of a machines 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”


Gary's site.........This myth is Busted
Can machines that don't air test well, go deeper in the soil ?
No absolute Crap !! this is scientifically impossible if a machine air tests badly it will detect badly in the soil despite 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. If you suspect these results are wrong, please go out there and do the buried coins test for yourself. I think you will be amazed!!!!.

[www.garysdetecting.co.uk]

George Payne says basically the same thing,but I can't find the page yet, besides I'm done with this thread .....JJ

Daniel Tn Wrote:
-------------------------------------------------------
> Just for fun, and because it dawned on me that I
> had never really air tested my GPX, I took it out
> to see what it could do in the air. I have used
> these things for a long time now and know what
> they are capable of in bad ground, including red
> clay. I have more hours on pulse machines in the
> last 6 or so years than I have on VLF machines.
> Anyway I was not disappointed in the air test
> numbers, as those are pretty much the same as what
> we see in the ground with the GPX.
>
> Using the stock 11 inch coil and simple Normal
> timing, everything else at factory presets. I did
> a noise cancel and tested a Quarter, Dime, Nickel,
> Copper penny, and a .58 minie ball.
>
> Quarter - 17 inches
> Nickel - 19 inches
> Dime - 15 inches
> Penny - 15 inches
> Minie - 15.5 inches
>
> In the ground there is not much deviation or loss
> from that, vs the VLF machines that may air test
> close or better to those numbers.


Some good info Daniel.
Ever air tested the 5x10 commander coil??

Re: the "food for thought that you can chew on", there's nothing to chew on, it's all well-known stuff that's been discussed plenty of times before, I agree with 100% of it.

And regarding PI testing:
Here's a post from Eric Foster on another forum, about PI testing:

"There is no reason an air test should be worse than an "in ground" test, except for noise. When I do tests in my garden, which is in quite a noisy location, it is very noticeable that the noise diminishes as the coil is lowered toward the ground, even from 6 inches down to 1inch height. For an air test, always have the coil horizontal. Noise signals are polarized so that a vertical coil will always pick up far more noise than a horizontal one. For a realistic air test, lay the coil on a piece of 1in thick wood, MDF, or plastic on the ground surface, then wave a target over the top of the coil. The range obtained will not be measurably different to that if the target was buried. The above is true for PI detectors, but not necessarily so for induction balance types"



Edited 2 time(s). Last edit at 05/16/2016 09:16AM by Pimento.

Id say EMI is important ...... especially if you are new. Grabbing a new machine on Christmas with little experience turning it on and air testing it on a dime in the living room may well lead you to believe it works better in the dirt/sand out there in no where land. Common sense tells one ...... if the air test is done properly its a good gage. Once you start adding all that soil to be processed its a new ball game. Thats why you might just want to air test a few machines when buying....... because all machine arent equal, even new ones can vary. Auto GB may change things as well when air testing.

Dew



Edited 1 time(s). Last edit at 05/16/2016 09:59AM by dewcon4414.

I had a big plastic barrel that i drilled holes down the side and slid in small plastic tubing into, then filled with soil. At the time i had an etrac and set the coil flat and stationary on top, got a thin piece of wood with a coin taped to the end and slid it in and out of the tubing at different depths down the side of the barrel and the depth results were very very good, i guess as the detector could gb to the dirt?

OK, I found this in another forum and there are some technical responses. Essentially what they indicate is this:

Air testing will show a machine's depth potential. So if one CZ machine air tests at 8", and one CZ tests at 11", the 11" machine will always test deeper in the same soil/conditions.

Quote

I have no electronic background but once had a detector's radio signal described to me by a Navy man who was trained on sonar and radar and all things related. He said a detector's signal would always work at its best potential in the air where the minimal interference existed. A vacuum chamber is the only environment that would be better for it to work in. Needless to say we don't live in a vacuum. He went on to say any water or dirt you will encounter can only absorb or block your detector's signal.

Quote

I just got off the phone with an engineer at Fisher Research Labs and this is what he told me: "Only in very rare conditions will a detector read deeper then it reads in an air test. We have units that air test at 14" but in actual hunting conditions they will only go to about 9 inches."

And the technical explanation:

Quote

physics is physics. If a specific transmitter with long wave propagation characteristics (2.3-70 Khz) with a set RF power output such as a metal detector has a specific transmitting range and detection, it will be ideal and optimal in air. Ground loss tangent, eddy currents, magnetic inhomogeneities associated with minerals and other factors will mean there will always be a net loss in ground unless volume density reduction is involved or water saturation enhances propagation. Assuming a metal detector has the right processing hardware, software and properly coded algorithms in the spatial frequency domain, detection range will always be best in air assuming the above did not take place. The air test is great for determining free air loss characteristics and ultimate potential of a metal detector in non-mineralized loamy or sandy soil. A metal detector with the right hardware and software that air tests very well will usually (not always) perform better than one that does not air test as well.

Example, two Etracs one with a specific software version (v3) that codes a mineral gradient different than say Etrac number 2 with a different firmware and hardware surface mounted components and PCB. Version 3 air tests at 13" on a quarter version 2 air tests at 10" on a quarter. Version 3 will have better in ground performance than V2. This is why you see F75 and F75 LTD, SMALL CHANGES IN HARDWARE AND SOFTWARE. The LTD version will air test significantly better in air and ground!

Here is a link to that discussion: [www.treasurenet.com]



Edited 3 time(s). Last edit at 05/16/2016 01:09PM by adamBomb.

adamBomb Wrote:
-------------------------------------------------------
> OK, I found this in another forum and there are
> some technical responses. Essentially what they
> indicate is this:
>
> Air testing will show a machine's depth potential.
> So if one machine air tests at 8", and one tests
> at 11", the 11" machine will always test deeper in
> the same soil/conditions.
>
> I have no electronic background but once had a
> detector's radio signal described to me by a Navy
> man who was trained on sonar and radar and all
> things related. He said a detector's signal would
> always work at its best potential in the air where
> the minimal interference existed. A vacuum chamber
> is the only environment that would be better for
> it to work in. Needless to say we don't live in a
> vacuum. He went on to say any water or dirt you
> will encounter can only absorb or block your
> detector's signal.
>
> I just got off the phone with an engineer at
> Fisher Research Labs and this is what he told me:
> "Only in very rare conditions will a detector read
> deeper then it reads in an air test. We have units
> that air test at 14" but in actual hunting
> conditions they will only go to about 9 inches."
>
> And the technical explanation:
>
> physics is physics. If a specific transmitter with
> long wave propagation characteristics (2.3-70 Khz)
> with a set RF power output such as a metal
> detector has a specific transmitting range and
> detection, it will be ideal and optimal in air.
> Ground loss tangent, eddy currents, magnetic
> inhomogeneities associated with minerals and other
> factors will mean there will always be a net loss
> in ground unless volume density reduction is
> involved or water saturation enhances propagation.
> Assuming a metal detector has the right processing
> hardware, software and properly coded algorithms
> in the spatial frequency domain, detection range
> will always be best in air assuming the above did
> not take place. The air test is great for
> determining free air loss characteristics and
> ultimate potential of a metal detector in
> non-mineralized loamy or sandy soil. A metal
> detector with the right hardware and software that
> air tests very well will usually (not always)
> perform better than one that does not air test as
> well.
>
> Example, two Etracs one with a specific software
> version (v3) that codes a mineral gradient
> different than say Etrac number 2 with a different
> firmware and hardware surface mounted components
> and PCB. Version 3 air tests at 13" on a quarter
> version 2 air tests at 10" on a quarter. Version 3
> will have better in ground performance than V2.
> This is why you see F75 and F75 LTD, SMALL CHANGES
> IN HARDWARE AND SOFTWARE. The LTD version will air
> test significantly better in air and ground!
>
> Here is a link to that discussion:
> [www.treasurenet.com]
> on/196086-air-testing-metal-detectors-does-work.ht
> ml

Your opening line here in your post---I wouldn't necessarily agree with it.

The word detect--- just what are we talking about.

You see it can have different meanings.

What do I mean by this???

A machine may indeed air test deeper than another say on a nickel.

But the machine that air test deeper,,,may not detect the nickel as a nonferrous target in higher mineral vs the detector that was beat out when compared to air test.

Now the detector that indeed beat the other may actually give a signal using discrimination on the deeper nickel--- the tone and meter reading ( if applicable) could be in error. ( calling nonferrous targets actually ferrous)

Of course it should be said here,,,a detector's True All metal depth ( again if applicable) will have lower loss percentage wide vs using discrimination when the same detector is compared air test distance wise vs in ground depth wise ( any and all mineral levels of soil).

From my experiences,,detectors with boost processes,,sure they seem to get an advantage when airtestiing,,even using discrimination--- but throw one of these babies over some high mineral ground,,,boost process more or less unusable or won't provide advantage-- actually most times brings disadvantages for depth.



Edited 2 time(s). Last edit at 05/16/2016 01:05PM by tnsharpshooter.

Hi,,Personally I don't think I would buy a used detector without an air test being done...It's a lot harder to get a detector dealer to do one on a new machine....Most (99.9%) of my comments above were geared towards the use of a VLF machine....Adam in regards to this:::::"Air testing will show a machine's depth potential. So if one machine air tests at 8", and one tests at 11", the 11" machine will always test deeper in the same soil/conditions.".........This statement is probably talking about the same make & model of machines.....This may not apply on two different brands of machines especially if they share different frequencies etc.....I have witnessed brand A machine air test a coin at 18" and brand B air test a coin at 10"... brand B would win hands down in the in ground tests....I believe brand B's lower frequency and it's ability to handle the dirt better gave it the edge over brand A..... And lastly, certain brands seem to suffer less loss of penetration in the dirt than others.....JJ

PS: Disregard this statement I could not stop myself..............."besides I'm done with this thread"

Figuratively speaking the mildest soil is air.

But I guess it could be possible for even air to be different.

Seems by looking at the TV,,the air here in Tn maybe a lot milder than the air in China.

Can air actually support particles containing mineral???

I'll leave this question for the experts..

Have been in a few dust storms in some areas with it seems higher mineral soil.



Edited 1 time(s). Last edit at 05/16/2016 01:19PM by tnsharpshooter.

Ok, I changed that to make it so the machines were the same. I think this is really what it comes down to - how well does the machine handle the conditions. A machine that air tests a dime at 8'' isn't going to pick them up in the ground at 12 inches unless there is a halo effect. But a machine that air tests a dime at 10'' might detect much less depth than that machine that picks it up at 8'' due to the way they handle the ground. This is why PIs which air test the same as a VLF go deeper than the VLF in tough ground conditions but are probably the same in low mineralized ground. Same can be said with VLF machines that are dual frequency vs single frequency in salt water.

So this would make air testing valuable for your machine and machines designed for similar conditions. Then the next part of that is how well is your machine going to work in the conditions you are trying to detect at. So I am a beach hunter and if my excal/CZ can get 8'' depth on a dime in an air test than thats what I should expect on a low mineralized beach and that number will go down as the ground gets more mineralized. But if my excal air tests the dime at 8'' but my CZ 6'' I would expect the excal to have great depth in low and high mineralized ground...unless the CZ handles the mineralization better...right? And the only way to test that is actual ground tests.



Edited 1 time(s). Last edit at 05/16/2016 01:22PM by adamBomb.

Hi,,,,,The halo affect is a very controversial subject the experts say no & I say yes.....Good Luck..........JJ

You may be right as well when talking about the freq the machine is running at.