Detection distance, ground vs air

[green]

I'm wondering if I test the detection distance of a coin with a PI detector with GEB on and adjusted to cancel ground will the detection distance be different in ground or air. WM6 posted a ground detection method http://www.geotech1.com/forums/showt...723#post228723. Looks like it might be a good way to test detection distance in the ground. Wondering if using a piece of 1 inch plastic water pipe to keep the hole from caving in would effect the test. Would it be a valid test for ground vs air detection depth? Should I expect the detection depth to be different, air vs ground?

[ivconic]

I'm wondering if I test the detection distance of a coin with a PI detector with GEB on and adjusted to cancel ground will the detection distance be different in ground or air. WM6 posted a ground detection method http://www.geotech1.com/forums/showt...723#post228723. Looks like it might be a good way to test detection distance in the ground. Wondering if using a piece of 1 inch plastic water pipe to keep the hole from caving in would effect the test. Would it be a valid test for ground vs air detection depth? Should I expect the detection depth to be different, air vs ground?

That's very important question, i've been asking myself so many times while watching similar tests.
I am standing at point that there is not possible to mimic real world situation with artificial set up on similar testing beds. Not even close. And that's the huge problem that generates lot of confusion and mixup.
For example, how to mimic the situation with let's say Roman bronze coin laying in soil for 2000 years? All those time undisturbed. It is not possible.
Such coin will most certainly have "hallo" field around and will present 3x larger target ( there is no exact rule, sometimes it will be 5x larger target and sometimes even smaller target than it physically is) than the coin someone buried in soil just the other day... or last year; it doesn't make significant difference at all. It's the "variable" so unpredictable that will totally spoil any chance for proper conclusion.
That's why real world situation is one thing and artificial set up situation will always be quite another thing.
...
PI detector with adjusted GEB will probably be "deeper" in air than in soil, it's logical.

[homefire]

Like any other MD the Ground Signal is going to clutter the Rx Signal to some point. Any signal filtered by the GEB includes Target signal too.

That's my story and I'm sticking with it ! LOL

[green]

Like any other MD the Ground Signal is going to clutter the Rx Signal to some point. Any signal filtered by the GEB includes Target signal too.

That's my story and I'm sticking with it ! LOL

The target causes an amplitude and phase shift with a VLF detector so I was thinking with target in ground or air would make a difference. The target causes a amplitude change with a PI detector. The signals add so I was thinking GEB would subtract the ground signal and the target signal would be the same in air or ground with GEB on and adjusted to cancel the ground signal. Not the same with GEB off. Maybe my thinking is all wrong. If I found a target distance in air that caused an integrator out reading 50 to 100 for some signal resolution and then measured the signal with target in the ground at the same distance, all with GEB on. Would that indicate whether there is a difference or is there a better test?

GEB on effects the target signal the same with the target in the air or the ground.

[homefire]

Regardless using GEB or not the Ground induced signal is going to affect the ability to distinguish a target or not. Like seeing something in a Snow Storm..

HF

[Nexus]

My experience with GPX5000 and Garrett ATX shows that there is no difference between air and in ground depth with them. At least non that I can measure out of the random error level.
The reason for PI not to lose depth in the ground is simple. It does not discriminate ground interference like most IB detectors.
Now there are those who insist that PI goes actually deeper in the ground especially in mineralized soil, but I have found no evidence of this.

[Qiaozhi]

The target causes an amplitude and phase shift with a VLF detector so I was thinking with target in ground or air would make a difference. The target causes a amplitude change with a PI detector. The signals add so I was thinking GEB would subtract the ground signal and the target signal would be the same in air or ground with GEB on and adjusted to cancel the ground signal. Not the same with GEB off. Maybe my thinking is all wrong. If I found a target distance in air that caused an integrator out reading 50 to 100 for some signal resolution and then measured the signal with target in the ground at the same distance, all with GEB on. Would that indicate whether there is a difference or is there a better test?

GEB on effects the target signal the same with the target in the air or the ground.

The method a PI detector uses to achieve ground balance is entirely different to a VLF detector. In a ground-balancing PI there are two samples taken (ignoring the EFE sample in a mono-polar PI for now to keep it simple). Firstly the usual main sample is taken, and typically between 5us and 25us later a second (GEB) sample. The idea is that both samples will contain the ground signal, and this will remain substantially unchanged between the two samples. Therefore, subtracting an amplified version of sample 2 from sample 1 will remove the ground signal. The amplification of sample 2 is required to compensate for the exponential decay of the received signal, and the amount of gain is used to adjust the ground balance. However, since the target signal is also present in both signals, a certain amount of the target signal is also lost, and consequently using GEB in a PI detector results in a loss of depth. On the other hand, without GEB, the ground conditions could be too bad to detect without it.

If you're not using a bipolar TX (and that's true for many hobby PI detectors) then you also need an Earth Field Elimination (EFE) pulse. In this case you have: S1 = main sample, S2 = GEB sample and S3 = EFE sample.
The calculation is then: X = A1(S1 - S2) - A2(S3 - S2)
which subtracts the ground sample from the main and EFE samples before finding the difference.
A2 is the ground balance control gain, and adjusting this will eliminate ground.
The same result can be obtained by adjusting the sample pulse widths proportionally, instead of keeping them the same as in the above example.

An alternative calculation is: X = A1(S1) + A2(S2) - A3(S3)
where A2 = A1 + A3
This gives the same result.

As a practical example, the White's TDI works as follows:
Turn on TX for 100us.
Shut off and enter flyback.
Wait for 10us and take main sample.
At the end of the main sample pulse, wait a short time and take the GEB sample.
At the end of the GEB sample pulse, wait a long time and take two EFE samples.
Use a differential integrator to subtract the EFE1 from the main sample.
Use a second differential integrator to subtract EFE2 from the GEB sample.
Subtract A1(main - EFE1) - A2(GEB-EFE2), and adjust A2 for ground balance.
In the TDI, all the samples have the same width (between 5us and 25us), and the delay between main and GEB samples is also between 5us and 25us.
The spacing between GEB and EFE samples is 50us or more.

[Tibuck19]

Can anyone speculate the Depth lost with VLF in ground targets Vs Air ? Example my TGSL can detect a penny at 28cm/11inch in air with grand balancing done with a piece of ferrate, What in ground depth can I expect for a normal north American soils ?

[kt315]

not. there is same concept as Gallo - Formed for a long time, the conductive salts are carried out in the surrounding soil.
the gallo is INCREASING the depth, be cause general volume of metal+gallo is more than only the naked metal.
ie depth in ground approx equel depth in air despite on the ground.

[Tibuck19]

not. there is same concept as Gallo - Formed for a long time, the conductive salts are carried out in the surrounding soil.
the gallo is INCREASING the depth, be cause general volume of metal+gallo is more than only the naked metal.
ie depth in ground approx equel depth in air despite on the ground.

Really, That makes sense, I was always told that Vlf air test couldn't be used as a reference, for actual detecting depth, however if what you say is right, I have nothing to worry about.

[Alexismex]

I have a testing bed ground for 15 years with samples of iron recipient with copper and brass waste, aluminum car wheels, from 60 cm to 3 meters deep , in this area I test my pulse detectors, I can affirm that there is several factors that influence the detection,
1) the halo effect is real : now I detect much better than 10 years ago in the deep samples (3meters) with the same detector,
2) another important factor as the soil is mineralized I detect much better in the winter when the soil is very dry that in summer in the rainy season when the soil is humid,
3) another rare and proven many times (probe more than 100 times in this terrain) is the detection with a tracking of detecccion in movement Est- West is sometimes better than tracking North-South and without any explanation again it is the opposite way I detect better ???? will depend on electric current in the earth who know???

[WM6]

3) another rare and proven many times (probe more than 100 times in this terrain) is the detection with a tracking of detecccion in movement Est- West is sometimes better than tracking North-South and without any explanation again it is the opposite way I detect better ???? will depend on electric current in the earth who know???

If answer is not simple in targets shape and target orientation, then we need to think about
Earth magnetic field lines in interaction with coil magnetic field lines:

(this is frequent confusing "phenomenon" in deceptive world of LRL locators also)

https://www.google.com/url?sa=t&rct=...JXg8RiSjpQsjpT

[Koala]

Can anyone speculate the Depth lost with VLF in ground targets Vs Air ? Example my TGSL can detect a penny at 28cm/11inch in air with grand balancing done with a piece of ferrate, What in ground depth can I expect for a normal north American soils ?

nope


here in the UK.

Dry powdery yellow sand. Near as I can tell is 100% the same as air tests

A field I was in in Scotland that had a lot of coke on it. You struggled to get 3"

Most fields here are closer to air test distance. Often digging coins below pinpointer depth which is 9"

[qute1]

i agree here in east Anglia we have a mostly loamy soil which mostly agrees the air tests but in Wellingborough and Kettering areas they have a red coloured iron (and gold) rich clayey soil in which it is difficult to get 2" even with the best pi's (vallon even).

[DonCaffeDelaSkobalj]

Hey Aleximes

I am glad finaly to find one smart person here which has comfirmed existence of "Tha Halo" effect, the basics teaching of all LRL hunters. Bad detection due to humidity was based on phenomenon difraction in conatct with ions from the water in the ground or contact with humid air. Best E-W detection is due to Etheric wind (non electromagnetic nature) which blow from East to West (never contrary).

Best wishes Aleximes !
..................................

People here don't listen self proclamed Gurus from bananarepublic Slovenia or whatever else who said BIG LIE that "Halo effect is interaction between earth mag. field and coil mag. field". Halo is a REAL and EXIST whatever you want it or no. Nature of Halo phenomenon is extremely complex and need a lot of experiments including fronend reasearch of interference from Halo induced Scalar Magnetic field, against Earth's Scalar Mag. Field. All of this is due to a REAL EXISTING NATURE of Vector Magnetic Potential, which is a primary source of Vector (Hv = rot A) and Scalar field (Hsc** = -div A). The first one born the "Hot currents" with transversed kinematic, while the second one "Cold currents" with longitudinal kinematic.

But....., because this forum is for HALO NON-BELIVERS, i can't continue detailed explanations, simply because a wrong public is at outside of HaloGold coin.

Best Regards
DonCaffe