In not for sure machines should be airtested with coil Vertical

to the earth....

I dont usually airtest a metal detector with coil standing vertical on a table...

I did the other day for the F44 video and noticed my numbers were weaker than in ground...

I have always tested my detectors in the AIR coil horizontal to the earth but facing up and got the measurements off the backside of the coil towards control box...Ive alwasy gotten the greatest airtest numbers with coil like this....(HORIZONTAL)

So now I wonder if TRUE airtest numbers SHOULD NOT be got from a vertical measurment...the numbers i get with the coil MY WAY are adding 3 inches to my airtest...nickle at 14 dime at 13..


Coils I believe are designed to work in horizontal plain to the earth, not vertical..

EMI noisy or silent or whatever has a greater chance to wreak havoc on your test when coil is vertical..

Ive done my first and last vertical airtest ..

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 06/02/2015 07:24PM by Keith Southern.

I always do air-tests with the coil horizontal because (a) that's how they're used in real life (b) loop antennas will pick up more radio interference when vertical.
Radio interference can help or hinder depth (in my opinion). In order for a machine to 'give a beep', the signal level produced by the target has to exceed a certain threshold. If there's RFI noise, then this adds to the target's signal, effectively making it larger, so less target signal is needed to exceed the threshold. But it's obviously very jumpy, and this resulting extra depth is a bit unpredictable. And it's well-documented how it can hinder performance.

Regarding "in the field" radio interference, I think that having the coil close to the ground is better than, say 10 inches above. Radio antennas in general work better when they're higher up, the close ground must hinder the coils' RF pickup in some way. So possibly the best way to air-test is to fix the coil upside down, fairly close to real ground, and then do the tests. But the coil must not move at all, and obviously there should be nothing metal in the ground at the test location. You don't need to try and ground balance, it's irrelevant as the ground isn't moving. I've never actually tried air-testing this way, though.



Edited 1 time(s). Last edit at 06/02/2015 10:31PM by Pimento.

You guys have totally confused me now! - not that that is hard to do.

Most folks air test by arranging the coil so that a line drawn across the coil is perpendicular to the ground. Now the coul is rotated up 90 degrees fronm it's usual searching orientation - Let,s call this Position A

The altermnative would be to have the same line parallel to the ground (the same alignment as ehen the coil,is in use detecting). Lets call this Position B

Keith, is your "horizontal" alignment "Position A" or "Position B"?

Rick Kempf
Gold Canyon AZ- where there is no gold

Tom----Where are you on this Tom????

PI's are should alwaysbe air tested thru a matrix horiz with the search coil. The matrix can be anything: piece of wood................

DeepTech Vista X with 3 search coils.
Works for me

I agree, Sven, that's true for PI's, as they measure the ground, even when the coil is not moving, so placing the coil at 'normal height' above the ground and then moving targets above the coil is the best way to air-test them.

VLF's try and filter out the wobbling ground signal. If it's rock solid because the coil is stationary, they will completely eliminate the ground signal that's picked up. And if the coil is in the air, away from everything, then there's no ground signal to filter out, anyway. So it doesn't matter, either way.
I often wondered if my method posted previously would be the best way to airtest BBS/FBS machines. They have a reputation for air-testing badly, I feel this is because the lack of real ground upsets their auto-ground-balance system, with resulting effects.



Edited 1 time(s). Last edit at 06/02/2015 11:02PM by Pimento.

A vertical coil (perpendicular to the ground) is probably experiencing greater EMI and electrical sferics from vertically polarized electric sources. But that it should decrease sensitivity by 3" on a coin seems too severe.

Perhaps somewhere in the house or nearby EMI was the culprit. I'd repeat the test and see if the delta changes.

dont do it like this..VERTICAL




Do it like this but outside..Horizontal



I really dont want to be close to the earth for my test as I am just doing a airtest not a mineral airtest combo...


what I usually do is hold detector rod straight up in the air and test targets back towards the housing you can get some great airtest depths with a coil suspended above the earth about 4 feet or more in the air and coil parallel to the earth flat coil plane to earth plane...

At least I have an idea of what maximum depth COULD be SOMEWHERE ,,LOL..

The more testing I do though im thinking of making a device to just hang the coil from a treelimb attached to the lower rod then measure like that ...

may do a video of my thought process..

Keith

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



Edited 2 time(s). Last edit at 06/02/2015 11:22PM by Keith Southern.

So Keith, they say one picture is worth 1000 words can you give us two pictures!

Now I'd like one word for each picture – horizontal or vertical?

The first picture is?

Second picture is?

I know you probably think it's obvious, but trust me it's not! – At least not to me!

Thanks advance for your polite patient answer and thank you so much for all your hard work.

Rick Kempf
Gold Canyon AZ- where there is no gold

Hmmm! A coil is an attenna - magnetic fields are created based on how the coil is wound (and freq, and power, etc) If you are far enough from anything that affects the magnetic field I see no difference between parallel to plain of earth vs perpendicular to plain of the earth.

So Keith based on what you are observing I have to conclude it is the earth that is affecting the results. Based on that I would say if the coil was 10,000 ft in air parallel or perpendicular would be too close to call. I wonder then how far above the earth you have to be before the earths effect is nill.

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!

Bryanna, it's not the magnetic pickup, it's the electric field that picks up the RFI. And most interfering sources are vertically polarised, so a vertical antenna picks them up better.
As for Rick, well the Horizon is horizontal, provided you're not too drunk.

The T2/F75 platform (prior to the EMI quiet V2) are ideal examples of witnessing that air tests should be performed with coil parallel to the ground. There is nearly an entire different 'group' of EMI when the coil is vertical. Have you ever detected a target...... (with coil obviously parallel to the ground).................. then set your detector down to dig the target (placing to coil in a position other than parallel with Earth............. and then you hear a different group/type of EMI?
Yes...... Vertical & Horizontal EMI polarization does indeed differ.

Hi,,,Tesoro recommends air testing with the ground balance control set half way.....I think if you ground balance to a ferrite rod vertical or horizontal the results should be the same....JJ

Alles klar Herr Kommisar!

Thanks for editing your post Keith and labeling the photos

Pimento - I have seen the horizon at all kinds of angles while sober - doing aerobatics in a T-38 mostly! lol

Rick Kempf
Gold Canyon AZ- where there is no gold

Seems reasonable to what Keith is saying, however just check the videos with individual air tests and guess they are all doing it wrong....
I guess air tests have their place but lets test them in the ground where it counts and with the ground being different from State to State tests have to differ as some are highly mineralized and some not.....

Most of the time I tape the lower rod with one inch masking tape. Do a wrap at 6", 8", 10" up to around 16" from the top, flat surface of the coil. Then just hold the detector up in the air with the coil in a horizontal plane and test away if I'm looking for a air test distance number. Don't even have to write on the tape.

The nice thing about the tape on the lower rod is that I can leave it on all the time and do a quick check in the field for silent emi effects if I happen to care at the time. Kind of depends on what I'm looking for as to whither or not I care.

HH
Mike

Thats exactly how I airtest Mike and why I get some good airtest numbers most of the time..




Keith



Mike Hillis Wrote:
-------------------------------------------------------
> Most of the time I tape the lower rod with one
> inch masking tape. Do a wrap at 6", 8", 10" up
> to around 16" from the top, flat surface of the
> coil. Then just hold the detector up in the air
> with the coil in a horizontal plane and test away
> if I'm looking for a air test distance number.
> Don't even have to write on the tape.
>
> The nice thing about the tape on the lower rod is
> that I can leave it on all the time and do a quick
> check in the field for silent emi effects if I
> happen to care at the time. Kind of depends on
> what I'm looking for as to whither or not I care.
>
>
> HH
> Mike

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

Yes - true I should of said electric field. But my basic thoughts are correct in that if far enough away from interference should be no difference between verticals or horizontal. Also good point on the RFI polarization - suspect it has a lot to do with what Keith observed Thanks.

Pimento Wrote:
-------------------------------------------------------
> Bryanna, it's not the magnetic pickup, it's the
> electric field that picks up the RFI. And most
> interfering sources are vertically polarised, so a
> vertical antenna picks them up better.
> As for Rick, well the Horizon is horizontal,
> provided you're not too drunk.

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!