Air test comparisons?

Sounds like you have very low mineralization in your area Detector. That's nice! I have noticed even in Colorado the the farther you move away from the mountains the lower the mineralization unless you are near a river. The park areas and private lawns around me measure as moderate levels. Shallow coins less than 3 inches generally exhibit the stability between air and ground that you described. When you get deep the coins will progressively give higher VDI readings (between 4 and 8 inches). This changes depending on what mode I am hunting with on the DFX. Here are some observation on Wheat Pennies and Silver Dimes that I have performed in the field.

Wheat Penny at 5 to 7 inches. (I dug over 400 this year)

Air (79-80)
15Khz (80-83)
3Khz (85-87)
Correlate (85-87)
Best Data (83-85)

Silver Dime at 5 to 7 inches (I dug 34 this year)

Air (80-81)
15Khz (80-82)
3Khz (92-93)
Correlate (89-91)
Best Data (84-85)

I can generally tell when I am digging Silver. The tone holds steady and rolls a bit more for Wheats. Throw an old Spruce tree overhead and the acidity will almost hide those Wheats. Dimes seem to come in just a little lower. 15Khz is the most accurate. 3Khz always comes in real high. I hunt with correlate to deal with iron masking. It comes in high as well. So you can see that air and ground readings are very different for me. I am only using a recovery speed of 17 and a sweep speed of 1, this could have something to do with these results. I have been using the Super12 coil almost exclusively. Like you said Detector, sometimes you just get a weird target that does not play buy the rules. I have taken the time on approximately 20% of my targets to change settings and experiment before I dig.

Keep Swing'in
Jack

UK Brian said:

The DFX results were compared on this forum soon after it started and proved discrimination can't be trusted.

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This is quite simply not true. Anyone who has used a DFX for any length of time will agree. Discrimination is very consistent on targets less than 7 inches. The VDI and tone vary depending on soil but are for the most part constant within an area. I generally hunt private yards and public grassed areas. It would be rude to dig everything and destroy the lawns. The discrimination on the DFX is precisely why I can go out and find old coins and not leave a place looking like a bombing range. As a side note. Targets in the Nickel range are always a good idea to dig. Thats where the a lot of the gold is.

Keep Swing'ing
Jack

I agree somewhat with what you are saying, but... the DFX like most machines at 8" goes thru some changes that only an experience user will know. Wrap around may move a nickel or dime to the negitive side of the VDI. Most of the time these tests are done by companies with shall we say an agenda. Otherwise, its very difficult for someone to be skilled enough with all those machines to tweak them for optimum performance. So, im assumeing most are done with OUT OF THE BOX performance. Until you have some time under your belt with your machine you cant rely on other peoples performance. Because you may never achieve their level of performance with that machine. Too many people are trying to find a shortcut to making a lot of good finds....aint happening, you have to pay your dues with your equipment.

dewcon said:

but... the DFX like most machines at 8" goes thru some changes that only an experience user will know. Wrap around may move a nickel or dime to the negitive side of the VDI.

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I have a Wheat penny in my test garden that does this. I have it buried 10 inches deep, or at least thats where it was a year and a half ago. I agree experience is the best discriminator once developed. I am still working on mine. I am sure it will be a continuing education.

Keep Swing'in
Jack

Not just on this post but other places I have read about detectors getting 8, and up to 12 inches with a stock coil, in soil. That just does not seem right.
Alghough I have not used it much, when I was using the MXT I dont remember ever getting any solid hits over, say, 5 or 6 inches. It could be I am not as versed as I think I am with the MXT but I doubt it.
I gotta go detect.... later.

Alghough I have not used it much, when I was using the MXT I dont remember ever getting any solid hits over, say, 5 or 6 inches. It could be I am not as versed as I think I am with the MXT but I doubt it.

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That has been my experiences as well Bajanick. I can remember a few times when my DFX was dead on solid sound and VDI, like on a nickle at 8", but that was the exception. Most of the time after about 5-6", depending on conditions, both the sound/tone and VDI become less reliable. But for the most part, for me, below 5" and I get the same reading in the ground I get in the air. There can be a slight variation, but you can get a slight variation in the air as well.

Point being, an air test can give you a good idea of what to listen for and look for on the same target in the ground. Giving some value to an air test.

Bajanick said:

Not just on this post but other places I have read about detectors getting 8, and up to 12 inches with a stock coil, in soil. That just does not seem right.
Alghough I have not used it much, when I was using the MXT I dont remember ever getting any solid hits over, say, 5 or 6 inches. It could be I am not as versed as I think I am with the MXT but I doubt it.
I gotta go detect.... later.

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The answer to your question is in what you wrote.

I dont remember ever getting any solid hits over, say, 5 or 6 inches.

For the real deep ones, you won't necessarily get a solid hit. Indeed, many may just be a "whisper" type signal, characterized by a repeatable rise in the threshold volume as you sweep over it. This is the MXT mixed mode capability in action.

In general, you will not get a solid beep unless the signal strength is high enough for the Target ID & discriminator circuit to do their thing. In other words, deep coin sized targets will frequently not give you solid hits.

I agree with UK Brian about air testing.

Come on Detector and Rudy, i know you guys have dug coins deeper than 8" with a solid tone. I dug a dime and two wheats today that a deaf man could have heard and all were over 8". Yes there was a lot of bounce on the screen, but the tone was undenyable. Its rare that i let the screen determine what i dig. I think too many people are "taking their detectors for a walk" and just skipping over some great finds. Sweep speed has a lot to do with it... even in air tests you will move the coil or probe until the sound is to your likeing not realizing what you did. There is a lot of ground to cover, hey but there is always tomorrow .

Electronic parts tolerance

A lot of electronic parts have a tolerance of 10 or 20% in their value. Does anyone know if one machine off the assemble line can vary by 10 or 20 percent on performance and still pass inspection. I just did an air test on my Prizm 4 and got 5.5 inches at the center of an 8 in coil. The speed I moved the coin across the coil had a lot to do with detection distance. Moving slow it would not detect 5.5 inches. I was at Folly beach and I found a .25 clad at least 9 or 10 inches. I can not air test that deep.

First test using a zinc penny above

Firt test using a penny zinc penny above

dewcon said:

Come on Detector and Rudy, i know you guys have dug coins deeper than 8" with a solid tone. I dug a dime and two wheats today that a deaf man could have heard and all were over 8". Yes there was a lot of bounce on the screen, but the tone was undenyable. Its rare that i let the screen determine what i dig. I think too many people are "taking their detectors for a walk" and just skipping over some great finds. Sweep speed has a lot to do with it... even in air tests you will move the coil or probe until the sound is to your likeing not realizing what you did. There is a lot of ground to cover, hey but there is always tomorrow .

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Dewcon,

You are right, I've dug coins much deeper than 8" that came through loud and clear. I've also hunted in ground so badly mineralized that getting a reliable signal past 6" was by no means assured.

Let me clarify my use of the term tone. I use tone ID to help me determine what my DFX is seeing in the ground so I don't need to look at my VDI all the time. I do get a solid sound on many targets 8" or more, but from about 5-6" and deeper, the tone ID becomes less reliable.

pennysaver

I don't know what the accepted tolerances are with detector manufactures, but I have yet to own a lemon, and I've owned many different detectors over the years. I saw many post that their DFX would only get 6" in an air test. I was so confused because my air tests were far different, I did a video to show I get 9-10" with the factory Coin & Jewelry program on a 10k ring. While I could never expect this depth in the ground on this ring, on a beach it would be quite obtainable. I suspect you are not getting your best air test depth because you're looking for that solid sound or ID.

I think where some people see such a large difference in their air tests and ground tests can be explained. I think it may lay in the ground balancing, or lack there of, of some detectors used in these tests. For me ground balance is second to none on my priority list. I think a good GB(ground balance) is essential for good depth, good ID'ing and good target separation. I suspect if you have a detector that has a factory preset GB(misleadingly often called an "automatic GB) then an air test will not live up to your ground tests. You will see very poor air tests and much better in ground experience.

Most detectors first look to see if a target exists by monitoring the GB point for a sharp quick change/phase shift. Once this occurs, then the signal is sent to the discrimination circuits for analyzing. The reason the Whites MXT is considered to be more sensitive and have better depth than the DFX is it's superior GB system. It uses the same GB system as their GMT which is very aggressive and very fast. I think a lot of these air tests vary because either they are not taking the time to get a proper GB, or their detectors have a preset GB which isn't going to give you a good air test compared to its ability in the ground. So for this reason I say air tests can be misleading as far as depth and sensitivity goes.

Nice video. Thanks for the effort.

Detector,

To get good air test results on an MXT (and by extension the M6) is to first lock the ground balance. Otherwise the MXT will track to the target.

staffordshire metal detectors in the uk did a test of some sort on detectors.
I hope this link works

http://www.staffsmetaldetectors.co.uk/depth_test.htm

Pennysaver, there's such a difference that I only buy detectors from dealers who allow me to pick from three or four of a model which I test on their in ground test bed and then swap the coils round to sort out the best of the bunch.
When I got a test arranged on U.K. Detector Net there was a variation of up to two inches between the best and the worst performing XLT. A similar test of the DFX produced the result of only one inch difference but if you had the lemon it was three inches down from the best of the bunch.
It applies to all makes. Tesoro was noted for having both hot and cold models.
Florida Electronics (Mac 1 Turbo), Troy Shadows (true ones, not the X2 by Tesoro) and a few other brands made the point of using military or medical grade componants and the reduced tolerance they accept makes all the difference to the final product. The reason for the depth of the Nexus range was not due just to the coil design which had been used on other detectors before but because Georgi was scrapping a very large percentage of the coils that other manufacturers would let pass to save on cost.

The Staffordshire test Smuger refers to failed to impress over here because as a dealer the machines test were often trade ins or ones that he had obtained off E-Bay. Some lemons, some fiddled with internally etc being compared with brand new detectors of the brands he sells.

I agree Brian there deffently are differences in detectors. Some people beleave they have a hot machine just because they have to use less sensitivity than most people. Sometimes thats just a less than great coil or bad connection line. I have used machines that i KNEW werent up to par... sent them in and sure enough they needed recalibarted or a new coil. Dont be fooled thinking you have a hot machine... it could be EMI or a calibration issue that needs to be fixed.