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What does Jeff Foster say?
- Thread starter Rob (IL)
- Start date
Jeff Foster
New member
Hi Rob,
In the book, "The MXT Edge," I compare all five of the White's MXT search coils that where available prior to publication. (I hope to get a chance to compare the 12" Spider in the near future.)
Coils are ranked for EMI susceptibility, In-Air (very low mineralization) performance, and In-Mineralization performance for increasingly strong ferrous mineralization ground.
The 6x10 DD coil did much better in the EMI tests on the MXT than it did on the DFX. This was the big surprise for me and this anecdotally seems to be consistent with more glowing comments on this coil from MXT users than from DFX users.
In terms of target ID performance, in "good" ground, the stock 9.5 inch coil does better, deeper, than the 6x10DD coil.
"Good" versus "Bad" ground is covered in detail. Briefly:
A simple means of estimating the strength of the ground mineralization is presented in the book (although not as flexible as the DFX technique) that utilizes a deliberately set ground-balance error and the coin depth indicator. (As I stated many times, the GND reading does not provide an indication of how "bad" the ground is.) This technique provides info on how strong the ground mineralization response is, relative to the strength of a coin-sized target at different distances from the coil. For example, ground mineralization that has a response comparable to a coin 10 inches from the coil (10 MXT coin-inches) would be far weaker than a mineralization response that is similar in strength to a coin 1 inch (1 MXT coin-inch) from the coil.
The relative performance of the search coils are shown, in terms of target ID consistency, for ground conditions that range from 12 coin-inches (very low, aka in-air) to 0 coin-inches (mineralization as strong as a coin in contact with the search coil
In the book, "The MXT Edge," I compare all five of the White's MXT search coils that where available prior to publication. (I hope to get a chance to compare the 12" Spider in the near future.)
Coils are ranked for EMI susceptibility, In-Air (very low mineralization) performance, and In-Mineralization performance for increasingly strong ferrous mineralization ground.
The 6x10 DD coil did much better in the EMI tests on the MXT than it did on the DFX. This was the big surprise for me and this anecdotally seems to be consistent with more glowing comments on this coil from MXT users than from DFX users.
In terms of target ID performance, in "good" ground, the stock 9.5 inch coil does better, deeper, than the 6x10DD coil.
"Good" versus "Bad" ground is covered in detail. Briefly:
A simple means of estimating the strength of the ground mineralization is presented in the book (although not as flexible as the DFX technique) that utilizes a deliberately set ground-balance error and the coin depth indicator. (As I stated many times, the GND reading does not provide an indication of how "bad" the ground is.) This technique provides info on how strong the ground mineralization response is, relative to the strength of a coin-sized target at different distances from the coil. For example, ground mineralization that has a response comparable to a coin 10 inches from the coil (10 MXT coin-inches) would be far weaker than a mineralization response that is similar in strength to a coin 1 inch (1 MXT coin-inch) from the coil.
The relative performance of the search coils are shown, in terms of target ID consistency, for ground conditions that range from 12 coin-inches (very low, aka in-air) to 0 coin-inches (mineralization as strong as a coin in contact with the search coil
Hey Rob----Yes Jeff does do this in a lot of diff, ways---The 6"X10 DD does beter than the 9.5" in mineralization ground, but in low mineralization ground the two are close, I have had the book for a few months now, I will be going back to Ganes Creek Alaska for the 3 time now, and think the book is well worth the money----Jack
Jeff Foster
New member
"What do you mean by MXT coin- inch?"
A coin-inch is a term I use to describe the strength of ground mineralization.
The depth indicator on an MXT is calibrated to relate signal-strength to the depth of coin-sized targets. When the MXT is ground-balanced to the ground's VDI number, the depth indicator (really just a signal strength indicator) responds just to the buried target.
However, if the ground-balance is not balanced to the ground's VDI number, the "depth indicator" (remember, it's really just a signal strength indicator) can be made to respond to the ground's mineralization alone.
The ground-balance system only hides the effects of ground mineralization
A coin-inch is a term I use to describe the strength of ground mineralization.
The depth indicator on an MXT is calibrated to relate signal-strength to the depth of coin-sized targets. When the MXT is ground-balanced to the ground's VDI number, the depth indicator (really just a signal strength indicator) responds just to the buried target.
However, if the ground-balance is not balanced to the ground's VDI number, the "depth indicator" (remember, it's really just a signal strength indicator) can be made to respond to the ground's mineralization alone.
The ground-balance system only hides the effects of ground mineralization
Jeff, I have your book and read it. I've also read your description of "phase no." vs. actual ground mineralization. I'm still confused. Can you explain, once and for all, what exactly "phase" as measured on the MXT means compared to mineralization and "bad" ground? I know that any metal or mineral has a phase component and an amplitude component and that the detector discriminates based on the ratio of these two.
Thanks!
Thanks!
Jeff Foster
New member
'what exactly "phase" as measured on the MXT means compared to mineralization and "bad" ground?'
Here's a copy of a summary post I recently wrote that may help:
I don't know if this will help or not. I've devoted much attention to detailing ground mineralization in both "Digging Deeper with the DFX" and "The MXT Edge," but here's a summary stab at the problem. Numbers are added to the paragraphs in an attempt to help facilitate questions on the topic.
(1) Mineralized soil is soil that contains stuff to which a metal detector's search coil reacts, which is not a buried target. Mineralization itself is the stuff to which a metal detector's search coil reacts when the search coil is near soil (and is not a target).
(2) There are two distinct types of mineralization
Here's a copy of a summary post I recently wrote that may help:
I don't know if this will help or not. I've devoted much attention to detailing ground mineralization in both "Digging Deeper with the DFX" and "The MXT Edge," but here's a summary stab at the problem. Numbers are added to the paragraphs in an attempt to help facilitate questions on the topic.
(1) Mineralized soil is soil that contains stuff to which a metal detector's search coil reacts, which is not a buried target. Mineralization itself is the stuff to which a metal detector's search coil reacts when the search coil is near soil (and is not a target).
(2) There are two distinct types of mineralization
Thanks a lot, Jeff! I got it now. To summarize, the VDI phase reads whether the ground is predominantly magnetic or salty NOT how "bad" it is as far as QUANTITY of magnetic or salt. Hate to be so dense, but it took a while.
Here near Portland Oregon, the phase always reads pretty high. I always thought that it corresponded to "bad" ground, but I couldn't figure out how we could have that much magnetic content all over the place ;-) Now I think it is more the fact that we have LOTS of rain here which washes away any salt type minerals and leaves a predominance of magnetic material which is read. Next I need to actually measure how "bad" the ground really is using your method. There must be something going on, because around here, 6" is about the limit for a silver dime in discriminate (doesn't matter which detector - I've had them and tested the best ones). 12" coins is dreaming around here ;-)
George
Here near Portland Oregon, the phase always reads pretty high. I always thought that it corresponded to "bad" ground, but I couldn't figure out how we could have that much magnetic content all over the place ;-) Now I think it is more the fact that we have LOTS of rain here which washes away any salt type minerals and leaves a predominance of magnetic material which is read. Next I need to actually measure how "bad" the ground really is using your method. There must be something going on, because around here, 6" is about the limit for a silver dime in discriminate (doesn't matter which detector - I've had them and tested the best ones). 12" coins is dreaming around here ;-)
George
Jeff in MI
New member
I thought I knew my MXT pretty well, but Jeff sounds like a "real" expert. I like the way he explains things.
Thanks, Jeff in Flint, MI
Thanks, Jeff in Flint, MI
Jeff Foster
New member
You got it. Here's a post from a couple of years ago that has related info:
More Mineralization Info
Enjoy.
More Mineralization Info
Enjoy.
hardrockminer
New member
Mr. Foster,
Bought your book about a month ago
It's great I love books on a subject because its easier to home-in on your area of interest and use as a reference , than DVD's. I've had a MXT for a couple of years & really not really understood there potential. After Steve Herschbach post on his forum about the MXT & the reference to your book, I bought your book.>>>>>>>>>>>>>>>>Your knowledge of all levels of operation of the MXT is awesume + differant coil potentials.>>>>>>>>>>>>hardrockminer
Bought your book about a month ago
It's great I love books on a subject because its easier to home-in on your area of interest and use as a reference , than DVD's. I've had a MXT for a couple of years & really not really understood there potential. After Steve Herschbach post on his forum about the MXT & the reference to your book, I bought your book.>>>>>>>>>>>>>>>>Your knowledge of all levels of operation of the MXT is awesume + differant coil potentials.>>>>>>>>>>>>hardrockminerJackpine Savage
Active member
referring to electrically conductive "stuff" approaching 0?
I admit I get a bit confused on the mineralizatin issue primarily because my ground here is "easy". One condition I see with detectors that have phase readings (and one with a Fe bargraph) is that low mineral wet quartz sand on fresh water beaches will show high phase readings yet the depth obtainable on coins can be as much greater than in air tests. One of the newer multi purpose detectors with auto tracking sometimes reverts to a "preset GB" range when tracking over certain fresh water beaches. In the case of these beaches is "electrically conductive" the right term to use??? Could there be some condition other than conductive salts involved?? anyway, it is nearly a perfect medium for most detectors. One of the above mentioned detectors in the 13 Khz range was unable to handle the VDI wrap of iron in the low mineral sand, the 7.5 Khz machine was flawless.
Tom
I admit I get a bit confused on the mineralizatin issue primarily because my ground here is "easy". One condition I see with detectors that have phase readings (and one with a Fe bargraph) is that low mineral wet quartz sand on fresh water beaches will show high phase readings yet the depth obtainable on coins can be as much greater than in air tests. One of the newer multi purpose detectors with auto tracking sometimes reverts to a "preset GB" range when tracking over certain fresh water beaches. In the case of these beaches is "electrically conductive" the right term to use??? Could there be some condition other than conductive salts involved?? anyway, it is nearly a perfect medium for most detectors. One of the above mentioned detectors in the 13 Khz range was unable to handle the VDI wrap of iron in the low mineral sand, the 7.5 Khz machine was flawless.
Tom
Jackpine Savage
Active member
Jeff,
In the older post linked to you stated:<p>But, a high GND number does not indicate strong mineralization. It only means that the mineralization that is there is predominately ferrous. It could be very weak ferrous mineralization without much conductivity (moisture in which salts are dissolved or solid mineral conductivity outright), or it could be strong mineralization. The GND reading cannot tell you how strong the mineralization is and therefore cannot tell you whether a smaller coil is in order.
Where I get confused is in the use of the term "conductive ground" as it relates to detectors! To me and my experience here, highly conductive ground sounds like a good thing when in fact, ferrous mineralization combined with salts (like on some ocean beaches, is a very bad thing!
We need to come up with a name for the conditions described in bold above other than "damn good ground"
Tom
In the older post linked to you stated:<p>But, a high GND number does not indicate strong mineralization. It only means that the mineralization that is there is predominately ferrous. It could be very weak ferrous mineralization without much conductivity (moisture in which salts are dissolved or solid mineral conductivity outright), or it could be strong mineralization. The GND reading cannot tell you how strong the mineralization is and therefore cannot tell you whether a smaller coil is in order.
Where I get confused is in the use of the term "conductive ground" as it relates to detectors! To me and my experience here, highly conductive ground sounds like a good thing when in fact, ferrous mineralization combined with salts (like on some ocean beaches, is a very bad thing!
We need to come up with a name for the conditions described in bold above other than "damn good ground"
Tom