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australian electronic gold prospecting forum.com  |  Common interest forum.  |  General chat and discussion forum (Moderator: bugwhiskers)  |  Topic: Detecting Larger Nuggets 0 Members and 1 Guest are viewing this topic. « previous next »
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Aziz
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« Reply #60 on: Sunday February 1 2015 20:43:59 AEDT PM »

Hi all.

If ML won´t be able to offer/achieve the 40% detection depth increase, I will be doing it with ease.
But you guys aren´t really interested in team-working or sharing. Why should I share my knowledge with you now?

You have disappointed me. Very.
^
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WM6
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« Reply #61 on: Sunday February 1 2015 23:20:15 AEDT PM »

  

No detector in history has cleaned up the goldfields better than all the Minelab models.

I read somewhere that most gold has been found using old fashion BFO and TR machines and not with modern TI devices.
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« Reply #62 on: Monday February 2 2015 08:24:33 AEDT AM »

Aziz, I'm not that much into seeking gold but you know that I'll help as much as I can.
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« Reply #63 on: Monday February 2 2015 10:19:44 AEDT AM »

  
Hi all.

If ML won´t be able to offer/achieve the 40% detection depth increase, I will be doing it with ease.
But you guys aren´t really interested in team-working or sharing. Why should I share my knowledge with you now?

You have disappointed me. Very.
^


  Come on now Aziz.  Just about everyone here has offered help, its just you have ideas that only you understand.  I am no electronics expert, but I could probably get just about anything you want in electronics.  Just let me know what you need.
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« Reply #64 on: Thursday November 30 2017 09:02:26 AEDT AM »

Any word on that Dave Emery patent being published or granted ?
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Dontbstme
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« Reply #65 on: Sunday January 20 2019 01:38:40 AEDT AM »

Ok guys. This topic is ancient now, but it requires some clarity.

Why PI does not detect the really huge gold nuggets at the dreamed super depths?
Because it can not - this is the simple answer. Someone have mentioned the "long time constants" issue from the beginning of the tread and this is the very reason why the limits of PI have been reached long time ago. Not conspiracy or greed. Even much bigger coils would change this reality very little, not enough to justify the enormous difficulties to utilise them.

On the other hand VLF can do better with the "long time constants", much better, BUT not on every terrain and certainly not on the  heavy magnetic soil. There is a level of magnetic interference that VLF can handle with huge coils better than PI, but beyond that it becomes useless.
However not all ground in Australia is highly magnetic and definitely not every large gold nugget was found in the worse highly mineralised soil.

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« Reply #66 on: Sunday January 20 2019 10:14:54 AEDT AM »

  
Any word on that Dave Emery patent being published or granted ?

I have been informed that its about to be granted.
doug smile
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« Reply #67 on: Sunday January 20 2019 10:27:20 AEDT AM »

  
Even much bigger coils would change this reality very little, not enough to justify the enormous difficulties to utilise them.
I don't fully agree with this. Ground loops will  potentially detect large objects much deeper than any hand held coils. The reason is that with coils the Rx signal falls  as 1/r^6 for objects beyond the diameter of the coil.eg for an 18"mono  the Rx signal at 36" is 1/64th that of the object at 18"For a  large ground loop  the Rx signal falls off as 1/R^2  ie only by factor of 4. This is why Eric Foster and the late Jimmy Stewart were working on  ground loops.
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« Reply #68 on: Sunday January 20 2019 11:05:01 AEDT AM »

  
  
Even much bigger coils would change this reality very little, not enough to justify the enormous difficulties to utilise them.
I don't fully agree with this. Ground loops will  potentially detect large objects much deeper than any hand held coils. The reason is that with coils the Rx signal falls  as 1/r^6 for objects beyond the diameter of the coil.eg for an 18"mono  the Rx signal at 36" is 1/64th that of the object at 18"For a  large ground loop  the Rx signal falls off as 1/R^2  ie only by factor of 4. This is why Eric Foster and the late Jimmy Stewart were working on  ground loops.
doug smile

Here is a ground loop system (Ultratem deep mode) used for detecting large bombs to depths of 3.5 M. This  system would i am sure detect large  nuggets far deeper than anything currently available.
  
  
The transmitter can generate up to 200 amps into a 100x100m loop and in the TD switch off in 50 usecs! For nugget hunting a much smaller Tx loop would be used.
doug smile
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« Reply #69 on: Sunday January 20 2019 11:18:39 AEDT AM »

  
On the other hand VLF can do better with the "long time constants", much better, BUT not on every terrain and certainly not on the  heavy magnetic soil. There is a level of magnetic interference that VLF can handle with huge coils better than PI, but beyond that it becomes useless.
However not all ground in Australia is highly magnetic and definitely not every large gold nugget was found in the worse highly mineralised soil.

 Yes you have highlighted  some the limitations of VLF technology  for nugget hunting ie  the high and variable X  signal over heavy magnetic ground and particularly VRM ground.Most of  our goldfields in Australia tend to be quite mineralized and some are just horrific So any VLF technology will be some what restricted as to where it can be used.
doug smile
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bugwhiskers
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« Reply #70 on: Sunday January 20 2019 11:20:25 AEDT AM »

  
Any word on that Dave Emery patent being published or granted ?
[/quote
  
Any word on that Dave Emery patent being published or granted ?

Dave phoned this morning. It has been granted and he has the certificate. The web crawlers haven't picked it up yet. I will post the link when available.

Search on US 10181720
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« Reply #71 on: Sunday January 20 2019 18:45:36 AEDT PM »

  
  
On the other hand VLF can do better with the "long time constants", much better, BUT not on every terrain and certainly not on the  heavy magnetic soil. There is a level of magnetic interference that VLF can handle with huge coils better than PI, but beyond that it becomes useless.
However not all ground in Australia is highly magnetic and definitely not every large gold nugget was found in the worse highly mineralised soil.

 Yes you have highlighted  some the limitations of VLF technology  for nugget hunting ie  the high and variable X  signal over heavy magnetic ground and particularly VRM ground.Most of  our goldfields in Australia tend to be quite mineralized and some are just horrific So any VLF technology will be some what restricted as to where it can be used.
doug smile

I have done some tests on a "horrific" mineralised soil comparing GPX5000 with 10" mono to a very capable VLF with 10"DD, not on gold but on small ancient copper coins. If the two detectors were set to equally silent to the ground interference they both had the coin at 8" with this difference that the VLF also added very reliable direct discrimination, both visual and audio.
I know what the general perception regarding VLF is, but it is based only on what the big companies have to offer and they do offer much to put it mildly.

A question.
How would you describe a "horrific" ground in comparison to Iron ore? What percentage of Iron (or other metals) in ore would you say corresponds to the horrific definition?
I am asking so I can use some comparative method of testing.

I have also got as far as working VLF on pure black magnetite with limited results compared to PI, but working never the less. Considering no other VLF including the mighty CTX3030 would get to work there at all it's a step forward I would say.
I also managed to penetrate 92% Iron ore and get a tiny hammered gold coin across with VLF and with stable signal.
That tiny gold coin for some reason is undetectable by PI detectors.
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« Reply #72 on: Sunday January 20 2019 19:00:09 AEDT PM »

  
  
  
On the other hand VLF can do better with the "long time constants", much better, BUT not on every terrain and certainly not on the  heavy magnetic soil. There is a level of magnetic interference that VLF can handle with huge coils better than PI, but beyond that it becomes useless.
However not all ground in Australia is highly magnetic and definitely not every large gold nugget was found in the worse highly mineralised soil.

 Yes you have highlighted  some the limitations of VLF technology  for nugget hunting ie  the high and variable X  signal over heavy magnetic ground and particularly VRM ground.Most of  our goldfields in Australia tend to be quite mineralized and some are just horrific So any VLF technology will be some what restricted as to where it can be used.
doug smile

I have done some tests on a "horrific" mineralised soil comparing GPX5000 with 10" mono to a very capable VLF with 10"DD, not on gold but on small ancient copper coins. If the two detectors were set to equally silent to the ground interference they both had the coin at 8" with this difference that the VLF also added very reliable direct discrimination, both visual and audio.
I know what the general perception regarding VLF is, but it is based only on what the big companies have to offer and they do offer much to put it mildly.

A question.
How would you describe a "horrific" ground in comparison to Iron ore? What percentage of Iron (or other metals) in ore would you say corresponds to the horrific definition?
I am asking so I can use some comparative method of testing.

I have also got as far as working VLF on pure black magnetite with limited results compared to PI, but working never the less. Considering no other VLF including the mighty CTX3030 would get to work there at all it's a step forward I would say.
I also managed to penetrate 92% Iron ore and get a tiny hammered gold coin across with VLF and with stable signal.
That tiny gold coin for some reason is undetectable by PI detectors.

Horrific ground is that ground containing VRM maghemite. Frequency dependent magnetic susceptibility  soils are a huge problem for metal detectors.
The tiny gold coin i suspect has a very small Tc.
doug smile
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« Reply #73 on: Sunday January 20 2019 19:23:08 AEDT PM »

  
  
  
  
On the other hand VLF can do better with the "long time constants", much better, BUT not on every terrain and certainly not on the  heavy magnetic soil. There is a level of magnetic interference that VLF can handle with huge coils better than PI, but beyond that it becomes useless.
However not all ground in Australia is highly magnetic and definitely not every large gold nugget was found in the worse highly mineralised soil.

 Yes you have highlighted  some the limitations of VLF technology  for nugget hunting ie  the high and variable X  signal over heavy magnetic ground and particularly VRM ground.Most of  our goldfields in Australia tend to be quite mineralized and some are just horrific So any VLF technology will be some what restricted as to where it can be used.
doug smile



I have done some tests on a "horrific" mineralised soil comparing GPX5000 with 10" mono to a very capable VLF with 10"DD, not on gold but on small ancient copper coins. If the two detectors were set to equally silent to the ground interference they both had the coin at 8" with this difference that the VLF also added very reliable direct discrimination, both visual and audio.
I know what the general perception regarding VLF is, but it is based only on what the big companies have to offer and they do offer much to put it mildly.

A question.
How would you describe a "horrific" ground in comparison to Iron ore? What percentage of Iron (or other metals) in ore would you say corresponds to the horrific definition?
I am asking so I can use some comparative method of testing.

I have also got as far as working VLF on pure black magnetite with limited results compared to PI, but working never the less. Considering no other VLF including the mighty CTX3030 would get to work there at all it's a step forward I would say.
I also managed to penetrate 92% Iron ore and get a tiny hammered gold coin across with VLF and with stable signal.
That tiny gold coin for some reason is undetectable by PI detectors.

Horrific ground is that ground containing VRM maghemite. Frequency dependent magnetic susceptibility  soils are a huge problem for metal detectors.
The tiny gold coin i suspect has a very small Tc.
doug smile

Here are some good papers on the  on magnetic soils and Frequency dependent magnetic susceptibility.
Workshop on Soil Magnetism:Multidisciplinary Perspectives,Emerging Applications and New Frontiers Report
  
Another  with very heavy maths!!
  
doug smile
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« Reply #74 on: Sunday January 20 2019 19:56:26 AEDT PM »

Some more "light reading on VRM and magnetic soils.
Transient VRM Response From a Large Circular Loop Over a Conductive and Magnetically Viscous Half-Spac
e
very very heavy maths!!!
  
Another
  
The magnetic relaxation effect on TEM responses of a uniform earth
N.O. Kozhevnikov *, E.Yu. Antonov
  
Viscous magnetization of 0.04—100 jum magnetites
  
Soil Electromagnetic Properties and Metal Detector Performance Theory and Measurement
G. Cross, Terrascan Geophysics
  
 Technical Note TN-36
THE MAGNETIC SUSCEPTIBILITY OF SOILS IS DEFINITELY COMPLEX
J. Duncan McNeill
April, 2013
  
doug smile
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« Reply #75 on: Sunday January 20 2019 20:55:32 AEDT PM »

There got to be a way to simplify your answer Doug.
I need an example of rock or ore that can be used for a comparative measurements. It does not have to describe the universe or the deepest mathematical formulae.

I am in a possession of stones that exhibit variable conductivity and magnetic properties measured in different directions on the same samples and they have proven to be real crap, but still not an impossible barrier.

May be you can trow a few rock samples over the post for me. I'll pay the shipping cost what ever it will be.
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