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  #41  
Old 12-22-2017, 08:51 AM
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You only know what you are finding and not what you are missing.You are missing probably 25% of the finds from masking or from choice of frequency used. I don't really believe in the halo effect, it has more to do with the coil sweep/ground conductive properties/angle of sweep upon the target, whether the geomagnetic field and ground disturbance of where you are searching. Be grateful for what you are able to find, curse what you are not and never give up !

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  #42  
Old 12-22-2017, 10:04 AM
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Those guys who do believe in the halo effect and are iusing detectors that are not known for depth might get a real surprise if they get a deep detector and go back to the same sites they beat to death.... just saying

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  #43  
Old 12-22-2017, 10:09 PM
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Originally Posted by calabash digger View post
Those guys who do believe in the halo effect and are iusing detectors that are not known for depth might get a real surprise if they get a deep detector and go back to the same sites they beat to death.... just saying

Sure would , then we don't have to rely on the halo effect to have a chance at the deep stuff.

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  #44  
Old 12-22-2017, 10:19 PM
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On more than one occasion , Ive pulled a coin from the ground and still got a good signal from the discolored impression left in the ground by the coin until further inspection destroyed the impression and scattered it , poof ! no more signal. That's the halo , and it can work even when the coin is gone. That equals bigger target profile. With all the experience you guys have , its hard to believe you never noticed this happening yourself.


The controversy continues.....

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  #45  
Old 12-24-2017, 09:22 AM
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You need to get a go pro and film that next time it happens... would love to see a detector hitting the lech out from coins.

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  #46  
Old 12-24-2017, 11:13 AM
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Originally Posted by calabash digger View post
You need to get a go pro and film that next time it happens... would love to see a detector hitting the lech out from coins.
I've had it happen too. I'll try to get some video next time.

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  #47  
Old 12-24-2017, 11:31 AM
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Originally Posted by ohiochris View post
On more than one occasion , Ive pulled a coin from the ground and still got a good signal from the discolored impression left in the ground by the coin until further inspection destroyed the impression and scattered it , poof ! no more signal. That's the halo , and it can work even when the coin is gone. That equals bigger target profile. With all the experience you guys have , its hard to believe you never noticed this happening yourself.


The controversy continues.....
That 'Stomp' trick seems to break this halo/aura anomaly up for me...settles everything down somewhat...Like an unexpected punch to the jaw of the Earth... to confuse it and set it back a bit and let it knows who's boss for a minute......less backscatter ghost signal interferance or something?.....disrupts the ghost signal chaff and lets the good tone targets pop through crisper?...

I dont know if this description makes any sense?..... but it works, or I wouldnt do it.......especially in an area with several targets under the coil at the same time...super cool and helpful for identifying and unraveling a tight multidenom pocket spill especially...in amidst iron scrap for sure.. .... a simple quick brisk stomp and resweep..takes no time...no thinking about the concept of things and what goes on down there or pondering the dirt/metal symbiotic relationship...Mystery....Cut through the pre fight trash talking !!!! with a good sock to the jaw...

I also 'hop coil' in these situations instead of a side to side sweep...Stomp, Hop, Stoop N Stab...there you are my beauty! Like my byline states...metal likes to be in the ground, and the ground dont like to give it up easily...

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  #48  
Old 12-24-2017, 11:53 AM
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The think to remember is that unlike a coin iron will eventually deteriorate away to the point where a masked coin will become detectable. It's just a matter of time. You may hunt a site for years and years and then that time comes where a piece of iron that had been masking a coin rots away enough that the conductive signal prevails. Boom! a good coin out of a site that had been hunted to death by the best. Found with a $50 Bounty Hunter.

Stomping just speeds up the deterioration process but breaking up the leached halo of the iron.

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  #49  
Old 12-30-2017, 04:27 PM
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I'm not a believer in the halo effect, i've dug old coins that have been in the ground a 1000yrs, and many that have left a mass of stain in the soil, but once i've removed the coin, none of my machines have ever sounded off on the leached stain in the soil.

I don't believe either that a standard vlf will go deeper in soil than in air on a solo sitting target.
I know of a manufacturer said it was scientifically impossible for a vlf to detect deeper in air than in ground, then all of a sudden he broke the news he had invented a detector that could do that very thing, load of bollock$ in my opinion.

My machine will air test a large copper at about 2ft, hands up who thinks it will find the same coin in ground at 3ft lol.
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  #50  
Old 12-30-2017, 04:34 PM
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Originally Posted by ghound View post

My machine will air test a large copper at about 2ft, hands up who thinks it will find the same coin in ground at 3ft lol.
I can hit a beer can at 3 feet in the ground, whats your point?

Just because you have not personally witnessed it, it must be impossible huh?

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  #51  
Old 12-30-2017, 04:53 PM
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Next time you find say a 10" deep coin that has leached into the soil, remove the coin and test the leaching with your detector.

If it doesn't signal the leaching an inch away, ask yourself how it can signal it at 10"
A coin degrading into tightly packed soil may help it's electrical connection, that i can buy into.



Originally Posted by Jason in Enid View post
I can hit a beer can at 3 feet in the ground, whats your point?

Just because you have not personally witnessed it, it must be impossible huh?

Last edited by ghound; 12-30-2017 at 05:16 PM.
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  #52  
Old 12-30-2017, 05:52 PM
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Originally Posted by ghound View post
Next time you find say a 10" deep coin that has leached into the soil, remove the coin and test the leaching with your detector.

If it doesn't signal the leaching an inch away, ask yourself how it can signal it at 10"
A coin degrading into tightly packed soil may help it's electrical connection, that i can buy into.
I HAVE seen that.

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  #53  
Old 12-30-2017, 06:46 PM
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HALO EFFECT and related ground oddities
Dave Johnson, FTP-Fisher 9 April 2012
Halo Effect
There are lots of reports by detectorists of “halo effect”. The story is usually that a buried object (for instance in
a test garden) became more detectable the longer it was in the ground; or, that a long-buried object was detected
at a depth beyond what would have been expected. The popular theory is that corrosion products create a
conductive “halo” around the metal object, increasing its effective size. Here’s my take on the subject.
Soil disturbance I believe that many reports of “halo effect” are actually a misinterpretation of soil
disturbance. When an object is buried, the act of digging and refilling the hole creates a localized soil anomaly
which causes the detected signal to either add to or subtract from the signal from the metal object. What
actually happens depends on the kind of soil and the details of how the detector processes signals, but most
often the detectability of the target is reduced. Over time the disturbed soil settles and becomes mixed with
surrounding soil by earthworm activity etc. such that the anomaly is gradually erased.
Gold Gold doesn’t corrode. Most detectorists say that they have observed that gold exhibits no halo effect.
In the case of natural gold, it is often found in an accumulation of magnetite, which may either increase or
decrease detectability depending on circumstances, but most often it will decrease detectability. The effect of
magnetite, which is disturbed upon removal of the gold from its natural setting, could lead a detectorist to
believe they’ve observed a halo effect when in fact there was none.
Iron Iron does corrode. This reduces the amount of metallic iron, which reduces the signal produced by the
iron target. However, in many soils, the corrosion products create a ring of high magnetic susceptibility rust
particles surrounding the object, and as the searchcoil sweeps over the object, the rust particles bounce the
signal around. The way signals are processed in most modern machines, the bounce from the rust particles
boosts the signal from the conductive metal at the center of the rusted mass, raising its apparent conductivity
making it harder to discriminate out. Detectorists are often puzzled that when they pull the iron target out of
the ground and air test it, it seems a rather weak target and discriminates out easily. What happened is that the
rust anomaly stayed in the dirt.
Copper (including copper alloys such as brass and bronze) In alkaline soils, copper alloys are fairly stable,
but in acid soils they corrode sometimes fairly rapidly especially in the presence of sulfur. The result is a green
ring of corrosion products around the metal piece the mass of which is reduced by corrosion. There are many
reports of presumed halo effect in relation to copper alloys, such an interpretation being encouraged by the
obviousness of the corrosion halo.
But there’s this little problem: the electrical conductivity of the corrosion halo is very low compared to metal.
Therefore we need other interpretations. Interpretation #1: the object in question was a high-conductivity
coin, for example a wheat penny. Corrosion makes it thinner, increasing its effective resistance. Although the
total signal is weakened, the resistive component of the signal which is primarily responsible for detection of
metal objects is actually increased. Interpretation #2: maybe the chemical corrosion processes also change the
iron chemistry of the soil in the corrosion halo, either increasing or decreasing their magnetic susceptibility.
This could theoretically impact detectability. ………Some experienced detectorists may say that these two
theories are inadequate to explain what they have actually observed. And that may be true. These theories just
happen to be the best ones I’ve got for now, they’re not a final word on the subject.
Silver “Big picture” fairly similar to that of copper. In most soils, silver is much more resistant to corrosion
than copper alloys. Corrosion products of silver may have higher electrical conductivity than those of copper,
but still, for a given amount of silver the electrical conductivity of the corrosion products is far lower than that
of silver in solid metal form.
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  #54  
Old 12-30-2017, 08:40 PM
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Congratulations, you learned how to copy and paste!

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Old 12-30-2017, 11:07 PM
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Originally Posted by ghound View post
HALO EFFECT and related ground oddities
Dave Johnson, FTP-Fisher 9 April 2012
Halo Effect
There are lots of reports by detectorists of “halo effect”. The story is usually that a buried object (for instance in
a test garden) became more detectable the longer it was in the ground; or, that a long-buried object was detected
at a depth beyond what would have been expected. The popular theory is that corrosion products create a
conductive “halo” around the metal object, increasing its effective size. Here’s my take on the subject.
Soil disturbance I believe that many reports of “halo effect” are actually a misinterpretation of soil
disturbance. When an object is buried, the act of digging and refilling the hole creates a localized soil anomaly
which causes the detected signal to either add to or subtract from the signal from the metal object. What
actually happens depends on the kind of soil and the details of how the detector processes signals, but most
often the detectability of the target is reduced. Over time the disturbed soil settles and becomes mixed with
surrounding soil by earthworm activity etc. such that the anomaly is gradually erased.
Gold Gold doesn’t corrode. Most detectorists say that they have observed that gold exhibits no halo effect.
In the case of natural gold, it is often found in an accumulation of magnetite, which may either increase or
decrease detectability depending on circumstances, but most often it will decrease detectability. The effect of
magnetite, which is disturbed upon removal of the gold from its natural setting, could lead a detectorist to
believe they’ve observed a halo effect when in fact there was none.
Iron Iron does corrode. This reduces the amount of metallic iron, which reduces the signal produced by the
iron target. However, in many soils, the corrosion products create a ring of high magnetic susceptibility rust
particles surrounding the object, and as the searchcoil sweeps over the object, the rust particles bounce the
signal around. The way signals are processed in most modern machines, the bounce from the rust particles
boosts the signal from the conductive metal at the center of the rusted mass, raising its apparent conductivity
making it harder to discriminate out. Detectorists are often puzzled that when they pull the iron target out of
the ground and air test it, it seems a rather weak target and discriminates out easily. What happened is that the
rust anomaly stayed in the dirt.
Copper (including copper alloys such as brass and bronze) In alkaline soils, copper alloys are fairly stable,
but in acid soils they corrode sometimes fairly rapidly especially in the presence of sulfur. The result is a green
ring of corrosion products around the metal piece the mass of which is reduced by corrosion. There are many
reports of presumed halo effect in relation to copper alloys, such an interpretation being encouraged by the
obviousness of the corrosion halo.
But there’s this little problem: the electrical conductivity of the corrosion halo is very low compared to metal.
Therefore we need other interpretations. Interpretation #1: the object in question was a high-conductivity
coin, for example a wheat penny. Corrosion makes it thinner, increasing its effective resistance. Although the
total signal is weakened, the resistive component of the signal which is primarily responsible for detection of
metal objects is actually increased. Interpretation #2: maybe the chemical corrosion processes also change the
iron chemistry of the soil in the corrosion halo, either increasing or decreasing their magnetic susceptibility.
This could theoretically impact detectability. ………Some experienced detectorists may say that these two
theories are inadequate to explain what they have actually observed. And that may be true. These theories just
happen to be the best ones I’ve got for now, they’re not a final word on the subject.
Silver “Big picture” fairly similar to that of copper. In most soils, silver is much more resistant to corrosion
than copper alloys. Corrosion products of silver may have higher electrical conductivity than those of copper,
but still, for a given amount of silver the electrical conductivity of the corrosion products is far lower than that
of silver in solid metal form.

There are some problems with this guys logic.....

" But there’s this little problem: the electrical conductivity of the corrosion halo is very low compared to metal. "

......sure , but the electrical conductivity of the corrosion halo in most cases is much HIGHER than the ordinary soil surrounding it. Not only that but the corrosion halo is at times saturated with moisture , increasing conductivity...either way the overall result is often ( though not always ) a bigger profile , more conductive than the soil surrounding it. While that slightly larger profile might be partly a slightly less conductive halo your detector is going to call it ALL the same because the base metal itself is larger than the halo , they are touching , and together they are massively more conductive than the surrounding soil

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  #56  
Old 12-30-2017, 11:13 PM
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Originally Posted by calabash digger View post
You need to get a go pro and film that next time it happens... would love to see a detector hitting the lech out from coins.
Believe me....I wish I had recorded it. But that leech impression is usually destroyed in the retrieval process , so its not like you can predict when you will be able to test it.

Its an epiphany moment , once you see that it all makes sense. That's the halo

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  #57  
Old 12-31-2017, 12:39 AM
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That guy is Dave Johnson, he's chief designer at FT, also worked for Fisher, Tesoro, Whites etc, it's worth taking his view on board.

Originally Posted by ohiochris View post
There are some problems with this guys logic.....

" But there’s this little problem: the electrical conductivity of the corrosion halo is very low compared to metal. "

......sure , but the electrical conductivity of the corrosion halo in most cases is much HIGHER than the ordinary soil surrounding it. Not only that but the corrosion halo is at times saturated with moisture , increasing conductivity...either way the overall result is often ( though not always ) a bigger profile , more conductive than the soil surrounding it. While that slightly larger profile might be partly a slightly less conductive halo your detector is going to call it ALL the same because the base metal itself is larger than the halo , they are touching , and together they are massively more conductive than the surrounding soil
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Old 01-05-2018, 02:46 PM
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Originally Posted by ghound View post
That guy is Dave Johnson, he's chief designer at FT, also worked for Fisher, Tesoro, Whites etc, it's worth taking his view on board.

But that dont make him correct , and my earlier point addresses something he is not taking into consideration. With his job , he is an authority on detector design , not necessarily an authority on all things detecting. A job title does not trump the combined experience of many long time detectorists who have seen and experienced in the field the very thing he is trying to dispute. But thats ok , until you actually get the chance to see it for yourself , the doubt is not surprising.

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  #59  
Old 01-06-2018, 03:01 AM
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Originally Posted by NCtoad View post
Just curious about this. I've heard people say their detector will only airtest x inches, but goes deeper in the ground. Then I read that a proper airtest is the max you can expect out of your detector. I know ground conditions are the determining factors for an object in the ground and EMI can really make an airtest go wonky. Is there a definite answer?
Outside, people would only consider a valid test one with no EMI. But indoors, people are divided as to air tests being the highest setting that provides a beep, or is it the highest setting that gets a beep without any extra noises?

The in house noises are not likely heard at the nearest park or school.

Almost any detector will air test 10" on a dime if average or above. Some cheaper units will air test 8"-9" on a dime. Anything that does 11"+ amazing.
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Old 01-08-2018, 10:47 AM
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Years of experience may count in this situation if your constantly digging coins in this condition. In my experience, i'd say 95%+ of the coins i dig are on old pasture, coins that have been in the ground a 1000yrs, copper coins so degraded and leeched into the soil there a fraction of their original size, but yet i'm to find one where the leeching gives a reading that would be obtainable at any depth worth while.
I've no idea how you have seen this happen and yet i haven't, even though the vast majority of my coin finds have been in the perfect settings for the leeching to be a factor.
So, on my next hunt I'll take along my camera and video my findings and share them.

If you don't think Dave Johnson's theory's are from an experts view, an expert who needs to know how old coins are signaled and received on the machines he designs, well so be it.

Originally Posted by ohiochris View post
But that dont make him correct , and my earlier point addresses something he is not taking into consideration. With his job , he is an authority on detector design , not necessarily an authority on all things detecting. A job title does not trump the combined experience of many long time detectorists who have seen and experienced in the field the very thing he is trying to dispute. But thats ok , until you actually get the chance to see it for yourself , the doubt is not surprising.

Last edited by ghound; 01-08-2018 at 11:45 AM.
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