Simple mod. for the AN-19/2 nets another 2" on Gold

[Anonymous]

Hi Ralph,
Actually, when I was writing the "tools of the trade" column, I did address the issue of the "Halo Effect" on a couple of occasions.
The problem is, too many people have dug a very deep hole to recover an object and when the object was placed back in the hole, it wouldn't even respond at all.
So, the first thing to come to mind is something like the "Halo Effect" had to cause this condition, right? Nope, but that is ok, because nobody would believe the truth anyways.
If people would just apply common sense 101, there would be much less discussion about this matter.
Lets take a PI and the fact that one can take an ounce bottle of very fine gold dust and not be able to detect it at all, even by rubbing a bottle of it on the coil surface. Why, because the delay of the gold dust is simply too short.
Now, this is a visible ounce of gold. So, how can gold so thin that it can't be seen "leach" out around a nugget and make the nugget appear tremendously bigger? I don't mean a little bit bigger but make a small nugget appear huge!!! It would have to be huge to be detected at the depths some people say they have found small nuggets.
Even nuggets like those of John B's which are quite large and visible, yet can't be "seen" by most PI's. If large visible nuggets can't be detected, then how in the heck can a buried nugget create an invisible "halo" that can be detected.
The same goes for coins. How can someone find a dime at a depth that they can't detect a freshly buried quarter, or even a recently buried half? Better yet, the dime weighs the same as a new one. So, what leached?
This condition expands all known targets with the same general results.
So, what is really causing the added depth?
I know, magic!!!
Reg

 

[Anonymous]

It was not uncommon to be working an area one day when the ground was extremely dry, and get a ground balance level that we considered "normal". Then, overnight rain showers would come along and the following day we would notice our ground balance points considerable different than where they had been set for the same areas the day before.
I think the perception of "halo" effect has much more to do with the surrounding ground matrix and mineralization / moisture levels than any so-called "leaching" ground effect caused by the targets themselves. Of course iron is a different story, and large iron in the ground for long periods of time will absolutely produce stronger target signals than freshly buried iron. But we're talking about two different types of metal, ferrous vs. non-ferrous.
Something else you can try next time you dig a fringe depth non-ferrous target with your current machine, is to dig up the coin (or whatever) and totally disturb the soil for several inches around where the target was located in the ground. Now replace the item at the same depth level, and cover it back up "loosely" with the same dirt. You will not likely be able to detect the item at that same fringe depth range. But repack the dirt very tightly back over the target, and you will again be able to detect it in most cases. This shows us that the soil itself, or more specifically the mineralization in the soil, is causing the field of the coil to carry farther than it might in the air alone, or through the loosely packed soil alone. There has to be a "conductive continuity" in place for the field to reach the target, and the mineralization, most notably iron-based mineralization or salts, act to enhance the range ability of the electromagnetic field produced at the coil. This is also partly verified by the fact that on dry land sites with little or no mineralization in the soil, there is little effective difference in detection range between dry and wet soils. But once higher iron-based mineralization areas have moderate moisture added to the matrix, there is a substantial increase in detection range in many cases. The same holds true for large rusty iron that has been in the ground for long periods of time, having moisture added to the surrounding matrix, making those items detectable at what sometimes appear as unbelievable depths. The oxidation of the iron itself increases the iron mineralization in the surrounding soil. But "leaching" halos from non-ferrous metals make negligible difference in the surrounding soil matrix or in the detectability of the object. It's the surrounding matrix and its level of iron-based mineralization or salts and moisture content that affects the iron or salts that make the difference, not the tiny levels of "non-detectable" oxides or sulfides that form around the non-ferrous targets.
So next time you hear of "halo effect" causing extreme depths obtained on coins or relics, think again. It's the GROUND MATRIX between the coil and the "halo" that is giving you the edge.
Ralph

 

[Anonymous]

IT is a NON MOTION PI DETECTOR.
That means the COIL does NOT have to be moving to DETECT a target.
HH God Bless,
Matt (SD,CA)

 

[Anonymous]

Hi Ralph,
The ground matrix consists of both iron oxides and "salts" that can affect the overall response of an object.
On a VLF type, the effects on the disc mode are quite distinguishable because of the signals seen in the "X" channel.
Normally, on solid ground that hasn't been disturbed, the ground signals are relatively "slow" because the ground matrix is reasonably a constant and any variations are the result of variations in coil height. This is why motion detector's work.
The ground signal generally produces a response that is less than 3 hz, while targets normally respond with a higher frequency, say maybe 5 hz to 10 hz or so.
Now, by using filters, one can reduce the ground signal and still enhance the target signal.
Disturb the ground by digging it up and these disturbances become very pronounced simply because the ground now consists of "smaller pieces" and these now become tiny legitimate targets that produce signals in target range of frequencies.
The result is a mess at best. Normally, TID's will read high or may even reject a target, depending upon its depth. In other words, targets may or may not be seen in the disc mode even when reasonably shallow. A lot depends upon the overall ground signal strength. The All metal mode isn't much better since the ground now generates a less than stable signal that either adds or subtracts from the desired target signal.
I have found that similar things happen on a PI also. Disturbed or rough ground can effectively reduce the overall depth capabilities. Again, a lot depends upon the type of ground involved.
I found I could effectively "till" the ground in a creek bed and have little or no effect on my PI, but do the same thing in a clay base area, and I could see a distinct depth loss, especially when using small test targets such as small lead objects.
Reg

 

[Anonymous]

Hello Matt,
Congrats with your mine detector, I once owned the same AN-19/2 mine detector as you did only mine was stock. It operated well but without the mods as yours but didn't fare as well.
I'm not sure if the "SD" is for San Diego but here in California most beaches south of L.A get worst further down south to San Diego, Makes it tough for most Pi's to operate well here in California.
I have to agree with you as I've seen even the best Pi's not able to operate near full sensitivity or even 3/4 sens because of California's tough wet beach sand/surf.
Thanks for sharing your results with the mine detector,
HH, Paul (Ca)

 

[Anonymous]

Hi,
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[Anonymous]

I don't believe the powdering of the sample metals was intended to simulate this so-called "halo effect", but was to show that the object reduced to such a minute form ceased to be detectable due to its lack of conductive continuity, and the resultant shortening of the decay time of the eddy currents that are necessary for PI detectors to "see" the object or material. The basic fact is that if the eddy current decay period of the object or material is shorter than the machine is designed to detect, it CANNOT be detected.
You mention the crumbling 9k rings, but were they analyzed as to their true gold content or just identified by assumption from a marking ? I have never found a true gold or gold alloy item in such a state other than one that had obviously been treated with mercury to remove much of the constituent gold content, leaving a very porous and fragile shell of the base metals intact. Gold alloys, much like nickel alloys, tend to inhibit chemical leaching beyond the "skinning effect" unless it is the AU being removed from the base metals instead of the base metals from the gold, in which case special acids or electrolysis would be necessary, neither of which readily occur in nature. Of course, where 9K is concerned, we are talking about only 37.5 percent gold content and the balance normally being a combination of silver and copper, but silver too tends to inhibit the leaching effect nearly to the level of gold, and actually better than nickel. In the case of a 9K alloy consisting of only gold and copper, the leaching effect could be more dramatic because of the molecular percentages of mass involved, i.e. the alloy is produced according to weight, leaving a considerably higher mass of copper to gold due to the wide differences in the specific gravity of the two metals.
Another possibility that has been raised in regard to the "halo" phenomenon is that the mere presence of a metallic object in the ground for long periods of time may in some way alter the natural field of the surrounding iron-based mineralization near the object. Since the magnetic field of the earth acts in a way similar to what is produced artificially by a metal detector (but at a much lower level), and since non-ferrous metals tend to "deflect" such fields rather than "attracting" such fields as in the case of ferrous-based metals or minerals, it has been suggested that such a deflection may actually concentrate very slightly higher "natural field" presence around the object itself. Whether such would create enough of a variation to add to the detectability of a non-ferrous metal object is another matter, and I tend to think along the same lines as Reg, Bill, Eric, and many other experienced detector users that a combination of soil mineralization (iron and salts) and moisture content will determine the overall detectability of any given target far more than will the so-called and often over-exaggerated "halo effect".
Ralph

 

[Anonymous]

I live in the north county San Diego. The beaches in north San Diego to Pacific Beach have very large amounts of black sand. San Digeo has couple of beaches with mild black sand. They are Imperial Beach & Coronado.
Imperial Beach is kinda funny. Very little black sand for a California beach. But once you dig in and break the top layer of sand it gets VERY black from the RAW SEWAGE drain off from Mexico!! I have only hunted I.B once. It did have bunch of targets though. You should see now nasty the clad looks after being in the water! San Diego has around 40 miles of beaches. Some are rock/pebble to almost white sand like Imperial & Coronado.
HH God Bless,
Matt (SD,CA)

 

[Anonymous]

I've found all machines suffering in bone dry soil but the one that maintained its depth best was the old Whites Supreme (2 or 2.5 khz). I've finally got hold of a Headhunter Wader that runs at around the same frequency to see if it maintains its depth as well or if it is an effect of coil or circuit design rather than frequency. Only problem is our longest period of dry weather has just ended.

 

[Anonymous]

Hi Ralph,
What is happening here, is that with the shaft extended, and the threshold set to one tick per sec., if you now retract the lower shaft into the top shaft, the tick rate increases. This indicates that the detector is "seeing" the upper aluminium shaft. The signal is cancelled by re-adjusting the threshold control back to one tick/sec. If it were a motion detector, then the tick rate would readjust itself automatically back to the original setting.
Eric.

 

[Anonymous]

Hi Kev,
Sorry if I disagree with you but everything I have been able to determine contradicts the idea of oxides, etc as being the cause of the added depth via the "halo" effect.
First, one has to fully understand just what is necessary to generate an eddy current, which is what is really necessary if a target is to be detected. Simply stated, the target has to produce an eddy current that counters the primary field. This is true of a VLF or a PI type instrument.
The previous discussion about filing an object to "dust" and then failing to detect it, was done. It was presented help explain that small non-contiguous pieces do not produce a signal anywhere close to those of a solid object.
Similar experiments could be tried using very thin conductive paper such as a gum wrapper. Now, bury such a piece even flat and the depth will be very limited, simply because of the "thickness" of the material.
One of the "invisible nuggets I received from John B is almost the size of a person's small fingernail. Now, a nice solid nugget of similar size can be detected, maybe 8" or so. However, this visible, somewhat solid "invisible" John B. nugget isn't even detected by most PI's including the GP. On my adapted PI operating at about 7.5 usec delay, I can detect it about 3" max. This is the response of a visible, contiguous piece of metal that can't be detected by some detectors, yet invisible oxides can?
Do oxides generate eddy currents? Yes, but not in the concentrations at at depths people are claiming.
Lets take the ground for an example. First, it already produces a form of eddy current that is detectable. However, The intensitity of the ground signal drops off dramatically as the coil is raised even a little. Even the signal from a large piece of basalt dies off after a few inches and this is from a relatively large object.
Now, if a very large oxide type signal from the ground or even from a piece of basalt will subside very quickly, then how could the "minute" oxide signal from an oxidizing non-ferrous object produce a much more intense response at depth. More importantly, is this "target oxide signal" much stronger than the ground oxide signals?
Now, what is claimed is the "oxides" from a buried target will produce a signal greater than if an object made of similar material of larger size is used. Like I said, "dimes" are found at depths that are greater than quarters can be found. Huh? Are we saying that oxides produce better or stronger signals than actual metals?
If oxides could produce such responses, then why isn't such a response still there once the primary object is removed? Yes, I have dug coins where I dug a "clump" and carefully removed the coin from the clump causing the minimal of disturbance around the coin. Now I have tried to "detect" any trace of a residual "halo" and got nothing, zilch, zero etc, of a response.
I will go back to my original claim as to why objects are found "deeper" than can normally be done.
It is "magic".
Reg

 

[Anonymous]

I understand it is a SAT issue that would retune to the original setting if it were a motion machine. I'm not familiar with the particular machine but was confused in the description of what was being used to confirm it as a no-motion machine, since there was still relative motion between the coil and shaft in the example used.
Motion and non-motion always seemed to be misnomers to me, since in order to detect a target, the coil of either does in fact have to be moved. Whether the signal continues after the coil stops is a matter of the self adjusting threshold or "re-tune". But to detect the signal, there has to be some "comparison" involved, otherwise how do we know there is a "change" to indicate the presence of the target in the first place ? <img src="/metal/html/wink.gif" border=0 width=15 height=15 alt="">
Ralph