OK it's time for the 4th or 5th annual Winter Halo debate!:chase:

[BarnacleBill]

I've recently seen some posts on other forums about halos. I of course know that they're all wrong. So I'll re-post a link to my tome on halos.

http://www.findmall.com/read.php?55,634509,634509#msg-634509

No kidney punches or eye gouging please.

HH
BarnacleBill

 

[KurtB]

Thanks a lot. Now I won't be able to sleep. No really, thanks for all the time and effort you put into this hobby.


Kurt

 

[Jackpine Savage]

Another belief is that as the halo increases in size, a penny for example, would begin to appear to a metal detector as a larger coin. i.e. The penny pictured below with the quarter, has a portrayed halo that should make the penny detectable as deep as the quarter. Nope don't work that way. If it appeared like a quarter to the detector the TID would equal that of a Quarter

But the one challenge to this is that after a coin with a halo has been recovered, the halo is not detectable. That observation has been challenged though, by the thought that once the soil matrix with the leeched metal is disturbed, it is now so diffuse it is undetectable. And if you were able to magically remove the coin without disturbing the surrounding soil, then the halo would remain detectable. This is fantasy. Take a gram of pure gold or pure silver and grind it into small filings. Place those filing in a vial and even the best gold detectors won't see 'em. Stating that disturbing of the ground causes the halo not to be seen is "junk science".

Antenna radials and leached halos vs skin effect. EM radiation causes current flow in a target. Eddy current generation is what is needed to create the disturbance in the field picked up by the receive coil. therefore it is and always has been my postulation that any leached metal oxides (in contact with the targets surface) have a negative effect on current flow. Old coins in ground tend to read lower not higher on a TID scale. Nickels reading higher are a different kettle of fish.

I read some where that it is impossible to measure exactly what happens electrically on in ground undug targets with or without halos so this subject wll always and forever be open to debate.

The earth is round.. don't crucify me!

Tom

 

[BarnacleBill]

Where's Ivan Putski when you need him.?

HH
BarnacleBill

 

[BarnacleBill]

The question's been posed via PM, why can't you detect a Halo. Well I think you can with sufficient density per mass. And a very nice example of this exists, a saltwater beach. The salt acts like a evenly dispersed metal of sufficient density to cause the detector to react to it. AND over the years strong anecdotal experience using a dual freq detector has demonstrated to me that I can find coins at saltwater beaches, at greater depth than freshwater beaches. Does this not suggest that the salt acting as a halo, is carrying greater current to the target.

And y'all thought this thread was dead. Oh no, I'm flogging this dead horse till it cry's out "Alpo!".

HH
BarnacleBill

P.S. For the non-U.S. based readers, Alpo is a dog food, containing shall we say, meat byproducts.

 

[Steve(MS)]

I don't know the answer but something is going on. I have seen it for myself this "halo" or whatever it needs to be called. Some have suggested that the microscopic material that settles around the object causes a battery sort of effect. Maybe the area just around the object is made friendlier for a detector to pick up. Ok I guess for the nay-sayers, I have given more ammo, sort of like the beep-diggers....
who never pass an iffy signal.,...... couldn't let that subject die either.

 

[Rivermarine1]

Have any of you rescaned a hole where you pulled an old coin and got a faint signal for just a moment or so. My guess it is just the residuals caused by the leaching into the soil which would be the halo.

 

[Jackpine Savage]

horse byproducts!

Wanna share what ya been tipplin Bill?

 

[Steve(MS)]

I wouldn't think halo by itself would be detectable, at least not with a standard metal detector.
I think the area around an object that has been influenced is similar to minerals in the ground, that is it is too small for a signal but it allows for easier detection.
Mind you, this is all theory, kinda like our president doing what is best for the country.
Maybe my feeble attempt to make sense of halo is equal to his abilities.......
neither of us know what we are talking about:
I wouldn't think anyone would deny that iron objects cause a halo effect.
Next up copper and other soft not so precious metals, ever dig up a coin, made of copper or other brass item that has this thick crud and it has deteriorated the surface of the item?
My thinking is if this is happening the item then it wouldn't be a stretch to think there is influence in the immediate surrounding dirt, right?
The question arises though does this help or hinder a detector's ability to get the signal.
I would imagine the halo doesn't always help....
Then for precious metals, this is the real sticking point, they definitely don't leave a stain in the ground like what is seen by other metals, maybe they leave no halo whatsoever, there are many that don't believe in any halo effects, did the metal detector brands dream this all up early on?
Maybe the halo effect has nothing to do with the leaching effect?

 

[Jackpine Savage]

Ah now your starting to come around Steve An analogy is AGW. Is it man's contribution to carbon dioxide in the atmosphere or natural variability at work?

Bill's tome below in "halo'ed ground" points out depth of detection on salt water beaches. The problem with his postulation is the huge variability of conditions found on beaches from day to day, month to month. Sometimes newer objects (no chance to develop a "halo") are deep and sometimes loss of sand reveals the good older stuff that may have been in place long enough and undisturbed by movement to develop a halo. The one thing that is close to being constant is the wet salt sand.

Wet salt beaches are not the only ground condition that improves depth of detection. This takes us into the wet vs dry ground realm.

Tom

 

[BarnacleBill]

You've been out in the back yard with the Mortons box again haven't you, admit it, you have Saline envy!

HH
BarnacleBill

 

[Jackpine Savage]

I don't envy your cobble beaches! You gotta get a hold of a C$ to try on your freshwater cobbles!

Mr. Bill could fix you right up!