Halo everybody

[Anonymous]

In my never ending quest to rid myself of ingnernce I have been pondering halo effect. First off, what is it? I mean, it is obviously electron flow, but is it an electromagnetic field? If that is the case then wouldn't it be rightly assumed that non-ferrous metals would not exhibit it? Is it an electric charge (dissimialer metals I.E. iron, ground minerals, soil acidity and moisture content)? I have detected large chunks of metal well beyond the optimal depth of my coil and have to assume that I detected the halo of the object. I have also read that old coins "read" different than fresh drops. Is this to the decay of the halo? What is different about the signal? Can someone steer me to a source of information on this? Thanks to all for the info on this and others! HH

 

[Anonymous]

Halo effect huh! Well with my somewhat limited knowledge I

 

[Anonymous]

I think I can help a little but I am no expert on the subject. All metals will generate eddy currents when excited by a electromagnetic field. Eddy currents from ferrous metals also have magnetic properties causing a unique phase shift in the return. Oxides are formed as metals rust or corrode causing the halo effect. This metalic oxide is also detectable creating a larger target. Gold and some other metals don't break down and create a halo. Although most detectors get better depth in damp soil, this may not be the best time to hunt as iron has the biggest halo and the oxide is more conductive when wet. Hope this helps a little and I'm sure there are experts out there who can explain better. HH

 

[Anonymous]

One day while detecting at the beach I got a weak signal in the damp sand at low tide. I dug down about 12 inches and still heard the weak signal in the center of my hole.
I use a Sovereign with a 15" double D coil so I need to rotate the coil 90 degrees to pinpoint the target.
I also use a Sunray probe for locating those elusive targets that are sometimes very deep.
This target caused me to give it particular attention so I was determined to locate it, not disturb it, so I could actually see where it lays in the sand to get an accurate measurement of depth.
I kept digging, an inch at a time and got down to about 16" and used the probe between digs until I got a signal. The probe has about a 3" depth range.
Now I knew I was getting close, as I heard a distinct signal in the probe and kept removing thin scrapes of sand until I could see a round blob under the sand. This blob (green) was the halo that that formed around a clad dime (1967). When I disturbed the halo to reveal the dime laying in the spot where I detected it, I could no longer hear it using the large coil on the surface, as I had made the coin look smaller by disturbing the halo. The dime was 18" deep and if it were freshly buried or disturbed by a storm be beyond the range of my coil. That experience made a believer out of me about halos.
Also, the halo and extreem depth causes the sound frequency ID and digital reading of the target to be lower than usual.
This extra effort on this dime gave me confidence in knowing what my machine was capable of doing on the beach. I have seen remnents of that halo or funky green blob, on undistrubed coins many times. These coins tend to have been in the same damp/wet spot for more than 10 years.
bbailor

 

[Anonymous]

No such thing effectively. The extra depth people think they are getting from the 'halo' is the electrical current caused as the acids in the soil attack the metal of the coin/item.
If you have a test bed several years old and its a very dry summer why does the detection depth drop? The amount of metal(halo)leeched into the soil is still present.
No water/dampness then the electrical activity stops.

 

[Anonymous]

So that in effect you are saying that targets that occasionally disappear and are difficult to locate when the area around them is disturbed is in effect the result of the moisture suddenly evaporating?
I also believe I threw in the word

 

[Anonymous]

It seems to me that if metals are leaching into the soil that the target will apear to be larger than it is? Since moisture will effect conductivity ever stand in a puddle and get shocked and doing the same thing on dry ground did not?
It seems obvious there will be more halo detection in moist ground than in dry.

 

[Anonymous]

And that was my point.There have been those times when the ground was so moist that it seemed to me that it amplified everything in the ground and the number of targets increased at low discrimination. And so my response to Charlie. It sounded like he was saying no such thing as a halo existed. Maybe I misunderstood.
Pap

 

[Anonymous]

The halo effect is always in effect depending on the ability of the acidity of the soil to leach metal from the target and into the surrounding soil. Since the halo is not remotely as dense as the target itself it is not as stable or conductive but adds to the conductivity of the target. In dry or arid soil the conductivity of the halo is less than in wet or damp soil due to this lack of density, but then water makes everything more conductive - like standing in a puddle and sticking your finger in a socket. <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt="">
The longer a target is in the ground the greater chance of the halo increasing in size such as a piece of junk degenerating into nothing but rust. You'll detect it but when you dig for it and destroy the rust image your signal disappears and we have a phantom target.
Bill

 

[Anonymous]

Good answer Bill, I have been chasing those ghost signals for years. I don't mind as long as they don't start chasing me! HH