Coin$trike Question

[onpoint]

Could someone answer this question if poss please, I have been digging holes and putting coins in them, when I run my detector over them the coins do not regester ? Is this because the soil is lose ?
Thanks for Reading my post
clinton

 

[BJ in Okla.]

Test Garden for Experimenting with Your Metal Detector
Halo Effect
One of the first things many beginners do is to bury a few coins to see how deeply they can be detected. The usual result is disappointment because people do not know that newly buried coins are quite difficult to detect. The reason for that is absence of so called "Halo Effect" which has been developed as the time passes: coins become electrically more associated with surrounding earth materials and the molecules of metal begin to "leak" into the surrounding soil.

That is why the "halo effect" is responsible for one type of "elusive" signals. Such form of signal disappearance usually takes place during the recovery of an iron target, or any target that your detector is adjusted to reject. For example, after having been buried in the ground for years, an iron object that is larger than a square nail tends to develop a strong halo around it - an aura of both nonconductive and conductive properties that make the motion discriminate mode create the positive response.

When the searchcoil passes over this iron object, you hear a "good" signal even if the Discrimination is set up on "reject iron." Sometimes the signal does not repeat with each sweep of the searchcoil. You decide to dig it anyway. During the recovery, you disturb the ground around the object, thus removing the halo which has been created around the iron target by oxidation. Once this happens, the motion discriminate mode does not create the positive response anymore as it rejects the iron target thoroughly - you get no signal.

Construction of Test Garden
You should construct your Test Garden to help you learn the capabilities of your detector and educate yourself about what you intend to find. A test garden cannot completely prepare you for what you may encounter in a real hunt situation. However, it can help you better understand the effects of ground minerals, moisture content, target angle, oxidation/rust, trash proximity, target defects, surface textures and provide practice in target pinpointing.

You should create your test plot as soon as you purchase your detector. After a while, your test garden will be ready for experimentation, and your detector will be able to pick up signals from the coins buried by you at different depths. First of all, select the area and scan it with no discrimination so you can remove all metal from the ground. Select targets such as various coins, a bottlecap, a pulltab, other objects of different metals and a few nails. Also select a pint jar filled with scrap copper and a gallon can.

Bury all these objects in rows about three feet apart and make a map showing where and at what depth each item is buried. Bury coins at varying depths, beginning at two inches. Continue, with the deepest buried about 10 inches deep. Bury a coin at about two inches but stand it on edge, another coin at about three inches with a nail nearby, and so forth. Be creative! Bury the jar at twelve inches to the top of its lid. Bury the gallon can with the lid two feet below the surface. The target locations should be marked with colored nonmetallic objects such as golf teeth for instance.

The purpose of the buried coins is to familiarize you with their characteristic sound. The jar and gallon can will help you learn to recognize "dull" sounds of large, deeply buried objects. Experiment with different sizes of searchcoils as well as different program settings of your detector. Your test garden is important because your success in scanning over it will be a measure of how well you are progressing and how well you have learned your equipment. Remember that you must make an accurate map and keep it up to date when you change and/or add to your test garden.

Good Luck!

 

[Canewrap]

I don't want to start something, but where are you getting your information on "halos"? My experience indicates that non-ferrous items do not leach any appreciable material into the soil, certainly not enough to create a larger target to the detector. A halo, if you want to call it that, will form around iron items as they rust into the ground. But, the real reason you get a lousy signal from freshly buried targets is that you're introducing voids into the soil, which will scatter and absorb EM waves differently than the solid, voidless soil will. If the target has been in the ground long enough these voids will disappear as the ground becomes compacted and soil leaches into the air pockets. This will allow a more uniform return of signal, back to the detector. I've also had people tell me that its the soil matrix being disturbed. I'm sorry, if that were true, a freshly buried target would never become more detectable as the soil matrix (natural layering) stays disturbed as soon as you turn over the soil. I do however, agree wholeheartedly with your suggestions about the value of a target garden to help the detectorist to train their ear.

 

[Streak!]

"Halo's" are a commonly distributed myth. While I guess a halo is "possible" on certain targets.....the vast majority of targets we dig would take a thousand years in undistrubed soil to make any appreciable difference in detecting ability.(with the exception of iron and iron alloys) I DO however believe disturbing the matrix ( I think this is just a matter of semantics) will affect a targets detectability. Soils contain all manner of conductive salts and minerals.....and adding them or subtracting them will make a measurable difference. What I call the "matrix" is simply undisturbed dirt. Still......the major reason for the apperance of the "halo' effect is exactly what you cited. disturbed.......void filled soils from freshly burying a target. When I construct a test garden..............I compact and add a bit of moisture to the soil. I DONT dig a hole either...but rather drill a hole in the soil with an auger bit....place the target flat in the bottom of the hole.....and wet and compact the soil with a dowel or something similar so its close to what it was before it was disturbed. Most of My test garden targets have been in the dirt for 15 years......so I think they are as close as they can be to natural finds by now. Someday I'm gonna dig em up (probably when I move).....and see if they are at the same depth they were when planted.

 

[BJ in Okla.]

I just did a google search and found that site and made a copy & paste, to help Clinton, until someone that knew more that me came a long !
If I wanted a test spot, I would dig a hole in a clean area and then push the coin into the bank,
pack the dirt back and poor some water on it...

Are you going to tell me that you have never seen a halo on a IH or a V nickel that has been in the ground for a 100 years ???
I have seen units that would hit on a fresh planted coin and units that would not....
Also I think soil has something to do with it also, I have dug Barber dime's that were clean and a few that were as big as a quarter with the soil stuck to the dime and it had to be soaked in lemon juice to get the crust off of the dime,,have you ever dug any silver like this ???

 

[BJ in Okla.]

Below is a quote from a book... by Bob Sickler

Halo Effect
A conductive increase in Target size as seen by the metal detector's electromagnetic field.
The effect is caused by excessive target oxidation permeating the soil directly surrounding the target.
Associated with long term burial or highly acidic soils...

 

[jmaryt]

he's runnin' for president!..being backed by all the "aliens" in the country!

(h.h!)
j.t.

 

[BJ in Okla.]

n/t

 

[Canewrap]

I hear you guys are trying to invade my home planet. Call NASA -- please get off Mars.

 

[BJ in Okla.]

Yur funny

 

[Mike Hillis]

Yep....its because you have disturbed the ground.

You can air test and pick the coin up. But when you put it into freshly disturbed ground at the same distance you can't pick it up. The ground signal is overpowering the coin signal. Consider it a form of target masking. Once you tamp that ground down good, water the whole area and wait a bit of time for it to reconnect to the surrounding soil it will hit a bit better.

Why: The detector is measuring and responding to the rate of change of a target signal. Normally the ground is a fairly constant signal. A coin in the ground is fast changing signal. The detector cancels out the constant or slow changing signal of the ground and reports on the fast changing signal of the coin. When you disturbed the ground to bury the coin, that section of ground is now a fast changing signal that is much more powerful than the coin because it is much bigger. The only reason the detector didn't give an audio response to the ground is because the ground signal is also canceled out.

Regarding halos, some metals create a halo and others don't. But all metals will electrically bond to the soil in some form or another which will increase their rate of change to a greater degree than normal. Thats why you can make significally deeper finds than what an air test would support.

HH

Mike

 

[BJ in Okla.]

I know from testing, that if you dig a hole,drop in a coin, put the dirt back, tamp it, some units will pick it up and some will not. I only did this one time with the units that I had, and I think the one that did the best was a Fisher 1265x....All units 8" coils.
I find more coins after a good rain in the spring and late fall, than I do in the hot dry summer ground.
I have seen cracks 4" wide here and I guess if a coin was at the center of the crack and drops down the crack, no one will pick it up....

HH..BJ

 

[jmaryt]

fortunately "aliens" can't vote because they are far from their home galaxy!

(h.h!)
j.t.

 

[BJ in Okla.]

n/t

 

[Scully]

This is a really good discussion. I too used to believe in "halo" affect on all targets, but over the years that belief seemed to fade away. One of the main reasons is really deep targets. Quit often you get a really deep signal, only create a hole 10" deep and then you loose the signal. In this example, the target is still there, 2" deeper, still in matrix and "unidsturbed" dirt, but now your machine looses the signal. Why? Because now you have 10" of "air" over the target and the magnetic field reacts differently.

Granted, iron will leach heavily AND create a halo, but I no longer believe the other metals do to any degree that we could measure. After talking with Canewrap several weeks ago, I have been thinking about his belief and it really makes sense. Dave Johnson, Fisher engineer, also claims there is no such thing as "halo".

Great discussion you guys, thanks.

 

[Canewrap]

Nmsg

 

[onpoint]

Thanks very much Gents for all of your input on this subject, I still have to make myself a test garden ( at my poor mums house as I live in a flat. ) I am still only scraching the surface as far as detecting is concerned its amazing how much there is to learn to stand a better chance of finding goods and how detectors work, I will of course try to learn more as I find this hobby very exciting, I now wish I paid more attention to my history lessons at school ha ha.
I have found you all to be genuine people on this forum and am proud to be apart of it.
thanks again and good luck and health to you also.
HH. Clinton

 

[jmaryt]

hot damn!..better hope not!..only the "nutbags" will run!

(h.h!)
j.t.

 

[littlebigman]

You have to turn your detector on first before it will indicate a target.
Thats how my coinstrike works.