Chris's Metal Detecting Page -
Digging the Deep Coins - "Flying Blind"
Chris's Mineral
Collecting Page is mainly about [what else?] mineral collecting,
but I
thought I'd put a little bit of Treasure Hunting stuff up here as
well... I may start enlarging this little sub-section if time
allows. Behold, Chris's Metal
Detecting Page.
I consider this
one of the enjoyable challenges of metal detecting. It is pure
sport, the exact opposite of what a lot of people would do if they
could (i.e., buy something
with a video monitor that shows a picture of exactly what's in the
ground).Years ago when I had my first White's detector, I thought I was hot stuff with my target ID meter: a needle would point to the word corresponding to what the buried object [probably] was. This was the pinnacle of metal detector technology, circa 1986. No pulltabs for me, no sir. OK, maybe a few pulltabs.
Then one day I met up with some other hobbyists who had Fisher and Garrett metal detectors. They didn't have target meters, just a bunch of knobs... yet they were finding coins. In fact, they were finding more coins than I was! How could this be? They had no VDI, no depth indicator, no nothing.
It didn't take me long to realize something I've seen reinforced many times over the years: a purely knob-type machine in the hands of a pro will often beat the latest target ID technology in the hands of a neophyte.
I also realized that a lot of old hands at this sport don't like to become too reliant on visual ID meters. As experience slowly taught me, it's because the meters sometimes aren't accurate. Meters don't do it intentionally. They just get it wrong. This happens especially when the coin is deeper than the meter can reliably interpret. The meter quits long before the detector reaches its maximum depth.
Now that we have some background, let's go on a trip to find some deeply-buried coins.
We walk into the old park and pick a spot (after, of course, we make sure it's OK that we detect here). Forget the wide sweeps and fast ground coverage that the beginners like to use. It's time to slow down and stay in one area- preferably an area that has produced coins before. Sweep width is going to be narrow, maybe two feet at first, narrowing even more when you get a blip. Go back and forth ten or twenty times over that blip. See how it responds when you vary the sweep speed. Is it smooth? Repeatable? Sweep the target from another angle, maybe just 30 degrees to the previous axis. Walk around the target and keep sweeping it from different angles. Does the signal disappear? Does it appear to move a few inches away when swept from another angle?
Is that smooth, repeatable sound we're getting a coin, a pulltab, a piece of foil, or a nail? Here we're not relying on LCD screens or multi-tone audio. With a machine like the Tejon, the Vaquero, the Silver uMax, etc., we rely on the discrimination and the quality of the mono-tone (i.e., broken or smooth). We also have to rely on stubborn persistence, digging many targets that others would leave behind because they didn't look and sound "just right" on the latest piece of equipment. Guess what? Some of these overlooked signals are coins! The other detectorists thought they found it all. I am always thankful when others are in a hurry to move on to other sites.
Don't worry about junk. You're going to dig some of it; that's all there is to it. Long-buried square nails will often fool the discrimination- on any machine. In practical terms, that means you will dig many nails. In the typical "hunted out" area, there could be double handfuls of nails for every coin you find. Perhaps you could hit a streak and get as many coins as nails. Nobody can know what the day will bring.
We're after the deep coins, so we're listening for signals that are quiet and narrow. Take your time! Move just one inch off center and the signal isn't there. The way to tackle this ground is focus mentally on small sub-area of the small area you've picked out to hunt. Don't let your eyes wander all over the place-- look at a 1 foot square piece of ground at a time... really search it.
It's all about the narrow, faint signals.
Before we discuss the three types of coin signals, let's talk about the kind of signal that's probably not a coin. Suppose you swing the coil two feet, and the beep seems to last for half that distance. Let's suppose you pick the coil up six inches from the ground and still get a loud signal. That is not going to be a coin. With practice it becomes easy to tell when you're dealing with an oversized object. It could be a beer can, a piece of sheet metal, a strap hinge, or almost anything. Crushed beer cans at shallow depths will act "round" but give a loud signal even when the coil is held off the ground several inches. If you're lucky enough to find a silver dollar and it happens to be shallow, you may think you're dealing with such an object. For this reason, some coin hunters dig signals even after they say "yep, probably a beer can"... once in a great while these loud signals turn out to be something very interesting. Recently I got one of these loud signals and decided to dig it "just to get it out of the way". It turned out to be an old axe head, a relic definitely worth keeping.
Now let's talk about the signals that might be coins.
The "textbook" coin signal is "round". What I mean is that the signal will have the same characteristics no matter what angle you choose to scan it. As you walk around the target while swinging the coil back and forth, the sound will still be smooth and repeatable from all angles. If it beeps for half an inch one way, it will beep for half an inch every other way. In other words, it "sounds" the same size no matter what angle you choose to scan it. This "classic" coin signal also has well-defined edges; it begins and ends at obvious points rather than fluttering, hesitating, or fading in and out gradually.
Dig every one of
these "textbook" signals, especially if your discriminator knob is set
at "pulltab" and they're still good.Here's a
hint. Just because this signal is solid and smooth doesn't mean
you won't miss it. You could hunt a ten foot by ten foot area
several days in a row and still find you've missed a few. The
signal is solid, and when you hear it you should recognize it as good,
but you might not hear it! If the coin is 6 inches deep, the
active portion of your coil's field is only a couple inches in
diameter. You could swing right by it and not get that "hot spot"
right on top of the coin.Remember, some nails and other junk can mimic the classic "coin" signal. Don't let this discourage you. After enough practice, when you get a signal that makes you say "that HAS to be a coin", you will be right more often than not.
Next is the "iffy" coin signal. I don't know who coined the phrase "iffy signal", but it's in wide use among detector hobbyists now. Exactly how the "iffy" ones sound (as opposed to the good ones) will vary between detector brands and models, but you will learn them by experience. The iffy signal may not sound like a coin at all. However, it should be repeatable along at least one axis. You may scan it east-west and it sounds good; approach it from north-south and it may disappear or break up. Most of the ones that sound great along one axis but disappear altogether from another are nails; however, coins can and do sound this way sometimes as well.
Beyond this is the "very iffy" signal. Not only isn't it consistently good from all angles of approach, but it also doesn't really sound that solid along any axis. It doesn't sound like a winner no matter how you scan it. This one is probably junk, but there is a chance it may be a coin... perhaps on edge or next to a nail. A nearby zone of heavy mineralization may be distorting the field. It could be any number of reasons.
If you have
found any coins at all
in an area, dig ALL these signals in the immediate vicinity. You
may be pleasantly surprised. Recently I got one of these highly
"iffy" signals and decided to pursue it. The previous dozen or so
of this kind had all been nails, but I was running out of daylight and
really hoping I'd finally hit a coin. Well, that's what it
was. It turned out to be a 1912 Barber dime at a depth of 9
inches. Badly worn, it's maybe a $2 coin on a good day... but
finding a Barber coin, any Barber coin at all in the ground, is one of
the thrills of this pastime. Finding a Barber coin at 9" deep, especially in a hunted-out area, is an experience money cannot buy. $600 can buy you a machine that can detect the dime at 9", but it cannot buy you the skill and patience that guarantees you put your coil on that exact spot and decide to dig it. In this way it's similar to golf, billiards, fishing, and a number of other sports- one can easily buy all the right gear but not use it to its fullest potential.
After you cut the soil plug and fold it away from the hole, scan the hole again. Sometimes the signal goes from questionable to very solid just from taking this couple inches of dirt out of the way. This is a highly encouraging sign. Every time this happens, I tell myself "this could be a coin!" Well, often it's still just a nail-- two or three inches off to the side of the hole, no less-- but at least you know you're not chasing a phantom when this happens. On the other hand, if the signal goes from highly iffy to nonexistent after folding back the plug, chances are it's a small bit of foil or other trash that's very shallow. You'd do well to extract it from the plug and get it out of the way so you don't re-detect it at some later point. This kind of work can help un-mask coins in the future, as well.
 |
All of the rusty
iron
pictured at left gave very solid signals that didn't discriminate
out. As soon as the earth was disturbed and the rust halo broken,
the signal deteriorated. A big
chunk of iron at 10" deep can sound just like a coin at 6"
deep. The only way to tell is to dig it. |
While we're on the subject of signals that change when the hole is dug, I'd like to talk about something odd that I've noticed.
Silver is the most highly-conductive metal on the discrimination scale. It should not discriminate out, right? Certain hobbyists will claim that silver does not form a "halo" in the soil. Explain the following situation, then:
You get a broken signal; You fold back the soil plug and the signal becomes smoother; you dig a bunch of soil out of the hole, the signal disappears; then you scan the soil you've piled up next to the hole-- no signal there either. You scan the pile again and notice there is in fact a faint, broken "junk" signal you missed the first time. It was probably a nail, and it's acting this way because you broke the rust halo, right?
You turn the detector to All Metal mode and get a loud, repeatable signal.
This time it's not a nail, though. When you finally pick out the culprit, it turns out to be a silver dime!
I've had this happen at least a dozen times.
If we're to assume silver coins produce no halo in the soil, then I can't imagine why this happens. Ground balance has a limited effect on this strange occurrence, but fiddling with the settings suggests it isn't the main factor. Why should the discriminator circuits reject a silver dime that's only a couple inches from the coil and not covered by any intervening dirt or minerals? Nobody has explained this satisfactorily.
In this article I've written about what I think is the most valuable technique for finding older coins. Some people will say success is all about "research". That is partially true, but... you can research the stuffing out of a place, but if you don't put your coil over that deep coin, you are going to miss it. Even sites that have never been hunted may lack any shallow coins; it depends on the ground conditions, erosion, leaf deposition, and a number of factors.
If you don't dig that "iffy" signal, you will be leaving something in the ground that might be a deep coin. Consider Schroedinger's Cat. If you don't dig the signal, the target remains a superposition of all possible metal objects that could produce that sound. You have to collapse the probability states and make it be something definite. (Ok, so it's not technically a Schroedinger's Cat situation, but it works for me.)
You have to dig it to know what it is.
One last thing, for beginners who may not know already:
Digging every
signal in a small area can turn a place into a mess. Don't try
to "clean out" an area of all its metal in one day. After you dig
a few holes in one general area, you may want to give it a rest and let
the grass recuperate. Turning someone's land into a muddy
mess is not going to get you invited back, and it may damage the hobby
in the long run. If you are working a spot and really want to
"grid" it and dig every signal, stretch it out over a span of months if
possible. Hunting the deep coins is a long-term
proposition. Nobody goes into a spot and cleans out all the deep
coins in one day- it's just not possible or even a good idea to
try. Take your time. Enjoy each swing of the coil. Learn
from it. Be sure to FILL
ALL HOLES you dig, and make sure you tamp the grass plugs down
firmly. Wild animals often come along and tear out plugs that
aren't tamped down securely. Skunks, racoons, dogs, and even
squirrels will dig up plugs in search of things to
eat. Filling holes
back in without leaving obvious traces you've been there is THE most
important part of the metal detecting hobby. If you can't do this
right, you'll ruin the future of the hobby for yourself as well as for
everyone else. Practice in your own back yard until you can cut a
grass plug, extract the target, fill the hole, and put the plug back so
nobody will even know you were digging there. Avoid digging plugs
in very dry weather. Conversely, don't try digging when the
ground is mush. It should be damp but not soaking wet. When you dig a
plug, don't sever all the grass roots- try to leave the plug attached
to the rest of the grass along one edge, like a
hinge. If you know the coin is shallow, instead of
digging a plug, make a small incision with a screwdriver and pry the
coin up from the ground. Practice these techniques before
digging on any property you don't own. And above all, ask
permission before you go on someone else's land.Main page
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