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Why
Don't I Find Rings & Hammered Coins Regularly
Desi Dunne
Contribution # 99103 submitted by Desreally
April 24, 2001
Good question.
Ever wonder why you don't come home with the results you thought
you would just because you had secured a top of the line detector?
Having the most expensive machine will not guarantee you will find
everything there is to be found on any given site (inland or wet
beach) if you do not properly understand how important it is to
understand the relationship between ground effect and discrimination.
Besides plain good luck there are several other deciding factors.
Essentially, it has everything to do with the soil. The physical
make up, neutral, lightly or heavily mineralised, proximity of junk
items buried in the soil etc. Moisture content of the soil. It appears
to be a deciding factor in depths acheivable if a site is searched
while the soil is still wet, possibly soon after a recent rainfall.
Of course, rejection plays its part too and by this I mean discrimination
levels. You might notice on a very dry site some large items can
be found with surprisingly weak signals.
Typically, an enthusiast will consider the best machine he or she
can afford to do the job they want i.e find targets at good depths
and discriminate out the junk items. But herein could lie your problem.
Your rotary discriminator control could simply be advanced too far.
OK, it is all very well to do some tests at home to denote where
items will "drop off" the scale i.e. no longer giving
an audio response. Go on site and introduce some mineralised soil
to a depth of a few inches, have many junk targets embedded in the
soil and this can have a detrimental effect on the results you achieve
(if any). Even at a moderate level of rejection, say small iron
or light foil it can still determine if or not you will "see"
targets at even a few inches. It would be just great if all the
items we want were just under the first inch or two of soil, but
they are not. So, a small ring, buried at 5" might not register
a sound if you pass over this said same ring in soil which is slighly
mineralised and if you have your discriminator rotary control set
to reject to just beyond foil.
Now it is very obvious to the experienced detectorist that the least
(preferably none) discrimination is used. But to the novice the
discriminator rotary control might be unwittingly advanced so far
which will guarantee no signals from small rings, some Celtic, Roman
and medieval coins due to their small mass and small surface areas
presented to the search coil.
If searching for these kinds of items the level of rejection should
be no more than necessary to reject small nails only, in order to
maintain sensitivity to these items. In some regards this is where
the Explorer can come into its own as this feature is available
in the Select option and is utilised by many Explorer owners.
At high levels of rejection (discrimination) only higher conductive
items such as large targets, and/or large copper and silver coins
will be found on a usual basis. Now in itself there is nothing at
all wrong with this, indeed it is nice to come home with some nice
old silver coins to admire.
But no smaller and low conductive items will have any chance of
presenting themselves to you, but will be left to a more savvy,
less discriminating (excuse the pun) and possibly "slower"
type searcher?
So, take note, check on site to see where you should set the disc
control; in air at home maybe the item started to break up at 5,6
or 7. But as I said, introduce some mineralised soil and the same
target might start to break up at between 3 and 4, so essentially
you will "not hear it" at all and walk on leaving it in
the ground. The golden rule has to be use the least discrimination
you can stand, but dig everything you are not sure of.
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