The techniques of detection of the " senior " researchers imply obligatorily a good knowledge of the " ground effects ". These famous " ground effects " made much speak about them these last years and due..., they are impossible to circumvent! They represent a considerable embarrassment in certain cases!

Even if you have the best detector of the market, who cancel them or is entirely saying... (comme protest it without modesty some control them), it is better in my opinion to know them well, and especially not to be unaware of them.

" pros " of detection, (I want to say those which have a solid experiment, which likes their leisure and which often practises), of it are fully conscious, and always hold account of it, although certain recent apparatuses became less sensitive for their harmful purposes.

RESUMONS:

The " ground effects " are of two kinds for a metal detector: " positive " or " negative ", by an effect of increase or reduction of the " audible sound threshold ", or " basic threshold " of the apparatus. This was especially valid with the old detectors of the type T.R (transmitter-receiver). With the recent apparatuses whose majority work without " audible threshold ", it is difficult to be appercevoir of the presence of these " effects ". It is in position " all-metals ", or " pinpointing " (ciblage) and sometimes with the helmet only, that certain detectors " detect " the " ground effects ", by approaching the head of detection with deux-trois centimétres of the ground! They thus disturb the electromagnetic waves of the detector, by forming a kind of barrier more or less dense, following the place where you are, preventing a propagation (penetration) correct.

It is known as of a " ground effect " which it is " negative " when by approaching the head of detection of the ground, the audible threshold decreases or even disparait complétement. If the sound augment, it is known as " positive ". In a case as in the other, they are awkward, and it is to better have an apparatus which controls them as well as possible.... if not one can lose much in-depth performance!

Foot-note: I remember a case which goes back to about fifteen years; I saw, of my eyes considering, a detector, (however rather good for the time) to cancel a currency posed on the ground!!! It is true that the ground was " hyper-mineral-bearing ", the discri was regulated only on " average nail ", and it still too was!

The " ground effects " are omnipresent; no detector can cancel them, even " pulsated inductions " (P.I). They can on the other hand reduce their harmful effects considerably! for my part, I believe people or the manufacturers or publicities, which protest well high, that the performances of THEIR detector are exactly the same ones in the air as in the ground, without specifying, neither on what a mode, neither on what a ground, nor on what a nivau of discriminination selected.... as if that did not have any species of importance!

I rappele for whatever purpose it may serve, that the more one " goes up " in " discri ", the more one " loses " in-depth. What means that when one is persuaded to be in the presence of a strong ground effect or of an eliminated sound, one may find it beneficial to lower the discri and to check with a nivau low, even if it means to dig a little more for déchets.Mais all the senior ones know it!

Therefore and until proof of the opposite, all the apparatuses lose in the ground, in particular if it is mineral-bearing. The easy way in fact quite simply consists in buying the detector which loses less, and especially with learning how well to make use of it! Because with a same apparatus, in a neutral ground (better of the cases) and in a hyper-mineral-bearing ground (solid mass-exchange...) especially if the discri is strong.....