This is probably one of the most overlooked factors in metal detecting. Operators will become proficient in the use of their machines, or rather I should say: "Proficient in the use of their Control Boxes", but very often know very little or nothing about their search coils.

This is caused primarily by the lack of information.

Manufacturers do not tell you too much about them, beyond the fact that they may be submerged in water, that they should be held at such and such a place while tuning or balancing, or that they should be moved slowly or rapidly, etc.

If you can understand some basics of what type of radiation pattern your search coil makes, then you are likely to make more finds with your metal detector.

No matter how proficient you are in the use of the controls on your control box, without your search coil, you would find absolutely nothing.

When you turn on your metal detector, and electromagnetic field begins to radiate from the search coil. You may think that because you have a particular metal detector; that it operates different from someone elses, thus is the reason the other person finds more than you. This is not true, as far as electromagnetic fields are concerned.

Lets think about it for a minute. If the radiation patterns were different, some operators would be able to find and pinpoint coins at different locations under the search coil.

As we all know, the only place under your search coil that a coin may be pinpointed is at the coils center. I know, some of you will say, "But I pinpoint my coins by turning my coil so that I pinpoint on the edge." While this maybe true, you need to listen to the rest of the story. The strongest or most concentrated point of the electromagnetic field is at the center of the search coil.

As you move further from the coils center, the electromagnetic field becomes more "Spread Out" or weaker.

In order for you to find a very old, deeply buried coin, you would have to find it at the center of your search coil.

If we take any buried coin and center the coil over it, and take a reading on our meter, if we have one, and then move the coil very slightly in any direction, we will see a rapid loos in signal. This due to the loss of our electromagnetic filed. This is why we must have our coil exactly centered over the coin in order for us to get accurate pinpointing and accurate depth.



As you can see, as you move away from the center of the coil, you begin to loose the electromagnetic field. This is the reason why we need to do overlapping strokes in order to cover the ground more completely. NO ONE EVER COVERS THE GROUND COMPLETELY. To do so, you would probably have to spend an entire lifetime on an area the size of a football field.

If you understand your elector-magnetic field, you will be able to just "Smile", when someone tells you that an area is all worked out.

Another way to tell if an area has been worked heavily, although it has nothing to do with the electromagnetic field is this: If you arrive at an area where there are children, and they come running to see what you are doing, chances are that there haven't been too many metal detectors around, or by now the children would have become bored with being ignored.

If children pay you little or no attention, you can bet that there have been plenty of metal detectors around.



IF we are told that our metal detectors will find a penny at eight inches, and assuming that the soil conditions are perfect, and that the metal detector will in fact find a penny at eight inches, then we must assume that the effective radiating pattern at eight inches is the size of a penny or larger.