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Shadow Research Center

More On GB'ing In Low Or No Mineralization

Actually your method works well when the ground does have mineralization. However, with ground that has very little or no mineralization it is better to start off with the GB control fully clock-wise and then start the coarse adjustment by turning it counterclockwise while pumping the coil slowly from approximately 12 inches to 2 inches above the ground. By starting fully clock-wise you will always have a tone when lowering the coil to the ground. The most important point in this process is to adjust the GB Control counterclockwise until the threshold tone disappears. If the threshold tone does not disappear then it is not possible to manually ground balance properly and Fixed GB should be used.

When the tone does disappear during the coarse adjustment then you know that manual GB is possible and you are very close to the ground balance point. Now, the fine tuning process is to continue pumping the coil and adjust the GB control clockwise slightly until the tone volume is the same when lowering and raising the coil. At this point your detector is perfectly ground balanced, BUT searching at this ground balance setting will cause a great deal of ground noise when in the discrimination mode. So to overcome this problem you should adjust the GB control clockwise about another ¼ to ½ turn. Now you are ready to switch to the DISC Mode, adjust the SENS & DISC controls and start searching.

To put all this into words, the process seems to be very complicated but in reality it is simple, quick and easy. The two main things to remember are 1) You must first find the point where the threshold tone changes from positive to negative (tone disappears). 2) You must operate with a slightly more positive GB setting than normal otherwise ground noise will be bothersome.

I hope this helps.

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