A realistic air test for PI coils by Eric Foster quote

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This is a quote from Eric Foster from another forum
talking about the right way to air test a PI coil and target
if the target is not buried in the ground.

For a realistic air test, lay the coil on a piece of 1in thick wood, MDF, or plastic on the ground surface, then wave a target over the top of the coil. The range obtained will not be measurably different to that if the target was buried. The above is true for PI detectors, but not necessarily so for induction balance types, where the operating frequency can make a very noticeable difference.