this invention relates to metal detectors used to detect metal targets in soils wherein the detector is insensitive to signals induced by a received magnetic field due to perpendicular components of a uniform conducting half - space , including metal detectors simultaneously capable of suppressing signals due to components of substantially log - uniform viscous superparamagnetic soil , and including metal detectors using repeating transmit signal cycles resembling a pulse induction - like waveforms . it discloses signal processing , in particular synchronous demodulation functions which may simultaneously substantially suppress signals due to perpendicular components of a uniform conducting half - space in a received magnetic field , signals due to components of substantially log - uniform viscous superparamagnetic soil , and signals due to a movement of the receive coil with respect to a static magnetic field .