A directional drilling system, a drilling hammer and a fluid flow telemetry modulator use a plurality of magnets arranged to convert rotational motion into reciprocating linear motion. Various types of motor can provide rotational motion to a part of the magnets and various linkages and other devices can cause steering or operation of a modulator valve. A torsional drilling hammer uses a plurality of magnets arranged to convert reciprocating linear motion into reciprocating rotational motion. A motor and linkage drives the linearly moving part of the magnets, and the rotating part provides torsional impact be striking the linearly moving part of the magnets.