An impulse rotor generator is provided for generating power in response to a primary mud flow in a drill string. The generator comprises a power rotor, at least one stationary magnetic pickup, and a pickup coil mounted on the at least one stationary magnetic pickup. The power rotor is positioned at least in part in the primary mud flow and is rotatable in response to the primary mud flow, the power rotor having an axis of rotation that is transverse to said primary mud flow. The power rotor is provided with a plurality of magnets affixed thereto, the magnets being arranged so as to magnetically couple with the at least one stationary magnetic pickup. Upon rotation of the power rotor in response to the primary mud flow, a current is produced in the pickup coil mounted on the at least one stationary magnetic pickup.