Abstract: A pulse generator is provided for energizing a coil with period bipolar current pulses for the purposes of airborne prospecting. The pulses have a generally square waveform, and the pulse generator includes a resonant DC to AC converter circuit including a DC input and an output coupled to the coil. A control circuit is provided for controlling the switching of the converter, and a resonant capacitor is connected in parallel across the DC input. A decoupling diode is provide for decoupling the resonant capacitor from the DC input when the voltage across the resonant capacitor exceeds that of the DC input. The converter includes first and second resonant charging sub-circuits, first and second resonant discharging sub-circuits, first and second freewheeling sub-circuits and first and second exponential charging sub-circuits.