A grounded grid oscillator and a single dee resonant system for use with a frequency modulated cyclotron are described. 7.5‐Mev deuterons have been accelerated with dee voltages up to 15 kv and a frequency range from 9.5 to 12 megacycles. 15‐Mev protons have been accelerated with voltages up to 11 kv and a frequency range from 19 to 24 megacycles. Coupling constants, phase correction, amplitude modulation, and discharge phenomena are discussed.