An oscillator‐amplifier unit, suitable for supplying radiofrequency power to a cyclotron of medium size, is described. The power stage of the unit employs 4 RCA 833 air‐cooled tubes operating at 80 percent efficiency with an input of 5 kw. Power is supplied to theD's through a resonant line, giving a peak radiofrequency voltage of about 45 kv. A 1‐microampere beam of 3.1‐Mev deuterons is obtained.