A Cherenkov oscillator operating simultaneously at two different wave bands
(3 cm and 8 mm) is described in this paper. Experimental results from the
oscillator are reported. The measured output power is 10 MW at 3 cm wave ba
nd, and 1MW at 8 mm wave band. The operating modes for BWO and R-orotion ar
e E-01 and E-13, respectively.