When external reflections are added to the helical gyro-BWO, the simultaneous excitation of several longitudinal modes are experimentally implemented. Radiation of 24 GHz band with average power of 0.9-1.2 kW with typical distance between spectral components 96-120 MHz, 232-280 MHz and 464-640 MHz corresponding to excitation of longitudinal modes with different indexes was obtained.

The multifrequency radiation in a pulsed gyro-resonance backward-wave oscillator (gyro-BWO) of the Ka-band based on a waveguide with helical corrugation are obtained. The radiation power achieved 30-35 kW with a pulse duration of about 120 μs and a repetition rate of up to 10 Hz. Due to the change in the magnetostatic field in the interaction region and the pitch factor of the particles, the center oscillation frequency and the distance between the main spectral lines are tuned in the 32–35.5 GHz and in the 360–550 MHz ranges, correspondingly.