Backward wave oscillators for the 17 to 41 KMC band

Two K-band backward-wave oscillators developed for the Evans Signal Laboratory will be described. The specified frequency range of the one oscillator is 17 to 27 KMC/sec, while that of the other is 26.5 to 41 KMC/sec. The circuit element employed in each case is a unifilar tape helix designed to operate over the desired frequency band within a voltage tuning range of approximately 500 to 2000 volts. The appropriate standard rectangular waveguide and flange is used for the RF output connector. The power output of the lower frequency tube ranges from about 20 to 100 milliwatts while for the higher frequency tube it varies from approximately 4 to 10 milliwatts. Constructional details will be described, including the type of attenuators employed and the nature of the helix to rectangular waveguide transition. Typical operating characteristics of each oscillator including tuning curves and power output curves will be presented.