Abstract: A spin tuned magnetron has a spinner the axially facing end of which lies in an inclined plane and an anode vane ring having an annular flange the end face of which lies in an inclined plane so that the amount of overlap of the flange and spinner varies as the spinner rotates. (In the FIG. 4A the spinner and the ring are shown spaced far apart; in practice they are spaced so that the planes coincide when parallel).

Abstract: In a spin-tuned magnetron a plurality of anode vanes disposed in an annulus form resonant cavities and a spinner, carrying a plurality of apertures rotates coaxially with the annulus to pass through the cavities and vary the resonant frequencies. This expedient gives a frequency variation which is predictable. This invention provides a less predictable frequency variation by modifying the shape of at least one of the vanes and at least one of the apertures. The aperture is in one example modified by cutting a slot between one aperture and the edge of the spinner.