Abstract: The invention relates to a tunable magnetron having coaxial cathode and anode systems (13 and 11, 12) which define therebetween an annular, evacuated interaction space (18) and a rotatable tuning body (20, 24) supported by two ball bearings (21, 22). The tuning body (20, 24) with its bearings (21, 22) is situated in an evacuated space (25) communicating with the interaction space (18). A magnetic circuit having two pole shoes (16, 17), situated one on each side of the interaction space for producing an axial magnetic field through the interaction space (18), is closed through the rolling bearing (21) situated closest to the interaction space. In order to prevent magnetic interaction forces between the rolling bodies from influencing the rotation in the case of continuous operation, in particular if the bearings have no retainer ring, at least the rolling bodies in the bearing (21) situated closest to the interaction space (18) are made of non-magnetic material, e.g.

Abstract: A tunable magnetron is disclosed comprising a first tuning body rotatable in an annular groove formed by axial slots in the anode plates for rapidly varying the magnetron frequency. The rapid frequency tuning is combined with a slow or quasi-stationary frequency variation produced by a second axially displaceable tuning body having conductive projections which extend into the resonant cavities between adjacent anode plates from the end thereof opposite the first rotatable tuning body. The entire tuning range of the first tuning body is shifted along the frequency scale by an axial displacement of the second tuning body.