Abstract: An inductive output tube includes a capacitative tuner in the form of a plunger which is moveable inside the integral output cavity of the inductive output tube so as to vary the capacitance between an input and output drift tube and hence the resonant frequency of the output stage. The tuning plunger is moveable by protruding through a wall of the vacuum envelope of the output cavity, so as to allow the capacitance to be changed by operation of the tuning plunger by manual or automatic means from outside the cavity.

Abstract: The present invention concerns a rising sun magnetron comprising an anode ring having a series of radially inwardly-projecting teeth-like elements of a relatively high thermal coefficient of expansion. Each element (27) has a vane (21) of material of relatively low thermal coefficient of expansion secured on either side thereof so as to define alternate long and short cavities and an associated length of material (26) also of low coefficient of thermal expansion lying between the adjacent pair of vanes (21) and acting as a fulcrum for the associated vanes when the element (27) expands due to temperature rises.