An electron tube, for example, a transmitter tube of the triode type, comprising in an evacuated envelope a mesh or cage cathode (3) and an anode (1). By providing a control electrode (4) near the cathode (3) on the side thereof remote from the anode (1), the output power of the tube can be controlled by means of a potential difference between the control electrode (4) and the cathode (3).

An electron tube comprises an evacuated envelope including an anode forming a section of the envelope and a plurality of alternatively-disposed metallic and insulating annular members. The anode includes an anode ring having a plurality of slots formed therein to provide stress reduction. The anode ring is attached to one of the metallic members thereby providing a low impedance electrical interconnection therebetween.

An air-cooled electron tube comprises an envelope including an anode forming a section thereof. A plurality of discrete radiator fins having a proximal end and a distal end are disposed so that the proximal end of each fin is adjacent to the anode. A radiator band having an interior surface circumscribes the radiator fins so that the interior surface of the band is adjacent to the distal end of the fins. The band includes at least one projection, and preferably two, formed around the interior surface of the band. The projection is raised about 0.38 mm above the interior surface and terminates in a sharp edge which pierces the distal ends of selected ones of the radiator fins so as to contact the distal end of each of the fins, thereby urging the proximal ends of the fins into contact with the anode.

In a controllable high-power electron tube in the form of a tetrode, the anode direct voltage is reduced to less than 10 kV with an anode efficiency of greater than 80%. The tube includes coaxially arranged electrodes including a cylindrical indirectly heated full walled matrix cathode containing BaO, a cylindrical control grid, a cylindrical screen grid and an anode, where the spacing between the control grid and the cathode and the spacing between the control grid and the screen grid is less than 1 mm. Such a tube can be used for achieving AM broadcast transmitters which are distinguished by a compact construction, the overall efficiency remaining largely unchanged.

To increase the frequency without restricting the power and vice versa, of vacuum tubes such as triodes and tetrodes for high-frequency amplification, especially for radio and television broadcasting designers are often limited by the relatively high output capacitance between the anode and the grid of the tube. To reduce this capacitance, especially when the tube is in a circuit for extracting energy from coupled cavities, the cavity coupling is integrated into the tube itself.