Abstract: A cooling system for a screen grid electron tube such as a high power, high frequency transmitter tetrode which has coaxial formed electrodes and bushings and has an air cool screen grid terminal formed of two angular screen grid terminal elements 1 and 2 spaced from each other in the axial direction together with their bushings 3 and 4 so as to form a cooling air coaxial passage 7 so as to cool the screen grid terminal elements 1 and 2.

Abstract: A circuit for preventing retarding field oscillations in electron switching tubes, includes a feeding diode connected to the plate of the switching tube, and a power supply for generating the retarding field voltage, the power supply being connected in parallel with the switching tube through the feeding diode.

Abstract: In an exemplary embodiment, a transmitting tube has a coaxial design of the electrodes and their lead-ins and includes a cathode formed of a hollow cylinder which is secured at one end to an annular cathode lead, and at the other end is secured to a cathode cap which is supported at a power supply lead extending coaxially within the hollow cylinder. In this cathode, the carrier is not to consist of wire, so that inhomogeneities on the cathode surface are avoided. To this end, the disclosure provides that the hollow cylinder consist of pyrolytic graphite and be coated with a thin metal layer, preferably consisting of tungsten carbide and thorium, or a thorium oxide.