Patent GB-586149-A (GB)
Title: Improvements in or relating to thermionic valves
IPC: H01J1/13
Filed: 1942-05-22
Abstract: 586,149. Thermionic valves and circuits therefor. STANDARD TELEPHONES & CABLES, Ltd., and MADDOCK,A. J. May 22, 1942, No. 7036. [Classes 39 (i) and 40 (v)] A signal-translating arrangement comprises a thermionic valve having at least two sections V1, V2, Fig. 16, means for applying signals to each section and for deriving a translated signal from the output of each section, the valve including a cathanode electrode CA serving as the anode of one, section and as cathode of another section and being heated to electron-emissive temperature by the heat generated by its anode dissipation. The cathode C of the first section may also be heated by electron bombardment from filament F, thus forming the anode of a diode which does not handle a signal. The battery B gives both the anode supply for the diode and the grid bias for the first section G1, CA. The sections may be enclosed in the same envelope, or in different envelopes, any of which may be gasfilled, the cathanode then being part of the wall between the envelopes. In one form, filament C, Fig. 29, grid Gl and cathanode CA form the first section and cathanode CA, grid G2 and water- or air-cooled anode A form the second section, all the electrodes being supported by rings clamped between insulators 1, 2, 3, 4. The cathanode CA forms a gas-tight enclosure so that the seals 1, 2 can be broken to renew the filament without spoiling the vacuum in the other section ; or a preliminary diode may be similarly demountable. In another form, the cathanode CA, Fig. 28, is formed of strips perpendicular (as shown) or parallel to the electron stream and grids G1, G2 are aligned with the strips so as to focus the streams striking and leaving the cathanode and reduce the current through the gaps b. Suppressor grids p may be placed in the gaps. Other grids may reduce electron emission in undesired directions and parts of the electrodes may be treated with non-emissive material to the same end. Electrons may be emitted from the bombarded side of the cathanode, the incident and emergent beams being separated by a screen S, Fig. 26, or a magnetic field, or both. Circuit elements may be incorporated in the envelope. The sections of the valve may act as amplifiers in cascade, and two such valves may be connected in push-pull, both for radio- and audiofrequencies (Figs. 2-5, not shown). By splitting the input circuits, the necessity for separate insulated anode batteries may be avoided (Figs. 12, 13, not shown). For anode modulation, the low-frequency output from the first section is applied, through transformer T, Fig. 6, to a choke L which modulates the radiofrequency output from the second section ; a push-pull arrangement is described, and, again, the anode batteries can be arranged in series (Fig. 17, not shown). A radio- or audiofrequency may be applied in parallel to all sections, with the outputs connected in series (Figs. 8, 21, not shown). By reversing the phase of the input to one section, two such valves can be connected in push-pull (Fig. 9, not shown) ; anode modulation from an external source can be applied to this arrangement through condenser Q, Fig. 10, to choke L, which can be made small since it carries no steady current. In the push-pull arrangement shown in Fig. 14, the low-frequency input LF1 is applied to the first sections and the output LF0 is taken from the cathode circuit, the radio-frequency input RF1 being amplified independently by the second sections in the usual way ; the radio and audio circuits may be reversed. This inverted or cathode follower principle may be applied to a two-stage pushpull radio- or audio-amplifier, the output from the first sections being applied, through L, Fig. 18, to the cathanode, the grids G2 being earthed. In a similar single valve arrangement, the audio-frequency input LF1, Fig. 20, is applied to the first section, and a radiofrequency input RF1 to, the second section, the cathanode being insulated except for starting by the dotted connection K. The potential of the cathanode varies at' audio-frequency and series modulates the radio-frequency output.