GB439868A - Improvements in or relating to electron discharge tube arrangements - Google Patents

Abstract

439,868. Discharge apparatus; thermionic valve circuits. COSSOR, Ltd., A. C., Highbury Grove, London.-(Assignees of Ardenne, Manfred, Baronvon; 19, Jungfernstieg, Lichterfelde-Ost, Berlin) March 12, 1934, No. 7810. Void [Abridged as open to inspection under Sect. 91 of the Acts, Sept. 12, 1934]. [Classes 39 (i) and 40 (v)] A " virtual cathode " is produced by means of an incandescent cathode, preferably indirectly - heated, a positively-biassed grid and a grid at or about the potential of the cathode. The second grid is made of fine wire with a close mesh, so as to reduce the effect of external fields on the electrons inside that grid. A control or modulating voltage may be applied to the second grid. Very accurate spacing of the electrodes is necessary, and the cathode is operated at a low emission temperature. The oscillation generator shown in Fig. 2, has an indirectly heated cathode K, a grid G<1> at a positive potential, a retarding grid G<2> at or about cathode potential, a grid G<3> at a high positive potential, and an anode A at a negative potential producing a brake field. The grid G<3> and anode A are connected with a Lecher circuit having a variable condenser C, chokes D and a resistance R for damping any oscillations set up in the cathode system. A modulating potential is applied to the grid G2. In a modification a second Lecher system is connected between the grids G<1>, G<2>. In the cathode-ray tube shown in Fig. 4, the cathode K is surrounded by a Wehnelt cylinder C, the grid G<1> is at a positive potential, and the retarding grid G<2> has a small opening which may be closed by a fine wire grid. A tube with a "virtual cathode" may also be used in (a) a modulatable relaxation oscillation generating circuit, Fig. 5 not shown, (b) a receiver with reaction and detection in one stage, Fig. 6, (not shown), (c) a circuit for voltage amplification, with a resistance in the anode circuit, Fig. 7 (not shown) ; the modulation may be applied to a separate control grid as well as to the second grid, Fig. 8 (not shown).