Patent GB-447039-A (GB)
Title: Electronic tube
IPC: H03B13/00
Filed: 1934-08-09
Abstract: 447,039. Cathode-ray tubes. RADIOAKT. - GES. D. S. LOEWE, 10, Wiesenweg, Steglitz, Berlin. Aug. 9, 1934, Nos. 22996 and 22997. Convention dates, Aug. 9, 1933 and Aug. 31, 1933. [Classes 39 (i) and 40 (v)] In a cathode - ray tube of the type described in Specification 443,364 in which a narrow crosssection of the beam is reproduced on the anode by focusing means other than the deflecting devices, the narrow cross section is produced mainly or entirely by electronoptical concentrating means instead of a slot. Several circuits in which such a tube is employed for producing oscillation and amplifying are also described. Fig. 1 shows such a tube in which the cathode 1, which has a long narrow emitting surface, is arranged within a concentrating electrode system comprising two plates 3 inclined to each other and connected with the earth or a weak positive potential and a slotted plate 4 at full anode potential. The concentrated beam thus produced is focused on the anode 15 by a system comprising plates 7 and 8 connected to each other and to the plate 4 and a base plate 9 carrying two inclined plates 10, 11. The focal length of the system depends on the potential of the plates 10, 11 and their inclination to the plate 9. If the beam is to be deflected in one direction only the deflecting plates 12, 13 cover nearly the whole space between the focusing system and the anode ; if it is to be deflected in two directions the deflecting plates parallel to the wide surface of the band cover as little of this space as will allow of the required sensitiveness and the plates parallel to the narrow surface cover as much as possible. A further control may be effected by space-charge control of the electrode of the electron band. For this the more negative electrode of the preliminary concentration system may be employed, or a separate electrode within the system. In this case it may be necessary to employ a diaphragm in addition to the concentration system for producing the required cross-section. The plates and other elements may be secured as described in Specification 435,382 or 438,117. A suitable cathode for the tube consists of a metal tube with a groove filled with alkali earth oxide on to which barium may be atomized. After activation the cathode is heated to evaporate barium from the metal surface. The metal may be placed in the angle between the plates 3, where it also acts as a getter without being deposited in undesirable parts of the tube. The cathode may be heated by hot filaments arranged in the same line with it and screened by plates closing the ends of the space between the plates 3. Fig. 3 shows an arrangement of the tube to produce oscillations. The anode is in two portions 15, 16 each of which is connected to that one of the deflecting plates 12, 13 which is on the opposite side of the tube. The plate 12 and the anode portion 16 are connected to one end of an oscillating circuit 22 and the plate 13 and portion 15 to the other end of this circuit, which is maintained at a fixed potential, alternatively this fixed potential may be applied to the middle point of the circuit. The form of the oscillation transmitted is regulated by giving a suitable shape to the edges of the portions of the anode, which are preferably of a metal of high melting point, and the leads have a considerable'cross section, e.g. 2 sq. mm., to carry off heat. A screen may be provided behind the slot between the portions of the anode. Modifications of the above-described circuit with potentiometers whereby different potential may be given to different plates are also described. By biassing one of the deflection plates so that the cathode stream normally strikes one anode portion only the tube can be used as a relay to start an oscillating circuit, and by connecting a source of oscillating current to one of the deflecting plates the tube can be used as an amplifier, the two portions of the anode being connected to the output terminals and having equal anode resistances in their circuits. Arrangement of the tube for producing oscillations in connection with a quartz crystal are also described.