GB261013A - Frequency selecting thermionic valves - Google Patents

Abstract

261,013. Loewe, S. Nov. 4, 1925, [Convention date]. Vacuum tubes. - A quartz crystal or other piezo-electric body is inserted into a valve so as to render it selective for definite frequencies. In one arrangement, a quartz body 3, Fig. 1, rest, on a metallic support connected to the cathode 1 and is excited by a flattened portion 5 of the grid or plate conductor. If an alternating voltage having a frequency equal to one of the natural oscillation frequencies of the quartz is applied to the cathode and grid terminals, the grid is strongly excited. Alternatively, the leading-in conductor 6 terminates in the enlargement 5, and the grid is connected by a wire to a point on the surface of the quartz. A grid condenser and grid leak may be arranged within the valve. In another arrangement, the anode loosely supports a piece of quartz, for instance by parallel rings surrounding it. At the frequency of oscillation of the quartz, piezo-electric alternating voltage is added to that of the anode. The voltage of the anode may be adjusted either so that only the positive piezo-electric voltage surges appreciably affect the anode current, or so that positive and negative half-waves are equally effective. Fig. 4 shows a multiple electrode system in one valve, the two cathodes 17. 18 being preferably in series. Coupling between the first anode 21 and the second grid 20 is effected by means of a condenser 23 and a resistance 31 inside, or a resistance or choke outside the valve. The piexo-eleetric body 25 is excited by an electrode 26 connected to the first anode 21. A leak resistance 24 is connected to the second grid.