GB443602A - Improvements in and relating to cathode ray devices - Google Patents

Abstract

443,602. Wireless receiving - apparatus ; cathode-ray tubes. FERRANTI, Ltd., CHILCOT, A. L., and TAYLOR, M. K., Hollinwood, Lancashire. Sept. 25, 1934, No. 27548. [Classes 39 (i) and 40 (v)] Visual tuning-indicators for radio receivers comprise an evacuated cathode-ray device containing controlling means receiving varying voltage bias to vary the angle of divergence of either an electron beam or a shadow within such beam, and so to produce corresponding changes in the illuminated area on a fluorescent anode. An elongated, directly or indirectly heated cathode b, Fig. 2, is arranged between an anode c coated with fluorescent material and a semi-cylindrical control electrode d having its axis co-planar with the cathode b. Negative potentials varying with the strength of the signal carrier wave are applied to the electrode d to vary the breadth of the electron beam to the anode c. These potentials are generated across a resistance j in the circuit of a rectifier anode h, the modulation component being applied to the grid o of the triode amplifier through a condenser n. With the electrodes b, d connected directly across the resistance j as shown, the edges of the illuminated area on the anode c are blurred due to the modulation component but this may be avoided by a condenser and resistance circuit allowing only the D.C. component of the voltage across the resistance j to control the beam from the cathode b. In modified constructions of indicator, the electrode d comprises two surfaces shaped to follow the contour of the outer streams of electrons and having a junction line co-planar with the cathode b, or is replaced by a wire between the cathode and anode to cast a variable shadow on the anode. In other modifications, the electron beam passes up into an openfronted or slotted box-like anode coated with fluorescent material on the front of its rear wall, with or without a metal gauze across the bottom, or into an inverted V-shaped anode c, Fig. 5, with a slot r at the front and coated on the front of the back limb with fluorescent material. The indicator may be contained within an envelope only slightly larger than the electrode assembly or within the envelope of the rectifier or other valve of the receiver.