Improvements in and relating to the production and/or modulation of periodic electric currents

Abstract

Abstract 328,680. Harries, J. H. O. Feb. 4, 1929. Vacuum tubes. - In a tube for effecting frequency-multiplication or modulation, a, jet of cathode rays travels over a " record," or target, having non-uniform characteristics, the relative position and/or velocity of the pick-up and record being suitably varied. In the arrangement shown in Fig. 1, the cathode stream 4 is caused to trace a closed curve on the target or record 5 and the output current is taken off between a pair of the electrodes 2, 3, 5. The target 5 is formed as a record of periodically varying properties thus : it may be of highly resistive material, Fig. 7 (e), having a corrugated surface with a conductive layer, or having a conductive edging 24, Fig. 7 (f). Variations in current strength are effected as the cathode stream passes over the surface, and modulation or fresuency multiplication is effected either (i) by variation of the angular speed of the stream or (ii) by variation of its radial position. Means may also be provided (Fig. 4 not shown) for rotating the target 5. In a modification, Fig. 2, the record 5 may intercept the cathode stream falling upon an electrode 7, and in this case the record may be of mesh or of thin material having varied thickness; or it may be a disc with radial slots or with a circular slots of varying width, Figs. 7 (a) - - 7 (d). The cathode stream may impinge on a fluorescent screen (Fig. 3, not shown) the secondary radiation passing through a record, which may be a photographic film, to a device sensitive to it. Instead of travelling in a circle the stream may oscillate linearly, the record being suitably modified to give the desired frequency. The vacuum tube may be of a demountable type, and the cathode stream may pass through a thin metal partition.

Inventors

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