Patent GB-375568-A (GB)
Title: Improvements in or relating to electrical oscillation generators
IPC: H03B5/30
Filed: 1931-07-13
Abstract: 375,568. Valve generating circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London. -(Assignees of Hansell, C. W. ; Port Jefferson, Long Island, New York, U.S.A.) July 13, 1931, No. 20119. Convention date, July 18, 1930. [Classes 40 (iii) and 40 (v).] The. frequency of an oscillation generator is stabilized by producing unreflected waves in a mechanical oscillator from the output energy, transforming these waves back into electrical oscillations and feeding the latter to the input circuit of the generator. As shown a screengrid valve 2 has tuned grid and plate circuits 24, 26 and a lead 10 is taken from its plate to the electrode 14 of a piezo-crystal 12 cemented to a metal rod 8, a whole number of mechanical half-wavelengths long, and earthed at 52. A piezo-crystal 18 cemented to the other end of the rod 8 is associated with the grid of the valve the crystals and rod being clamped between the heads 46 by bolts 48 and between insulating blocks 50. The rod 8 may engage a rubber block 54 if it is desired to prevent standing waves therein. The mechanical waves produced in the rod by the crystal 12, react on the crystal 18 and produce potentials of stable frequency which are transferred in correct phase to the valve grid. Whether the bar should be an odd or even number of halfwavelengths long is determined by the orientation of the crystals 12, 18. In a modification Fig. 2 (not shown,) the rod is made of permanently magnetized iron and the crystal 18 is replaced by a pick-up coil in which currents are induced by the vibrating end of the rod and which is connected to earth and through a blocking condenser to the valve grid. In a further modification, Fig. 3 (not shown), the rod is biased and influences electrostatically a plate in proximity to its end and connected to the valve grid. The crystal 12 may also be replaced by alternative energy converters, and the rod may be replaced by a liquid or gaseous column with end diaphragms actuated in any of the ways already described. The oscillations in the tuned circuit 26, Fig. 1, may be utilized by a modulator 36, frequency multiplier 38, sideband filter 40, amplifier 42 and radiating system 44. In a further arrangement, torsional waves are produced in the rod 8, Fig. 4, (shown with its ends turned out) by vibrating the armature 68 by means of coils 82, 84 provided with magnetic cores 86, 88 and connected in series as a tuned circuit in the plate circuit of the generator 2<1>. The waves after travelling along the rod cause the vibration of armature 66 and the production of oscillatory current in the coils 72, 74 connected in series as a tuned circuit in the grid circuit of the generator 2<1>. Springs 70 provide the restoring forces for the armatures 66, 68 and with this arrangement the valve 2<1> is an ordinary triode owing to the inherent lowness of the frequencies produced. The rod is an exact number of mechanical half-wavelengths long and the phase relationships are dependent on the coil connections. A push-pull oscillator in which the restoring forces on the torsional armatures are electromagnetic is also described, Fig. 5 (not shown).