GB468271A - Improvements in or relating to electrical oscillation generators - Google Patents

Abstract

468,271. Valve circuits. STANDARD TELEPHONES & CABLES, Ltd. May 5, 1936, No. 12688. Convention date, May 29, 1935. [Classes 39 (i) and 40 (v)] In a magnetron oscillator, the modulating potentials are applied simultaneously to the field coil 18 and to'auxiliary electrodes, while the carrier oscillations are applied to the main electrodes. The auxiliary electrodes may comprise end plates 50, 52 or portions 100, 102 of a quadrantally split anode. The highvacuum tube 10, Fig. 3, has a coil 18 for producing a magnetic field which may be axial or inclined, and has end plates 50, 52 so biassed positively as to increase the oscillatory output, or biassed negatively to protect the ends of the glass or quartz envelope from bombardment and sputtering. According to the invention, modulating potentials derived from a microphone 64 are applied both to the coil 18 and to the end plates 50, the adjustments being such as to produce distortionless amplitude modulation free from frequency modulation. Frequency is stabilized by a piezoelectric resonator 90 coupled to the magnetron through a tapped transformer 96 and tuning- condenser 80, and the output is taken from conductors 81, 83. In a modification, Fig. 1 (not shown), the plates 50, 52 are excited in the same phase by a simple transformer instead of the tapped transformer 70, and the tuning system 80, 90 is replaced by a pair of Lecher wires. In a further modification, Fig. 4, a magnetic core 122 having polepieces 129 coaxial with and external to the envelope is provided. The anode is split into four quarter-cylinders ; the tuning circuit 80, 90 is connected by conductors 81, 83 to one pair of opposite quarter-cylinders, while the modulating transformer 116 is connected to the other (separately biassed) pair as well as to the magnetizing coil 124. In a further modification, Fig. 6. (not shown), the modulating voltage is applied to only one quarter-cylinder, the opposite quarter-cylinder being kept at a fixed potential for the purpose of stabilizing the oscillations. The Specification as open to inspection under Sect. 91 describes also a further modification, Figs. 7, 8 (Cancelled, not shown), in which the anode is split into two halfcylinders which are connected to the modulating circuit as well as to the source of carrier ,current. There may be an iron core with a biassing coil as well. as a modulating coil, Fig. 9 (Cancelled, not shown). Various other combinations in which the foregoing features may be used are mentioned. This subjectmatter does not appear in the Specification as accepted.