Patent GB-406967-A (GB)
Title: Improvements in series oscillators
IPC: H03C5/00
Filed: 1932-05-27
Abstract: 406,967. Valve generating and modulating circuits. DUBILIER CONDENSER CO. (1925), Ltd., Victoria Road, North Acton, London.-(Assignees of Nyman, A. ; Dobbs Ferry, New York, U.S.A.) May 27, 1932, No. 15088. Void [Abridged as open to inspection under Sect. 91 of the Acts, May 28, 1932]. [Class 40 (v).] Oscillations are generated by a number of valves having their anode-cathode paths in series and a single frequency control. Fig. 4 shows oscillator valves 61, 62, 63, in series with a tuned circuit 64 connected across a supply 65. The grids are biassed from potentiometer 34 and by the bias resistance 67 and back-coupling is effected to the coil 66. The output is applied to a series amplifier 76, 77, arranged in parallel to a modulating series amplifier 90, 91, and associated with the output valve 78. The series arrangement of oscillator valves is stated to result in stabilitv of frequency so that frequency control is not necessary. The output circuit 104, 105 serves as a radio frequency filter and by adjustment of the resistance 106 may be arranged to widen the frequency band transmitted. The oscillator back-coupling 66 may be dispensed with and the required radio frequency potentials from the output to the valve electrodes be obtained from the condenser bridge 68-73. In a similar manner condenser bridges are associated with the amplifying valves to compensate for valve capacities. A piezo-electric crystal may be arranged in the grid circuit of one of the oscillating valves to increase the stability. A number of frequencies may be generated simultaneously (Fig. 3, not shown) by arranging a number of tuned circuits in series with the series oscillator. Modulation may be applied to all frequencies simultaneously by modulating on the oscillator circuit by applying the modulating potentials to the grid of one of the series connected oscillator valves or each individual frequency may be separately modulated in frequency or amplitude by means of a variable series or shunt impedance to the appropriate tuned circuit. Fig. 6 shows condenser bridges 115, 116, 117, and 122-125 for applying radio frequency voltages to the grid and cathode circuits of the oscillatory valves. Modulation may be effected by valve 127 which controls the grid bias potentials or by valve 134 which controls the radio frequency potential of the cathodes of the valves. Alternatively choke modulation may be used in which case an audio frequency choke in the high tension supply with separate modulating valves (Fig. 7, not shown) may be used. The tuned output circuit may have the anode supply taken to a centre tapping and condenser bridges connected to the two sides of the tuned circuit. Screen grid valves may be used as oscillators (Fig. 8, not shown) and modulation may be effected by valves in series with the oscillator valves. (Figs. 8 and 9, not shown.) The oscillator valves may be arranged in pushpull with modulating valves in series with the push-pull pairs (Fig. 10, not shown). Fig. 11 shows a push-pull oscillator 284-287 with choke control push-pull modulators 270-273. When the series oscillator is frequency stabilized by means other than the series tuned circuit, e.g. by a piezo-electric crystal detuning of the series circuit enables the carrier and one sideband to be suppressed.