GB586788A - Improvements relating to oscillation generators - Google Patents

Abstract

586,788. Valve generating circuits. STANDARD TELEPHONES & CABLES, Ltd., SMYTH, C. N., and GRANT, A. S. April 9, 1942, No. 4696. [Class 40 (v)] In a generator, the output of which is dependent upon two or more variable factors, e.g. applied voltage, filament temperature, or tuning adjustment of a resonant circuit, means . are provided for controlling one of the factors as another is varied, so as to obtain optimum, or a predetermined output. The Figure shows a control arrangement for a velocity-modulated oscillator, e.g. the coaxial line oscillator described in Specification 537,490 in which a control circuit PP is used to control the oscillator anode potential so as to maintain oscillation as the resonator frequency is varied. A silicon-tungsten crystal detector may detect the oscillator output and provide a controlling voltage which is fed to terminals B and causes the valve V1 which was biassed to cut-off to pass current. In this way the charging of condenser C1 which, with neon lamp V3 and resistance R1 generates a saw tooth voltage which is applied to the amplifier V2, is arrested so that the power supply PP will remain constant at the point reached in the sweep voltage applied to the anode. Unwanted modes of oscillation may be prevented from applying a voltage to terminals B by coupling the crystal to the oscillator through a length of attenuating cable which will prevent the setting up of standing wave patterns. Alternatively the circuit or the resonator may be modified so that a high impedance is developed only in a predetermined frequency range. The control circuit is given a time constant sufficient to maintain the voltage steady throughout the modulation cycle and may have a non-linear relation between the input and the control voltage developed.