GB618514A - Transmitter control circuit - Google Patents

Abstract

618,514. Valve generating circuits; radio - navigation. STANDARD TELEPHONES & CABLES, Ltd. March 29, 1946, No. 9791. Convention date, April 2, 1945. [Classes 40 (vi). and 40 (vii)] A circuit for generating a composite signal consisting of a plurality of signals having constant mutual ratio of amplitude, for use in a radio beacon system, comprises a number of oscillators of different frequencies, the output of each being amplified and applied to a load output circuit, a control output circuit being coupled to each amplifier from which a voltage is derived and applied to each oscillator to correct for variations in the output amplitude the voltages being compared with a common delaying voltage so that a common reference is obtained for all the oscillators. In the Figure, the signals from three resistancecapacity oscillators of different frequencies are amplified separately and part of the output of each amplifier is rectified, the control voltage obtained from each rectifier if different from the delaying voltage which is common to all three circuits is fed back as a bias voltage to the grid circuit of its own oscillator valve, the common delaying voltage to all three control circuits ensures that the ratio of the amplitudes of the signals remains constant. Negative feedback is obtained in the oscillator stage by means of resistor 10 and in the amplifier stage by cathode resistors 28 and 29 and the delaying voltage is obtained from a common supply source 5 which may be stabilized. The amplifier output transformers 34 have a split secondary winding, one half 41 of which is used to derive a voltage for the oscillator control circuit and the other half 35 supplies an output direct to a mixing circuit 38; in the case of two of the amplifiers, an output is also supplied from this winding to the stator coil of a variometer. In the mixing circuit 38, the outputs of the three amplifiers are combined with that obtained from the rotor coil 40 of the variometer. The variometer comprises two stator coils at an angle of 90 degrees to one another, each of the stator coils inducing a voltage in the rotary coil which varies sinusoidally in amplitude. Due to the relative position of the stator coils, the amplitude variations in the rotor are 90 degrees out of phase, the input to the mixing network 38 thus consists of two varying amplitude voltages and a fixed amplitude voltage connected directly to the mixing network. The composite signal which is the output of the mixer is used to modulate an R.F. transmitter, the modulated energy being transmitted in the form of a beam rotated in timed relation with the rotary coil of the variometer so that the radiation pattern will contain three modulation components having a unique mutual ratio for any given azimuth position of the rotating beam. Specification 33270/46, as open to inspection under Sect. 91, is referred to.