GB372090A - Improvements in or relating to high frequency signalling - Google Patents

Abstract

372,090. Wireless transmitting systems. SOC. FRANCAISE RADIOELECTRIQUE, 79, Boulevard Haussmann, Paris. April 29, 1931, No. 12660. Convention date, May 6, 1930. Addition to 270,749, [Class 40 (v), Wireless signalling &c.]. [Class 40 (v).] The system of modulation by phase-variation of the kind described in the parent Specification is characterized by the use of a balanced-bridge of four tuned impedances, an unmodulated carrier-wave being supplied across one diagonal of the bridge and a modulated carrier-wave, in quadrature with the first, being fed across the other diagonal. The resultant waves, after amplification, are superimposed in opposition in a common circuit feeding the aerial. The balanced bridge comprises four inductances L1, Section 3, Fig. 1, shunt resistances r<1> and two push-pull valves, and is tuned to the frequency of the carrier-wave by condensers C1, C1<1> in the diagonals of the bridge. The bridge circuit is energized by unmodulated waves from a master-oscillator, Section 1, through a coupling L<1>0, and with modulated waves from the same source through a coupling LO and an amplifier, Section 2, the output from which is modulated by the valve amplifiers shown in Section 4. The bridge is capacitatively coupled by the condenser CC1 to the primary circuit L<11>, C<11>, and gives a band filter effect as regards the modulated energy. The modulated currents are in phase-quadrature with the unmodulated wave owing to the tuned coupling. The subsequent amplifier stages 5, 5a are accordingly excited respectively through the couplings L0, L<1>0 to a constant degree but in a varying phase these amplified currents being reproduced in the output circuits L6, C6 of the stages 6, 7 and 6a, 7a respectively. By adjusting the sense of the intervalve couplings the unmodulated excitation due to the coupling L<1>0, Section 1, gives rise to no potential differences across the condensers CC6 feeding the aerial, whilst the modulated currents transferred through the coupling L0, Section 1, set up aerial oscillations similar to the currents flowing in the circuit L11, C1, Section 2. The arrangement is stated to increase the maximun output obtainable from the valve amplifier stages. The anode of each valve comprises a primary circuit L3, C3 damped by the internal resistance of the preceding valve and capacitatively coupled by a condenser CC3 to a secondary circuit L<1>3, C<1>3 damped by a shunt resistance r3, the net effect being that of a band filter. Gridbias for parallel-connected amplifier valves in stages 6, 7 is taken from separate windings such as those shown from the secondary of the coil L<1>4. Valve capacities are neutralized in each case by a coil L7 and condenser N. A corrector circuit L, C, R in Section 4 comper.sates for irregularities in the filter action of the valve anode circuits in Sections 3, 5, 5a, 6, 6a, 7, and 7a.