GB470131A - Improvements in modulated carrier wave receivers - Google Patents

Abstract

470,131. Wireless receiving systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. June 8, 1936, No. 16035. Convention date, June 6, 1935. [Class 40 (v)] Comprises a phase or frequency modulated receiving system in which demodulation is effected by means of a multi-grid valve, the retarded signal being applied to one grid and the unretarded signal to another. In the form shown in Fig. 2, the signal is fed through an intermediate frequency amplifier and bandpass filter to a retardation network 6 loaded with an adjustable resistance R. Tappings are taken from the beginning and part of the way along the network to grids G1, G2, of a valve 8 which operates as a detector, and feeds an audio frequency amplifier 9 through a resistance condenser coupling unit 15. The unit 15 may be replaced by a low-pass filter. In a modification shown in Fig. 1, the retardation network is formed by a filter 33 having a sloping characteristic. Here the signal is fed through an intermediate frequency amplifier 3, 5 and if desired through a frequency multiplier 26 and second detector 27, to amplifier valves 30, 31. The valve 30 feeds grid G1 through the filter 33 and the valve 31 the grid G2 through an impedance 34 and condenser 36. In a modification of this, to remove amplitude distortion due to the sloping characteristic of the filter 33 two valves 8 having a push-pull output are employed, the grid G1 of the second valve being fed through a filter which slopes in the reverse direction to that feeding the first. With this arrangement amplitude modulation may be received by changing the output connections of the valves 8 from push-pull to series. Specification 448,448 is referred to.