GB408531A - Improvements in or relating to radio receivers - Google Patents

Abstract

408,531. Valve circuits for wireless reception ; impedance networks. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London- (Assignees of Travis, C.; 354, West Allen's Lane, Philadelphia, U.S.A.) Oct. 11, 1933, No. 28073. Convention date, Nov. 8, 1932. [Classes 40 (iii) and 40 (v).] In orde r to avoid the use of a visual tun ing meter &c. in a receiver embodying automatic gain regulation, a double-humped characteristic is given to the coupling between a carrier amplifier and gain control detector. As shown, a superheterodyne receiver comprises a radio-frequency amplifier 2, first detector 4, oscillator 6, intermediate-frequency amplifier 9 and second detector 10, while some of the intermediate-frequency energy is amplified by a valve 11 fed through a condenser 12 from the input of valve 9, and rectified by a diode 19. The anode circuit of the diode 19 includes a potential divider 21, 22, 23 from different tappings of which gain-control potentials are applied to the grids of valves 2, 4 and 9 through resistances 24, 25 and 27 respectively. The intermediatefrequency coupling transformer 16 between the valves 11 and 19 has a double-humped characteristic as shown in Fig. 2, so that more intermediate-frequency energy is passed therethrough if its frequency is displaced either above or below the required value by inaccurate tuning of the oscillator and high-frequency stages, to produce a reduction of amplification in the receiver proper, the maximum amplification for small changes of the tuning dial occurring when the incoming signals are correctly tuned. Alternatively, the double humped characteristic may be produced by a tuned circuit 15, 17, Fig. 4, coupled to the valve 19 through a condenser 15<1> and also to a further tuned circuit 33<1>, 161 or by a network of inductances and capacities 15, 50, 51, 52, Fig. 5, connected as shown as a coupling network between the valves 11 and 19.