GB439288A - Improvements in or relating to radio receivers - Google Patents

Abstract

439,288. Valve circuits for wireless reception. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London.-(Assignees of Smith, R. M. ; Marlton Pike, Merchantville, New Jersey, U.S.A.) May 29, 1934, No. 16035. Convention date, June 30, 1933. [A Specification was laid open to inspection under Sect. 91 of the Acts, Nov. 30, 1934.] [Class 40 (v)] A diode-amplifier valve is used in a receiver as a carrier frequency amplifier, a diode detector and as a modulation frequency amplifier by reflexing to keep the size, current consumption, cost and number of valves as low as possible. A receiver for use in motor cars or the like comprises a supersonic heterodyne circuit in which the intermediate frequency amplifier 28 is of the screen grid or pentode type as shown in Fig. 1 and includes one or more diodes for rectification. A reflex circuit is used and the intermediate frequency valve is used also as an audio frequency amplifier. The diode load comprises resistance 57 and the portion of potentiometer 59 below the slider 58 and is connected by shielded lead 61 to the low potential side of the intermediate frequency input circuit 37, and provides automatic volume control over lead 64. In a modification, Fig. 2 (not shown), a separately biassed diode is used for the automatic volume control so that this is delayed. In a further arrangement, Fig. 3 (not shown), similar automatic volume control is used but the voltage may be taken from a potentiometer tapping which may be conjointly operated with the audio-frequency volume control. In this arrangement one end of the volume control potentiometer is earthed and the potentiometer is connected in parallel with part of the load resistance through condensers while a condenser between the tapping and earth provides simultaneous tone and volume control. In a further modification, Fig. 4 (not shown), the potentiometer serves as the diode load and provides the grid bias for the amplifying valve. The Specification as open to inspection under Sect. 91 comprises also a switch in the modification, Fig. 4 (not shown), so that all the voltage or only the portion of the voltage between the potentiometer tapping and earth may be used for automatic volume control. Fig. 5 (Cancelled), shows an arrangement in which the volume control potentiometer 128 regulates both the audio frequency passed from the anode circuit of the valve 28 to the amplifier 160 and the transfer of intermediate frequency energy from the anode circuit to the detector circuit. Thick lines show the diode detector circuit and the reflex path for the audio signal. Fig. 6 (Cancelled), shows a modification in which the same volume control is used as previously for high frequency but the audio frequency potentiometer 128 is in the grid input circuit to the amplifier 160 instead of providing the audio frequency anode load of the valve 28 which avoids distortion due to the reduction of the anode load. This subject-matter does not appear in the Specification as accepted.