GB467163A - Radio wave transmission and reception systems - Google Patents

Abstract

467,163. Wireless signalling. HILLS, J. L. Oct. 10, 1935, Nos. 27991/35 and 23338/36. [Class 40 (v)] A carrier wave is transmitted the frequency of which is continuously varied over the whole or part of a predetermined band, a supersonic heterodyne frequency being produced at the receiver by a local oscillator the frequency of which is also varied continuously, but differently over the same band. In the intercommunication system described, at each station the transmitter itself is used as the source of local oscillations for the receiver and the frequency bands of the various transmitters become segregated by automatically varying the direction of transmitter frequency variation when an incoming signal approaches the frequency of the transmitted signal. Alternatively a muting circuit may become operative when an audible intermediate frequency is produced. As shown the frequency of a transmitter T is cyclically varied by the rotation of the movable plate of a variable condenser 1 at about five to seven revolutions per second by a motor 2 through a gearbox 3. The receiver comprises an aerial 6, and a frequency changer D1 fed by incoming signals and signals from the adjacent transmitting aerial 5. The output from the following aperiodic I.F. amplifier, IFA1, is applied through switch S1 to the second detector D2 feeding a telephone instrument P and if desired a tuned relay system C1, R1 actuating apparatus B or a rectifier 7 and meter Ma. A muting device M may be associated with the detector D2 coming into operation when the intermediate frequency is reduced to 4000 or 5000 cycles. Alternatively the direction of rotation of the condenser 1 may be reversed when the intermediate frequency reaches this value by means of a tuned circuit C2 operating a relay R2 acting on the gearbox 3. A single station may be selected by connecting the detector D2 through switch S1 to an I.F. amplifier IFA2 which has a tuning control 10 and a selectivity control 11. For direction finding a rotatable loop aerial 6a feeding a frequency changer D1a and IF amplifier IFA3 is provided its output being combined in opposite phase with that from the aerial 6 by moving the switch S1 to the contact 15. According to the first Provisional Specification the carrier frequency variations may be dependent upon temperature, pressure, or other physical variations.