GB592570A - Improvements in or relating to radio direction-finding systems - Google Patents

Abstract

592,570. Directive wireless signalling. WESTERN ELECTRIC CO., Inc. Oct. 26, 1943, No. 17682. Convention date, June 28, 1941. [Class 40 (v)] In a radio direction finding system, the voltage induced in a receiving aerial is phase modulated by cyclic movement of the aerial to vary its distance from a transmitter, the phase of the modulation being compared with the phase of a locally generated reference oscillation to determine the bearing of the received wave. A dipole 1 mounted on the end of an arm 2 secured to a vertical shaft 4 driven by a motor 3, moves in a circular path 19 in the horizontal plane and is coupled by slip rings 6 and line 5 to a radio receiver comprising local oscillator 8, R.F. amplifier and first detector 9, I.F. amplifier 10 and a second frequency changing stage comprising beat oscillator 11 and detector 12. The second or low intermediate frequency is fed to a converter or slope circuit 13 which converts frequency or phase modulation to amplitude modulation and is followed by a final detector 14, the output of which consists of a lowfrequency equal to the aerial revolution frequency. The output from a reference generator 15 driven from the shaft 4 is fed through a phase adjuster 18 to a phase difference indicator 17 of known type which is also fed with the receiver output. The measured phase difference is a direct indication of the bearing of the received waves from a given reference direction. Specification 408,211 and U.S.A. Specifications 984,108 and 1,510,792 are referred to.