GB420669A - Improvements in or relating to wireless direction finding systems - Google Patents

Abstract

420,669. Directive wireless signalling. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, DOWSETT, H. M., 47, Drayton Gardens, Winchmore Hill, and WALKER, L. E. Q., 98, Wymering Mansions, Maida Vale, all in London. May 6, 1933, No. 13250. [Class 40 (v)] In a directionfinding system in which the transmitter radiates television signals corresponding to a picture giving an indication of the position of a rotating beam and the identity of the transmitter, said signals are transmitted from an omnidirectional aerial and are interrupted for a predetermined interval for each scanning operation during which arbitrarily chosen signals are radiated from the rotating beam aerial. As shown, a frame aerial 1 rotates with a scale 2, picture signals corresponding to that part of the scale indicating the direction of the aerial 1 and to a station identifying panel 3, being produced by a Nipkow disc 4 and light-sensitive cell 5 connected to a transmitter 6 and omni-directional aerial 7. Two of the apertures in the disc 4 are omitted so that two of the scanning lines in the picture reproduced at the receiver appear blank. In the intervals due to this omission the aerial 1 is energized from a, transmitter 10 modulated by a cell 9 which is illuminated by a lamp 8 through holes in the disc 4 when the cell 5 is unilluminated. At the receiver, the picture is traversed by a blank line which varies in brightness according to the position of the aerial 1 at the transmitter and hence enables its position to be determined. A mechanical commutator or other switching device prevents radiation from the aerials 1, 7 during the periods in which they are not being modulated by the scanning device. A common carrier source is preferably provided for the two transmitters. Specification 402,443 is referred to.