GB158927A - Improvements in aerial systems employed in wireless signalling - Google Patents

Abstract

158,927. Franklin, C. S. Sept. 24, 1919. Directive signalling; duplex signalling.-Two or more unidirectional systems of the type described in Specifications 24098/14 and 5783/15 are spaced a fraction of a wave-length apart in the direction of signals to be received. Oscillations in these two systems are combined by phasing circuits with a common receiver. Each system is arranged to give a similar polar curve, and the resulting curve from combining the two systems is better than either taken separately, giving almost complete cancellation behind the station. In an example, Fig. 1, A, B, C, D are four frame aerials erected in the line of communication. A, B are combined through tuned circuits E, F coupled to them. The circuits E, F are mistuned equally but in opposite senses to a degree dependent on the spacing between the aerials, so that waves from one direction along A, D will produce oscillations in them of exactly opposite phase, and waves in the other direction, oscillations of slightly different phase. The circuits C, Dare similarly combined through G, H. The circuits E, F are both coupled to circuit O and the circuits G, H tQ the circuit P, and O, Pare both coupled to the receiving-circuit S. Each of the systems separately has a polar curve showing loops behind the station at 120‹ to the line of communication. In the present invention, circuits 0, P are mistuned equally but in opposite senses to a degree such that waves from this direction will produce in them oscillations of exactly opposite phase and will therefore produce no effect in circuit S. Thus the combined systems give zero reception at 90‹, 120‹ and 180‹ with the line of communication. A method is mentioned in which each of the four frame aerials mentioned above is replaced by two frames at right-angles connected to a radiogoniometer. This is stated to give zero reception in six controllable directions and to be particularly desirable in the case of duplex working.