GB306487A - Improvements in or relating to directional wireless signalling - Google Patents

Abstract

306,487. Brandes, Ltd., (Assignees of Kolster, F. A., and Kruesi, G. G.). Feb. 21, 1928, [Convention date]. Directive signalling; thermionic generators. - A uni-directional aerial system comprises a combination of three antennae 11, 12, 16, Fig. 1, of which the members 11, 12 are preferably combined to form a loop. The member 16 is shunted across the loop at a point nearer the conductor 12 than 11. As the junction is not a nodal point, current flowing on the conductor 11 will divide between the conductors 16 and 12, the phase of the current in the former being shifted through a definite optimum angle relative to that flowing in the latter by means of a capacity reactance 19, and also by adjusting the three-plate condenser 17, 18. The combined effect of the currents in the conductors 16, 12 is equivalent to an imaginary conductor B at a distance d from the conductor 11, carrying a current substantially equal to that flowing in the branch 11 but dephased by a definite angle. This arrangement produces a cardioid curve of radiation, the main axis of which can be warped or shifted by adjusting the capacity reactances. The aerial system may be energized by a valve oscillator 21 with capacity back-coupling through a tuned loop 22 and condenser 28, and a signalling-key 23 inserted in the plate circuit, the high-tension supply being protected by chokes 24. The aerial conductor 11 is directly connected to the highpotential end of the plate inductance 22, the other side of the aerial system being coupled by distributed capacity. Various modified forms of coupling are described, Fig. 10 showing an arrangement for permitting the directional loop to be rotated through brush contacts 40. The loop as a whole is preferably less than one quarter of the working wave-length, the distance between conductors 11 and 12 being from one-tenth to one-fifteenth of the wave-length.