GB167490A - Improvements in antennae systems for wireless signalling - Google Patents

Abstract

167,490. Ges. f³r Drahtlose Telegraphie. Aug. 6, 1920, [Convention date]. Aerials; directive signalling. - In an aerial system comprising a directional and unidirectional antenna in combination, the polar diagram of the system may be .varied by varying the electrical constants of the antennµ, or the system may be arranged to have different polar curves for different wavelengths by making the two antennµ of different damping. Fig. 3 shows the resultant polar curve C for a combination of an unidirectional and a directional antenna having separate polar curves A, B, respectively. The dead angles GH, IK may be adjusted to any position by varying the relative amplitudes of the two antennµ. This is preferably effected by inserting in the unidirectional aerial an adjustable ohmic resistance. For preventing interference, the dead angles may be arranged so that a receiver lies in the dead angle from a disturbing transmitter, or so that transmitters lie in the dead angles of a receiver. The centre of the directional antenna should lie in the unidirectional antenna and the two may be combined on a single mast, Fig. 5, in which case the unidirectional antenna should be provided with an additional capacity. In a modification, the unidirectional antenna is formed by earth-connecting a point of symmetry on the frame antenna through a tuning element; the receiver being coupled to both antennµ when the system is used for reception. Preferably, for reception, the unidirectional antenna 1, Fig. 7, is coupled to the receiving circuit through the directional circuit 7. Fig. 8 shows resonance curves L, M for two antennµ each tuned to the wave N and having different dampings, the difference between which, for reception without disturbance, should be as great as possible. Curve C, Fig. 9, represents the polar curve for the wave N at which the amplitudes are the same, and waves of this length coming from the direction T will not be heard. The curve U corresponds to waves Q for which the amplitudes are different, and waves of this length coming from direction T will be heard. This arrangement may be employed when using continuous waves and signalling by de-tuning, both antennµ being tuned to the de-tuned wave.