GB467013A - Improvements in or relating to directional radio systems - Google Patents

Abstract

467,013. Directive wireless signalling. AGA-BALTIC RADIO AKTIEBOLAG, and DALEN, S. G. Jan. 7, 1937, No. 500. [Class 40 (v)] In a directiona transmitter comprising at least two antenna systems arranged to transmit signals of different frequency, a least one being arranged for rotating directed transmission so tha a beat tone varying in intensity is received a communication con cerning the direction of the minimum is also transmitted, enabling the bearing at the time of disappearance of the beat tone to be ascer tained. A motor 1 Fig. 2, first causes con tact 3 to operate anc oscilator 01 modulatec at audio frequency by the photo-cell and film device 4, 5, 6 and amplifier F1 1 transmits an identification signal over the antenna A1 which has a polar diagram a, Fig. 1. Contact 7 then operates and oscillator 02 transmits a frequency differing from that of 01, over antenna A2 and rotating ganiometer 8; the polar diagram being b and c, Fig. 1. At the same time antenna A1 transmits some signal such as a bell or verbal information, recorded on the film, which is heard together with the beat note of varying intensity to indicate the position of the rotating field. One of the transmitted frequencies is continuously interrupted and restarted to provide an intermittent interference note to facilitate observations of intensity variation In a modification, Fig. 4 (not shown), the non-directional antenna system is given a polar diagram as in Fig. 3, to improve the minimum and prevent swamping of the direction indications. In order to obtain the two frequencies for transmission, one H.F. oscillator may be used and modulated at the required beat frequency in a push-pull modulator which eliminates the carrier; one or both side bands then being transmitted by the directional system.