GB562284A - A glide path radio beacon - Google Patents

Abstract

562,284. Directive wireless signalling. STANDARD TELEPHONES & CABLES, Ltd. Jan. 15, 1943, No. 774. Convention date, Jan. 19, 1942. [Class 40 (v)] An antenna system for producing an equisignal glide path for landing aircraft comprises a pair of parallel radiators 9, 10 spaced apart in the same horizontal plane and energized alternately, or simultaneously, with currents in phase and with currents substantially out of phase so as to produce two sets of interleaved lobes 61, 6<11>, 6<111> and 7<1>, 7<11>, 7<111>, the glide path being indicated by the lobes 6<1>, 7<1>. In order to prevent a pilot being misled by picking up signals from the lobes 6<11>, 7<11>, &c., an additional radiator 11 produces a radiation pattern 8 having no radiation in the direction of the lobe 6<1>, the pattern 8 being modulated by the same signals as the lobes 7<1>, 7<11>, 7<111>, so that the pilot hears the signals when off the correct glide path. In Fig. 2, the radiators 9, 10 are energized alternately in different phase relation by keying means 19, 20 through different modulators 17, 18, the relative phase being determined by phase shifters 14, 15. The carrier source 16 is connected through a separate modulator 17<1>, similar to 17, direct to the radiator 11. In a modified system, Fig. 3 (not shown), the radiators are continuously fed through conjugate networks of the kind described in Specification 491,359 so arranged that one horizontal radiator transmits only side bands of the modulation frequencies and the other transmits the side bands and also unmodulated carrier, the phase relations being such that the side band of one modulation frequency produces lobes corresponding to 6<1>, 6<11>, 6<111>, whereas the side band of the other modulation frequency produces lobes such as 7<1>, 7<11>, 7<111>. Carrier modulated by one of the modulation frequencies is fed to the third radiator corresponding to 11 in Fig. 2. In further modifications, Figs. 4 and 5 (not shown), the radiator 11 is supplied with carrier of a slightly different frequency from that fed to the radiators 9, 10. Specification 537,530 also is referred to.