| 摘要 |
618,274. Radio navigation. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. Aug. 21, 1946, No. 24971. Convention date, Dec. 13, 1938. [Class 40. (vii)] A course-defining radio beacon in which energy is radiated omnidirectionally from a central antenna and also in a figure of eight radiation pattern from two antennae spaced on either side of the central antenna and fed in phase opposition so that the energy radiated in the second pattern is substantially zero along the course and in which one of the radiating systems is inverted in phase in dot-dash signal rhythm has the energy radiated over the figure of eight pattern deeply modulated and the non- directional radiation modulated at the same frequency, but to a relatively small depth, the carrier wave being relatively larger in amplitude. A mathematical proof is given showing that such an arrangement gives the narrowest course (assuming that differences in sound amplitude of less than 7.5 per cent cannot be discerned for the sake of example) and it is shown that adjusting the depth of the weakly modulated radiation alters the effective width of the beacon axis. It is also shown that the beacon is less subject to masking due to the demodulation effect produced by unwanted signals. |
