| 摘要 |
1,141,516. Radar. SOUTH AFRICAN INVENTIONS DEVELOPMENT CORP. 29 Nov., 1966 [14 Dec. 1965], No. 53471/66. Heading H4D. The Specification describes an improvement in secondary radars of the Tellurometer type in that, instead of varying the carrier frequency of the signal transmitted between the two antennae of the points, the distance between which is to be measured, in order that variations in the measured distance at various carrier frequencies caused by ground wave reflections may be averaged out, said carrier frequency remains constant and distance measurements are made with at least one of the antennae at various heights above the ground. The variation of the measured distance with antenna, height is shown for an actual distance of 88À57 metres in Fig. 2. Figs. 3 and 4 show that whereas the measured distance may appear to remain nearly constant for various carrier frequencies, Fig. 4, measurements for various antenna heights, Fig. 3, show large variations, indicating that, opposite to theory, the predominant wave between the antennae is the ground reflected wave.
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