Quadruple-site diversity experiment in Austria using 12 GHz radiometers

The paper reports on a quadruple-site diversity experiment using 12 GHz radiometers in Austria. Separations between sites were 10.9 to 26.2 km, providing orthogonal path separations (vertical or horizontal) of between 9.3 and 25.9 km. The radiometers were directed along the future look-angle of the ESA satellite OLYMPUS (azimuth 223.16° from true North, elevation 25.43°). The measurements were conducted from May 1980 to April 1983, with dual-site joint uptimes exceeding 94.9% for all combinations. The experimental results indicate that, for this location and geometry, dual-site diversity performance is insensitive to separations above 10 km, all pairs achieving similar diversity gain statistics. The results were close to those predicted by the Hodge model, with the prevailing weather direction having a significant influence on diversity performance. In general triple- and quadruple-site groupings provided better improvement in diversity than the dual-site combinations but, while the statistical improvement was slight, the number of joint events was significantly reduced from dual-site combinations