Probability that Ordinate is Exceeded,0/© Fiaure 9. Probability distribution of hot spot occurrence inside sinqle story wood frame house v/ith metal sidings (worst case) exposed to a 2.57 GHz satellite signal (’'lei Is and Tryon, 1976) The variability of the inside signal level (e.g., +9 dB) was in all cases about twice as high as the outside reference level (e.g., + 4 dB). Figure 9 gives the probability distribution of the individual Lf values for two rooms in a house (metal sidings, signal coupled through the roof) which had the lowest median for (5.1 dB) of all houses measured. The 10 percent probability of a HSP occurring is insignificant in view of the large scatter of the data points. 5.2. Fields in Anechoic Chambers The reflectivity level in anechoic chambers has been studied extensively for obvious reasons (Appel-Hansen, 1973; Crawford, 1974; Donaldson et al., 1978). A statistical sampling of data points (Wells and Tryon, 1976; Donaldson et al., 1978) is not sufficient to capture the complicated three-dimensional interference pattern. A free-space SWR probe has to be scanned along several orthogonal axes because a high degree of uncertainty exists about E. (x, y, z). The examples in Figure 8 show that reflecting objects in the quiet zone or missing absorber material quickly deteriorate any low reflectivity level. The local maxima are
RkJQdWJsaXNoZXIy MTU5NjU0Mg==