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问:下表a～d四项的1～5组数据是从图1、图2的接收天线特性示例中读取的。试问这5组数据中哪一组是正确的? 答:运用所学的接收天线特性的基本知识,从图1、图2中正确地读数,再对照表列的5组数据,即可得到解答。由图2得G_(54)=10dB。第58频道的VSWR最小。由图1得W_(-3dB)=2×20°=40°。前后比为18dB。与表列数据对照,只有第2组数据完全符合,故第2组数据是正确的。问:图3是一共用天线电视接收设施的
Q: The 1 ~ 5 sets of data of the four items a ~ d in the following table are read from the receiving antenna characteristics of FIG. 1 and FIG. 2. Q: Which of the five data sets is correct? A: By using the basic knowledge of the characteristics of the receiving antenna, we can obtain the correct data from Figure 1 and Figure 2 and then compare the 5 sets of data listed . From Figure 2 G_ (54) = 10dB. Channel 58 has the smallest VSWR. From Figure 1 W _ (- 3dB) = 2 × 20 ° = 40 °. Before and after the ratio of 18dB. In contrast with the tabulated data, only the data in the second group are completely consistent, so the data in the second group is correct. Q: Figure 3 is a common antenna television reception facilities