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--- cert_exam:tech_radio_op_1:b:freq:h-free_space_propagation [2019/12/31 10:57] – 作成 fu
+++ cert_exam:tech_radio_op_1:b:freq:h-free_space_propagation [2020/01/02 19:59] (current) – fu
@@ Line 1: / Line 1: @@
 ======自由空間伝搬損と送受信点間距離======
+自由空間の伝搬損Lは
-  *
+\[
+ L = (\frac{4 \pi d }{\lambda})^2
+\]
+<color red>これは覚える</color>
+伝搬損がdBで与えられた場合には、\\
+$dBの値 = 10 log_{10} 真数$ \\
+で計算するlogにかかる係数は20ではないので注意する
+\[
+L(dB) = 10 log_{10} \frac{P_t}{P_r} = 10 log_{10} (\frac{4 \pi d}{\lambda})^2 = 20 log_{10} \frac{4 \pi d}{\lambda}
+\]
 ===== 出題履歴 =====
   * H28/1 A14