Differences

This shows you the differences between two versions of the page.

--- cert_exam:tech_radio_op_1:b:freq:h-free_space_propagation [2020/01/02 19:29] – fu
+++ cert_exam:tech_radio_op_1:b:freq:h-free_space_propagation [2020/01/02 19:59] (current) – fu
@@ Line 5: / Line 5: @@
  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