132CHAPTER 18 18.55(a) For the first measurement, the equivalent circuit is as shown in Figure 1. From this, 12abyyyRRRR R==+=so 112yRR=(1) For the second measurement, the equivalent circuit is shown in Figure 2. This gives 212acyxRR RR==+(2) Substitute (1) into (2) to obtain 211122xR=+, or 14xR=−(b) If R, then 1213 and 6.0 R=Ω= Ω2.8 xR=ΩSince this exceeds the limit of 2.0Ω, the antenna is inadequately grounded . 18.56Assume a set of currents as shown in the circuit diagram at the right. Applying Kirchhoff’s loop rule to the leftmost loop gives
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