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An antenna has a radiation resistance of 68 Ω, a load resistance of 10 Ω, and a power gain of 16. Its directive gain is

1. 15
2. 16.02
3. 17.08
4. 18.35

Correct answer: 18.35

Solution

Efficiency eta = R_rad/(R_rad+R_loss) = 68/78 = 0.872. Directive gain = power gain / eta = 16/0.872 = 18.35.

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