Discussion
The radiation resistance of a Hertizian dipole antenna of length \(\frac{\lambda}{60}\) is
Answer: B
The radiation resistance of a short dipole is \(80\pi^2 (l/\lambda)^2\), which for \(l = \lambda/60\) is about 0.22 ohm (option B).
\[ R_{rad} = 80\pi^2\left(\frac{1}{60}\right)^2 \]
\[ R_{rad} = \frac{789.6}{3600} \approx 0.22\ \Omega \]
The value 0.493 ohm (A) would belong to a longer dipole, near \(\lambda/40\). The values 2.2 and 22 ohm are 10 and 100 times too big, as if the length were \(\lambda/19\) or \(\lambda/6\).
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