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The radiation resistance of a monopole of height 1cm and operating at frequency 100MHz is ____ Ω.(a) 4.83m(b) 4.38k(c) 4.38m(d) 4.83kThe question was posed to me during an interview for a job.This interesting question is from Radiation in section Radiation, Baluns & Polarization of Antennas

Answer»

The correct choice is (c) 4.38m

The explanation is: The radiation RESISTANCE of a monopole is 1/8 times the CURRENT element.

\(R_{rad}=10\pi^2 (l/\lambda)^2\)

For a monopole height h= l/2 => l= 2H

\(R_{rad}=10\pi^2(\frac{2h}{\lambda})^2=40\pi^2 (\frac{hf}{c})^2=40\pi^2 (\frac{1×100×10^6}{3×10^{10} })^2=4.38m\Omega\)


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