General exam question G9D07
Subelement G9, ANTENNAS AND FEED LINES· Group G9D
Which of the following describes a log-periodic antenna?
- A.Element length and spacing vary logarithmically along the boom (correct answer)
- B.Impedance varies periodically as a function of frequency
- C.Gain varies logarithmically as a function of frequency
- D.SWR varies periodically as a function of boom length
WhyA log-periodic antenna's element length and spacing vary logarithmically along the boom. A log-periodic antenna's defining feature is that both its element lengths and the spacing between successive elements scale by a constant ratio (logarithmically) along the boom, which is what gives it consistent performance across a wide frequency range, answer A. Its feed point impedance and gain don't cycle periodically or logarithmically with frequency the way B and C describe, and it isn't specifically SWR-versus-boom-length that defines the design, so B, C, and D are wrong.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2023-2027 NCVEC Element 3 pool (public domain); the explanation above is original writing, see our methodology.
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