General exam question G9A04
Subelement G9, ANTENNAS AND FEED LINES· Group G9A
What causes reflected power at an antenna’s feed point?
- A.Operating an antenna at its resonant frequency
- B.Using more transmitter power than the antenna can handle
- C.A difference between feed line impedance and antenna feed point impedance (correct answer)
- D.Feeding the antenna with unbalanced feed line
WhyReflected power at an antenna's feed point is caused by a difference between feed line impedance and antenna feed point impedance. Reflected power appears at an antenna's feed point whenever the feed line's characteristic impedance doesn't match the impedance the antenna actually presents there, some of the forward power has nowhere matched to go and bounces back, answer C. Operating right at resonance (which tends to make the antenna's impedance mostly resistive) doesn't by itself guarantee a match to the feed line, excess transmitter power doesn't create reflections (it just raises the power involved), and simply using unbalanced feed line isn't inherently a mismatch, so A, B, 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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