General exam question G9A01
Subelement G9, ANTENNAS AND FEED LINES· Group G9A
Which of the following factors determine the characteristic impedance of a parallel conductor feed line?
- A.The distance between the centers of the conductors and the radius of the conductors (correct answer)
- B.The distance between the centers of the conductors and the length of the line
- C.The radius of the conductors and the frequency of the signal
- D.The frequency of the signal and the length of the line
WhyA parallel-conductor feed line's characteristic impedance depends on the spacing between the conductors' centers and the radius of the conductors themselves. A parallel-conductor feed line's characteristic impedance is set by its geometry, specifically the spacing between the conductors' centers and each conductor's own radius, since those two dimensions determine the line's distributed inductance and capacitance per unit length, answer A. Neither the line's overall length nor the signal's frequency changes the line's characteristic impedance, that impedance is a fixed geometric property of the line itself, 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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