Extra exam question E9F11
Subelement E9, ANTENNAS AND TRANSMISSION LINES· Group E9F
What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is open at the far end?
- A.The same as the characteristic impedance of the line
- B.An inductive reactance
- C.A capacitive reactance (correct answer)
- D.Infinite
WhyA 1/8-wavelength transmission line open at the far end presents a capacitive reactance to an RF generator. An open 1/8-wavelength line is shorter than the 1/4-wavelength needed to fully invert an open into a short, so it presents a capacitive reactance at its input, the mirror-image case of a shorted 1/8-wave line's inductive reactance, answer C. It doesn't present the line's own characteristic impedance, doesn't present an inductive reactance (that's what the shorted version does), and it isn't infinite, that would only describe the open termination itself, not looking into 1/8 wavelength of line.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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