Extra exam question E9F12
Subelement E9, ANTENNAS AND TRANSMISSION LINES· Group E9F
What impedance does a 1/4-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.The same as the input impedance to the generator
- C.Very high impedance
- D.Very low impedance (correct answer)
WhyA 1/4-wavelength transmission line open at the far end presents a very low impedance to an RF generator. A quarter-wavelength line inverts whatever impedance is at its far end, so a line left open at the far end (very high impedance) presents very low impedance back at the generator, the opposite of the shorted case, answer D. It doesn't present the line's own characteristic impedance, doesn't simply mirror the generator's own input impedance, and it doesn't present very high impedance, that describes the shorted 1/4-wave case instead.
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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