Extra exam question E9E06
Subelement E9, ANTENNAS AND TRANSMISSION LINES· Group E9E
Which of these transmission line impedances would be suitable for constructing a quarter-wave Q- section for matching a 100-ohm feed point impedance to a 50-ohm transmission line?
- A.50 ohms
- B.62 ohms
- C.75 ohms (correct answer)
- D.90 ohms
WhyA 75-ohm transmission line is a suitable choice for a quarter-wave Q-section matching a 100-ohm feed point impedance to a 50-ohm line. A quarter-wave Q-section's required characteristic impedance is the square root of the two impedances being matched: the square root of 100 ohms times 50 ohms works out to about 70.7 ohms, and 75 ohms, a standard, readily available transmission line impedance, is the closest practical match to that calculated value, answer C. 50, 62, and 90 ohms don't come as close to the calculated 70.7 ohm requirement.
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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