Basic Qualification · B-006 Feedlines and antenna systems · B-006-010-008
Which of the following transmission lines will give the best match to the base of a quarter-wave ground-plane antenna?
- A 300-ohm balanced transmission line
- B 75-ohm balanced transmission line
- C 75-ohm coaxial cable
- D 50-ohm coaxial cable
Correct answer: D — 50-ohm coaxial cable. From the official ISED question bank, verified word for word.
Why
A quarter-wave ground-plane antenna naturally presents an impedance close to 50 ohms at its base, which matches perfectly with 50-ohm coaxial cable. The full explanation — and one for every question — is in Pro.
Practise this section
Getting the signal out: antennas, feedlines, SWR, baluns, matching, and why antenna length depends on frequency.