Basic Qualification · B-006 Feedlines and antenna systems · B-006-010-007
What configuration of radials will match an elevated quarter-wave vertical antenna to a 50-ohm coaxial cable?
- A Downward sloping quarter-wave radials
- B Horizontal quarter-wave radials
- C Horizontal half-wave radials
- D Upward sloping half-wave radials
Correct answer: A — Downward sloping quarter-wave radials. From the official ISED question bank, verified word for word.
Why
Downward sloping quarter-wave radials create the right electrical balance to match an elevated vertical antenna to a 50-ohm coaxial cable because the downward angle lowers the feed point impedance to the desired level. 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.