Basic Qualification · B-006 Feedlines and antenna systems · B-006-013-009
What is the approximate length of the wire for a horizontal loop tuned at 7.15 MHz?
- A 41.96 metres
- B 10.49 metres
- C 20.00 metres
- D 42.80 metres
Correct answer: D — 42.80 metres. From the official ISED question bank, verified word for word.
Why
A full-wave horizontal loop at 7.15 MHz needs a wire length calculated by dividing the speed of light by the frequency, then multiplying by a factor of about 0.95 to account for how radio waves travel slower in wire than in empty space. 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.