Basic Qualification · B-006 Feedlines and antenna systems · B-006-011-010
For a three-element Yagi antenna, what approximate element spacing (in wavelengths) provides the best compromise between gain and front-to-back ratio?
- A 0.10
- B 0.50
- C 0.75
- D 0.20
Correct answer: D — 0.20. From the official ISED question bank, verified word for word.
Why
A spacing of 0.20 wavelengths strikes the right balance for a three-element Yagi, placing the reflector and directors close enough to interact strongly for good gain while keeping the rear signal low. 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.