Basic Qualification · B-007 Radio wave propagation · B-007-006-009
When is propagation on the 80-metre band generally the LEAST effective?
- A Daytime in summer
- B Evening in winter
- C Evening in summer
- D Daytime in winter
Correct answer: A — Daytime in summer. From the official ISED question bank, verified word for word.
Why
During the day, the Sun's ultraviolet light creates a dense layer in the upper atmosphere that absorbs lower frequency signals like those on the 80-metre band. The full explanation — and one for every question — is in Pro.
Practise this section
How signals travel: the ionosphere and its layers, skip, ground wave, sporadic E, and which bands work when.