Basic Qualification · B-007 Radio wave propagation · B-007-004-002
Why can you not hear distant 160-metre and AM broadcast stations during daytime hours?
- A The splitting of the F region into two sub-regions
- B The weather below the ionosphere
- C The ionization of the D region
- D The presence of ionized clouds in the E region
Correct answer: C — The ionization of the D region. From the official ISED question bank, verified word for word.
Why
During the day, sunlight creates a layer of ionization called the D region low in the atmosphere. 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.