Basic Qualification · B-007 Radio wave propagation · B-007-001-007
What makes radiocommunication out to 200 km possible at lower HF frequencies during the daytime?
- A Tropospheric ducting
- B Skip wave
- C Space wave
- D Ground wave
Correct answer: D — Ground wave. From the official ISED question bank, verified word for word.
Why
Ground wave allows signals to follow the Earth's surface, hugging the curve to reach distances up to 200 km even when the ionosphere is busy reflecting other frequencies during the day. 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.