Basic Qualification · B-007 Radio wave propagation · B-007-007-005
What is a sporadic-E condition?
- A Variations in E-region height caused by sunspot variations
- B A brief decrease in VHF signals caused by sunspot variations
- C Patches of dense ionization at E-region height
- D Occasional duct formation in the E region
Correct answer: C — Patches of dense ionization at E-region height. From the official ISED question bank, verified word for word.
Why
Sporadic-E happens when thin, highly concentrated clouds of ionized gas form unexpectedly in the E-region of the upper atmosphere, allowing VHF radio signals to bounce much farther than usual. 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.