Basic Qualification · B-007 Radio wave propagation · B-007-005-004
What is the solar-flux index?
- A A measure of solar activity that is taken annually
- B A measure of solar activity that is taken at a specific frequency
- C Another name for the smoothed sunspot number (SSN)
- D A measure of solar activity that compares daily readings with results from the last six months
Correct answer: B — A measure of solar activity that is taken at a specific frequency. From the official ISED question bank, verified word for word.
Why
The solar-flux index measures how much radio energy the Sun emits at a specific frequency, usually 2800 megahertz, which helps predict how well the ionosphere will reflect signals. 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.