General exam question G3A01
Subelement G3, RADIO WAVE PROPAGATION· Group G3A
How does a higher sunspot number affect HF propagation?
- A.Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies (correct answer)
- B.Lower sunspot numbers generally indicate greater probability of sporadic E propagation
- C.A zero sunspot number indicates that radio propagation is not possible on any band
- D.A zero sunspot number indicates undisturbed conditions
WhyHigher sunspot numbers generally indicate a greater probability of good propagation at higher HF frequencies. A higher sunspot number tracks with more solar ultraviolet output ionizing the upper atmosphere more strongly, which generally raises the highest frequency the ionosphere can still refract back to Earth, so higher sunspot numbers mean a better chance of good propagation on the higher HF bands, answer A. A zero sunspot count doesn't mean propagation stops entirely (lower HF bands still work fine), and sunspot number isn't specifically linked to sporadic E or to "undisturbed" conditions the way B and D claim.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2023-2027 NCVEC Element 3 pool (public domain); the explanation above is original writing, see our methodology.
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