Question
How does a higher sunspot number affect HF propagation?
Answer Options
- A) Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies
- 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
Correct Answer: A
Explanation
Sunspot numbers are a direct measure of solar activity, specifically the number of dark spots visible on the Sun’s surface. A higher sunspot number indicates increased solar activity, which results in more ultraviolet (UV) and X-ray radiation being emitted toward Earth. This intense radiation creates a denser and more highly ionized F2 ionospheric layer.
A denser F2 layer is capable of refracting radio waves of higher frequencies back to Earth, resulting in a higher Maximum Usable Frequency (MUF). Therefore, higher sunspot numbers generally indicate a greater probability of good long-distance propagation on the higher HF bands, such as 15, 12, and 10 meters.
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