How does a higher sunspot number affect HF propagation?
The correct answer is A: Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies. How higher sunspot numbers affect HF propagation is that higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies. More sunspots mean more solar activity, which ionizes the ionosphere more, allowing higher frequencies to propagate. For amateur radio operators, high sunspot numbers mean better conditions on higher bands (10m, 12m, 15m). Understanding this helps predict propagation conditions.
Exam Tip
Higher sunspots = better propagation at higher frequencies. Think 'H'igher 'S'unspots = 'H'igher 'S'olar activity = 'H'igher frequencies propagate. More sunspots mean more ionization, allowing higher frequencies to propagate. Not about sporadic E, not impossible propagation, not undisturbed conditions.
Memory Aid
"Higher sunspots = better propagation at higher frequencies. Think 'H'igher 'S'unspots = 'H'igher frequencies. More sunspots mean more solar activity and ionization, allowing higher frequencies to propagate. Key relationship for HF propagation."
Real-World Application
During high sunspot numbers (e.g., 150), 10 meters and 15 meters open regularly with good propagation. During low sunspot numbers (e.g., 10), these higher bands may be dead, but lower bands (40m, 80m) still work. Higher sunspot numbers mean better conditions for higher frequency bands.
Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Lower sunspot numbers don't indicate greater sporadic E - sporadic E is independent of sunspots. Sporadic E is caused by different mechanisms.
Option C: Incorrect. Zero sunspot number doesn't mean propagation is impossible - lower bands (160m, 80m, 40m) can still work. Propagation is still possible, just not on higher bands.
Option D: Incorrect. Zero sunspot number doesn't indicate undisturbed conditions - it indicates low solar activity, which actually means disturbed conditions for higher frequencies.
题目解析
The correct answer is A: Higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies. How higher sunspot numbers affect HF propagation is that higher sunspot numbers generally indicate a greater probability of good propagation at higher frequencies. More sunspots mean more solar activity, which ionizes the ionosphere more, allowing higher frequencies to propagate. For amateur radio operators, high sunspot numbers mean better conditions on higher bands (10m, 12m, 15m). Understanding this helps predict propagation conditions.
考试技巧
Higher sunspots = better propagation at higher frequencies. Think 'H'igher 'S'unspots = 'H'igher 'S'olar activity = 'H'igher frequencies propagate. More sunspots mean more ionization, allowing higher frequencies to propagate. Not about sporadic E, not impossible propagation, not undisturbed conditions.
记忆口诀
Higher sunspots = better propagation at higher frequencies. Think 'H'igher 'S'unspots = 'H'igher frequencies. More sunspots mean more solar activity and ionization, allowing higher frequencies to propagate. Key relationship for HF propagation.
实际应用示例
During high sunspot numbers (e.g., 150), 10 meters and 15 meters open regularly with good propagation. During low sunspot numbers (e.g., 10), these higher bands may be dead, but lower bands (40m, 80m) still work. Higher sunspot numbers mean better conditions for higher frequency bands.
错误选项分析
Option B: Incorrect. Lower sunspot numbers don't indicate greater sporadic E - sporadic E is independent of sunspots. Sporadic E is caused by different mechanisms. Option C: Incorrect. Zero sunspot number doesn't mean propagation is impossible - lower bands (160m, 80m, 40m) can still work. Propagation is still possible, just not on higher bands. Option D: Incorrect. Zero sunspot number doesn't indicate undisturbed conditions - it indicates low solar activity, which actually means disturbed conditions for higher frequencies.
知识点
Sunspot numbers, HF propagation, Higher frequencies, Solar activity
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.