Which of the following types of propagation is most commonly associated with occasional strong signals on the 10, 6, and 2 meter bands from beyond the radio horizon?
The correct answer is B: Sporadic E. Sporadic E (Es) is the propagation mode most commonly associated with occasional strong signals on the 10, 6, and 2 meter bands from beyond the radio horizon. Sporadic E creates temporary 'clouds' of intense ionization in the E layer of the ionosphere that can refract VHF signals.
Sporadic E is most common during summer months and can provide contacts on 10 meters, 6 meters, and sometimes even 2 meters over distances of 500-1500 miles. The 'sporadic' name comes from its unpredictable nature - it appears and disappears without much warning. When sporadic E is active, these bands can 'open up' and provide excellent long-distance contacts that aren't normally possible on VHF.
Exam Tip
10/6/2 meter long-distance = Sporadic E. Remember: Sporadic E is the most common propagation mode that provides strong signals on 10, 6, and 2 meters from beyond the radio horizon.
Memory Aid
"**S**poradic **E** = **S**trong **E**xtended range (think 'SE = SE' = Strong Extended range)"
Real-World Application
During a summer afternoon, you're monitoring 6 meters and suddenly hear stations from 800 miles away coming in strong. This is sporadic E - temporary intense ionization in the E layer is refracting 6-meter signals, allowing contacts far beyond normal range. The opening might last minutes or hours, then disappear. This is the 'magic' of 6 meters and why it's called the 'magic band' - sporadic E can make the impossible possible.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Backscatter is less common and typically provides shorter distances than sporadic E on these bands.
Option C: Incorrect. D region absorption actually prevents propagation, it doesn't enable long-distance contacts.
Option D: Incorrect. Gray-line propagation is more relevant to HF bands, not the primary mode for 10/6/2 meter long-distance contacts.
题目解析
The correct answer is B: Sporadic E. Sporadic E (Es) is the propagation mode most commonly associated with occasional strong signals on the 10, 6, and 2 meter bands from beyond the radio horizon. Sporadic E creates temporary 'clouds' of intense ionization in the E layer of the ionosphere that can refract VHF signals. Sporadic E is most common during summer months and can provide contacts on 10 meters, 6 meters, and sometimes even 2 meters over distances of 500-1500 miles. The 'sporadic' name comes from its unpredictable nature - it appears and disappears without much warning. When sporadic E is active, these bands can 'open up' and provide excellent long-distance contacts that aren't normally possible on VHF.
考试技巧
10/6/2 meter long-distance = Sporadic E. Remember: Sporadic E is the most common propagation mode that provides strong signals on 10, 6, and 2 meters from beyond the radio horizon.
记忆口诀
**S**poradic **E** = **S**trong **E**xtended range (think 'SE = SE' = Strong Extended range)
实际应用示例
During a summer afternoon, you're monitoring 6 meters and suddenly hear stations from 800 miles away coming in strong. This is sporadic E - temporary intense ionization in the E layer is refracting 6-meter signals, allowing contacts far beyond normal range. The opening might last minutes or hours, then disappear. This is the 'magic' of 6 meters and why it's called the 'magic band' - sporadic E can make the impossible possible.
错误选项分析
Option A: Incorrect. Backscatter is less common and typically provides shorter distances than sporadic E on these bands. Option C: Incorrect. D region absorption actually prevents propagation, it doesn't enable long-distance contacts. Option D: Incorrect. Gray-line propagation is more relevant to HF bands, not the primary mode for 10/6/2 meter long-distance contacts.
知识点
Sporadic E, VHF propagation, 10/6/2 meters, Beyond horizon
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.