What is a characteristic of VHF signals received via auroral backscatter?
The correct answer is B: They are distorted and signal strength varies considerably. A characteristic of VHF signals received via auroral backscatter is that they are distorted and signal strength varies considerably. Auroral backscatter creates a distinctive, fluttery, distorted signal quality.
Auroral backscatter occurs when VHF signals are scattered by the aurora (Northern/Southern Lights). The aurora is a region of ionized particles in the upper atmosphere that can scatter radio signals. Signals received via auroral backscatter have a characteristic 'fluttery' or 'raspy' sound due to the constantly changing ionization in the aurora. Signal strength varies rapidly as the aurora changes. This is a rare but exciting propagation mode that can allow VHF contacts over hundreds or even thousands of miles.
Exam Tip
Auroral backscatter = Distorted, varying signal. Remember: VHF signals via auroral backscatter are distorted and have varying signal strength. They have a characteristic fluttery, raspy sound.
Memory Aid
"**A**uroral **B**ackscatter = **A**ltered **B**y aurora (think 'AB = AB' = Altered By aurora, distorted)"
Real-World Application
You're monitoring 2 meters during an aurora event. You hear a station that's normally too far away, but the signal sounds distorted and fluttery - the audio has a raspy, 'underwater' quality, and the signal strength rapidly varies. This is auroral backscatter - your signal is being scattered by the aurora, allowing the contact but with characteristic distortion. The signal might be strong one moment and weak the next as the aurora changes.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. While auroral backscatter can provide long distances, 10,000 miles is extreme. Typical distances are hundreds to a few thousand miles.
Option C: Incorrect. Auroral backscatter can occur at various times, not just winter nights. It depends on auroral activity, which is related to solar activity.
Option D: Incorrect. Antenna direction for auroral backscatter depends on where the aurora is, not necessarily west. You point toward the aurora.
题目解析
The correct answer is B: They are distorted and signal strength varies considerably. A characteristic of VHF signals received via auroral backscatter is that they are distorted and signal strength varies considerably. Auroral backscatter creates a distinctive, fluttery, distorted signal quality. Auroral backscatter occurs when VHF signals are scattered by the aurora (Northern/Southern Lights). The aurora is a region of ionized particles in the upper atmosphere that can scatter radio signals. Signals received via auroral backscatter have a characteristic 'fluttery' or 'raspy' sound due to the constantly changing ionization in the aurora. Signal strength varies rapidly as the aurora changes. This is a rare but exciting propagation mode that can allow VHF contacts over hundreds or even thousands of miles.
考试技巧
Auroral backscatter = Distorted, varying signal. Remember: VHF signals via auroral backscatter are distorted and have varying signal strength. They have a characteristic fluttery, raspy sound.
记忆口诀
**A**uroral **B**ackscatter = **A**ltered **B**y aurora (think 'AB = AB' = Altered By aurora, distorted)
实际应用示例
You're monitoring 2 meters during an aurora event. You hear a station that's normally too far away, but the signal sounds distorted and fluttery - the audio has a raspy, 'underwater' quality, and the signal strength rapidly varies. This is auroral backscatter - your signal is being scattered by the aurora, allowing the contact but with characteristic distortion. The signal might be strong one moment and weak the next as the aurora changes.
错误选项分析
Option A: Incorrect. While auroral backscatter can provide long distances, 10,000 miles is extreme. Typical distances are hundreds to a few thousand miles. Option C: Incorrect. Auroral backscatter can occur at various times, not just winter nights. It depends on auroral activity, which is related to solar activity. Option D: Incorrect. Antenna direction for auroral backscatter depends on where the aurora is, not necessarily west. You point toward the aurora.
知识点
Auroral backscatter, VHF propagation, Signal distortion, Aurora
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.