Question
Which of these emission modes is best for auroral propagation?
Answer Options
- A) CW
- B) SSB
- C) FM
- D) RTTY
Correct Answer: A
Explanation
When a radio signal reflects off the constantly moving, turbulent curtains of ionization that form the aurora, the reflection mechanism introduces severe distortion into the signal. The effect on voice signals (SSB or FM) is a distinct, raspy distortion that often renders them unintelligible.
Because of the turbulence and distortion, the emission mode best suited for auroral propagation is CW (Continuous Wave), or Morse Code. Although the reflected CW signal is also distorted and often sounds ‘raspy’ or ‘fluttery,’ the human ear and brain are highly effective at integrating the received energy to decode the simple on/off (dit/dah) components of the signal, allowing communication when voice or data would fail.
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