Which propagation mode involves a radio wave reflected by the ionosphere and returns to Earth?

Which propagation mode involves a radio wave reflected by the ionosphere and returns to Earth?

• A. Sky Wave
• B. Direct Wave
• C. Ground Reflected Wave
• D. Surface Wave

Answer: (A)

Sky wave propagation is the mode where a radio signal is sent upward toward the ionosphere, and the ionized layers reflect it back down to Earth. When the frequency is suitable, the wave is refracted by the ionosphere and returns to the surface at a distant point, enabling long-range communication beyond line-of-sight. This bounce can occur once (a single hop) or several times (multiple hops) between the ionosphere and the ground, depending on frequency, time of day, and solar activity. Direct waves travel straight-line to the receiver with no reflection, ground-reflected paths involve bouncing off the Earth’s surface rather than the ionosphere, and surface waves propagate along the Earth's surface, typically at lower frequencies. Sky wave is the only mode described that relies on ionospheric reflection to reach distant receivers.

Sky wave propagation is the mode where a radio signal is sent upward toward the ionosphere, and the ionized layers reflect it back down to Earth. When the frequency is suitable, the wave is refracted by the ionosphere and returns to the surface at a distant point, enabling long-range communication beyond line-of-sight. This bounce can occur once (a single hop) or several times (multiple hops) between the ionosphere and the ground, depending on frequency, time of day, and solar activity. Direct waves travel straight-line to the receiver with no reflection, ground-reflected paths involve bouncing off the Earth’s surface rather than the ionosphere, and surface waves propagate along the Earth's surface, typically at lower frequencies. Sky wave is the only mode described that relies on ionospheric reflection to reach distant receivers.