Plain English Meaning
A radio signal that bounces off a high layer of the atmosphere and comes back down a long way away, letting it be heard well past the horizon.
Full Definition
A radio wave that travels upward from a transmitter, reflects off the ionosphere, and returns to earth at a distant point. Sky wave propagation allows certain low- and medium-frequency signals to be received far beyond the line-of-sight range of the transmitter.
Context Anchor
Seen in radio communication and radio navigation discussions, especially when explaining long-range reception, night effects, or signal interference.
Derivation
Called a 'sky wave' because the signal travels up into the sky, reflects off the ionosphere, and returns. The name distinguishes it from a 'ground wave,' which follows the curve of the earth along the surface.
Analogy
Think of throwing a ball upward so it comes back down far away. A sky wave is not a ball, but the idea is similar: the signal goes up first, then returns to Earth at a distant place.
Grounding Statement
A sky wave matters when a radio signal reaches the aircraft by bouncing back from high in the atmosphere instead of coming directly from the transmitter.
Intuition Check
Sky wave does not mean a weather wave or a visible wave in the sky. It means a radio signal that travels through the upper atmosphere and returns to Earth.
Example Sentence 1
At night, sky wave interference made the ADF needle drift, so the pilot cross-checked the bearing with VOR before trusting it.
Example Sentence 2
At night the ionosphere rises, extending sky wave range and sometimes allowing contact with stations on the opposite side of the continent.