Question
Sun March 02, 2008 By:

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Expert Reply
Mon May 12, 2008

 surface wave or a ground wave  can refer to a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient. In radio transmission, a ground wave is a surface wave that propagates close to the surface of the Earth.

sky wave : Sky waves are reflections from the ionosphere.

Skywave is the propagation of radio waves bent (refracted) back to the Earth's surface by the ionosphere. As a result of skywave propagation, a night-time broadcast signal from a distant AM broadcasting or shortwave radio station (or rarely, a TV station) can sometimes be heard as clearly as local stations. Most long-distance HF radio communication (between 3 and 30 MHz) is a result of skywave propagation. For decades Amateur radio operators, limited to lower transmit power than commercial radio, have taken advantage of skywave for distance or DX communication.

 

space wave:

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