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Antennas for transmitting skywaves are typically made from horizontal [[dipole antenna|dipoles]] or bottom-fed loops, both of which emit [[Horizontal polarization|horizontally polarized]] waves. The preference for horizontally polarized transmission is because (approximately) only half of the signal power transmitted by an antenna travels directly into the sky; about half travels downward towards the ground and must "bounce" into the sky. For frequencies in the upper HF band, the ground is a better reflector of [[Horizontal polarization|horizontally polarized]] waves, and better absorber of power from [[vertical polarization|vertically polarized]] waves. The effect diminishes for longer wavelengths.
For receiving, [[random wire antenna]]s are often used. Alternatively, the same directional antennas used for transmitting are helpful for receiving, since most noise comes from all directions, but the desired signal comes from only one direction. Long-distance (skywave) receiving antennas can generally be oriented either vertically or horizontally, since refraction through the ionosphere usually scrambles signal
n, and signals are received directly from the sky to the antenna. ==See also==
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