Shortwave radio is radio transmission using shortwave frequencies, generally 1.6–30 MHz (187.4–10.0 m), just above the medium wave AM broadcast band.
Shortwave radio has an ability to enter a state of skywave or skip propagation, in which the radio waves are reflected or refracted back to Earth from the ionsophere, as opposed to being absorbed. This is a particularly important characteristic: it allows the transmitted signal to be reflected around the curve of the Earth, thus shortwave is not line-of-sight. This allows for very long distance communications.