Longwave radio frequencies are those below 500 kHz, which correspond to wavelengths longer than 600 meters. This range includes the low frequency band, and part of the medium frequency band. Longwave signals have the property of following the curvature of the earth, making them ideal for continuous, continental communications. Unlike shortwave radio, longwave signals do not reflect or refract using the ionosphere, so there are fewer interference-caused fadeouts. Instead, the D-layer of the ionosphere and the surface of the earth serve as a waveguide directing the signal.