Radio waves that propagate near the Earth's surface and partially bend around it due to diffraction are called ground or surface radio waves. The longer the wavelength, the lower the losses in the ground and the diffraction attenuation. Therefore, ground-wave communication is used in the LF, MF, and HF bands, as well as in the HF and MB bands for mobile operation and for short-range communication (a few to tens of kilometers). Short waves can propagate as ground waves in the lower-frequency part of the band, and as ionospheric waves.
Radio waves shorter than 8–10 meters, under normal ionospheric conditions, cannot be sufficiently refracted in the ionosphere to return to Earth. Therefore, the propagation of meter and decimeter radio waves generally occurs only by means of the surface wave.
In VHF radio communication, only the direct wave is used. The communication range depends on obstacles along the wave path, antenna height above ground, and transmitter power, but even under the most favorable circumstances the maximum range can be 50–70 km.
Related articles: Direct radio wave, HF, Frequency range, Short radio waves, Ultra short waves (VHF, Ultra short waves).