mediumwave Medium wave (MW) is a part of the medium frequency (MF) radio band used mainly for AM broadcasting, AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. Duri ...

broadcasting Broadcasting is the data distribution, distribution of sound, audio audiovisual content to dispersed audiences via a electronic medium (communication), mass communications medium, typically one using the electromagnetic spectrum (radio waves), ...

, a mush area is a region where the

ground wave Ground wave is a mode of radio propagation that consists of currents traveling through the earth. Ground waves propagate parallel to and adjacent to the surface of the Earth, and are capable of covering long distances by diffracting around the E ...

and sky wave from a transmitter are received at approximately equal signal strength, resulting in interference between the two, which will typically cause serious fading. The effect can reduce the coverage area of a transmission at night, even in the absence of interfering signals from any other source. It can be mitigated to some extent by the use of a tall

mast radiator A mast radiator (or radiating tower) is a radio mast or tower in which the metal structure itself is energized and functions as an antenna. This design, first used widely in the 1930s, is commonly used for transmitting antennas operating at l ...

of up to about 0.6 wavelengths height, which increases the ground wave field strength while reducing high-angle sky wave radiation.

References

Radio frequency propagation {{Telecomm-stub