maximum usable frequency (radio) (MUF)

The Maximum Usable Frequency (MUF) is specified for the radiation of high frequency from an antenna.

The MUF frequency is the highest frequency that is optimally reflected by the ionosphere at a given elevation angle. The MUF frequency refers to two locations or geographic areas on the Earth's surface that are connected by a space wave radio link. In addition, the MUF frequency takes into account different times of day because they affect the reflectivity of the ionosphere. The 85% value of the Maximum Usable Frequency is considered the Frequency of Optimum Transmission ( FOT). The just usable lowest frequency is the Lowest Usable Frequency( LUF).