MAXIMUM USABLE FREQUENCY (MUF)

In radio transmission using reflection from the regular ionized layers of the ionosphere , the upper frequency limit that can be used for transmission between two points at a specified time . ( 188 ) Note: MUF is a median frequency applicable to 50% of the days of a month, as opposed to 90% cited for the lowest usable high frequency (LUF) and the optimum traffic frequency ( FOT ).