Medium Frequency (MF)
Medium frequency (MF) refers to the radio frequency band from 300 kHz to 3 MHz. In aviation, MF includes the upper portion of the NDB navigation frequency range (535–1750 kHz overlaps with commercial AM broadcast) and some long-range communication applications. MF signals use ground wave propagation, extending range beyond line of sight.
MF in Navigation
NDBs operate from 190 to 1750 kHz — spanning both the LF and MF bands. Commercial AM broadcast stations in the MF band (535–1750 kHz) can also be received by ADF receivers and used as informal navigation references (homing). However, commercial stations are subject to greater error sources than dedicated NDB beacons.