Medium Frequency (MF)

The range of radio frequencies between 300 kHz and 3 MHz, commonly used in marine communication and navigation systems.

Medium Frequency (MF) is a segment of the radio spectrum that plays a pivotal role in maritime operations. Falling between 300 kHz and 3 MHz, this range is particularly significant for its ability to propagate over long distances, especially at night, due to the phenomenon of ionospheric reflection. This makes it reliable for ship-to-ship, ship-to-shore, and distress communications. In the maritime context, MF is most notably associated with the Global Maritime Distress and Safety System (GMDSS), where it is used for transmitting safety information and emergency signals, such as Digital Selective Calling (DSC) on the 2187.5 kHz frequency and voice communications on 2182 kHz.

MF is also used in marine navigation, particularly in Non-Directional Beacons (NDBs). These beacons emit signals that vessels can use to determine their position relative to the beacon. This is especially useful in coastal areas or when navigating in poor visibility. However, MF signals are susceptible to interference from atmospheric noise and man-made sources, which can impact their clarity. Despite these challenges, the medium frequency range remains an indispensable tool in the maritime industry, ensuring safety and efficiency in communication and navigation.