Medium frequency (MF) refers to radio frequencies (RF) in the range of 300 kHz to 3000 kHz. Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten to one hectometers (1,000 to 100 m). Frequencies immediately below MF are denoted Low-frequency (LF), and the next higher frequencies are known as High-frequency (HF).
500 kHz was for many years the Maritime distress and emergency frequency, and there are more NDBs between 510 and 530 kHz. Navtex, which is part of the current Global Maritime Distress Safety System occupies 518 kHz and 490 kHz for important digital text broadcasts. In recent years, some limited amateur radio operation has also been allowed in the region of 500 kHz in the USA, UK, Germany and Sweden.
Many home-portable or cordless telephones, especially those that were designed in the 1980s, transmit low power FM audio signals between the table-top base unit and the handset on frequencies in the range 1600 to 1800 kHz.
There are a number of Coastguard and other ship-to-shore frequencies in use across the range from 1600 to 2850 kHz. These include, as examples, the French MRCC on 1696 kHz and 2677 kHz, Stornoway Coastguard on 1743 kHz, the US Coastguard on 2670 kHz and Madeira on 2843 kHz. RN Northwood in England broadcasts Weather Fax data on 2618.5 kHz.
2182 kHz is the international calling and distress frequency for SSB voice maritime communication (radiotelephony) on the marine MF bands. It is analogous to Channel 16 on the marine VHF band.
Lastly, there are aeronautical and other mobile SSB bands from 2850 kHz to 3500 kHz, crossing the boundary from the MF band into the HF radio band.