Medium Frequency (MF) refers to the radio frequency range between 300 kHz (kilohertz) and 3 MHz (megahertz) on the electromagnetic spectrum. It is higher in frequency than Very Low Frequency (VLF) and Low Frequency (LF) but lower than High Frequency (HF). Here are some key points about MF:
- AM Broadcast Band: The MF band includes the frequency range used for AM (Amplitude Modulation) radio broadcasting. In many regions, this includes frequencies from around 530 kHz to 1700 kHz. AM radio stations use MF frequencies to transmit audio content, such as music and news, to a wide audience.
- Navigation: While VLF and LF are often used for long-range navigation, MF frequencies can also be employed for short-range navigation and communication, especially in maritime and aviation applications.
- Aeronautical Communication: MF frequencies are used for communication between aircraft and air traffic control (ATC). This includes both voice communication and data transmission for navigation and surveillance.
- Maritime Communication: MF is important for maritime communication, including ship-to-ship and ship-to-shore communication, as well as navigational aids like Non-Directional Beacons (NDBs).
- Amateur Radio: Some MF bands are allocated for amateur radio use. Licensed amateur radio operators can use MF frequencies for experimentation and communication.
- Emergency and Distress Frequencies: Certain MF frequencies are designated internationally for emergency and distress communications. These are monitored by authorities for distress calls and coordination of search and rescue operations.
- Ground Wave Propagation: MF signals are capable of ground wave propagation, which means they can follow the Earth’s curvature and provide relatively reliable coverage over moderate distances. This characteristic is important for broadcasting and local communication.
- Interference and Noise: MF frequencies can be affected by both natural and man-made interference, including atmospheric noise and electrical noise from electronic devices. Careful engineering and filtering are often required to mitigate these issues.
- Regulation: The use of MF frequencies is regulated by national and international authorities to prevent interference and ensure efficient spectrum utilization.
While AM radio broadcasting remains a significant use of MF frequencies, other communication technologies and frequency bands have largely supplanted MF for many applications. However, it continues to play a crucial role in certain sectors, such as aviation, maritime, and amateur radio, where its propagation characteristics are advantageous.