MF/HF (300–3,000 kHz / 3–30 MHz)
Combined Medium Frequency and High Frequency (MF/HF) radios can transmit over thousands of nautical miles as the signal can be ‘bounced’ off the ionosphere to overcome line of sight issues. This makes them an ideal tool for ocean going ships to communicate without the need to pay a service provider for ‘airtime’.
As part of the Global Maritime Distress and Safety System (GMDSS), Single Side Band (SSB) MF/HF radios capable of Digital Selective Calling (DSC) are required on all SOLAS vessels operating outside of sea area A1 in order to maintain a continuous automatic watch on designated channels, listening for any distress signals. Rescue groups also monitor these channels.