MF/HF-SSB Marine Radio Distress, Safety, & Hailing

The International Telecommunication Union (ITU,) the same organization that sets international regulations and treaties governing Marine VHF usage is also responsible for the Marine Medium and High Frequency spectrum. The intent is to provide the maritime radio communications user with a group of standard distress, safety, hailing, and working frequencies that are known to all mariners and can be used worldwide.

In the medium and high frequency bands (2) of the most common distress communications types are voice radio and Digital Selective Calling (DSC) alerts with DSC becoming the preferred method of initiating distress communications before switching over to voice communications.

When using DSC, the simple push of the distress alert button on a MF/HF-SSB radio that is tied into a GPS, you automatically transmit all the information needed to initiate a search. When the situation allows, the use of both DSC and voice communications in combination is the preferred method and will probably result in a faster response.

International Distress, Safety and Hailing Frequencies

The following MF & HF marine radio frequencies have been set aside by the ITU as distress, safety, and hailing frequencies. These frequencies are internationally accepted and can be used for ship to shore and ship to ship hailing, broadcasting of marine safety information, and sending distress calls. They are guarded by most nations of the world and these frequencies will be found pre-programed into all newer MF/HF-SSB Marine Radios.

Voice Guard

International MF/HF Voice Distress, Safety, & Hailing Frequencies
Ship Transmit Ship Receive Simplex/Duplex USB/LSB
2182.0 kHz 2182.0 kHz Simplex USB
4125.0 kHz 4125.0 kHz Simplex USB
6215.0 kHz 6215.0 kHz Simplex USB
8291.0 kHz 8291.0 kHz Simplex USB
12290.0 kHz 12290.0 kHz Simplex USB
16420.0 kHz 16420.0 kHz Simplex USB
All distress, safety and hailing frequencies are simplex and Upper Sideband (USB) only.

DSC Guard

International MF/HF DSC Distress, Safety, & Hailing Frequencies
Ship Transmit Ship Receive Corresponding
Simplex/Duplex USB/LSB
2187.5 kHz 2187.5 kHz 2182.0 kHz Simplex USB
4207.5 kHz 4207.5 kHz 4125.0 kHz Simplex USB
6312.0 kHz 6312.0 kHz 6215.0 kHz Simplex USB
8414.5 kHz 8414.5 kHz 8291.0 kHz Simplex USB
12577.0 kHz 12577.0 kHz 12290.0 kHz Simplex USB
16804.5 kHz 16804.5 kHz 16420.0 kHz Simplex USB
Once a DSC alert has been acknowledged, the corresponding voice frequency is then used for voice communications.

International MF/HF Distress Frequencies - Download

Upon Receipt of a Distress Call

This would be a good time for the mariner to review the actions that should be taken if you receive a HF DSC Distress Alert.

HF DSC Distress Alert Flow Diagram - Download

Distress Listening Watch

Most seafaring nations maintain a watch on some if not all international distress frequencies. The major change being that more and more of these nations have abandoned maintaining a voice watch in lieu of maintaining a DSC only watch. This trend is likely to continue into the future, until at some point only DSC guards will be maintained on the DSC distress frequencies.

Because of this transition away from voice watches, it behooves the offshore mariner who depends on HF-SSB for communications to become intimately familiar with the alert and calling functions of their DSC radios.

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