2182 kHz

Radio distress frequency

2182 kHz is a radio frequency designed exclusively for distress calls and related calling operations in the maritime service.

2182 kHz is analogous to channel 16 on the marine VHF band, but unlike VHF which is limited to ranges of about depending on antenna height, communications on 2182 kHz and nearby frequencies have a reliable range of around during the day and or sometimes more at night. The reception range of even a well equipped station can be severely limited in summer because of static caused by lightning.

Historically, all stations using 2182 kHz were required to maintain a strictly enforced three minute silence and listening period twice each hour, starting at h+00ᵐ, h+30ᵐ. This allowed any station with distress, urgent or safety traffic the best chance of being heard at that time, even if they were at some distance from other stations, operating on reduced battery power or perhaps reduced antenna efficiency, as for example from a demasted vessel. As a visual aide memoire, a typical clock in a ship's radio room would have these silence periods marked by shading the sectors from h+00ᵐ to h+03ᵐ, and from h+30ᵐ to h+33ᵐ in green. Similar sectors were marked in red for what used to be the corresponding silence and listening period on 500 kHz from h+15ᵐ to h+18ᵐ, and from h+45ᵐ to h+48ᵐ. Effective 1 August 2013, the U. S. Coast Guard terminated its radio watch on the international voice distress, safety, and calling frequency 2182 kHz and the international digital selective calling (DSC) distress and safety frequency 2187.5 kHz. Marine information and weather broadcasts that had been transmitted on 2670 kHz ended at the same time. The U. S. Coast Guard does still monitor HF (4–22 MHz) marine distress / safety / calling voice and DSC frequencies.