SOS 500 khz

Save 500 kHz!


500 kHz was the international maritime Morse Code radio distress frequency for most of the 20th century. 

Ever listened to Morse Code signals in a movie with a marine theme?  There is a very good chance that those Morse signals would have been sent on 500 kHz

500 kHz was the frequency used by the RMS Titanic to send her plaintive cries for help that April night in 1912.

It was the frequency used by thousands of merchant ships to signal their plight in times of peace and war.

More often than not, 500 kHz was witness to a ship's Radio Officer's last moments.  Many Radio Officers literally died at their key as their ship fell victim to enemy action or was overwhelmed by the forces of nature.


We must not let the sacrifices of those brave men and women be forgotten! 


500 kHz was replaced in 1999 by the Global Maritime Distress and Safety System (GMDSS), which uses a combination of automated terrestrial and satellite communications. 

Morse Code at sea is no more.

Whilst official operation on 500 kHz has been discontinued since 1999, the frequency is still designated as a distress channel in the International Radio Regulations.  It is likely that this status will remain for some time.

The distress and safety status of 500 kHz will eventually be removed from the International Radio Regulations.  The frequency will then be 'up for grabs' by other interests, perhaps not even maritime related.


500 kHz has been instrumental in saving tens of thousands of lives in the last 100-odd years. 

It is fitting that 500 kHz be preserved as a 'radio spectrum national park' to commemorate those who paid the supreme sacrifice in its use. 

We must not let Governments auction the frequency off to commercial interests - 500 kHz must be preserved for use by historic marine radio stations. 


Amateur radio operators have expressed an interest in seeking a new frequency allocation in the vicinity of 500 kHz - this should be encouraged, however it is fitting that the actual frequency of 500 kHz (i.e. the band 499-501 kHz) be preserved for historic maritime stations.

Perhaps a way forward is to preserve 499-501 kHz for maritime historic stations, with the surrounding band (say 495-499 and 501-505 kHz) used by amateurs.

The US based Maritime Radio Historical Society have done a superb job in keeping the spirit of 500 kHz alive with their operation from the restored marine coast radio stations KPH and KSM. 

Staff from the society were recently interviewed in the 'Radio World' online magazine - read the article here.

More information on the MRHS proposal here.

The German Association of Maritime Radio Operators have also recently issued a public letter calling for the retention of 500 kHz as a museum frequency.  Read it here.

The Radio Society of Great Britain (RSGB) have published their submission to the UK radio licencing authorities for an amateur allocation near 500 kHz.  Read it here.

The UK based Radio Officers Association have developed a proposal for the preservation of 500 kHz as a Heritage frequency.  The proposal does not include scope for sharing of the band with amateur stations.   Read the proposal and the supporting documentation here.

Further information on German proposals here

The  Australian National Amateur Radio organisation, the Wireless Institute of Australia, have applied to their regulator for an amateur allocation from 505-515 kHz.  More info here.








This website has been specifically established to encourage preservation of 500 kHz for use by maritime stations.