[Elecraft] A Real SOS

[Ron D'Eau Claire]

The discussion of the Titanic's communications and the interference is a
reminder that many Hams have never heard the real thing. 

Shipboard transmitters were crystal controlled (after CW become the norm at
sea) and the post-Titanic international distress frequency of 500 kHz was
used for routine messages as well. So when an emergency occurred it was
often pandemonium, first until those on the channel realized there was an
emergency, and then QRM from those who could not hear the emergency traffic
while others tell them to QRT.

By 1980 receivers had grown very selective, but the fact was that a great
many ships still used a regenerative receiver as the "backup" in case the
main receiver was out of commission for some reason. 

Some of the signals in the link below sound like they have modulation. They
do. MCW was the norm for emergency traffic so they could be copied even on a
receiver without a BFO.  

The possibility of an SOS not being heard at all in the bedlam is what
launched the twice-hourly "silent periods" when all ships fell silent and
the R.O.s listened on 500 kHz for three minutes. 

This link is a real SOS recorded in 1980 when the MV Prinsendam had an
engine room fire and a flooded engine room. It begins with a series of long
dashes. That was the standard opening that was supposed to set off automatic
alarm bells on any vessels whose radio rooms were not operating at that
moment. The bells went off on the navigating bridge and right over the bed
were Sparks would be sleeping. Following the dashes the SOS and emergency
message begins. 

http://mikea.ath.cx/www.n1ea.coastalradio.org.uk/EJM_CD3_Track03_SOS_de_PJTA
.zip

There are other audio clips at:

http://mikea.ath.cx/www.n1ea.coastalradio.org.uk/index.html


Ron AC7AC