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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
