An interesting footnote for some of the newer Hams: Historically, the reason 500 kHz was chosen for emergency calling (SOS) was that such a high frequency was considered of little use for long range communications. Back before WWI, "everyone knew" long range communications required lower frequencies and some of the most powerful shore stations operated at frequencies as low as 17 kHz. The whole plan for disaster communications at sea was to alert *nearby* ships to provide aid, so a higher frequency with its shorter range was ideal. All ships subject to SOLAS (Safety Of Life At Sea) rules were required to carry a calibrated radio direction finder in the wheel house to "home in" on a 500 kHz signal to locate a lifeboat or ship in distress.
Along the same thinking, the local AM Broadcast band was put above the 500 kHz frequency - roughly 550 to 1500 kHz - where high power stations would have a range of perhaps some tens of miles, the experts said, suitable for bringing newfangled "broadcasting" into local households. And, of course, those pesky "Amateurs" can have the frequencies above roughly 1500 kHz (200 meters) and will certainly never get out of their own back yards on such high frequencies. Fortunately, that was one more time when all the experts were wrong. Ron AC7AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
