I am a bit of a communications history buff. I've been doing a little
> research about telecom in the days before transoceanic phone service
> before cables and satellites. The only way to bridge the oceans was
> hf radio. It's interesting to note that anyone with a shortwave radio
> could listen to all the international point-to-point phone traffic. I
> am going to assume that a form of independent sideband was used with a
> maximum of two or four circuits going to a specific country. Ssb is
> very easy to receive even with a standard shortwave radio of the day
> as long as it had a bfo to demodulate and recover the signals. I
> would like to know if any form of primitive encryption was used to
> make the circuits a bit more secure. It must have been very easy to
> literally monitor all the international traffic to and from a given
> nation. Anyone who can shed light on this subject would be
> appreciated to help scratch my historical itch.
For the most part, radiotelephone links didn't go SSB until the early
1960s, and there were still AM links hanging on well into the eighties here and there in the South Pacific.No encryption. No more than current ship-to-shore HF radiotelephone traffic uses today. That's why the Communications Act of 1934 made divulging communications to a third party illegal.
scott "C'est un Nagra. C'est suisse, et tres, tres precis."