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Author Topic: Radio telephone calls across the world 1932  (Read 2419 times)
G4LNA
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« on: January 13, 2018, 03:57:50 AM »

Following on from the thread about cables across the Atlantic, I thought this might be of interest, it gets interesting around about a minute into the film. One of the engineers goes on to describe the method of transmission by inverting the speech which sounds like SSB, is it? What do you think?

https://www.youtube.com/watch?v=SbvAwVGpMR0

The telephone exchange is probably Kingsway in Holborn London.
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AC7CW
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« Reply #1 on: January 13, 2018, 08:03:16 AM »

I don't feel that it was SSB. Faux security at best, no? I wonder how much spying went on!
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Novice 1958, 20WPM Extra now... (and get off my lawn)
KC8KTN
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« Reply #2 on: January 13, 2018, 08:09:27 AM »

AWESOME SUBJECT::   GREAT JOB::::::

Have A Blessed Day.       Be JOYOUS.........Be Safe ....    GOD BLESS..........

................................END OF TRANSMISSION............................
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G3RZP
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« Reply #3 on: January 13, 2018, 09:03:31 AM »

The SSB link on around 60kHz one way and around 80 the other opened in 1927. The US tx was at Rocky Point, NY and the rx in the UK was up in Scotland. Not sure where the US receiving station was but the tx was at Rugby. The cost was $72 a minute........I don't know how much that is in today's dollars, but I suspect it is  substantial.

For AM links, speech inversion offers some degree of privacy, and of course, there weren't that many people capable of building things to sort it out. Pure inversion of course could be sorted out in an SSB receiver, but splitting the voice frequency band into two or three or even more sub bands  and shuffling them so that starting  bands as  a, b, c, d, e and transmitting them as say e, c, a, d, b is more difficult to sort out with the technology of that era, especially if the order is changed frequently.
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WI8P
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« Reply #4 on: January 13, 2018, 09:48:13 AM »

Thanks for posting - I love stuff like this!   Grin
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DL8OV
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« Reply #5 on: January 14, 2018, 06:52:46 AM »

"splitting the voice frequency band into two or three or even more sub bands  and shuffling them so that starting  bands as  a, b, c, d, e and transmitting them as say e, c, a, d, b is more difficult to sort out with the technology of that era, especially if the order is changed frequently."

Wasn't that how the voice scrambler worked on the telephone line between Churchill and Roosevelt?

Peter DL8OV
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KC8KTN
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« Reply #6 on: January 14, 2018, 02:23:38 PM »

Again Awesome Information...

Have a Blessed Day... Be Safe ... GOD BLESS......
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G3RZP
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« Reply #7 on: January 15, 2018, 03:24:02 AM »

Peter,

Quote
Wasn't that how the voice scrambler worked on the telephone line between Churchill and Roosevelt?

Yes, but some pretty clever guys at the German Post Office worked out how to break the scrambling.
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