[GreenKeys] Tone frequency history?

[Bob kb8tq]

Hi

Frequency division multiplexing for telegraphy goes back quite a ways:
(note the use of tuning forks …)

https://www.its.bldrdoc.gov/isart/art06/slides06/gla_b/pg3.html <https://www.its.bldrdoc.gov/isart/art06/slides06/gla_b/pg3.html>

It was an established approach long before Teletypes came along. The whole 
“who worked out what” is very tangled. Folks write papers on just the tangled
part:

https://www.researchgate.net/publication/3200314_The_origins_of_carrier_multiplexing_Major_George_Owen_Squier_and_ATT <https://www.researchgate.net/publication/3200314_The_origins_of_carrier_multiplexing_Major_George_Owen_Squier_and_ATT>

It’s a pretty good bet that whatever got used for the early AFSK gear was based on 
the tone groups used on this or that FDM wireline setup. They came up with a
mind boggling number of these systems over the years and in various countries. 
Once microwaves came along, they appear to have re-invented them all over again. 

Some “quality time” spent digging into the various wired systems in use in the 1910 
to 1930 range  likely would turn up a candidate.

Bob

> On Oct 8, 2021, at 1:56 PM, Harold Hallikainen <harold at w6iwi.org> wrote:
> 
> 
> 
> On Fri, October 8, 2021 4:41 am, Nick England wrote:
>> AN/FGC-1 block diagram and general description is on this page
>> https://www.navy-radio.com/rtty-demod.htm
>> 
>> I think I have the manual somewhere and will scan it when I get a chance.
>> 
>> Nick
> 
> Thanks! I suspect this is the origin of the tones for amateur radio work.
> See paragraph b at
> https://www.navy-radio.com/rtty/ww2/FGC1-TM11356-abstract.pdf#page=5 .
> 
> 
> 
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