[GreenKeys] Tone frequency history?

[Harold Hallikainen]

On Fri, October 8, 2021 10:56 am, Harold Hallikainen 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 .
>

Looking further, I see at that the FCC authorized 850 Hz FSK on HF in 1952
(effective February 1953).
https://www.navy-radio.com/manuals/tty/rtty-journal/1953-1962/PDF/VO1NO1.PDF

In June 1955 (
https://www.navy-radio.com/manuals/tty/rtty-journal/1953-1962/PDF/VO3NO6.PDF#page=6
) it was proposed allowing any shift below 900 Hz with 170 Hz as a new
standard.

https://www.navy-radio.com/manuals/tty/rtty-journal/1953-1962/PDF/VO3NO8.PDF
, ARRL petitions FCC to allow shifts less than 900 Hz. August 1955.

https://www.navy-radio.com/manuals/tty/rtty-journal/1953-1962/PDF/VO3NO10.PDF
, October 1955, FCC NPRM to allow shift less than 900 Hz.

https://www.navy-radio.com/manuals/tty/rtty-journal/1953-1962/PDF/VO9NO10.PDF#page=7
, October 1961, ARRL proposes removing CW ID requirement for RTTY. I used
to do standard CW (on/off) ID. Also did FSK Morse ID by using the blank
(dah) and LTRS (dit) keys.

https://www.navy-radio.com/manuals/tty/rtty-journal/1953-1962/PDF/VO10NO4.PDF#page=3
, April 1962, FCC denied petition to remove CW ID.

Anyway, I could spend a LOT of time reading the RTTY Journal (
https://www.navy-radio.com/manuals/tty/rtty-journal/ ). Thank you Nick for
posting it!

After reading all this, I think the origination of the 2125 2975 tones was
from the military AN/FGC-1, as Nick and others have pointed out. Since
this was before common use of SSB (receivers had AM or CW modes), the CW
mode was used to enable a Beat Frequency Oscillator that was above the
received signal. This resulted in the frequency inversion between the RF
and AF. The BFO frequency could, of course, have been above or below the
received signal frequency. If below, there would not have been a frequency
inversion.

So, I think amateur practice of low space on RF and high space on audio
came from military practice. Where the military got this would be
interesting to read some day.

Harold



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