[GreenKeys] ITTY 850 shift?

[Harold Hallikainen]

On Sat, February 4, 2023 8:38 pm, Jim Haynes wrote:
> On Sat, 4 Feb 2023, Harold Hallikainen via GreenKeys wrote:
>>
>> Anyway, I think there may be advantages to 850 Hz shift with selective
>> fading and dynamic threshold control.
>>
> See QST April 1996 pp 78-79 "The Case for Wide-Shift RTTY by
> Brian Beezley K6STI.  Brian is the author of the original PC software
> RTTY terminal, RITTY.
>
> It's my belief, without any solid evidence, that 850 shift was originally
> chosen to get some tolerance for frequency drift in radio equipment of the
> 1930s-50s.  170 Hz shift for amateur RTTY came into wide use when we got
> better equipment, thanks to the needs of SSB operation.
>
> In amateur service it was tolerable to carry on a QSO with one hand on
> the receiver tuning knob; but in commercial/government/military service
> there was a need for reception without manual intervention over a period
> of hours at a time.
>

Thanks! The article is at https://p1k.arrl.org/pubs_archive/92385 . It
also says that we got 850 Hz shift from telephone equipment since the
1930s.

Harold
https://w6iwi.org