If I recall correctly, the frequencies of the standard audio tones
were taken from the Western Electric/Bell standards developed for
multiplex landline teletype which predated radio-teletype by years.
73,
Mike K1MK
At 12:13 PM 9/28/06, Jan Palmquist wrote:
>The old 850 Hz shift used 2121 and 2975 as
>frequencies.
>
>2125 is fifth harmonics of 425 Hz
>and 2975 is the seventh harmonics.
>
>So you can use a standard 425 Hz tuning fork
>as tuning aid.
>
>73 de Jan - SM5FUG
>
>
> > The following is posting for Chris, N3JLY, who is not on the
> RTTY-Contesting
> > reflector. If you respond, please copy Chris Smolinski
> > <csmolinski@blackcatsystems.com>
> >
> > Dick AA5VU
> >
> > ------ Forwarded Message
> > From: Chris Smolinski <csmolinski@blackcatsystems.com>
> > Date: Thu, 28 Sep 2006 11:29:19 -0400
> >
> > Hi Dick,
> >
> > Sure, please go ahead and post it, thanks! I'm sure someone out
> > there knows the history. I am curious if the shifts commonly used are
> > based on some engineering/technical reasons, or if they were
> > arbitrarily chosen.
> >
> >> On 9/28/06 8:45 AM, "Chris Smolinski" <csmolinski@blackcatsystems.com>
> >> wrote:
> >>
> >>> Someone asked me why much of the military RTTY on HF commonly uses
> >>> 850 Hz shift. I am curious if anyone knows the history behind the
> >>> selection of this shift rate, or if it was just arbitrary.
> >>>
> > ------ End of Forwarded Message
> >
> >
> > _______________________________________________
> > RTTY mailing list
> > RTTY@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rtty
> >
>
>_______________________________________________
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Michael Keane K1MK
k1mk@alum.mit.edu
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