[GreenKeys] RTTY Art

[Ralph Mowery]

,
>
> I read last night (in the RTTY handbook, the one that's 8-1/2 by 11 inches
> in size and has a blue cover) that audio tape recording is doomed to
dismal
> failure. The problem is speed control.
>
> Professional film sound recording systems have an extra track with a pilot
> tone on the tape, crystal tone generators at the recorder, and servo
> systems to correct the speed of playback for synchronizing.  Almost any
> tape recorder you have will wander enough to drift the tones outside the
> terminal unit's ability to follow it.
>
> Maybe modern sound card tty capture programs will follow a drifting
> signal.. If so, wonderful then it will work very well.
>
> Roy

About 20 years ago I and a few others in the local area played with
recording RTTY on audio tape.  We used some casette recorders and also an
inexpensive reel to reel recorder.  Using the 170 hz shift the results were
not very good for the pix tapes.  They were about 90 percent accurate for
the most part at 60 wpm speed.  Main reason is the speed of the recorders
would vary enough the tones would shift enough they would be out of the
filters of the demodulators we were using.  Using the scope hooked up to a
ST-6 you could see the tones shift out of the filters.   Maybe if one of the
PLL circuits would have been used to follow the drifting tones it would have
worked for us.  I think in the MMTTY program there is an emuliation of that
type of demodulator but I have not tried it.
I have not tried it but think the sound card in a computer should be stable
enought the tones would not shift.  I might have to give that a try just to
see what will hapen.  I would think that by the time one converts the rtty
signals in a computer to audio to store on a cd it might be beter to just
store the raw data.  I can not help but to see that you could put a lot more
data on the disc than you could audio that is recorded rtty.

Back in those days I used to copy Rickey  wa0cky sending the pix tapes.  I
think he had some kind of tape recorder that had the pixs stored on it and a
special interface that regenerated the tones at any of the standard speeds.

I have about 300 to 400 pf the old pix tapes but don't have time to work
with them right now.  I seem to remember the Winter Wonder land scene.  Hard
to tell if it have it stored away or not.
Probably took about 30  minuits or more  to send at 60 wpm.   Most pix were
sent at 60 wpm in those days as not everyone had a 100 wpm reperf and the
slower the speed made for  beter copy off the air.