[GreenKeys] Real RTTY

[Ralph Mowery]

----- Original Message ----- 
From: "John Becker" <w0jab at big-river.net>
To: <greenkeys at mailman.qth.net>
Sent: Friday, February 25, 2005 11:13 AM
Subject: Re: [GreenKeys] Real RTTY


> Now don't get me wrong on this but, my biggest
> pet peeve about most of these programs is that
> they don't seem to have any filtering. Back before
> these sound card programs came out when we ran
> things like the HAL ST-6 with crystal controlled
> AFSK and HI Q filters one could park their mark
> tone between someone else mark and space and
> NO ONE would miss a letter. But today if you do that
> you will get hate emails that you QRM'ed their QSO.
>
> I had a 8088 (top speed 10Mhz) playing RTTY 20
> years ago. But you just can't beat that smell or
> the sound of a machine banging RY's or CQ's
> onto paper....
>
>

The filtering for  the ST-6 was not all that sharp.  The front end filter
was very good.  The mark/space filter was (especially for 170 shift)
designed more like a FM discriminator.  They were very broad onver the 170
hz range.  I am not sure about the 850 shift filter but thought it was about
the same way.
I built 2 of the st-6 units from the pages of Ham Radio.  The first one was
not a true st-6 as I did not have the exact parts for it.  Later found some
circuit boards for the st-6 at a hamfest and I used the necessary parts for
tht one.  There was not very much differance in the way the two units copied
off the air.   Many hams were not using crystal conrolled AFSK generators
with the st-6 but another type .  I think it was called the AK-1,  Built one
of those also.  It was a unijunction transistorR/C oscillator.

You had a fast processor.  I built the glass teletype using an 8080 at 2
mhz.  Found a board with 1 K of rom and 1 k of ram on it.  Later added an 8
K ram board to it.  Wrote a simple program that did let me type ahead and do
the auto CR/LF after 65 characters and a space.  If it did not get the
space, it would do a forced CR/LF at the 73 position.  That may be a
forgotten thing for the sound card programs from what I am reading.  I have
not had time to check this out as I have been trying to get moved in a new
house for the last year and the old model 19 is not up and running.

I do agree there is nothing like watching the mechanical machines run.
Think that was what got me hooked on rtty when I saw my first one run at a
friends ham shack.

DE KU4PT