Re: [RTTY] HAL ST-8000

[Kok Chen <chen@mac.com>]

On Nov 9, 2004, at 1:09 PM, jduerbusch@charter.net wrote:

> There is a nice artice on putting the ST-8000 ahead of the PK-232 on 
> my website:
> http://www.qsl.net/k0bx

It is much easier to do than described in that article, really.

All you need to do is supply audio from the rig to the ST-8000 as if 
you are using the ST-8000 for real.  You then connect the AFSK output 
(yes, AFSK output) of the ST-8000 to the Audio input of the TNC (I'd 
used my ancient KAM Plus as the TNC).  Not counting the AC power cord, 
those are the only two connections you have to make to the ST-8000.  No 
RS-232, no nothing else.

The only difference from the standpoint of the TNC is that the audio 
comes to it from the ST-8000 rather than from the rig.

The rest of your station remains as is, the same computer program and 
all.

Think of it like wiring in an audio pre-amp to the audio line between 
the rig and the TNC.

It is obscurely documented in the ST-8000 manual (I don't have the 
ST-8000 manual in front of me, else I could point to the paragraph) as 
"Regeneration" I believe.  Many textbooks (and the Watkins-Johnson 
white paper you can find by Googling) and the Timewave 599zx calls this 
process "Remodulation."

What regeneration does inside the ST-8000 is that it demoduate the 
incoming audio as usual, but the resultant Baudot keying waveform is 
fed back to the built in AFSK generator of the ST-8000.

In this mode, the ST-8000 puts out an absolutely clean and strong AFSK 
RTTY signal; no noise, no QSB even if the input from the rig is full of 
QSB and QRM.

The only errors you print will not be from the TNC, but from the 
ST-8000 remodulating with the wrong bits to start with.  So you see the 
bits precisely as the ST-8000 see them, but the TNC is the one that 
does the conversion of the tones to Baudot and then to ASCII for your 
computer.

There are a couple of jumpers, or DIP switches (I don't recall which 
now) that you have to change inside the ST-8000 if memory serves; it is 
all documented in the manual.  It took me a while to find it in HAL's 
manual, since I was looking for the term "remodulation," but eventually 
found it by reading every sentence of the manual, page by page :-).  
But I knew it had to be there; it would have been too dumb not to 
include the function, and HAL guys are far from dumb.  So don't be like 
me, but go look for the word "regeneration" (I think that is what HAL 
called it) instead.

I know a couple of the HAL guys read this reflector.  They can probably 
help.

73
Chen, W7AY

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