Re: [amsat-bb] Isolation transformer and 9600 baud.

["SV1BSX" <sv1bsx@xxxxxxxx>]

...I agree completely with John KD2BD !

9600 Bps needs  direct-DC coupling between RX output-discriminator and TNC.
Any transformer through data-path is 100% unacceptable method.
9600 Bps is pure FSK. Don't confused that with 1200 Bps which is AFSK and
thus is possible to use a transformer for isolation.
I have not never heard something about isolation transformer on 9600 Bps.

73, Mak SV1BSX

----- Original Message -----
From: "John Magliacane" <kd2bd@yahoo.com>
To: <WA4SCA@amsat.org>; "'hobergenix'" <hobergenix@sbcglobal.net>;
"'AmsatBB'" <amsat-bb@amsat.org>
Sent: Monday, February 20, 2006 12:01 AM
Subject: RE: [amsat-bb] Isolation transformer and 9600 baud.


> --- Alan WA4SCA <WA4SCA@amsat.org> wrote:
>
> > Mike,
> >
> > By wild coincidence, I swept the response of a few audio transformers
last
> > week.
>
> ...
>
> > I tested some coupling transformers with 10K impedance, from All
Electronics,
> > and about the only difference was the better matching, and totally
irrelevant
> > lower frequency response.
>
> Actually, good low frequency response is pretty important to good 9600
baud
> FSK communications.  Remember, a 9600 baud baseband signal is pure
(filtered)
> data, not audio, so it really needs response down to DC, which is
something
> that won't pass through an audio transformer.
>
> Even though the individuals bits are "randomized" (scrambled) by the
"modem"
> (a really poor choice of words in terms of what it *really* is), a low
> frequency component still exists.
>
> It's not pure AC.  It's not "audio".  It's baseband "data".
>
>
> 73, de John, KD2BD
>
>
> Visit John on the Web at:
>
> http://kd2bd.ham.org/
> .
> .
> .
> .
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