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RE: 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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