[GreenKeys] ST-8000

[Jim Haynes]

I haven't used one, but I would hazard an opinion that it doesn't perform
as well as some of the recent modems implemented in DSP on computers.
But then we are at a point where FSK detection/demodulation is probably
about as far as we are going to get.  W1HKJ recently made a considerable
improvement in the FSK section of the fldigi software.  On my side-by-side
comparison the new one was only slightly better than the old one.  I think
that's probably because even the old one is about as good as it is going
to get given actual radio conditions.  You can calculate how well a
detector is going to perform in white noise, or in certain other kinds
of noise, but in practice the signal may be fluctuating above and below
the level of good copy so much that you can't see a lot of difference
between two detectors.

As I recall the ST-8000 uses switched-capacitor filters, as does the
later Dovetron model, as a way of letting you dial in the mark and space
frequencies.  The ultimate performance is decided right in that portion
with the channel filters and the detectors, the way the detector outputs
are combined and the post-detection filtering.  After that you can do a
lot of add-ons such as baudot-ASCII conversion and regenerative repeaters,
and those things are nice to have, but they don't affect the ultimate
performance.

I remember how excited I was when K6STI came out with his RITTY program
that synchronized to the character rate so it knew when to expect the
bit boundaries.  I was less excited when I found through experience that
it was only a db or two better than a more conventional demodulator,
because conventional demodulators are as good as they are.  There was one
guy who had an ST-8000 and insisted it was better than the K6STI software;
but I'm highly skeptical and suspect that he had some ill feelings that
biased his perception of things.

Jim W6JVE

jhhaynes at earthlink dot net