> SSB still wins in the bandwidth verses fidelity category.
>
> Carl Moreschi N4PY
> Franklinton, NC
Shhh, Carl, you used a bad word: fidelity. You see, almost nobody is even
considering fidelity in any of these discussions. Only bandwidth. As hams,
we're not suppposed to be concerned about fidelity... I mean, who do we think
we are, broadcast radio stations? We'll leave the really good audio to the
pros. We're mere amateurs, remember? Who ever heard of 'fidelity' in a 3 kHz
bandwidth, anyway?!
Seriously, there are a lot of very cool digital modulation schemes out there,
but pretty much all of them sacrifice fidelity (and sometimes even some
intelligibility) for gains in something else: occupied bandwidth, for example.
For those still with us, here is some homework: have you seen the new amateur
radio promotion video, available from the League's web site, called Amateur
Radio Today? This is the one narrated by Walter Cronkite. If you haven't done
so, download it and watch it. At about the 5:00 minute mark, there is a clip
from an actual ARISS contact with a school. Listen closely to the live audio
from the space station.
It is quite intelligible. Communications quality, I'd say. And I'm sure
whatever scheme NASA uses, it uses no more bandwidth than absolutely necessary.
(This is exactly how live NASA downlink audio sounds, by the way. I live near
JPL and they re-broadcast space shuttle audio on their 147.15 repeater during
all of the shuttle missions. I can't listen for more than 15 minutes at a time.
It reminds me of fingernails on a chalkboard.)
I intend for this to be my last post on the subject, lest I chase yet more
people off of the reflector, which is the last thing I want to do. I've already
belabored my point. Thank you. For the bandwidth.
Al W6LX
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