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Re: DIGITAL modes



This (and other messages on this subject) sounds like a great lead into an
article for Amateur Television Quarterly! You may want to copy these
messages onto the ATV sigs as well for more input. Many of them may not
monitor the amsat sig.

OSCAR Satellite Report will publish short articles on this subject if anyone
would care to write!

Sound like fun stuff. Keep up the forward thinking!

Gene Harlan - WB9MMM
Harlan Technologies - publisher of
OSCAR Satellite Report - OSR@hampubs.com
Amateur Television Quarterly - ATVQ@hampubs.com
http://www.hampubs.com


----- Original Message -----
From: "Bob Bruninga" <bruninga@nadn.navy.mil>
To: <amsat-bb@AMSAT.Org>
Sent: Sunday, October 08, 2000 9:34 PM
Subject: [amsat-bb] DIGITAL modes


> Concerning the advantages of DIGITAL:
>
> I'm hoping for the day we do Satellite HAM ATV.  It just wont happen
> with 6 MHz wide bandwidth analog.
>
> At a local ATV demo, a local ham demonstrated 300 KB ATV digital
> video. It was crystal clear and had noticible choppy video (kind of like
> what you see in teleconferencing etc.  But 100% adequate for all of the
> ATV applications I have ever seen...
>
> But the neat thing was that he showed the spectrum on a spectrym analyzer.
> It took less than 1 MHz, thus a more than 7 dB advantage in bandwidth.
> But then add the fact that you need a 30 dB S/N ratio for a good picture..
> Ok lets say 20 dB for a usable picture...
>
> whereas with a 10 dB S/N digital signal you can still decode a "perfect"
> picture, the overall improvement is more like 17 dB!  SO instead of
> needing a KW and an EME antenna to do Satellite ATV, you will be able to
> do it with only 50 watts and a decent antenna.
>
> HISTORY NOTE:  When we were one of the first stations to ever UPLINK Live
> ATV to the Space SHuttle on mission STS-37, we were using a 300W amp and a
> 40 FOOT dish antenna.  With digital, we could have done it with an ARROW
> antenna.
>
> But I AGREE 100%, that all amateur use of digital MUST use 1-to-ALL
> protocols so we can all "read the mail"...
>
> de WB4APR, Bob
>
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

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