Re: [amsat-bb] AO40 modes - Wideband Digital Modes?

[Bob Bruninga <bruninga@xxxxxxxx>]

On Mon, 19 Mar 2001, David Schick wrote:

> ... What are the modes that RUDAK [will be] in?...
> 
> >From the web page:  .... To do this, we'll need to assign a substantial
> >amount of our downlink power budget to a single 9600 baud downlink in
> >the 70 cm band. This leaves us with the challenge of finding
> >interesting applications for lower power...  modulation schemes...

A minority opinion that does not push the state-of-the-art, yet lets a
majority of hams participate in a small way, would be a dumb UI digipeater
at 1200 baud AFSK...  I know this is an anathma to digital progress, but
it does give every user with a TNC a chance to ping the bird and hundreds
of other like minded souls.

Our measurements indicate that for the average ham and average
implementation of 1200 AFSK and 9600 FSK, that 1200 AFSK actually picks up
several dB of weak signal performance (7 dB).  No, normal packet would be
absolutely rediculuous for AO40 since so many people would be in the
footprint at one time.  

But recent user applications that only need a single or a few UI packets
to complete a QSO have become very popular in the 10 years since the first
pacsats were launched.  Such a UI digipeater that only ALLOWED one packet
per minute or less per station would permit 60 or more stations to QSO.
As it became more popular, the  limit could drop downward to say one 
packet per 10 minutes (to permit 600 stations) or one packet per 30
minutes (the APRS standard) to permit 1800 stations to net on one uplink.

With GPS we can even assign time slots to improve channel efficiency from
20% (Aloha) to 100%..  This mode would allow anyone anywhere to uplink to
AO-40 their position and status and outgoing one-line messages (or
Email) using only a mobile FM rig, and omni whip antenna.  

The downlink would be monitored 100% full time and fed to the internet via
the existing worldwide distribution network (TELNET to 199.227.86.221) or
browse www.aprs.net

Just a thought...

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