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Re: APRS on satellites



>>> "Bill Bruno"  7/13/04 1:40:48 PM >>>
>I have an APRS... station running... so i understand the 
>APRS basics. What i dont know is how to work APRS 
>on the satellites. I assume i send a message or position 
>or weather packet as i would normally do...

Not really.  The joy of APRS and of APRS via satellites
is in human to human exchange of information in a net
of like users.   There is a grave missconception that
APRS is for 24/7 operation of unattended stations.
This is simply *not* what it was designed for.

APRS was designed to be the digital equivalent of the
way we hams like to operate a VOICE net on a repeater for 
example.  Where everyone is listening to what is going on 
and periodically each person gets to add in his two cents...
And everyone gets it.  Think of an APRS satellite pass
as a group event with everyone playing together instead 
of in competition with each other...

When APRS was invented it was to get away from all
the problems and innefficienceis of CONNECTED 
packet which is very inefficient via a satelltie because
of the ACK problems and can only be used point-to
point.  APRS lets everyone talk to everyone and see
everyone without any addressing...

Thus, during a satellite pass you usually address your
message to ALL so that eveyone gets it.  And sometime
during the pass you send your POSITION Packet so
that people can see on their maps where you are and
how this fits into the pass geometry unfolding before you.

Once your position and message have been digipeated
by the satellite then just watch everyone else and if you 
see someone or something you want to comment on, go 
ahead.  Even when sending to another specific station, 
it is common practice via the satellties to still address the
message to ALL so that everyone reading the mail
gets a copy and feels like they are participating too.

As to weather, I dont see any advnatage to sending
a WX packet unless your weather is  unusual and
worthy of immediate note over the whole country...

> but im not sure of how to "path" it to or thru the sat
>. I could use some advice.

That's easy.  Just send the packet via the callsign
of the satellite.  We have been trying to get all 
satellites to use the same generic aliases as APRS
does on the ground so that it doesnt matter.   And
fortunately ISS does use the aliases of RELAY,
WIDE and ARISS, and APRSAT.  We have also
recoemmended these for the APRS mode on ECHO,
but so far the DIGIpeater on ECHO has not been
enabled yet for users...

And PCsat is basically dead.  So right now, that leaves 
you with only ISS using the path of ARISS or SAPPHIRE 
(NO-45) using the path of KE6QMD...

Bob, WB4APR
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