Re: [amsat-bb] APRS portable without PC ?

[Bob Bruninga <bruninga@xxxxxxxx>]

Concerning sending Email using APRS from any dumb terminal program:

> What I want is an system that can send a message from everywhere on the
> world to my father (also amateur) at home in The Netherlands...
> I already have an portable 1k2 packet system, with an self made terminal.
> ... One message a day is ok....

That is very very easy and is exactly what APRS is designed to do...

1) Have him tune in the APRS frequency in Europe: 144.800
2) There he can see any message from you sent live from anywhere in world
   But since the channel is very,very busy, it is hard to find the one
   packet out of 1000 per hour addressed to you, unless you have APRS
   software at his station for receving it and capturing it.

3) OR, you can just send him an Email via APRS.  This is also trivial to
do.  From anywhere, just send a packet like this on  any APRS frequency:

  :EMAIL    :dads.email@email.com this is a message to dad from me

Where the :EMAIL : is padded to the standard 9 character field with spaces
as in all APRS messages, and the first WORD of the message after the colon
is the Email Address of your father.  Then the remaining part of the line
can be your message.

This single packet should get digipeated and injected into the worldwide
APRS system.  There a computer in New Jersey (USA)  should see it and pull
it off APRS and make an Email out of it and Email it to your dad.

It doesnt matter if you transmit this packet via PCsat, ISS or anywhere in
Europe on 144.800.  It should work.  But since this is amateur radio, you
should be more surprised when it does work, then when it doesnt.

> My main goal will be using the satellites as first node, because it
> guarenties all places on the world to have acces to the system, even in the
> desert, or south-pole :-) Then I would like to know how long it could take
> to get an message from e.g Australia to Europe ? Is it an matter of seconds,
> minutes, or even longer ?

Yes, for APRS messages, it is seconds. or never.  There is no store-and-
forward in APRS.  Thus, a message from the middle of the Pacific ocean
will not get anywhere via ISS or PCsat because there are no ground
stations to receive them and inject them live into the APRS system, except
for a specal mode built into PCsat.  PCsat will save any EMERGENCY,
PRIORITY or SPECIAL packet send in remote areas and REPEAT it all around
teh world once every 5 minutes so that it can be picked up later.  But
PCsat needs to be in a special mode for this and the uplink for that
service is not published.  I will be happy to give it to you, however, if
you will be traveling in those areas...

> When it is just a matter of seconds or minutes, then a small ACK is very
> usefull to know the message has reached its destination.

Yes, but remember the chance of a packet getting somewhere is X.  And the
chance of an ACK getting back to you is X*X.  And since X is less than
one, the chances for ACKS therefore are smaller than the message itself...

de WB4APR, Bob



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