[aprssig] APRS Bulletin/Announcement Format?

[Curt, WE7U]

On Thu, 25 May 2006, Robert Bruninga wrote:

> There are 5 required bytes, THey can be anything.
> PCSAT2 uses "BLN1PCSAT"

Ok.  I see in the Bulletin Group section (right after the
bulletin/announcement sections in the spec) that these are to be
used to select groups of bulletins that people can view.  Supposedly
if people don't do the selection they get all bulletins.  If they
select some bulletin groups, then they get those groups _and_ all
general bulletins.  Xastir shows all, not giving the user the option
to select specific groups.


> Bulletins are supposed to be replaceable and over-writeable.
> THat means that BLN1 should be REPLACED and OVERWRITTEN
> by an updates or subsequent BLN1's from the same station.
> This was VERY IMPORTANT to the concept of APRS, so that
> if there was a multi-line bulletin, but some part of it had to
> be updated, then only the CORRECTED line had to be sent,
> not the entire bulletin.
>
> But, again, this is another place where APRS clone software
> took shortcuts and simplistic approach and undermined
> the original concept.  Many just scroll new bulletins continuoulsy
> without end.

Xastir _does_ this overwriting based on bulletin/announcement
number.  I tested that yesterday.  I haven't paid much attention to
bulletins in Xastir up to this point, we read them just fine but
currently have to use the Send Message mechanism to send any out (no
specific Send Bulletin/Send Announcement dialog).


> THe original concept was that any given station would only
> have a certain number of ACTIVE bulletin lines.  And they
> were line-by line replaceable.  Hence the limit to a single
> digit was fine.
>
> I would hope that if you are goint to be hitting the network
> with lots and lots of bulletins, that you also should re-use
> old BLN#'s so that olderones are replaced as new ones
> update old info...

Yes, except there shouldn't be lots and lots of them.  We just need
to keep them separate by state in case 2 or 3 states activate at
once, and need to keep the incidents separate in case we get 2 or 3
activations in one state.


> Would that work in your application?

Yes.  One of our Firenet team came up with the idea of changing the
SSID based on the "incident".  This allows up to 10 bulletin lines
for each incident.  By adding the 2-letter state abbreviation to the
SOURCE callsign it allows up to 16 incidents per state.  By no means
am I expecting to send very many bulletins, but in some cases there
could be more than one incident per state, so this allows us to keep
the bulletins separate from each other and to overwrite earlier
bulletins for each incident with updated information, which is what
I'm after.

So...  This is an example of where we need separation between a few
different incidents (including separation by state so that we can
igate them to RF only in the areas of interest).  It appears to me
that this will function nicely for us if we add the state to the
SOURCE callsign and change the SSID of the SOURCE callsign based on
the incident.  That gives us 10 replaceable bulletins per incident,
and igating to RF based on the state affected.

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
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