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(I'm not Bob, but here's my take on your questions. Let's see how
close I come to Bob's answers)<br>
<br>
First, you might want to look at <a class="moz-txt-link-freetext" href="http://aprs.fi/bulletin/">http://aprs.fi/bulletin/</a> And then,
if you're curious as to the raw packets that generated that display,
drill into the individual station's raw display by clicking on the
callsign link and then the "raw" link right at the top of that
Station info page.<br>
<br>
On 11/8/2011 7:38 PM, Andrew P. wrote:
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
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<div dir="ltr">
I have some questions for WB4APR, about his concept of the
Mountain-Top Billboard display mode that the specs say an APRS
client should support (but apparently few do).<br>
</div>
</blockquote>
<br>
If you run Windows (or WINE on Linux), download a free copy of
APRSISCE/32 (<a class="moz-txt-link-freetext" href="http://aprsisce.wikidot.com/">http://aprsisce.wikidot.com/</a>) and check out the
Messages / Bulletins / View display, assuming of course that you've
actually received a few BLN* messages for which there is no APRS-IS
filter. You can use a t/m (get me all messages) and that will
deliver not only "normal" APRS messages but also all Bulletins.<br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
How exactly should this information be presented to the human
users? The spec talks about multi-line bulletins, but I can't
figure out how the multiple lines are uniquely identified and
ordered (other than when in NTS format, pg. 75 of the APRS 1.01
spec). The rest of it more or less makes sense, but please check
my understanding (before I waste a lot of time writing software
that behaves incorrectly):<br>
</div>
</blockquote>
<br>
Multiline bulletins are what the spec calls a "Bulletin ID". That N
is the line number and you are correct below in that a single
bulletin sourcing station can only have 10 lines (0..9) PER GROUP.
Since you have 5 characters available for the group name, you can
actually have LOTS of lines of bulletin, but only 10 per group. How
big do you expect your bulletin board to be, anyway?<br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
1. Amateur radio bulletins and announcements are identified by
the combination of the sending station callsign, the fourth
character of the addressee field (which bulletin or
announcement), and the 5-character group ID (which may be 5
spaces for non-grouped distribution). Because of the fourth
character limitations, any one sending station is restricted to
a maximum of 10 active bulletins (0 to 9) and 26 active
announcements (A to Z).<br>
</div>
</blockquote>
<br>
Yep. See above.<br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
2. National Weather Service bulletins use a totally different
addressee format, which "sort of" can map into the above
bulletin identifying logic, but not very well (by item #1
analysis, they would appear as only one bulletin '-' per group
["WARN", "WATCH", etc.], updated frequently with new content).
Do they support multi-line?<br>
</div>
</blockquote>
<br>
National Weather Service alerts don't even attempt (as far as I can
see) to be a bulletin. Bulletins MUST start with BLN and NWS
messages start with NWS per <a class="moz-txt-link-freetext" href="http://www.aprs-is.net/Wx/">http://www.aprs-is.net/Wx/</a><br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
3. Are there any other special categories that should be treated
differently than just directly addressed messages? Should
messages directly addressed to the receiving station be posted
on the bulletin screen?<br>
</div>
</blockquote>
<br>
See "Message Groups" at the bottom of page 72 in aprs101.pdf - Group
names are up to the user at the receiving end. Also, from the top
of page 73:<br>
<br>
<blockquote type="cite">The receiving station will read all messages
with the Addressee field set to ALL, QST or CQ.</blockquote>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
4. The status display for bulletins should display each
bulletin's 1-line messages consolidated together in order, with
some higher-order sorting of whole bulletins and announcements.
What is the recommended default sort order for whole bulletins,
in order of precedence? Time of last update? Callsign?
Bulletin/announcement ID?<br>
</div>
</blockquote>
<br>
Default sort order is on page 76 and states the following.
Personally, I inserted Group ID between callsign and
Bulletin/Announcement ID.<br>
<br>
<blockquote type="cite">This includes sorting by originating
callsign and Bulletin/Announcement ID.</blockquote>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
5. The bulletin board display should alert users when it is
updated with newer information. Does this include "no-op"
changes (receiving identical message text from a periodic
re-broadcast)?<br>
</div>
</blockquote>
<br>
Personally, I don't alert on receiving identical text, but have a
user selectable "Notify" option to receive a notification when new
or updated lines are received. And then I discovered that the
Kenwood and T2/Nuvi units display ALL bulletins received, so I
actually quit transmitting my routine bulletins via RF. They're
just too intrusive, IMHO.<br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
6. Presumably, directed station queries (APRS1.01 pg. 79) should
_never_ appear on the Bulletin Screen.<br>
</div>
</blockquote>
<br>
Yep, if it doesn't start with BLN, it's not a bulletin.<br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
7. Bulletins and announcements only stop showing up when the
originator stops sending them.<br>
</div>
</blockquote>
<br>
Or when the user gets tired of looking at the drivel.<br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
Also, for directly addressed messages with sequence numbers,
should the software immediately acknowledge receipt
autonomously, or should it wait for a human being to explicitly
tell it to acknowledge receipt?<br>
</div>
</blockquote>
<br>
You must ack immediately from the software. Failure to do so will
result in many useless retries which will eventually time out at the
transmitter and if you subsequently send an ack when the human reads
the message, the sender has probably long since quit looking for
it. The ack represents receipt by the APRS station, not necessarily
that the message was seen by said station's operator.<br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
Are there any updates in the APRS 1.1 or 1.2 specs that override
any of the above?<br>
</div>
</blockquote>
<br>
No overrides that I can recall, but there is a Reply-Ack extension
at <a class="moz-txt-link-freetext" href="http://aprs.org/aprs11/replyacks.txt">http://aprs.org/aprs11/replyacks.txt</a> that you'll probably want to
read and support.<br>
<br>
<blockquote cite="mid:BLU156-W32A2FAD887AABBB12ACE26B8DF0@phx.gbl"
type="cite">
<div dir="ltr"><br>
Looking forward to some good advice.<br>
</div>
</blockquote>
<br>
Be ready to do it, and re-do it. What platform are you targeting
your application to if I may ask? And if you're planning to release
it to the general amateur radio public, you should probably read
G4ILO's excellent description of what you can expect from your user
base:<br>
<br>
<a class="moz-txt-link-freetext" href="http://blog.g4ilo.com/2010/10/advice-to-amateur-programmers.html">http://blog.g4ilo.com/2010/10/advice-to-amateur-programmers.html</a><br>
<br>
Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32<br>
<br>
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