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[aprssig] Why Should a Digi Use a Path?

Robert Bruninga bruninga at usna.edu
Fri Jul 27 14:02:55 UTC 2007


> Can anyone give a clear & concise reason why 
> the majority of APRS digis should transmit 
> it's own position, wx or telemetry report with a path?

APRS is a ham radio network.  Except for appliance operators,
hams interested in RF comunications want to see its topology and
how it is interconnected (on RF).  APRS is the network.

Since the typical congestion limit for APRS RF communications is
pretty well defined by the "ALOHA limit" the New-N Paradigm
suggests that digis be visible routinely to their constituent
users in that ALOHA area, but minimize their packets beyond that
range.  Hence, a key feature of the New-N paradigm was to have
"proportional pathing" for the DIGIs.  That is, they would
beacon every 10 minutes direct, only once evrey 30 minutes to
the next tier, and only once an hour to the second tier.

This DRASTICALLY cut down on QRM on the APRS channel, while
providing increased local visibility and reduced situation
latency.

The new Local Voice Repeater Initiative is just an extension of
that concept to fully inform the user (no matter where he is) of
what frequency is best, where he is right now, for him to
communicate with other hams in that area.  But since voice
repeaters do not digipeat, and only have influence in their
immediate DIRECT input range, then these Voice Repeater Objects
are only transmitted LOCALLY and DIRECT by the well placed APRS
digis.

Thus, Each digi informs its local direct users, what voice
repeater they can surely hit.  While at the same time, limiting
this info to only the area where it can be used.  This entire
initiative is being added with practically zero impact on the
APRS RF network, because since these objects are originated at
the local digi (direct), the digi will only transmit them when
the channel IS CLEAR.  Thus, a freeby.

WX data however, has a little more scope.  WX data needs to be
seen over a slightly larger region to get the big picture in an
area.
Telemetry (KPC-3+) is usually only of interest to the OWNER of
the digi, and so the path only has to reach his location.

CONCLUSION:  The RF network should be designed for the RF users,
and for local operations should not be dependent on the
internet.  On the other hand, every local area should have an
Igate to tie it into the global APRS-IS system.  It's the best
of both worlds!

Hope that helps.

Bob
WB4APR





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