[MNAPRS] APRS UHF 446.175

[Doug Reed]

Using a path of NONE or LOCAL would just make it explicit that you
don't want the packet repeated by anyone. If it is heard by an I-gate
it would probably still be gated, but that is about it. I prefer LOCAL
over NONE, but I don't think there is an "approved" label for no path,
so you can use anything that makes sense to you. And if you have a
specific target station in mind, you can still use that station's
callsign in the path to make sure only they repeat the packet.

WIDE1-1 was the path originally intended for use by home stations or
"fill digis". It used to be RELAY but got revised in the New Paradigm.
It was intended to be programmed into home TNCs as an alias so the TNC
would repeat the packet when it heard anything addressed to RELAY, or
these days, addressed to WIDE1-1. This worked because even an ancient
TNC that never heard of APRS would properly respond to its programmed
MYALIAS. As a side benefit, a WIDEn-n digi should respond to WIDE1-1
and give the packet one repeat.

But it is preferred that you use WIDE2-1 if you only want WIDEs to
repeat the packet since WIDE1-1 would hit those home or fill digis
too. When I program a beacon for a WIDE digi, I use WIDE2-1 for the
path if I want it repeated by the next ring or use LOCAL or NONE for
infrastructure beacons that I don't want repeated outside the digis RF
footprint.

Then we get into WIDEn-n digis. They are the wide area digipeaters
intended to provide coverage over a large area. It collects anything
it hears addressed to WIDE and repeats it depending on the count after
the dash. Originally it could go up to WIDE7-7 but that becomes
completely untenable and with I-gates it is pretty unnecessary. These
days WIDE3-n is reserved for areas that are WAY out in the boonies
where it takes three hops to get to anyone. It is generally recognized
and suggested that nobody use greater than two hops except in a
special case. But it is still considered good for mobile and portable
stations to use WIDE1-1, WIDE2-1 as a path for that slight added
chance that you may be close enough to a home station and need its
help to hit the local WIDE.

The normal config for a WIDE includes an attempt to "kill" any packet
that requests greater than n= 2 or 3 for a path. If the digi hears
WIDE5-5, it will repeat the packet ONCE and terminate the path so it
doesn't get repeated again. Some versions of software, such as the
OpenTrack TNCs will terminate any packet with n greater than some
value, so it will kill even the WIDE7-6 packets that other software
will handle normally.

The other path that was added with New Paradigm was the state-wide
system based on MNn-n or whatever state abbreviation you want. The
packet is handled like a WIDEn-n packet except it will not be repeated
by a digi in the next state. This was intended to be for emergency or
other special use but I've never seen it actually used. But it is in
every digi I maintain.

My rule-of-thumb is that a good WIDE will hear 30-50 miles if it has a
good location. If it can't hear 30 miles, I don't think of it as a
WIDE. I tend to look for locations 60-80 miles apart for the next
WIDE. But that rule does break down when you get into hilly terrain
such as Winona to La Crosse, or up toward Bemidji. It is very helpful
to use aprs.fi to display "stations heard" on a map. I sometimes wish
for such a map with overlapping coverage from other digis. It makes it
easy to look at the map and figure out where the next hole is that
needs filling. I particularly like to look at the maps and see the
actual coverage from a site, including any offset for antenna pattern.

The bit of the New Paradigm that might get overlooked is that we no
longer want our APRS stations to be "polite". We don't want them to
wait for clear air, we want every station that heard a new packet to
retransmit that packet as soon as possible after it ends. No waiting,
just transmit immediately with the intention being that everyone who
heard the packet will transmit at the same time and walk on each
other. The only people who will TX the packet a second time are the
ones who didn't hear it the first time. If you ever hear a station
retransmit the identical packet a second time, it is because there was
an error in the software or it isn't programmed right..... The UITRACE
function is supposed to prevent that....

I recall two more special paths, RFONLY and IGATE. They do what they
say. RFONLY would not be gated and IGATE would go to the Internet but
not be digi'ed on RF. I suppose you could use IGATE as the path
instead of LOCAL if that is what you intended.

It has been a few years since I read the New Paradigm docs. I should
probably go back and read the www.aprs.org web site again to see what
else I've missed.... The APRStt and Voice Alert stuff was fairly new
to me....

Looking at the APRS world map, I note that Europe and Africa use
144.800 for APRS, just like we use 144.390. So the people out on the
east coast trying to hold a 2M QSO from the US to Europe should
probably monitor each others APRS frequency, just like we watch
Mountain Lake for APRS propagation alerts.... I wonder if they do???

73, Doug Reed, N0NAS.