No subject
Tue Jul 28 09:57:54 CDT 2009
dependent upon internet connectivity. Most of their records, and procedural
information is via internet. A decent speed ad-hoc connection must be in o=
ur
emergency 'bag of tricks.' There have been several ideas floated at local =
ARES
discussions. The hangup is: there are so many ways to get into the intern=
et,
it is unknown which one will actually be able to connect during an emergenc=
y.
=20
> aprs is entirely unnumbered and unconnected, and that's what makes it=20
> work well. it also seems like that would lend itself to useful, but=20
> slow data communications over a fairly wide area.
>=20
=20
Key work here is slow. Again, served agencies require better than dial up =
for
their service needs.
> anyone have any info on using digis to connect up to tncs far and=20
> wide, or passing files on 144.390?
>=20
> -jerry
Wyoming has an excellent APRS system of interconnected digis. They only ha=
ve about
13 digis for the whole state. Before a trip out that way, I looked up the =
digis and
igates in Wyoming. Seeing on a handful, I though coverage would be bad or
nonexistent.=20=20
=20
For the trip out there, thinking things would be very
sparse, I bumped up my packet rate, and put a linear on the output of the =
HT. I was
still lulled into thinking I wasn't being detected, because I couldn't hear=
my signal being
digipeated.
=20
Upon return, I found out the Wyoming guys have their act together. The dig=
is they do have are all located up pretty high, >10,000 feet in many cases.=
Their footprint is
massive. Because of this, the don't run them as digipeaters, but as remote=
receivers=20
and local TNCs=20
for a central (actually two) igate. This cuts down on the channel traffic,=
and the=20
central igate does packet filtering before dropping the packets into the in=
ternet. They
use 440 and 1296 as links. The result is tremendous coverage for almost th=
e entire state,
with very low collision rates and sparse digis. So I was applying my norma=
l 'flat land'
Iowa concepts of how APRS works to Wyoming. I was quite wrong.
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Jerry, I've been thinking about this since you sent it, and came up with so=
me ideas.<BR>
<BR>
<BR> <BR>
> Date: Wed, 5 Aug 2009 17:03:37 -0500<BR>> To: craprs at rf.org<BR>>=
From: info at n-connect.net<BR>> Subject: [CRAPRS] aprs backbone for emerg=
ency communications<BR>> <BR>> Posting from the CRAPRS mailing list:<=
BR>> is it possible to use the large number of aprs high level digipeate=
rs <BR>> as ax.25 digipeaters? <BR>
<BR>
Yes, but if they are all on the same channel, it will just clog up the chan=
nel with<BR>
collisions, or grind it to a halt because of overloading.<BR>
<BR>
<BR>
<BR>
>1200 baud is slow, and my past experiences <BR>> using it to transfe=
r files (back in the early 90s, for storm chasing) <BR>> used to yield a=
throughput of 600-900 bps when transferring files. <BR>> and then even =
worse at 150-300bps when using a digipeater in the <BR>> middle. I know =
channel congestion would be a huge problem trying to <BR>> use aprs digi=
s, and it would be slow as heck, but in an emergency, <BR>> you take wha=
t you can get.<BR>> <BR>> you wouldn't surf the internet with it, and=
would not even attempt to <BR>> transfer even graphical weather map fil=
es, but i envision a scenario <BR>> where it would be desirable to be ab=
le to send simple text traffic <BR>> that would be too hard to relay ove=
r the air with voice comms <BR>> reliably. for example, (from a year ago=
) a list of houses and names <BR>> of those holding out and staying behi=
nd after a a flood evacuation....<BR>> <BR>
<BR>
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