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[aprssig] Point-to-point telemetry addressing

Stephen H. Smith wa8lmf2 at aol.com
Fri Nov 24 23:49:57 UTC 2006

nlsa at nlsa.com wrote:
> Dear friends,
> I know almost nothing about packet radio or APRS so please forgive me 
> if my question is stupid.  My home station (W9IP-1) is near Syracuse, 
> NY and I'm trying to maintain a telemetry link with our cottage 
> (W9IP-2) about 35 km away.  

"maintain a telemetry link" ??   Unlike conventional packet, APRS 
stations don't "connect" to a specific other station.  You just do a 
one-to-many broadcast to any and all stations within earshot.

> The terrain is rough so a direct path doesn't work.  There is a good 
> APRS digipeter (K2AMB-3) near W9IP-1 and another good one (KB2FAF-10) 
> near W9IP-2.  The two digipeters "see" each other very well.  The one 
> near W9IP-2 is also an IGate, which is important because I want the 
> telemetry to show up on findu's database.
> I would think that ...
> W9IP-1's path to W9IP-2 would be APRS,K2AMB-3,KB2FAF-10,W9IP-2
> and that
> W9IP-2's path to W9IP-1 would be APRS,KB2FAF-10,K2AMB-3,W9IP-1

Why are you including your own stations at the end of the path?  This 
just makes your own (target) station try to digipeat the packet once more. 
Using specific callsigns instead of generic WIDEn-N is a good practice 
for something like this since it avoids having transmissions spreading 
out in every direction needless generating more QRM.   And you are 
correct that the directed path from each end will be a mirror image of 
the path from the other end. 

I assume from your usage of APRS as the first phrase in the path that 
you are using UIview,  since all other APRS applications  have the 
"destination" (any quasi-callsign beginning in APnnnn) in a separate 
field or entry from the digipeater path hops.  

If the device doing the telemetry is a stand-alone TNC rather than a 
program running on a PC, the path will be entered into it's hardware 
using an ASCII  terminal program for setup.  It will be something like:  
"APRS via KB2FAF-10,K2AMB-3"  [Exact syntax will vary depending on the 
particular TNC being used.]


Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      14400    [Think bottom of the 2M band]
Home Page:          http://wa8lmf.com  --OR--   http://wa8lmf.net

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"APRS 101"  Explanation of APRS Path Selection & Digipeating

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