[aprssig] "station which heard ... directly on the radio"

PE1RDW aprs at pe1rdw.demon.nl
Tue May 21 09:28:28 CDT 2013


On Tue, 21 May 2013 16:06:18 +0200, Georg Lukas <georg at op-co.de> wrote:


>
> This is true, according to APRS101.pdf. However, providing compliant
> behavior when converting AX.25 to APRS-IS requires a two-pass solution
> to look for the last digi element with the H-bit set and destroys
> information on the way (which of the previos digi H-bits were actually
> set?), so a lossless conversion back to AX.25 is not possible any more.
>
a lossless conversion back to AX.25 is also not desired, aprs was intended  
to work with the human readable interface of TAPR TNC2 interface (not the  
in europe more common TF2.7b format) IMHO a sloppy design but we are stuck  
with it, once it leaves the tnc or softmodem it becomes just a text header  
and does not even have to come from AX.25 in the first place, for exsample  
psk-63 stations use an fictional ssid of -63, this is not even posible in  
AX.25 and can there for not be translated back to AX.25

if you want to transport aprs data across the internet in an AX.25  
transparent way you need to use ax-udp not aprs-is, I have this running in  
my LAN using agwpe-pro and DigiNed, the only thing missing is a way to  
automaticly add links in a secure way but that might be fixable using  
BPQ32's ax-tcp implimentation, this is a variation on ax-udp and ax-ip  
where the ax.25 data is actualy wrapped inside a tcp/ip connection

-- 
73 Andre PE1RDW


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