[aprssig] Sending objects to RF via APRS-IS

[John Gorkos]

Hello-
  I'm working on implementing WB4APR's vision of AVRS, as described here:
http://www.aprs.org/avrs.html

So far, I have had a good deal of success and have about 2500 lines of code 
written that monitor the APRS-IS stream, track node status for both echolink 
and IRLP, and maintain real-time position information for active APRS 
stations.  I also have working CMD/ACK code for commands sent to the AVRS 
daemon via the APRS-IS stream.
One of the requirements spelled out in the avrs.html "spec" is that IRLP and 
Echolink nodes will show up as Objects on the users' radio.  Here is a sample 
use case:
John, AB0OO is driving in an unfamiliar city and wishes to make an Echolink 
connection to his home repeater.  He sends a "?" query to "AVRS" via APRS, and 
the AVRS server causes the local I-Gate to send two APRS objects (actually, 
items) with the position and QSY information for the two closest EchoLink 
nodes.  He then selects one of those objects, hits the Tune button on his 
D710, and his radio QSYs to the local echolink frequency with correct offset 
and tone.  He is then able to connect to his home repeater over echolink.

My question is, how do I properly structure an Object and send it via APRS-IS 
such that a Tx-enabled I-Gate will broadcast that object on the air?  What are 
the logical steps an IGate will go through to figure out if an object it hears 
on APRS-IS should generate an RF-transmit?

Incidentally, the AVRS server is periodically on-line as I work through it.  
If you feel like pinging it, send a "?" to destination "AVRS".  Right now, it 
only returns EchoLink nodes, but IRLP should be added in a day or so (kudos to 
both Jonathon and David for being so accomodating with my requests).

John Gorkos
AB0OO