[aprssig] Using SSID's outside 0 to 15

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Thu Mar 4 07:59:55 EST 2010

kai.brandt at hjemme.no wrote:
> If it's only one-way from HF to APRS-IS / V/UHF then it's probably ok.
> But if you want to send a message to the HF station i think this is going to be more problematic.

APRS messages do NOT use the AX.25 header for the intended recipient.  
The recipient of the message is in the payload portion which is sent in 
un-encoded ASCII on all mediums (that I know of).  Any replies or acks 
(which are really just APRS messages with special text) would be sent 
from the extended -SSID on HF or APRS-IS and would then (should then) be 
gated back to VHF as 3rd party packets within which the IGate's call 
goes in the AX.25 header and the gated source call again goes into the 
payload which can handle anything.

Check out aprs101.pdf or just look at a bunch of raw packets on your 
favorite APRS client (web or otherwise).  Or just send a message to 
KJ4ERJ-AP (an APRS-IS client) from your RF and see if you get an ack.  
If I'm around, we could QSO.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

PS.  Check out my APRS messaging description at 
http://aprsisce.wikidot.com/aprs-messaging-explained  Of course you 
won't get an ack or a response if there's no bi-directional IGates 
configured near your RF location.

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