okay so ive been running APRS for about 6 months now and the tracking side works fine, my position beacons are hitting the network and i can see myself on aprs.fi no problem. but when i try to send messages through the TNC to another station they just dont seem to arrive. the other guy can see my position beacon but never gets the message packets.

im running a TM-D710G into a Kantronics KPC-3+ and feeding into APRSIS32 on the PC. the messages show up in the software as sent and i can see them in the raw packet stream going out, but no ACK comes back and the other station says nothing arrived. ive checked the path settings and im using WIDE1-1,WIDE2-1 which should be fine for my area. digipeaters are clearly hearing me because the position stuff gets through.

anybody run into this before? starting to wonder if its something specific to how the KPC-3+ is handling the message format or maybe a SSID thing im missing

this tripped me up for a while too. check what SSID the other station is using versus what you have in your message destination. APRS messaging is pretty picky about that — if hes running as W1ABC-9 and you address the message to W1ABC it wont deliver properly even though the callsign looks right. also worth checking if the destination station is actually IGated and connected to the APRS-IS, because if hes RF only and there isnt a good digipeater path between you the messages can just die in the ether. the position beacons work because they dont need an ACK and they spread around more aggressively.

also double check your KPC-3+ firmware version, there was some weirdness with older versions and how they handled the message ack retries. cant remember the exact version off the top of my head but it was discussed on the aprssig mailing list a while back.

yeah what he said about the SSID thing is spot on. I spent like two evenings debugging something almost identical last winter and it turned out the guy i was trying to message had recently changed his mobile SSID from -9 to -7 and i didnt know. felt pretty dumb once i figured it out.

one other thing to check — are you running any RF-only message path or is everything going through the IGATE to APRS-IS and back? sometimes when both stations are on RF and the message goes up to the internet and tries to come back down it gets dropped if the destination station isnt being heard by a local igate on the receive side. bob bruninga used to write about this a lot, the whole messaging reliability thing on RF is honestly kind of a mess compared to just sending an APRS-IS message directly