Received Packets not being acted upon?

[darksidelemm]

A bit of an odd one for me. Configuration is a OpenTracker USB in KISS mode, hooked into a RPi. Usual ax25 stack configuration (I think...)

When I try and connect to a local packet node, the connect command is definitely transmitted, but when the node responde, it seems to be ignored by linpac, yet shows up in the monitor window:

Is this possibly a misconfiguration somewhere?

Thanks,
Mark VK5QI

[David Ranch]

Hello Mark,

In your screen capture, you show:

VK5QI-6 to VK5GR-10 ctl SABM+
VK5GR-10 to VK5QI-6 ctl I00^ pid=F0 (...
ADELSA:VK5GR-10} Welcome to vk5gr.ampr.org net...

The issue here is that your station is not hearing the acknowledgement packet (UA-). Here is an example of a working connection setup and teardown:

d710: fm KI6ZHD to LPRC3 ctl SABM+
d710: fm LPRC3 to KI6ZHD ctl UA-
d710: fm LPRC3 to KI6ZHD ctl I00^ pid=F0(Text) len 51
Welcome to LPRC3. K-net on Loma Prieta. -LPRC.net-
d710: fm KI6ZHD to LPRC3 ctl RR1v
d710: fm KI6ZHD to LPRC3 ctl I10^ pid=F0(Text) len 2
b
d710: fm LPRC3 to KI6ZHD ctl RR1-
d710: fm LPRC3 to KI6ZHD ctl DISC+
d710: fm KI6ZHD to LPRC3 ctl UA-

Check the audio levels coming INTO into your OpenTracker. Though AFSK1200 packet is pretty tolerant, you need to get the levels at least close.

--David
KI6ZHD

[darksidelemm]

Ahh, thanks David. I'm also wondering if the carrier detect is a bit slow, and might be missing shorter pacets (i.e. the acknowledge packet).

Thanks for the quick response,
Mark

[David Ranch]

Looking at the OpenTracker manual, are you using SWDCD? You want to ENABLE this and open up the squelch on your radio so the TNC listens to all potential packets all the time. If you are in a fringe area and cannot receive packets very well after you've tuned things as best as possible, you might consider feedline, a better antenna, etc. Also, though OT units are nice, also consider using a software TNC like Direwolf which has far better packet decoding rates than almost any other HW TNC.

Btw, though not very user friendly, read the comments in my packet startup script at http://www.trinityos.com/HAM/CentosDigitalModes/usr/local/sbin/packetrig.sh . That has all kinds of details on the various parameters you'll want to tune on the AX.25 side of things.

--David

[darksidelemm]

As it turns out, the firmware version I had in my Opentracker has a 'known' bug where it drops packets shorter than some limit (clearly just bigger than the acknowledgement packets).
In the process of updating the firmware, I managed to brick the unit because of another 'known' bug (not documented on their website mind you).

Anyway, I'm now using a Kantronics KPC-3 and that's all working fine.

[David Ranch]

Ugh... well, I've heard nothing but good things about Argent Data so I bet you can ship the unit back and get it repaired. I didn't realize that the OT line has become a full blown TNC with COMMAND support. I imagine the KPC3 will still perform better though. Good luck!