[OZAPRS] Questions about tncs

Matthew Cook vk5zm at bistre.net
Fri Jul 6 09:39:49 AEST 2018


Check how your TNC is detecting if the channel is busy.

Not many TNC's worked well in the day with open mute, in fact we used to
retrofit a small board to TNC's that would detect the AFSK tones and drive
the carrier SQ input on our TNC's.    What you describe is classic CSMA
"hold off" due to a busy channel.  I think you'll find that your TNC thinks
that the channel is busy, so it's not transmitting.  Since there is no way
for Xastir or Yaac to know if the packet has left, it retries.

Does your TNC have a carrier squelch input or software DCD (data carrier
detect), it may even have a DCD (or RX decoded) LED  if so what is it
telling you ?

I'm not familiar with your TNC per se, but can remember back to the time
where small fury creatures from alpha centari were real small furry
creatures from alpha centari.



On 6 July 2018 at 08:02, Max Bainrot <mbainrot at gmail.com> wrote:

> Hi all,
> I’m fairly new to the whole packet radio shenanigans and been tinkering
> away for the past couple of days and have been running into gremlins
> I’m currently using a mobilinkd tnc2 firmware on a home brew shield on a
> 16mhz Arduino which works o.k. but it seems like it has a really long delay
> between transmitting and receiving, like long enough for default settings
> xastir (more on that later) to get impatient and retransmit like 6 times
> before entropy has it that the acknowledgement makes it through.
> Is this just because the firmware is asking too much of the poor little
> atmega328p or is it something else? Doesn’t appear to be the radio(s) as I
> have two radios, wuxeon handheld and a tyt md380 (working 439.100 as there
> is no local digipeter) and switched radios between the sender and receiver,
> updated firmware on both Arduinos, the tncs where crashing before I
> attached ferrites to the cables but that appears to have fixed the issue.
> I haven’t confirmed beyond all doubt if the tnc is still randomly
> rebooting or not, going to hook the bus pirate (it has high z serial mode)
> up to the tnc’s serial lines to see if it’s singing it’s song of it’s
> people every time it transmits.
> The reset on connect jumper is enabled btw, is it xastir closing and
> reopening the serial port?
> I’m also using default settings in xastir for kiss tnc which could be
> another mistake I’ve made?
> Now onto the topic of xastir :) does anyone know where I can find the
> setting to slow it right down??? It resends wayyyyy too quickly which is
> both bad form and severely aggrevates the problem. I’m also thinking of
> rocking YAAC as it’s java based so I can use the latest version on all
> operating systems and I can slow it right down.
> Reason I am running down the open hardware and/or diy route is I am
> intending on cooking up a raspberry pi zero hat/cape, so want to leave
> options open for my future shenanigans.
> Many thanks in advance,
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