[Xastir] Strange ACK behavior with a Yaesu VX-8DR and Xastir 1.9.9 CVS

[Curt, WE7U]

On Thu, 19 Aug 2010, David A. Ranch wrote:

> I'm looking for information Xastir v1.9.9 (last July CVS release)'s 
> "Satellite ACK mode" feature.  Specifically, I was playing around with a 
> buddy (n1nec-7) who is on a Yaesu VX-8DR and I was in Xastir (running on 
> Centos5.5) in KISS mode on a Kenwood D710.  If I would initiate an APRS 
> message, his HT would almost instantly send an ack.   I was in Santa Clara, 
> CA and he's was Fremont, CA (<20 miles away) and I couldn't  directly hear 
> his local ACK.  I would receive the digipeated ack.   Unfortunately, Xastir 
> would NOT recognize the ack and thus Xastir would re-transmit the original 
> message to him again.

That problem may have been because of differences in the
digipeater's radio/TNC setup and yours.  If you're connected to the
mic/speaker of a radio you're using FM pre-emphasis/de-emphasis,
whereas other systems that are tied directly to the
modulator/demodulator are not.  That will give you an XX dB handicap
between those rigs.  I don't remember the exact number, but I think
it's 6dB, which is significant.

We end up with some TM-D700 digi's and some pre/de-emphasis digi's
that are all expected to act the same.  Then of course there are all
the home and mobile APRS rigs, some of which are Kenwood (no
pre/de-emphasis) rigs and some which are going into Mic/Speaker
connectors.  It's a big mess.


> Now, once I enable "Satellite ACK mode", Xastir would 
> accept his ACK and stop transmitting the original message.

Are you sure about that?  The code appears to disable separate ack
messages if you have that toggle set, so the only ack's you might
send are attached to the end of your next message in a different
format (free-ride ack's).  If the other end doesn't understand this
ack format then those won't work.  Xastir backs off quickly on the
sends also.  It may have been sending but at a reduced rate, or you
may have gotten another packet from the other end of the link with a
reply-ack tacked on to the end which Xastir decoded and caused it to
stop sending.


> BUT...
>
> Now, when I enable that "Satellite Ack Mode" and N1NEC would now initiate an 
> APRS message to me, I'd never ACK his message!  Grrrr...

That sounds backwards.  Satellite ack mode is where Xastir doesn't
send separate ack packets and is only used for satellite work.
Unless you're specifically using satellites you don't use that
togglebutton.

I can try a few messages to people today to test ack's.  Haven't
done messaging in a while.  I don't think anyone has broken that
code recently but I've been wrong before.

Most likely you're having path difficulties or the pre/de-emphasis
problem on one or the other end of your path.

-- 
Curt, WE7U.                         <http://www.eskimo.com/~archer>
    APRS:  Where it's at!                    <http://www.xastir.org>
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Windows:  Microsoft's tax on computer illiterates. - WE7U.
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