Order Tray | Contact Us | Home | SIG Lists

[aprssig] WinAPRS fails to accept ACKed messages

WB4GQK at aol.com WB4GQK at aol.com
Sat Nov 27 21:39:35 UTC 2004


Reference message from aa3jy at winlink.org  dated 11/24/04 9:20:02 AM  and
kb8uih at sbcglobal.net dated 11/26/04 9:21:16 AM

Hi all,

Let me set the record straight regards not responding to ACKs from messages I 
have transmitted. First of all it is not a software problem! It is not a 
hardware problem! It is not an operational setup problem! OK so what is it.

Let me go back to a large discussion that was held on the SIG last April. The 
main thrust of this discussion centered around TIMESLOTTING on HF 
frequencies. Prior to that discussion I had opened a discussion on the collisions that I 
can see and hear on 30 M APRS.

Now before I go into this discussion I want to set the record straight.. This 
is not intended in any way to be a complaint or putdown. Just please 
recognize I am stating facts not making any justifications or condemnations.

First of all this discussion will center around the massive amount of 
collisions I SEE and HEAR. Those of you who are familiar with the SGC 2000 know the 
TNC plug on the transmitter does not affect the audio so I can hear the AX25 
signals as well as watch the LEDs in the KAM+ in addition to observing the 
received signal strength in the SGC display monitor. Believe me all 3 are very 
informative and tell quite a story.

With that said let me provide a list of Weather stations that I consistently 
receive:
C6AGH
VP5DB
VP5DB-1
VP5DB-2
J73CS
J73ODM-3
EA2AAA
and occasionally
F5RAG-4
FG5FU
F5RZU-2

These stations are transmitting weather reports every 6 minutes in addition 
to station identification. I copy the first 4 stations 100% except when a 
collision occurs I will lose that data.

The two stations in P.R. are not as strong and I copy their transmissions 
about 50% of the time. Obviously the last 3 stations I only copy when propagation 
is very favorable. But the principle point here is all of these stations are 
transmitting weather every 6 minutes along with station IDs. From the top 4 
stations I normally receive 1200-1300 transmissions each over a 7 day period.

OK so what does all of this have to do with my station not receiving ACKs. 
Please excuse my simplistic way of describing what happens but, when I send a 
short message to Clay very obviously all the stations South of me as well most 
of the stations to the North and N.W of me also hear my transmission and they 
wait. When ever I transmit they standby until the transmission is over. When 
transmitting a one line  message the duration of the transmission is longer than 
a simple ID. As a consequence all these stations appear to STANDBY longer  
until my transmission is finished. The switch-over time in my SGC is about 25 
milliseconds but instantly when I start receiving I SEE and HEAR easily 2 
signals and occasionally 3 or more different transmissions. It appears everyone was 
just waiting for me to finish. So obviously Clay's ACK to me is lost in a 
collision with other stations South of me that perhaps he doesn't hear. The 
absolute opposite can be said for the stations in the South.  The only difference 
being is the weather stations are unattended, and do not address their messages 
to a specific station so they are not expecting to receive an ACK. Probably a 
good arrangement based on the density of all the transmissions I see/hear. 
Another interesting facet is apparently the short transmissions that include my 
ACKs to messages directed to me seem to get thru better.

I just don't believe anyone really realizes how many collisions I see and 
hear. It is truly phenomenal.  And as a consequence it takes several tries of the 
message in order to receive an ACK from just about any of the stations I 
contact on 30M..

This situation has been existing for at least a couple of years. And again I 
want to state I do not have a problem with this condition. In fact I do 
observe the weather data from the stations in the Turks and Caicos every other day 
or so, I find it very informative to provide me weather predictions that will 
arrive here within 36-48 hours.

As far as the sensitivity and reach of my station I have on a few rare 
occasions exchanged a simple hello to F5RZU-2 in France and G4GTH in G.B.

Is there a solution for this situation. I don't really know. Perhaps if the 
return ACK was delayed say 30-45 seconds perhaps the traffic density would be 
down so it could get thru. It's a very mute point.

Anyway I hope everyone can gain some information about this situation. At 
least it's something to think about, regardless if anything can be accomplished.

73 de Jim   




More information about the aprssig mailing list