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[aprssig] NE Illinois Balloon Tracks

Tim Cunningham tim_cunningham at charter.net
Fri Jul 24 18:53:52 UTC 2009


"Bill Diaz" wrote: <william.diaz at comcast.net>

lot of <snips>

>>If digis are correctly configured, multi-hop related QRM should be
>>minimized since they will all retransmit at the same time, to avoid
>>ping-ponging.
>
> Unfortunately most WIDE1-1 digis are not correctly configured.  Our
> recent experience in NE Illinois illustrated this rather vividly.  Saw 
> many
> timestamped packets that were delayed in excess of 30 seconds due to 3
> trackers beaconing from altitude at 30 second intervals with abusive 
> paths.
> Since  many digis have a dupe time of 30 seconds, these packets were
> dutifully digi'd again.  This ping-ponging caused the icons to jump back 
> and
> forth on the map.  Was very apparent when copying signals direct.

Here is a major problem!

In many balloon cases it is not a WIDE1-1 or a WIDEn-n digi problem. The 
biggest problem is the IGates sending the data back to the APRS-IS. The 
ping-pong effect observed on the Internet is huge. Many IGates are trying to 
process a full feed or more data than they can handle in a reasonable amount 
of time. The balloon launches have long proven this problem. They could 
beacon with no path and you would still see the ping-pong issue on an 
Internet feed due the numerous IGates that have horrendous delays getting 
data to the APRS-IS.

THIS IS A HUGE PROBLEM WITH IGATES! I am not sure I can emphasize this one 
any louder.

We have experienced numerous balloon launches in the Huntsville area longer 
than the past decade and every time we review the Internet feed and look at 
the data it is the IGates that are the largest contributor of the ping-pong 
effect just looking at data with 0 HOPS the ping-pong effect is still very 
evident on the Internet feed. If these offending IGates would use a filtered 
feed or a more reasonable filtered feed, most of the issues would evaporate.

It is my opinion based on loads data, that most of the ping-pong effect is 
related to IGate to APRS-IS speed mainly due to IGates trying to process 
more data than what their processor or data bandwidth can handle in a 
reasonable amount of time.

WIDE1-1 paths may contribute to the problem, but there is also another 
dimension related to the same issue on the Internet feed.


73's,
Tim - N8DEU
Decatur, Alabama






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