[aprssig] Weird Behavior on the APRS-IS

Stephen H. Smith wa8lmf2 at aol.com
Mon Feb 17 18:27:57 EST 2014

I plot Lynn's APRS-IS feed of the ISS object on my APRS web server maps at


along with off-the-air RX on both VHF and 30M HF.    The webserver has three 
maps: One of local 144.39 activity off-the-air in central Michigan, one of 30M 
HF activity off-the-air in all of North America, and a dedicated map showing 
what my Satgate is hearing via the ISS digipeater.

The last map automatically switches from a world map (that shows the ISS 
anywhere) to a more detailed view of North America when the ISS passes over 
areas I could plausibly receive from.

Last night, I noticed that the positions of the ISS on the Satgate map and the 
HF map were wildly different.   The Satgate map showed it near the eastern 
coast of Australia, while the HF map had it over the US Pacific Northwest. A 
quick check with http://heavens-above.net showed that the HF map was correct.

The satgate map was getting it's feed from  second.aprs.net  while the HF map 
was getting it's from firenet.us .

Normally, one assumes that whenever anything is fed into an APRS-IS server, it 
propagates to all the others within a second or two.   Here I was seeing a 
nearly 20-MINUTE delay.

I then noticed that KJ4ERJ's ISS object originates with  fourth.aprs.net.  I 
then thought maybe I could cut out some delays and latency by logging into 
fourth and getting as close to the source as possible.     When I connected to 
fourth, I got NOTHING !

What's going on here????



Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
EchoLink:   14400  [Think bottom of the 2-meter band]
Home Page:          http://wa8lmf.net

  Long-Range APRS on 30 Meters HF

High Performance Sound Systems for Soundcard Apps

"APRS 101"  Explanation of APRS Path Selection & Digipeating

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