[aprssig] Port 14580 Filter Bug? Or Is It Intentional?

Stephen H. Smith wa8lmf2 at aol.com
Sun Jul 8 12:58:16 EDT 2012

I am seeing an ongoing puzzling problem with the port 14580 filter port on 
APRS-IS servers.

I am filtering for ONLY the NWS watches, warnings, etc and Lynn's ISS object 
from the APRS-IS feed.     I am trying to add just these,   and nothing else 
from the Internet,  to maps that otherwise reflect only OFF-AIR HF and 
two-meter reception.   These are the maps served by my UIview UIwebserver at

.     <http://wa8lmf.net/map>    .

The filter expression is:

.      filter   b/WA8LMF/WA8LMF2/WA8LMF-63    t/w  t/n   s/: -e/WXSVR-AU   o/ISS*

I assume this should ONLY get me the weather stuff minus the similar stuff for 
Australia,  fire items since they have been in the news so much lately,  the 
space station, and my own mobile identities when I am on the road.

[WA8LMF is my 2-meter APRS mobile, WA8LMF-2 is my AX.25 30-meter HF mobile, and 
WA8LMF-63 is my 30-meter HF APRS-over-PSK63 mobile.   Combining direct 2M and 
HF off-air reception with the Internet feed of the same should ensure that I 
will show pretty much anywhere I go in North America.]

The problem is that other stations are "sneaking in" via the Internet feed, 
even though I am NOT filtering for them.  They are then appearing on my maps 
alongside the plots of RF-only stations which are the only ones (aside from 
myself) I want on the map display.  (The web server map displays are supposed 
to reflect what is currently being heard off-the-air in central Michigan - not 
the Internet.)

The only common thread I can see is that stations I once heard on RF and igated 
*TO* the APRS-IS later come back *FROM* the IS if:   either their station is 
beaconing on both RF and Internet, or if they beacon with an identical 
callsign/SSID on VHF and enter the APRS-IS from another igate.    This happens 
sometimes hours after HF propagation has caused the station to fade out on HF. 
    It's not obvious this is happening when you just look at the map, but is 
very obvious when you look at the station details and see "Q" constructs and 
TCPIP components in the path.

Is this a bug in the 14580 filter algorithm, or is there some intentional 
design decision to pass stations heard from other igates back to you if you 
previously gated them.    I.e. something analogous to the reverse-gating of 
messages if your igate heard a station recently and locally?



Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

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