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[aprssig] Is an Igate working?

Steve Dimse steve at dimse.com
Mon Dec 17 23:26:20 UTC 2012


On Dec 17, 2012, at 6:07 PM, Max Harper wrote:

> Have you tried http://www.db0anf.de/app/aprs ? If you go to this site and enter the callsign of the Igate on the right hand side of the screen in the search field and then on the left side of the screen click on Digipeater Users you can see all the stations that have been Igated by that station. Look at the colunm Last Heard. There are arrows for sorting so that you can see the most recent activity. But even this won't tell you how well everything is working, but it's better than nothing.
>  
Sites like this rely on the path information received from the APRS Internet System. The APRS IS is designed to transport the packet payload, not the path information. At every node in the APRS IS duplicate packets are removed. This makes the APRS IS unsuitable for propagation and network studies. 

For example, imagine that IGATE A is connected to APRS IS server Primary 1, while nearby IGate B is connected to APRS Tier 2 server Secondary 1. Assuming that all paths within the APRS IS are equally fast with no delays, the path of packets received will be different for databases connected to the different servers. If www.db0anf.de is connected to Secondary 1, then packets heard by both IGATES A and B will show they were IGated from IGate B, while findU (which connects to all the primary servers) will show they came from IGate B. Of course, the connections between nodes and IGates are not equal; reality is far less predictable, and of course IGates often use round-robin DNS so who they are connected to can change at any time. 

If you see a packet came through IGate A, you know IGate A is receiving. You still don't know if IGate A is able to IGate back to RF. If you look at a station between IGates A and B and see it is IGated only from A, you can conclude NOTHING about IGate B.

In summary I'll reiterate my mantra: Bad data is worse than no data!

Steve K4HG



> Max KG4PID
> 
> From: Bill Vodall <wa7nwp at gmail.com>
> To: TAPR APRS Mailing List <aprssig at tapr.org> 
> Sent: Monday, December 17, 2012 1:12 PM
> Subject: [aprssig] Is an Igate working?
> 
> Is there any aprs.fi/findu/aprsworld/? query to tell if an Igate is
> really working?  Something like how many packets gated to the system
> per hour/day/ever would be handy.
> 
> Thanks,
> Bill - WA7NWP
> 
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