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[aprssig] APRS iGate questions

Reuben Wells row at hopgarden.net
Sun Sep 5 21:18:13 UTC 2010


Matti, thank you very much for your help. Please excuse some of my 
questions I am very new to APRS

Matti Aarnio wrote:
> I am inclined to say that there are questionable digipeaters in the area.
>  2010-09-03 16:35:24 UTC: M0NAS-9>UQ5VT9,WIDE1-1*,WIDE3-3,qAR,M0NAS:`vC"mHk>/"4L}Neil mobile
>  ...
>  2010-09-03 18:08:33 UTC: M0NAS-9>UQ5VT9,WIDE1*,WIDE3-2,qAR,M0RXW-B:`vC"mHk>/"4L}Neil mobile [Duplicate position packet]
>
> Something digipeats, and puts out "WIDE1-1" with "has-been-digipeated" flag set.
>   
Just to confirm (from what I have read) it is the "}" that tells you 
that this has already been digipeated?

> Something else digipeats and processes WIDE1-1 by New-N rule, and something other
> digipeats with New-N rule -- but time spent in those two is about 1h30m.
> That 1h30m is mightly lot for APRS-IS to act as a limbo, so I suspect the digipeaters.
>   
Ok - I've added the owner of the digipeater in that area to this mail 
(g3rji.alanpaul at gmail.com).

> Could you get M0NAS-9 to try TRACE1-1,TRACE3-3, and drive similar loop around?
> That might supply sufficient clue as to what the buggy thing is.
>   
Neil (M0NAS) would you be able to repeat your route again at some point?

> Sorry to contradict you, but your telemetry data seems to be coherent,
> it is being sent out every 20 minutes (+ some seconds) until 17:20 UTC,
> when it stops.  By "coherent" I mean the sequence numbers are sequential
> until then.  (After every 6 telemetry messages there is a skip, because
> the telemetry subsystem puts out parms/equations, and unintentionally
> consumes one sequence value at it.)
>   
Ok - any idea how these could continue to be repeated with the device 
powered off? I'm presuming that nothing else would retransmit these 
messages. The device was definitely powered off at 14:27 UTC. 
Interestingly, looking in the aprx logs I see:

2010-09-04 06:29:42.996 M0RXW-B   R MB7UIK>APU25N,WIDE3-2:}M0RXW-B>APRX20,TCPIP,MB7UIK*:!5110.89NR00018.64E&Rx-only iGate (aprx2/OpenWrt 10.03 - row at hopgarden.net)
2010-09-04 08:40:39.196 M0RXW-B   R MB7UIK>APU25N,WIDE3-2:}M0RXW-B>APRX20,TCPIP,MB7UIK*:!5110.89NR00018.64E&Rx-only iGate (aprx2/OpenWrt 10.03 - row at hopgarden.net)


Does this mean that my beacon had been pulled off the Internet and 
transmitted ? [Again I notice the presence of "}"] So the log message 
above is actually me receiving my own beacon off RF, that I've never 
transmitted over RF.
> Also aprs.fi seems to have current view of the time. A beacon I sent
> 8 minutes ago is listed as being sent 8 minutes ago.
>   
I restarted the iGate at 19:00 UTC today.

> No. There is too much time spent in limbo. A TRACE may reveal it.
> More like bad firmware on some unmanned digipeater somewhere. I have seen
> TNC2s with UIDIGI to loose their marbles after a few months of continuous
> operation.  Their own beacons become garbled, and behaviour is overall
> erratic.  I can't rule out that KPC3+ units won't have similar problems.
>   
Ok - thanks. Looks like its an issue with a digipeater though and not my 
iGate.

> One of the sad omissions in TNC firmwares is that they very often keep
> a packet on transmit queue until it goes out without conception of timing
> out from the queue.  Now if a site is "busy" so that a digipeater is
> constantly receiving something (including packets), but considers channel
> to be busy, how long it keeps packets to be digipeated in the queue?
> When will the duplicate detection time out?
>   
Got it. If there was a problem locally and a lot of re-tranmission of 
packets from the Internet I guess its possible for packets to get held 
up like this.

Reuben



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