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[aprssig] APRS talk in Los Alamos?

J. Gary Bender, WS5N ws5n at wildblue.net
Wed Aug 31 19:08:25 UTC 2011


Thanks Tom.
Excellent explanation.  I will switch to Wide2-2 for normal ops around NM.  I doubt that I ever hit a true Wide1-1 fill-in anyway.
  --  73  --
  J. Gary Bender, WS5N
  Fence Lake, New Mexico USA

On Tue, 30 Aug 2011 18:18:07 -0600, Tom Russo wrote:
> On Tue, Aug 30, 2011 at 05:05:25PM -0600, we recorded a bogon-computron collision of the  flavor, containing:
>>
> [you might want to adjust your mail program to send only plain text email to
> APRSSIG --- those of us using old-fashioned text mail programs get to see
> all the HTML markup, which I've hand-edited out in my reply]
>>While there I hope you can monitor the APRS traffic around the city.  When I drive in to Albuquerque, I start hearing "MY POS" repeats sometimes three or four times each time I beacon.  I have heard it as much as 7 times!  I am running WIDE1-1,WIDE2-1 in the mobile.  I have my suspicions as to what is happening, but I don't have the expertise to analyze the situation and make recommendations.  I'd love to hear your take on it, if you see the same behavior.
> That's because all the nearby digis are ancient KPC-3 TNCs with old firmware,
> with broken handling of WIDEn-N:  they fail to mark the final hop as used,
> so if WIDEn-N were implemented normally the path you are using would only
> be a one-hop path:
>  first transmit:  WIDE1-1,WIDE2-1
>  First digipeat:  LAMOSC*,WIDE1,WIDE2-1
>  First digipeat(2):  SANDIA*,WIDE1,WIDE2-1
>  First digipeat(3):  CAPILA*,WIDE1,WIDE2-1
>  First digipeat(4):  ELKMTN*,WIDE1,WIDE2-1
>   (etc. for every digi that happens to hear you)
>  End of line, because nobody will digipeat this (WIDE1 is showing as the
>   first unused digi, and nobody will do anything with that).
> SO, the work-around is that all of these digis have a workaround in place:
> MYALIAS is set to WIDE1-1, with all the problems that go with it --- notably,
> no dupe checking on the first hop.  So you get THIS mess instead:
>  first transmit:  WIDE1-1,WIDE2-1
>  First hop:  LAMOSC*,WIDE2-1
>  First hop(2):  SANDIA*,WIDE2-1
>  First hop(3):  CAPILA*,WIDE2-1
>  First hop(4):  ELKMTN*,,WIDE2-1
> and then
>  Second hop:   LAMOSC*,SANDIA*,WIDE2
>  Second hop:   LAMOSC*,CAPILA*,WIDE2
>  Second hop:   LAMOSC*,ELKMTN*,WIDE2
>  Second hop:   SANDIA*,LAMOSC*,WIDE2
>  Second hop:   SANDIA*,CAPILA*,WIDE2
>  Second hop:   SANDIA*,ELKMTN*,WIDE2
>  and so on and so on.
> That is, if you use WIDE1-1 you're no better than the Bad Old Days of
> RELAY,WIDE, thanks to outdated hardware with outdated firmware.
> The KPC-3's are all donated hardware from WA5IHL who used to maintain a large
> number of normal packet nodes with them, and repurposed them in the early
> days of APRS.  It is not reasonable to expect that they'll all be replaced
> in any sort of short order with more modern hardware/firmware, so we're stuck
> with the local advice NOT to use WIDE1-1,WIDE2-1 in the central New Mexico
> area --- just use WIDE2-2 so that all dupe checking is actually done properly.
> With WIDE2-2, no ping-ponging is possible, you get fewer "MY POS" beeps
> on your D7X0, and the channel gets less congestion.



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