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[aprssig] WIDEn-N 'Decay Sequence'

Mark Earle wa2mct at mearle.com
Mon Jun 19 14:05:11 UTC 2006


 >I'm guessing that when the packet is re-transmitted, the
 >server software changes the text of what goes out. For example:
 >
 >Original transmission: abcdeWIDE2-2figk
 >First retransmission:  abcdeWIDE1-2figk
 >2nd retransmission:    abcdeWIDE0-2figk
 >and the next person that received it sees "Ahh, zero, don't
 >rebroadcast."

Almost! WIDE2-2 becomes WIDE2-1. If the 2nd number is non-zero then a 
station hearing the packet digipeats it and decrements the 2nd number.

It's not just servers. "Smart" tnc's running various firmware also do this 
- so no pc needed at mountain tops. (Note: A PC running DigiNed can do a 
LOT more! But most folks are averse to PC's at remote sites for a variety 
of reasons).

 >a user would specify "WIDE1-1, WIDE2-1", since the second
 >entry would 'override' the first.
 >

This is to accomodate "home" or "fill in" stations that are NOT on a 
mountain top. Your packet will be heard, digipeated, and possibly placed in 
to the aprs-internet system. (aprs-is). But the fill in doesn't change the 
packet.

So now you've been digipeated ONE time. If the digi hears your packet via 
the fill in, you get ONE more "hop". If the digi happens to hear you direct 
(say, you hit a digi, and the fill - in) the digi still only gives you one 
hop. The digi ignores the WIDE1-1.

So you get two total hops, get your packet to aprs-is, people locally see 
you. The objective (compared to runing, say WIDE5-5) is to have your pacet 
seen locally, but not state-wide or hundreds of miles away.

As Bob will tell you, APRS is a local tactical system. Emphasis on LOCAL.

The other advantage of WIDE1-1,WIDE2-2 is: Some old TNCs at hilltops can't 
do the fancy repeat and decrement. So those TNCs should act on the WIDE1-1, 
and give you one hop.

So, the idea is, no matter what - the mobile user sets up WIDE1-1, WIDE2-2 
and does not have to reconfigure. Useful for other than D700 users, 
trackers, etc.

A home station should set to WIDE2-1. The home station does not usually 
need to hit a fill - in.

See fix14439.txt   if you google for that it explains things in more detail.


       ) )    de WA2MCT Mark
      ( (     Echolink 99190      Grid Square EL17HQ
       ) )    You will be assimilated... oooh, coffee!!
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