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[aprssig] PATH clarification when travelling

Andre PE1RDW aprs at pe1rdw.demon.nl
Fri Jul 29 18:11:36 UTC 2005


Stephen H. Smith schreef:

> smithb at bpsmicro.com wrote:
>
>> [Apologies if this gets posted twice...]
>>  
>> Okay, I *think* I'm pretty clear on the new paradigm, but there's one 
>> lingering question to toss out. It involves a mobile taking a trip 
>> that'll involve travelling through areas that have upgraded to the 
>> new paradigm, and some that haven't.
>>  
>> If one were to set the path to, say "RELAY,WIDE1-1,WIDE2-1", would 
>> that be the best compromise? I'm well aware that stopping to change 
>> the path as you entered each area would be ideal, but without 
>> adequate info (eg. a centralized database) of what PATH works best in 
>> what areas, that's a tad difficult (not to mention inconvenient in 
>> some cases).
>>  
>> Specifically, if I'm in an area where RELAY has been discontinued, 
>> and a local digi hears the above packet, will it just ignore the 
>> RELAY and deal with the WIDE1-1? Or will the fact RELAY is in the 
>> packet cause the whole thing to be tossed out?
>>  
>> Brad.
>
>
> Packet paths are processed SEQUENTIALLY, not in parallel.   The first 
> hop in the string MUST BE USED FIRST before any subsequent hops are 
> acted on.    If RELAY doesn't get processed first, and marked as 
> "used" in the example above, you are not going to go anywhere!    A 
> full discussion of this issue is on my website at:
>      http://webs.lanset.com/wa8lmf/DigiPaths    
>
> In the case of the D700, or a TinyTrack, alternate paths can be stored 
> in the device (5 in the case of the Kenwoods, 2 in the case of the 
> TinyTrack) and then selected as needed enroute.     You might store a 
> path of  "RELAY, WIDE, WIDE2-2" in one mode,  and "WIDE2-2" or 
> "WIDE1-1, WIDE2-2" in the other. 
>
I think the only widely used digipeater option that can do preemtive 
digipeating is digi_ned, the in the usa widely used kpc digipeaters 
can´t do it and I doubt they ever will because the room in the rom is 
limited.
This problem will most likely be around for a few years yet.

73 de Andre PE1RDW




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