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[aprssig] APRS W,W and W,W,W example

Steve Dimse steve at dimse.com
Fri Feb 11 18:27:37 UTC 2005


On 2/11/05 at 10:07 AM Bill Vodall <wa7nwp at jnos.org> sent:

>Kantronics TNC's do dupe checking on WIDE2-2 but not generally on the
>WIDE,WIDE.   Thus with a WIDE,WIDE path you can get ping-ponging between
>digi's you won't get with a WIDE2-2.   The "3 to 5" number is probably a
>worst case which is seldom seen.  Normally it might be a couple extra packets.
>It all depends on how many WIDE digis are in a area that hear each other.
>
I understand all that, but as far as I can see, it only applies to paths of
order 3 and above, like WIDE,WIDE,WIDE and WIDE3-3.

How can a path with only two digis bounce back and forth?

Mobile transmit, Digi A repeats, Digi B hears that and re-transmits it. Sure,
Digi A hears digi B's re-transmission, but both the digi hops have been "used
up" and digi A will not transmit a second time. No bouncing occurred. If the
same original packet was also heard by digi B directly, then both will transmit
it, and if the timing works out, both will hear the other digipeat and repeat
it, regardless of whether the path is WIDE,WIDE or WIDE2-2...the dup checking in
TNC's is not payload dependent like in digi-ned, it is path dependent.

Steve K4HG





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