[aprssig] home fill-in digis & SSn-n

Robert Bruninga bruninga at usna.edu
Mon Aug 22 18:51:45 EDT 2005

>>> jdw at eng.uah.edu 08/22/05 6:07 PM >>>
>One thing I don't understand is why "fill-in" digis 
>are recommended to  only digipeat the first hop.
>If I'm in a dead spot, then I [also] need help getting 
>data back to me.  

Yes, but there are no current digis smart enough to 
know what packets need to be digipeated into a 
valley that has only one person driving through
it at any instant.  And trying to do it with an existing
digi for EVERY packet on the air is the kind of useless 
QRM that made the APRS channel such a mess in the 
first place.  

>If the big digi can't hear me, then isn't it fairly 
>reasonable to assume I can't hear it, either?

No, not at all!  You are in a valley, with no QRM and
can hear all the way down to your receiver noise
floor.  The BIG DIGI is hearing QRM from packets
over 5 states from 20 ore more surrounding digis...

A world of difference...

>Shouldn't an area that needs a fill-in digi need 
>it to fill-in in both directions? 

In most cases no.

de Wb4APR, Bob

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