[aprssig] TEMPn-N and callsign digipeating

[Robert Bruninga]

>This reinforces what I have always felt was fundamentally 
>wrong with  the "fill-in digi" concept.  If I need help 
>getting out, I need help  receiving, too!

Actually, in most cases, the fill-in digi is needed to let
the distant lower-power mobile with whip antnena get
into the distant digi over all the other QRM on the
channel as heard by the digi.    APRS in most areas
must be considered as a QRM limited network, not
an RF range limited network.

So getting in over QRM is the main advantage of a
FILL-IN digi far from the main digi.  

On the flip side, the mobile can hear very well, and
does NOT hear the degree of QRM that the digi
hears.  In fact, the mobile probably hears a small
10 to 20% of the QRM and so he has a much higher
probablility of hearing the main digi  than the digi
has of hearing him.

Yes, if the area is so far from the main digis in
an area that packets cannot be heard at all in the
black hole, then a full NEW-N digi is needed there.
But it might only need to run a watt or two to
fill in the area, while not adding too much to the
QRM that all the other digis have to hear.

Bob