[aprssig] Airborne Digis

[Robert Bruninga]

I may have not thoroughly thought this through, but my initial
reaction is:

1) Make the digi be a WIDE1-1 digi.  It will help where it can,
and it will not add much QRM.

2) BUT, The digi at altitude will have solid QRM on the input on
144.39, and although it can hear the weak SAR units udner it,
the chance that those will be clobbered by 200 mile away digis
on 144.39 is too high to make it worthwhile.


So, if the purpose of this is to make sure you hear your SAR
units, then they should TX on 144.99 so that they have an
uncongested channel getting into the digi (whatever digi is
avaialble on that freq)...

But then, this does not seamlessly work between good 144.39
areas and when the aircraft with the digi is up.

Maybe the best solution is the specialized trackers that can
alternate paths.  Send every other packet on 144.99 for the
potential when there is an aircraft in view.  But send on 144.39
most of the time...

OOPS, most trackers cannot auto QSY like that.

So I guess we are back to square one.  Make it a WIDE1-1 digi...
Or use a special pre-emptive SAR or SAR1-1 digi and assume the
ground control stations can hear the aircraft direct for the
one-time-digi.

Bob, WB4APR