[aprssig] Sub-second timeslots

[Scott Miller]

> good idea.  I wonder if the RMC is consistent across multiple GPS vendors?

Probably not.  I think it's the default for at least the Garmin GPS 18, 
and I think the top-of-second sentence is configurable now.  It might be 
that I have to make it an option on the tracker end as well.  I don't 
know that there's any guarantee that the NMEA sentences are aligned to 
the top of the second at all, but on the few I've checked so far that 
seems to be the case.

> But I like the idea of a spec to outline the concepts of time-slotting.  But it would be nice to test with at least one WIDEn-N path so that this technique coiuld be used through cross-band digipeaters.  I think having at least one hop should be conisdered a requirement.

An extra 7 bytes shouldn't be a problem.  Still, I'd rather have the 
brains for that sort of thing in the digipeater itself.  Or you could do 
it with a couple of KISS TNCs back-to-back...

Scott
N1VG