[aprssig] timeslotting on HF ? was > 15. APRS trackers on 10m (Robert Bruninga)

David Rush david at rushtone.com
Mon Nov 28 09:02:07 CST 2005

How about a VERY simple time-slot algorithm... such as the last letter of 
your callsign indicates the minute past the hour or half hour within which 
you're allowed to transmit?  Calls ending with A could transmit during 
hh:00:00-hh:00:59 and hh:30:00-hh:30:59, calls ending with B could transmit 
in hh:01:00-hh:01:59 and hh:31:00-hh:31:59, and so on.  The last four 
minutes of each hour or half hour could be reserved for something special, 
or simply a free-for-all.

Each user would have two one-minute slots per hour to work with.  Such a 
long slot accommodates manual timeslot-operation if necessary, and makes it 
easier to keep track of time, especially for small, PIC-based trackers that 
have very limited code space.

Within one's appropriate minute, users could pick a random time to transmit 
(or sub-timeslot within a local area if multiple regular share the same 

As far as I know, this should work equally well for most international 
callsign patterns, but I could be wrong.  Callsigns ending with a digit 
would use the last-most letter in the callsign, maybe?

I first thought of an even simpler algorithm, where the (first) digit in 
the callsign aligns with the last digit of the current minute, but then 
realized that most callsigns in a given area would end up with the same 
timeslot (at least the way calls here in the US are assigned).

Just thinking out loud, and knowing that simple is often a good thing...

David, KY7DR

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