[aprssig] KPC3+ WIDE setup

Robert Bruninga bruninga at usna.edu
Sat Jan 31 14:04:06 EST 2009

>> BLT
>> 1 EVERY 00:20:00 START 00:00:00  (direct) DIGI-ID
>> 2 EVERY 00:20:00 START 00:05:00  (direct) VHF object
>> 3 EVERY 00:20:00 START 00:15:00  (direct) UHF object
>> 4 EVERY 00:20:00 START 00:10:00  (1 hop)  DIGI-ID
> 20 minutes is too long for a repeater object. 

We agree.  But maybe you are not noticing how these packets
interleave.  The number 1 packet is every 20 minutes and the
number 4 packet is also every 20 minutes, but they are the same
packet offset by 10 minutes, so the effect is a 10 minute "rate"
locally, and a 20 minute rate via 1 hop.  That is what we call
Proportional Pathing.  It updates the immediate direct area at a
higher rate and 1 hop further out at half that rate.  You have
to consider the interleaving to see how this works together.  

The normal settings for Proportional Pathing on a New-N digi
have BLT's of 30 and 60 minutes in the BLT commands, but the
result (due to the interleaved start times) are a local packet
every 10 minutes, a 1 hop packet every 30 minutes and a 2 hop
packet every hour.  But you never see a "10" in the list.  It's
the interleaving that makes it work locally at the 10 minute

>> ...[this improves] the timing somewhat.. 
>> instead of having the random walk of packets 
>> from 4 different timers as you do...
> I purposely made it random...seems many other 
> stations "schedule" their transmissions at 
> 10, 20, 30, ect minute intervals, starting 
> at 00:00:00 or the like.  This causes collisions, 
> delays, and lost data.

I agree completely for home stations.  Too many of the follow-on
clones ignored the fundamental randomness that is supposed to be
applied to all transmissions to avoid just this problem.  

But for DIGI's, the clocks in TNC's drift.  I doubt any two of
their one-sec packets would stay in sync for more than a day.
THen it would take more than 600 days for them to drift back in
phase again.  Or, you can change your offset to any start time
you like:

1 EVERY 00:20:00 START 00:01:11  (direct) DIGI-ID
2 EVERY 00:20:00 START 00:06:13  (direct) VHF FREQ
3 EVERY 00:20:00 START 00:16:17  (direct) UHF FREQ
4 EVERY 00:20:00 START 00:11:19  (1 hop)  DIGI-ID

This gives a direct repeater ID every 10 minutes and a frequency
object every 10 minutes (though the frequency opject alternates
between your UHF and your VHF repeaters) and then the 1 hop digi
ID every 20.

Anyway, its up to you and your area, but that's how proportional
pathing is possible on the DIGI's under the New-N.


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