[aprssig] PPersistance and Slottime settings.

Bruce & Leigh Coates bruce.coates at sasktel.net
Fri Oct 28 07:24:28 CDT 2005


I posted this to the UIDIGI group but didn't get a lot of feedback so I'll 
try here.

I'm just preparing to replace a failed UIDIGI digipeater and am trying to 
figure out what would be a suitable setting for Slotime and PPersistance. 
Saskatoon, the home of the VE5BNC-3 IGate, has half a dozen highways that 
radiate out from it.  The idea is to set digipeater timing so that it packet 
tend to travel towards the central digi.

Here's how I think it works if two of my digipeaters hear the same signal 
from a station half way between them.  If this station uses a path of 
WIDE2-2, my hope is to have the outlying digipeat it first, followed by the 
central digi where it would stop.  What I'm trying to avoid is having the 
central one digipeat first and then every outlying digipeat the second hop.

Here are the timing parameters that I'm looking at.

Digi will use aggressive timing and will be more likely to be the first to 
digipeat.  This would be used on outlying digipeaters.
PPersistance = 255
SlotTime = 1

Digi will use more relaxed timing and will be less likely to be the first to 
digipeat.  This would be used by the digi in the middle of town.
PPersistance = 64
SlotTime = 10

First, am I right?
Second, should I care?
Third, is it worth trying to fiddle with the timing in the hope of 
optimizing things?

73, Bruce - VE5BNC 

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