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[aprssig] THOUGHTS ON RELIEVING APRS CONGESTION ON 144.39

Steven Heimann steven at nami.com.au
Thu Nov 18 09:11:31 UTC 2010


Bob




On Wed, 2010-11-17 at 13:32 -0500, Robert Bruninga wrote:

<snip>
> The number #1 problem with congestion on 144.39 is collisions on
> the inputs of the digipeaters.  The outputs of the digipeaters
> on 144.39 are not a problem, because they can hear the entire
> regions and hold off until there is a quiet instant.  If only
> digipeaters are outputting on 144.39, then the channel can carry
> FIVE times what it is carrying now.
> 
> So the goal is to move as many local stations *TX* to the local
> alternate channel.  All the locals will know it and so they will
> get immediately improved performance because they are TX'ing on
> a channel with no competition from ANY digipeaters or ANY out of
> area traffic.  This is a WIN-WIN way to do APRS.  Generally if
> 144.39 +600 (144.99) is available in an area, it makes a perfect
> local input channel for all locals.  They just have to remember
> to change to 144.39 simplex when they leave their area. 
</snip>

This strategy sounds neat and effective.  I am just trying to get my
head around the details and a practical setup.  I have had a look on
aprs.org for further information but can't find anything.  What is the
basis for the increase in capacity of five times?  Isn't the collision
problem still going to exist but just on the alternative input channel?

<snip>
> The local system still LISTENS for 1st-hop WIDE1-1 inputs on
> 144.39 visitors still get in perfectly and no change from the
> rest of the world.  But locals who want better performance for
> themselves (and hence, everyone else) will input on the
> alternate channel (Maybe 144.99).
> 
> Visitors to the area who want to improve their performance with
> a less congested input could also shift to the alternate channel
> (+600 like the locals).  He will know this is availablle by the
> BEACON from everyy digi in the area that is also listening on
> 144.99 input.  Their beacon will contain something like W2,
> MDn-N,alt 144.99 ... (this is for Maryland MDn-N digis)...
<snip>

Are you saying the WIDE2 digis listen on both frequencies?  Do the fill
in WIDE1 digis listen on 144.39 but pass the packet to the WIDE2 digi on
the second channel (144.99)?

Thanks for your insight.

Regards
Steven  VK2BOS




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