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[aprssig] Re: [ui-view] RE: APRS low-power-local ALT input channel>>144.34 ?

Robert Bruninga bruninga at usna.edu
Sat Sep 25 17:35:01 UTC 2004

APRS on 144.99 if available for local coordination:

I think what many people may not understand about this
proposal is how an alt-channel is different than 144.39.  
On 144.39 in a busy area, each DIGI hears the following:

1) A few packets per minute from a *few* Local users 
2) 20 to 40 packets per minute from surrounding DIGIs
3) 40 to 20 seconds of DIGI QRM (distant digis that hold off TX)
4) Lots and LOTS of collisions with no successful throughput

On an alt-input channel, however, the listen-only digi hears:

1) A few packets per minute from a *few* local users

It doesnt take much to conclude that the *few* local users
are better off on the alternate channel, and furthermore, that
there is absolutely no difference in their ability to hear
each other for collision avoidance on one or the other.  That 
is only a function of their geometry, NOT of which channel 
they are on.

It is a WIN-WIN situation all around.  This splitting of ALOHA
users among multiple input channels has been the primary
improvement mechanism for ANY Aloha network since they
were first defined in the 1960's.  It is fundamental to ALOHA
network design  Its time for APRS to consider it...

de Wb4APR, Bob

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