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[aprssig] SAR + APRS

Robert Bruninga bruninga at usna.edu
Wed Aug 20 20:53:44 UTC 2008


> 1) [for SAR]  They want to utilize much higher beacon 
> rates on Mobiles/Portables.  To allow for good tracking 
> during a search. 

> 2) Due to the increased beacon rate (proposed 2minutes) 
> we think we should maybe use APRSALT frequency of 144.990mhz 
> (it is available in our area).

You could easily use one minute rates for a SAR as long as you
had less than say a dozen units.  If you have more units, you
need to use GPS slotting.  And being on a different freq would
definitely help.

It would be ideal if the trackers supported proportioanl
pathing.  With proportional pathing, you could set a 1 minute
rate local simplex direct so everyone would see all their
nearest neighbors in simplex range every minuute.   But those
back at the EOC or headquarters (1 hop) could see everyone every
other minute.  And those back at the state EOC (2 hops) could
see everyone every 4 minutes just to oversee what was going on.

> My main question is if we utilize 144.990mhz can 
> we somehow get these people out on 144.390mhz without 
> causing tons of traffic problems. 
  
With proportional pathing, and a cross-channel 144.99 to 144.39
digi, the alternate-channel info would cross over to 144.39
every other packet back to the base.  Or every 4th packet...
Depending on how you set up the digi calls and proportional
pathing.

See: http://www.aprs.org/newN/ProportionalPathing.txt

Bob, WB4APR





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