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[aprssig] APRS SAR, continued; paths

Bob Bruninga bruninga at usna.edu
Tue Feb 5 04:27:27 UTC 2008


SAR ALIAS:

Someone in the last year told us about how all their DIGIs support the alias SAR.  I can't remember how they said they used it, so I'd like to hear if their ideas are the same as the ones I was proposing below..

original message:
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What we need is a way for the 4WD Mobiles to digipeat only the HT's, but for the HT's to still be heard by all the digipeaters.  You might consider the next option IF and ONLY IF, you have control over ALL the digipeaters in all areas where you may be required to operate:

SPECIAL SAR CONFIGURATION:

IF-(and-only-if) you can set up all DIGIpeaters in your
operating are area, then consdier this:

1) Add SAR to the UIDIGI alias list in all DIGIS
2) Put SAR in the UIDIGI alias list in all 4WD Mobiles
3) Set DIGIPEAT ON in all 4WD mobiles
3) Set path in all HT's as SAR,WIDE2-2
4) Set path in all 4WD's to WIDE1-1,WIDE2-1

This lets the HT's digipeat via all DIGIS and also via all 4WD's but does not have the 4WD's mobiles all digipeating via each other.  And this way, you can leave the 4WD's configured for digipeat all the time without any penalty.

I am open to comments if this is not viable.  But it seems like a pretty good approach to me.  But then you have to get the participation of all the digipeater operators in your plans.  Now, I did set the HT's above to a 3 hop path.  This assumes that most of the time, they are not on the air, except when they are out in the field and will most often be digipeating the first hop via the 4WD's.

You can fine tune the nuber of hops according to your area.  The way this works, is that the first hop of SAR will be digipeated only by those digipeaters with that alias.  They will do callsign substitution so that you can see what was the first hop.  The only down side is that if the HT is in view of a DIGI and a 4WD at the same time, then an extra copy of the packet is generated and this adds somewhat to QRM.

But if say a SAR event is going on in the immediate area of a
mountain DIGI, and these dupes are a problem because all the
HT's can also hit the digi direct, then it is a simple matter of asking the 4WD drivers to set their APRS menu DIGIPETER to OFF.

Bob WB4APR




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