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[aprssig] Beacon settings for SAR HT's

Robert Bruninga bruninga at usna.edu
Mon Feb 4 17:25:55 UTC 2008


In the following discussion, I will use the originators term of
"4WD" to mean the specialized 4 wheel drive SAR vehicles.  This
distinguishes them from any other mobiles that also might be on
the air in the area...

> I have my Mini-tracker set for Wide 1-1,Wide2-1

I assume you mean WIDE1-1,WIDE2-1.  The added space would not
work.

> and my MT1200 in portable mobile (Yaesu) box set for Wide 1-1,
2-2

I assume you mean WIDE1-1,WIDE2-2 here also.. This is a 3 hop
path that might be excessive in most areas, but maybe your area
is very remote...

> I note the HTs are set for RELAY,WIDE.

That was the default 10 years ago when those HT's first came
out.  You should change this to WIDE1-1,WIDE2-1.

> [To have the] 4WD continue to comm APRS 
> (among themselves, command post and to 
> internet) in mostly rural county AND to 
> have them serve as digipeaters for the HTs, 
> what settings would be optimal.

TWO POSSIBILITIES:

SIMPLE ONE:  In the D700's set UIDIGI to WIDE1-1, and set
DIGIPEAT OFF.  Then only turn DIGIPEAT ON when you have a
specific need for a particular 4WD to serve as a digi for
handhelds in its area.  If you leave it on, then all the mobiles
will digipeat each other all the time, and there will be just
too much QRM most of the time.

What we need is a way for the 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 [thought] the TH-D7 also could digipeat..

No.  It cannot.

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 firs
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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