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[aprssig] APRS SAR, continued; paths

Alan M. Fudge DVM pugacre at pacbell.net
Tue Feb 5 01:18:37 UTC 2008

Alan M. Fudge DVM

Foot Team:  El Dorado County Sheriff SAR 302
2008 Sierra West Training Officer
Ham Call:  K6PUG

Thanks Curt, Bob B, and Stephen for your replies.

On Feb 4, 2008, at 10:00 AM, aprssig-request at lists.tapr.org wrote:

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

- There is a mountain digi lower in the Sierras (Mt. Danaher) at the  
site of Fire antennas- put up by a USFS radio guy who is also a Ham.  
Otherwise not much up there.
>> 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.



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:


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 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>>

In additional to the operational management politics, I would think  
that all the 4WDs digipeating would be better- ground people drop  
into a canyon or behind a hill and they would be glad to hit at least  
whoever is in the area. And while the 4WD guys are pretty savvy,  
including the radios- these Kenwoods were purchased by our non-profit  
and then mod/programmed by a team member. They don't tend to change  
the settings (not unlike a public safety person). However with a  
convincing enough case to do so- it could be trained etc.

We actually have a portable digipeating station, currently in  
possession of a Mounted member, a programmer who works with Xastir  
and google mapping etc. and they have done some interesting training  
exercises. But I don't think the station has EVER been used in an  
active search, nor can we count on it showing up. We can always count  
on 4WDs to show up, if called out.

Then, the rules change in the far west of our county (closer to  
Sacramento)- where more population and infrastructure- our searches  
are split between High Sierra recreational and foothill recreational/ 
Alzheimers/child etc). So path settings closer to the metropolis  
might be different. I am just not sure that we could count on the  
daily changes.

But I will also review all the links (probably read most of them at  
least once before)- to make the case to lose the RELAY, WIDE.

And since this foot to 4WD "APRS radionet" has never been tested, I  
am not clear on what we can get by with. I just know even in the far  
west part of the county- away from roads and homes- you don't have to  
get out too far in public lands where the minitracker/HT Wide  
1-1,WIDE2-2 won't get out far enough to track on the internet vs.  
being on the main hwy.

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