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[aprssig] Thinking Out Loud About... Digipeaters

Tom Hayward esarfl at gmail.com
Thu Jul 23 17:15:39 UTC 2009


I think the best temporary digipeater configuration for a special
event would be "SAR7-7", as Curt WE7U has hypothesized. This scheme
was devised so that every Search And Rescue tracker would also be a
digipeater, forming a mesh network of many digipeaters. The trackers
would use a path of WIDE1-1,WIDE2-1,SAR7-7 and be configured to
preemptively digipeat SAR7-7.

The only tracker that I'm aware of capable of preemptively digipeating
is the Argent Data Systems Tracker2
(http://www.argentdata.com/products/tracker2.html). Each of your
digipeater stations would need one of these or another capable
digipeater software such as digi_ned.

The WIDE1-1,WIDE2-1,SAR7-7 path (SAR is arbitrary, you could use RACE,
EVENT, etc.) gets you into the standard APRS network when available,
but also allows for many hops in your temporary event infrastructure.
When every station/tracker is a digipeater, as long as every mobile is
in range of at least one other mobile, packets will be digipeated up
to 7 times within your temporary infrastructure.

Curt used to have a webpage that described this better, but I wasn't
able to find it.

Tom KD7LXL

On Thu, Jul 23, 2009 at 8:45 AM, Tim N9PUZ<tim.n9puz at gmail.com> wrote:
> Our local group here supports a couple of large public service events each
> year where under normal conditions APRS coverage is poor to non-existent in
> some areas. We have used it with good success to do vehicle tracking but we
> would like to start equipping rest stops and check points with full stations
> so we can do tactical messaging.
>
> To date we have added temporary digipeaters in the area and ended up with
> good coverage. We set them up more like a normal digi and did not use the
> WIDE1-1 as if they would be fill-ins. We are in rural Illinois so there was
> not a big metro area being trashed.
>
> The temporary digipeaters typically only have antenna heights of 15-30 ft or
> are in a vehicle left parked on top of a bluff or other high point for the
> day. The tougher of the two events used 3 of these digis this year and there
> were still areas that were not covered. Adding more are possible, we just
> aren't sure of the best way to configure things. These same areas were
> problematic for voice comms as well--repeater coverage isn't good.
>
> So,... the question becomes would a good configuration be for setting up
> temporary digipeaters with low antennas? I imagine with the antenna height
> constraints the temporary would not be any different than if we wanted
> permanent coverage in this same situation.
>
> Thanks,
>
> Tim, N9PUZ
>
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