[aprssig] TH-D7 and Group Code

Robert Bruninga bruninga at usna.edu
Tue Mar 7 13:06:21 CST 2006

>>> "Herb Gerhardt" <hgerhardt at wavecable.com> 03/04/06 11:57 >I think you are not reading the manual correctly. 
> The group code refers to messages that the radio 
>will receive and display, it does not "filter" the
>received stations in the station list.  All received 
>stations will still be entered into the list for every 
>"good" signal that radio hears.

But thats not how it is supposed to work.  If SPCL
is set, then only other stations sending to that
call will be captured UNLESS they are sending in
Mic-E format (D7 and D700).  ALl of them will still
be included.  But they can be filtered by RANGE.
Set yoru RANGE to filter out any staitons out of the
range of yoru SAR, and it shold work.


I am not sure how to filter that listing to just your SAR teams other than
going to a different frequency.  Of course that will work giving you a
"private" APRS system but at the expense of not being able to utilize the
existing APRS infrastructure of your existing APRS Network and digi's.  You
would have to install temporary digis in your search areas.  That would make
things much more complicated.

Keep in mind, that if your teams use a mapping GPS like the Garmin V, then
the stations can be plotted at the real time location on everyone's GPS map.
You can then set the scale so that you can see the position of each SAR team
on the GPS topo or street map.  You can also measure the distance and
direction of each of the other teams from your location.  Not all GPS's have
this capability of plotting the stations the Kenwood APRS radio hears on a
real time map so you will have to check the capability of the GPS units that
are being utilized.  On the Garmin units, the heard stations are plotted as
Waypoints and only the position of the last heard position is shown on the
GPS screen.

Also by using tactical calls, like TEAM1, TEAM2, etc, it will make it easy
to find these plotted waypoints in the Waypoint list of the GPS since they
will all be grouped together.

So, what you want to accomplish can be done quite easily but on the GPS
instead of the radio.  You can control the distance of stations you want
plotted on the GPS as Waypoints by specifying a distance of say 10 miles in
your Kenwood radio, then only the stations it hears that are within 10 miles
of that radio will be sent to the GPS for plotting.

Also keep in mind that the APRS program that is run in Base Camp is the
important one that needs to show the location of each team so the IC can get
a better feel for where his teams are located.  The teams can then be told
to move to other positions via radio communications.  I don't think that
each team being able to know exactly where the other teams are located is
very important during a search since it will distract the searcher from his
search duties which is what he is really out in the field for.  My idea is
just to put a tracker into each of the SAR team's backpack and let the SAR
teams perform their normal search duties.  The main person should be in SAR
Base with a real time APRS computer program running and zoomed into just the
search area.  That way the other distant APRS station really do not deter
from you mission.

Please keep me informed as to how your group makes out in utilizing these
trackers during your SAR activities.  This to me is one of the few "real"
uses for APRS and trackers.  This was the reason I first got into APRS.
Curt and I will be giving a presentation at our WA SAR Conference in mid May
on the Integration of APRS into SAR Activities, so any info you can provide
to us would be appreciated.  It will be a Power Point presentation, so if
you have any good digital pictures or Power Point slide, they would be

Thanks and good luck,
Herb, KB7UVC
NW APRS Group, West Sound Coordinator
Our WEB Site:  http://www.nwaprs.info 

  -----Original Message-----
  From: aprssig-bounces at lists.tapr.org 
[mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Steve Sobodos
  Sent: Saturday, March 04, 2006 5:46 PM
  To: aprssig at lists.tapr.org 
  Subject: [aprssig] TH-D7 and Group Code

  I plan on using the D7's in search and rescue. I thought that putting SPCL
in the group code (Unprotocol), the D7 would only "Hear" the other stations
with the same code. I quote from the manual :"Enter "SPCL". You will receive
only APRS packets that include SPCL as a Group Code."

  The use in SAR is that the teams can see how close and what direction the
other teams are. The problem in Southern California is that there are very
many other stations and the list in the D7 gets so long it becomes quite a
pain to find the other stations in the list. I set up a couple of D7's with
the Group Code of SPCL but the D7 still hears everybody.

  What am I doing wrong? Is there another way to filter the D7 beacons?

  The Group Code does me no good in UI-View as it seems to not be supported
as a filter. I end using the callsign in the exclusions list in the form
"!TEAM*" to only include calls that start with TEAM.

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