[aprssig] TH-D7 and Group Code

Steve Sobodos steve at scsvideo.com
Sun Mar 5 13:59:45 CST 2006

Well we had an urban search training deployment this morning and everyone in the command post were impressed with APRS. I had enough hardware for three beacons, two backpack and one vehicle. We had three "lost people" with one bloodhound tracking each. We teamed with bicycles and vehicles to hasty search based on the DOT and location of the bloodhounds. The CP watched the hound (actually the handler, me) on the real-time APRS monitor and re-vectored the hasty team ahead of us as we made turns etc.

The Bloodhound trackers are a hydration pack with the Garmin Etrex GPS on the front strap and the TH-D7 on the backside with a gain antenna. The command post is using UI-View/Precision Mapping with the exclusions enabled for !TEAM* which shows only our teams. We pre-loaded the laptop with aerial photos and topo maps for underlays. You can check out the history on FINDU to see where we were. TEAM1 was a vehicle and TEAM2 & 3 were on foot behind the dogs. 

Getting to your reply, I had hopped that the manual was being literal when it said the TH-D7 would only 'receive' stations with SPCL. I agree the CP is the most important and filtering is easy there. I just could see a scenario where we might ask a team to go find another that had gone off the air (voice and APRS) and the team could track using the D7 display to the last beacon from the other team. As for the waypoints in the GPS, we tried that but every beacon in Southern California was in the list and swamped the memory. The 10 mile limit would help that, we will try that next time.

I agree with you, SAR resource management without all the voice radio traffic is a great goal. There have been times we have been in a wide area wilderness search and every 5-10 minutes the CP is calling teams for GPS UTM coordinates, which are read back to verify, then hand plotted on a map.

Steve Sobodos
Orange County Sheriff's Department
Search and Rescue Bloodhound Team
"Sometimes, the light at the end of the tunnel is accompanied by bloodhounds."

  ----- Original Message ----- 
  From: Herb Gerhardt 
  To: Steve Sobodos ; TAPR APRS Mailing List 
  Cc: WE7U Curt Mills 
  Sent: Saturday, March 04, 2006 8:57 PM
  Subject: RE: [aprssig] TH-D7 and Group Code


  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.

  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 appreciated.

  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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