I'm a ham, but haven't done a lot with APRS other than sending a few messages through the ISS. What do you mean by a Bluetooth TNC? Can you recommend a specific model that would work well with the D72A? I plan on using that HT for my efforts as well.
Les Rayburn, N1LF
You don't need a TNC Les because the D72A can output the positions through the USB port and if desired, via the socket serial port where a cable can be plugged in for off loading of Waypoints. The TNC I refer to is the Mobilinkd which one can use with any H/T: https://www.mobilinkd.com/tnc2/
You don't need it.
The D72a can be plugged into a Windows tablet via USB and just about any APRS tracking program can be used to get your rocket on a map.
If you don't want to use a tablet, get a serial cable like this: https://www.gpsgeek.com/products/in...h-d7a-tm-d700a-aprs-to-garmin-4-pin-round-gps
for a round port Garmin 60Cs or CsX which can be had used on ebay and open source maps can be used: https://garmin.openstreetmap.nl/
which are free.
Or use this cable: https://www.gpsgeek.com/products/in...-aprs-to-garmin-etrex-emap-geko-gps-receivers
to use with a very cheap Legend: https://www.ebay.com/itm/Garmin-eTr...185239?hash=item1a2616e897:g:i6IAAOSwdGFYqPH4
The Legend is very basic but I recall it allows basic point to point navigation to the rocket. The 60Cs(X) is a prettier display.
With this setup, you have a secure one wire connection to the handheld mapping GPS that tracks in realtime. You really can't save any of the data from the flight but it is a full featured mapping tracker I've used for years. Oh yeah, you can go home and download tracks with the Garmin software but you have to remember to change the Garmin communication protocol to "Garmin" or it won't work The handheld mapping Garmin GPS units are designed to be readable in sunlight whereas a computer
screen needs to be buried in a box to prevent glare. It can be done though. When I want something easy to carry without having to do a timely setup, this is system I use. One can tell the mapping GPS to "navigate to" the rocket waypoint and it will compute a navigation solution in realtime during the flight.
Once the rocket is down, it will take you to the last known position. If you don't get any readings once the rocket is out of range, I open the squelch from time to time on my D72 and if I can hear a "scratchy" APRS brrrrrraaaaapppp, I know I' be within range soon to decode a valid position.
Look in your D72A manual about connecting up an external GPS unit. You have to select that the waypoints are being sent to the jack and the Garmin 60Cs(X) has to have the communication parameters set up for NMEA in/out 4800bps and the D72A needs to have the port speed set for 4800bps too. Once that is done and you select external GPS on the D72A, it will use the Garmin for your local position which of course you can see on the map and it will display the rocket on the map. You can select the icon that gets displayed on the map as the Garmin doesn't generally display APRS icons. You can set your D72A to display the APRS altitude with the rocker switch so you know
how high MSL and your map for position. You can also scroll to different screens on the 60Cs(X) to a Heading Situation Indicator that will
give you a bearing to follow with an arrow and it will also tell you how long
it will take you to get to the rocket position.
Ten years ago this was just about the only portable way to GPS track but cost like close to $1000.00 with a D7A(g). Now the costs have come down with used equipment and it's a very nice way to track on a map in hand. I don't recommend buying a used D7A(g) as the units are so old I have two of them that the oscillators have gone out of spec and the receive frequencies are no longer accurate. They're deaf with lousy range for APRS tracking.
Practice getting your orientation out in the field as once your rocket is out of sight, the map can give you the direction to look to try to
get a visual on the descending rocket and the APRS altitude can give you an idea when your main chute event is to occur.
I call out direction and you'd be amazed people are expecting to see the rocket coming in based on wind groundspeed and the
winds aloft take the rocket in another direction. I've had you yell out to turn 180 degrees from where they are expecting the rocket to
come in. That's the nice thing about GPS tracking, one can get an idea what the rocket is doing in "out of sight land".
Glare is the big nemesis of tracking on tablets and laptops. Large laptops are hard to carry out in the field. They can be usable if
one is interested in recording data for later easier review and relegate it to a base station whereas one uses a hand held solution
to go recover the rocket. Kurt