APRS

Lots of info

http://info.aprs.net/

USBlink http://www.g4ilo.com/usblink.html USB sound card + VOX interface to PTT switch + HT

Some notes on available hardware

Kenwood TH-D74A handheld with built in GPS and APRS
Kenwood TM-D710A mobile with a UBlox GPS, installed in the Yaris.
Kenwood TM-271A mobile which has a data interface buried inside.
Byonics Tinytrak 4
Byonics MT8000
My phone, a CAT S22.
Several abandoned Android phones

Other 2M HTs including two ICOM F11s which have no external power connectors (battery only) and a Kenwood TH-F6A

Breaking this all down I need a receiver to work as an iGate with a Pi 3, and a transmitter to implement a Digipeater.

The cellphone APRSDroid solution appeals to me too, later maybe. https://wcares.org/special-interests-3/aprs/aprs-hardwired-cell/

Step one is the iGate as a data sink since I can already use the Kenwoods as sources. There is no iGate close to my house. So that is my first need.

APRSDroid

I put a recent copy of APRSDroid on the CAT S22 phone and I've been playing with it in standalone mode, feeding location up over the phone's own data link.

It works, here is a screenshot of my walk to the post office today.

iGate on a Pi

Two common approaches (1) SDR (2) sound card + HT. I have a cheap USB sound card and a RTL-SDR on order now. The RTL-SDR appeals to me the most but it's receive only, so it can't function as a digipeater.

A good article on the sound card approach is here https://wcares.org/special-interests-3/aprs/aprs-raspberry-pi-virtual-tnc/ It's out of date but still good.

This is good too https://godseyonline.net/raspberry-pi-direwolf-digipeater-igate-soundcard-version/

Sam Buchanan's notes: http://www.vansairforce.com/community/showthread.php?t=30180

RTL-SDR + Direwolf http://km6zpo.com/how-to-build-an-aprs-igate-with-rtl-sdr-sdr-direwolf-and-pinpoint-aprs-for-windows/

Eventually, if I end up using one radio for receive and one for transmit, how do I isolate them? This is what duplexers are for, but not when you have two radios operating on the exact same frequency. Why would I do that anyway? Just use one radio. One way is two antennas, and pull the receiver input to ground when transmitting. http://www.ok1rr.com/index.php/technical-topics/39-yet-another-front-end-saver

Direwolf build

sudo apt install git-all libasound2-dev cmake -y
git clone https://www.github.com/wb2osz/direwolf
cd direwolf

Then read and follow instructions in README.md, basically

git checkout dev
mkdir build && cd build
cmake ..
make -j4
sudo make install
make install-conf

Xastir - this is a desktop app so I am not looking at it.

Argent Data Systems

Products for amateur radio including APRS applications

http://www.argentdata.com/

2m Transmitter MX146 from SRB -- This is a 500 mW transmitter, $70

OpenTracker+ is open source / open hardware and uses a Motorola MCU.

Tracker2

These are controllers, connects a data stream (eg weather or gps) to a Kantronics TNC.

They now have a Tracker2 with a 5 watt 2m radio now. T2-301 $229

Byonics

http://www.byonics.com/

Maker of TinyTrak controllers and MicroTrak transmitters

Purchased way back in 20 Aug 2010 and tossed into a "future projects" box. I got a TinyTrak4 controller kit and a MicroTrak MT8000 which is like a TinyTrak3 with a built in 8 watt transmitter.