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 Alba.
Byonics Tinytrak 4
Byonics MT8000
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.

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.

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on the sound card approach is here https://wcares.org/special-interests-3/aprs/aprs-raspberry-pi-virtual-tnc/ It's out of date but still good.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

Eventually, if I end up using one radio for receive and one for transmit, how do I isolate them? 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 - popular.

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.