Running APRS on Raspbian Linux

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By Even, KJ7BRE, Guest Speaker 6-10-19

SOFTWARE & HARDWARE
-Radio (Regtivis RT-23) (Baofang works fine)
-Laptop (Old windows Laptop with Raspian Desktop)
-Xastir and Direwolf Software Installs
-USB GPS (Buy Here)
-Baofang APRS Audio Cable (Buy Here)
-Headset Audio To Mic Speaker Audio Adapter


APRS is a fun part of the Amateur Radio Hobby. I took an old laptop that my grandparents gave me and put raspian linux on it. The software im using is Direwolf (Info Here) and Xastir (Info Here). Direwolf runs all the Audio TNC stuff and generates / decodes the APRS packets. Xastir connects to the direwolf through a local on board interface conection. Xastir adds the ability to easily change settings in Direwolf and view stations that you recive on a map.

Xastir has the ability for you to easily add items to your map for you to manage and transmit. It also allows you to send/recive messages. You can use this same setup to transmit your weather data onto the APRS system using the serial connection to your weather station. Though I have never expermented with that because I dont own a weather station with a serial port.

Transmitting wise, there is NO PTT line. The PTT is done on the radio using the VOX feature. Theirfor when a packet is sent, the radio hears audio so it starts transmitting. When your radio is on VOX, set the VOX delay to be as short as possable. Also be sure to have the senstivity cranked up. For a Baofeng, VOX level “1” works great! If needed, direwolf is able to send a tone before transmitting to allow sime for the VOX to key the transmitter. How to do this feature can be found out on the Direwolf user manual.

To explain how this works, im going to split the software in to 2 sections and the hardware into 1…

-Software “Direwolf”
Direwolf is the linux based program that takes the audio card and uses the headphone and mic jacks to TX (send) and RX (Recive) the APRS Packets. This software works as a standalone software but can be bundled with Xastir. Direwolf has the ability to manage GPS data coming from the GPSD system. It has the ability to create a digipeater and igate using the existing downloaded software package. Direwolf has no GUI but does show the raw and decoded incoming packets. It also shows the transmitted packets. This is shown in the termnal window you would have used to start and run the program.

-Software Xastir
Xastir works great if you just want to RX and TX packets over the internet insted of the radio. If you have an internet connection, you can see all stations recived by an igate. When bundled with Direwolf, the software can RX and TX over the radio. Xastir also acts like a GUI for Direwolf, allowingyou to change propertys like TX invertals and station symbol .ect. Xastir is connected to Direwolf over a local connection. Xastir looks to see if direwolf is running on startup of the Xastir software.

In order to allow this, you have to go to to the “interfaces” tab in the Xatsir software. Add an interfacem and chose the one with the callsign “WB2OSZ”. This is also where you would add your GPS. To add GPS to your station, be sure your GPS is connected to your device and all proper drivers are installed. If you use THIS GPS (the one listed in the parts list) the you will NOT need any drivers. Add an interface called GPSD. There is more info about how to do this on the Xastir and Direwolf pages.

-Hardware
The radio I used is a Regtivis RT-23. This radio is essentially a nice Baofang. From that, there is a cable that goes from the baofang style connector to a 2.5mm male headset connector. The cable is spectially made and can be ordered off Amazon using the link in the parts list in the left sidebar of this page. The GPS is a little Mag Mount USB GPS I also ordered off amazon. The computer is an old Windows XP laptop that I put Raspian Desktop on.

You may have seen this setup in person at the Amateur Radio Relay Group booth at SeaPac 2019. I also talked about this project on the Linux User Net on 6/9/2019. Thanks to KC7MM for the opportunity to present this project on the Net.

Reference Link From Evan Vander Stoep, KJ7BRE
https://kj7bre.arrg.org/project/aprslaptop.htm

Even, KJ7BRE also serves as a Net Control Station every Monday on the ARES District 1 Net locally from 7:30-PM-8:00PM on the linked K7RPT Repeaters, Our primary repeaters are the 147.32, 442.325, 444.125 and 147.04 megahertz linked repeaters all having a 100hZ tone.


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