Sunday, February 28, 2016

APRS on Raspberry Pi or Android Tablet

Before getting started here. I would like to thank Scott WZØW for the resource and idea he presented. It provided some new and fresh ideas regarding APRS.

What is APRS?

I think Wikipedia explains it well.

"Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time tactical digital communications of information of immediate value in the local area. In addition, all such data are ingested into the APRS Internet System (APRS-IS) and distributed globally for ubiquitous and immediate access. Along with messages, alerts, announcements, and bulletins, the most visible aspect of APRS is its map display. Anyone may place any object or information on his or her map, and it is distributed to all maps of all users in the local RF network or monitoring the area via the Internet. Any station, radio, or object that has an attached GPS is automatically tracked. Other prominent map features are weather stations, alerts and objects and other map-related amateur radio volunteer activities including Search and Rescue and signal direction finding."

I have used APRS for all except direction finding.. I might have to try that some day.. :)

I first got started with text over Ham Radio by playing with TNCs (Terminal Node Controller). This allowed for me to send digital text information over the local radio waves. it was cool and easy for the novice techie to understand. It was a lot like the old BBS systems I used to visit with my computer. Just over Ham Radio.

For you young folks a BBS was pre-internet days of computer techies communicating and sharing information with each other. You used a modem and a phone line to connect to other systems. Most BBS have moved on to least costly activities with the internet. Not to mention being able to reach a broader audience. A blog site is a great example of an old BBS. However, a BBS did not have a graphic interface like we do here on the web. (BBS was short for Bulletin Board System) There are still a few around today. 

Moving on to APRS on tablet..

As per discovery from reading Scott's site. I got myself a Mobilinkd device, much like Scott did. I found this device handy for two reasons.

1. It using an HT
2. Connect with it via Bluetooh. (less wires)

I have an old Kenwood TM-D700 which is one of the first mobile radios that came with a TNC installed to allow for APRS. Other than being installed in a vehicle, it is rather bulky to carry, and battery is heavy. Not very practical. A HT and a Tablet or Phone is quite a bit easier to carry. Gotta love technology.

Mobilinkd does have a setup process that they have generally documented. Took me a few tries to understand what they were wanting for the hardware setup to be. Also they have DCD setup by default. In their documentation they state that it needs to be on. It was not working with my tablet. But once I turn it off, everything was working fine. Following directions is good. but sometimes you gotta think out of the box. 

On both my phone and tablet. I have used APRS Droid on and off during the last couple of years. I have found it to be one of the better apps for APRS.

For us who are fans of the Raspberry PI. You can install some software named Xastir for APRS. You'll also need some additional blue tooth hardware for your pi.  A little USB adapter $5 - $10 can be found at your local tech store or Amazon. Xastir did not work for me. But you can still give it a try. You can refer to Scott's page, on how to get Xastir installed.

After trying Xastir, I felt really disappointed with the software. Its about 6 years out of date and leaves you wanting some much needed functionality.

The maps are out of date. So much so that if you select the wrong map from the options, you'll be stuck for about 1 minute on your screen from map to map. I was only able to get two of the maps working out of the several that are listed.

The software attempts to reach locations on the internet that are no longer available. (For example  The locations are where maps are / were stored. They are no longer there.

Once I was able to get my bluetooth TNC to work, software would still not transmit my packet information over the airwaves. I would hit the transmit now button, and nada! Receiving stations were just as bad. I would get garbage in the text, as if I had selected the incorrect baud rate for comms.

All in all, Xastir has a lot of catching up to do.

Xastir may have worked for other hams. But certainly not for my Raspberry Pi setup. My cellphone did much better than this.

Stepping back to Mobilinkd device. Of the three options I tried. There is only one device with any active GPS. Well, its not a real GPS, It simply gathers information from local systems to triangulate on your current position. So long as you stay within range of cell phone sites, your GPS function on your cell phone would work just fine. If you do manage to travel abroad and out into the boonies. The GPS on your phone will stop working the moment you loose your cell phone signal. Just something to keep in mind.

With a little trouble shooting. I'll have to say that the Mobilinkd device worked as expected. I feel its a good item to add to my Ham hardware collection.

73s for now..

Tracy - KD6VZQ