APRS

I have recently begun dabbling with APRS (Automatic Packet Reporting System) after attending Dayton and visiting the Byonics booth. A while back I built a Byonics Pocket Tracker for a ham friend but knew absolutely nothing about APRS at the time so when I saw the Byonics booth at Dayton I was curious. My main interest was the GPS receiver which I wanted to learn about to incorporate with a 10 meter synchronized beacon. Well after learning a liitle bit my curiosity was peaked and I had to build myself an APRS system.

My first step was to learn a little about APRS and how it works.

The follwing info was found at www.aprs.org

APRS is an amateur radio based digital communications system for local, tactical, real-time exchange of information among all members of a net, including map based displays for situational awareness. It was developed by Bob Bruninga - WB4APR.

APRS is used to transmit real-time information such as messages, bulletins, announcements and the locations of any stations or objects via amateur packet radio protocols. Real-time reporting of station position for mobiles is facilitated using the Global Positioning System. APRS is capable of transmitting a wide variety of data including weather reports, short text messages, radio direction finding bearings, telemetry data, and storm forecasts. These reports can be combined with a computer and mapping software to show the transmitted data superimposed on a variety of map displays.

Each symbol on an APRS map can display many attributes discriminated either by color or other technique. These attributes are:

Moving or fixed
Dead-Reckoned or old
Message capable or not
Station or object
Own object or other station object
Emergency, priority, or special

In its most widely used form APRS is transported over the air using the AX.25 protocol at 1200 baud Bell 202 audio frequency-shift keying on frequencies located in the amateur 2-meter band (North America 144.390 MHz, Europe 144.800 MHz, UHF: US Nationwide Proposed: 445.925). An extensive digital repeater, or digipeater network provides transport for APRS packets on these frequencies. Internet gateway stations (IGates) connect the on-air APRS network to the APRS Internet System (APRS-IS), which serves as a worldwide, high-bandwidth backbone for APRS data. Stations can tap into this stream directly. Databases connected to the APRS-IS allow web-based access to the data as well as more advanced data mining capabilities. For a view of APRS maps on the web click HERE

I built the TinyTrak4 by Byonics and it seems to work very well. Build time was about 1 hour and the instructions were simple to follow. After you are finished putting the TT4 together you need to load the firmware using Terraterm software.

Programming with TinyTraker4 Config software was fairly straight forward once you get a basic understanding of the path configurations.

WIDE1-1, WIDE2-2 (Will produce three hops and will take advantage of home fill-in digis. Use in rural areas with low APRS activity only.)

WIDE1-1, WIDE2-1 (Will produce two hops and will take advantage of home fill-in digis. Use in busy urban and suburban areas.)

WIDE2-2 (Shortest path string. Produces two hops by directly using two high-level digis. Will work almost anywhere but especially recommended in the American west where high-level digipeaters are really high-level; i.e. on mountain tops thousands and thousands of feet above users, and can easily be reached directly without the help of home stations.)

I am using my Yaesu VX-1R for the radio and one thing I have noticed is that many APRS digipeaters can be hard to hit without at least 10 watts output. When using my Yaesu FT-7800 I have much better success getting heard than with the VX1. I used a friend's Yaesu VX-5R with the TinyTrak4 and had a better success rate but still not as good a performance as the FT-7800.

For cable wiring diagrams for these radios see Yaesu HT and Yaesu Mobile

Here are some PC software applications for APRS:

AGW Packet Engine/AGWTracker Windows APRS Soundcard Program.

UI-View is a Windows APRS program

I have enjoyed experimenting with APRS and still have alot to learn and hope to gain a better and more full understanding of the potential of APRS in the future.

To see a list of Digipeaters in the US go HERE

For more information on APRS visit http://www.aprs.org/