Introduction to APRS by Paul Toth K2SEC

APRS - Technology Made Fun!

What do you get when you mix computers with Global Positioning System (GPS) technology, weather instrumentation and Amateur Radio. The answer is APRS, the Automatic Position Reporting System.

APRS was born in the early 1990ís as the brainchild of Bob Bruninga, an instructor at the U.S, Naval Academy in Annapolis, MD. Bobís dream was simple: provide a means of tracking a moving object in real time using GPS technology and a wireless radio beacon. The GPS technology existed, the product of a satellite network launched over the previous two decades by the Department of Defense. This satellite system, using precise, cesium-based clocks could track stationary and moving objects on the surface and provide accurate information on the latitude, longitude speed, course and altitude of any object on the surface. The GPS receiver used to acquire the incoming signals from above was relatively small and inexpensive.

The wireless link needed to beacon an objectís position information was also relatively accessible to Bob. You see, Bob is an Amateur Radio operator, callsign WB4APR. Bob selected "packet radio" a mode for digital communications, to transmit the GPS information to anyone who wanted to receive it.

Bobís first real test for this technology was the annual Pilgrimage from the Naval Academy to Veteranís Stadium in Philadelphia. Using APRS and a model GPS/Ham Radio station, Bob tracked the movement of the Navyís mascot from the time it left the grounds of the Academy until it arrived in the City of Brotherly Love.

Today, APRS has expanded in popularity and in purpose. GPS units have gotten smaller and considerably less expensive. The radio and Terminal Node Controllers (TNC) used to covert the position information for transmission have also gotten a lot smaller. And thanks to two other computer and Amateur Radio enthusiasts, twin brothers Keith (WU2Z) and Mark (KB2ICI) Sproul, APRS is now available for DOS, Windows and Macintosh computer systems.

APRSí role has also expanded. Amateur operators now use APRS to beacon LIVE weather data to National Weather Service offices nationwide including WX4TBW in Ruskin, FL. APRS has been adopted as an "official" technology for the NWS SKYWARN Severe Weather Spotter program. Many ARES, ACS and RACES organizations are using APRS as an Emergency Management communications tool. A Shelter Management function has been written into the Windows and Mac versions of the software. Of course, hams using APRS also use this tool to track Bicycle Races, Walk-A-Thons, Parades, Hot Air Balloons and many other fun endeavors.

What do you need to use APRS? Itís simple. A computer (286, 386, 486, Pentium or Macintosh), a 1200 baud Terminal Node Controller (TNC), a 2 meter (144-148 MHz) Amateur Radio transceiver and antenna and APRS software. Of course to transmit using an APRS system, you will also need a Technician Class or higher Amateur Radio license. If you are simply interested in receiving APRS signals, a radio capable of receiving 144.390 MHz (the National APRS frequency) can be substituted for the Amateur radio receiver. And registered APRS users can now access the world via a TCP/IP connection on the Internet.

APRS software can be downloaded from the Tuscon Area Packet Radio Website http://www.tapr.org. Select the SIGS hotlink on the TAPR Home Page. Then select the flavor of APRS software you wish to download, DOS, Windows or Macintosh. Itís that simple! Mac and WinAPRS can also be downloaded from http://aprs.rutgers.edu

For help with APRS in the TampaBay area, contact Paul-K2SEC at k2sec@amsat.org, Demos-KR4US kr4us@amsat.org or subscribe to the APRSSIG on the Internet by sending your email address to listproc@tapr.org.

Click here for a WinAPRS screen capture showing a typical format for weather monitoring.

Editor's Note: Since this article was first printed there have been several additions to the APRS family. Brent Hildebrand KH2Z now writesAPRS+ which will allow the use of the Delorme Street Atlas program with APRS. Not user software per se but without APRSserve we could not do a lot of things. Written by Steve Dimse K4HG this program lies in the background doing some very hard work. Both of these authors can be contacted from our home page. Florida has so many APRS users we have our own mailing list in addition to the national one, please see our home page for subscription instructions.