1. APRS - Automatic Position Reporting System
Amateur Packet Radio and the Global Positioning System
Intro: Ham since ’76 as a Novice WB0SBR. Got General Class in ’85 at 13 wpm N0AGX and upgraded to Extra in Became interested in digital radio in ’03 and became interested in APRS the beginning of ’04. Although only becoming active in APRS for a short time I am qualified to call myself an expert in APRS using the definition of Niels Bohr, a Danish physicist. “An expert is a man who has made all the mistakes which can be made in a very narrow field.” APRS is an amateur radio service utilizing packet radio technology used to disseminate live data to everyone on a network (radio and/or computer) in real time. Coupled with the global positioning system, it allows radio amateurs to automatically display the positions of radio stations and objects on a personal computer.
Don Downs, N0AGX

2. Elements
The system is composed of the following elements: Global Positioning Satellites, land based Global Positioning Systems, Mobile & Stationary transceivers, repeaters, and internet gateways. Unlike packet radio, the transmission are not “connected”. In other words all stations are able to receive the signal and repeat it, ensuring a wide path for the signal to reach its desired destination. The signal is actually limited by the number of hops it makes by the originator.

3. Signal Path
Digipeati’ng is the backbone to the reliability of APRS to reach others. Any station is able to rebroadcast the packet creating a wide coverage pattern. In general normal radio propagation provides coverage using three hops from south of Minneapolis, north to Hibbing – courtesy yours truly, west to Grand Rapids, and east to central WI.

4. Extended Radio Coverage
On extraordinarily good days, stations can be heard down into Iowa and up into Canada. The expansion of coverage due to atmospheric conditions tends to favor North and South rather than East and West.

5. System Configurations
There are a number of possible configurations depending on your needs and available equipment. Some units are self-contained comprised of the radio, GPS and TNC. A stand alone unit whose sole purpose is to announce its presence – a node - can be put together in which case the GPS becomes optional. The GPS is only necessary for other than stationary. By adding the digipeating function or digi, the system can be used by other stations as a hopping point. By adding the optional computer monitor, the location of the other stations in the system can be observed on the map.
Optional

6. Packet Radio Basics
The TNC performs the functions of encoding and decoding the digital signals as well as controlling the transceiver. This same function can be accomplished by software using the soundcard – eliminating the need for a TNC.

7. Live Data Via APRS Tracking by Latitude & Longitude Weather Conditions
Object Location
Text Messaging
Event Coordination
DX Reporting
Some examples of data sent over the APRS network are shown here.

8. Live Data Via APRS Tracking by Latitude & Longitude
A mobile or portable station can be tracked on the map as it travels across the country as shown by this truck traveling along I10. The ability exists to zoom in on this tracked station down to street level. Recently a friend of mine who runs APRS made a trip to Missouri. I was able to track him all the way into MO using a combination of radio and IGates. By itself this may seem to be no more than a high tech PAC Man, but by combining it with Echo Link – the two meter internet connection, I was able to determine his location and check into the local repeater and carry on a conversation.

9. Live Data Via APRS Weather Conditions
Station weather conditions can be transmitted for real time display of wind speed, direction, gusts, barometric pressure, temperature, dew point, wind chill, and precipitation with the use of a weather station. Weather data gathered in this manner can be registered with the National Hurricane Center as part of the Citizen Weather Observer Program. Data from non-amateurs appear with a unique identifier prefixed by CW. This data is used to provide weather trends to help validate prediction models. Isotherms help identify storm front locations.

10. Live Data Via APRS Object Location
Objects can be created to show locations of special events such as here – the Mesabi Wireless Ham Club meeting.

11. Live Data Via APRS Text Messaging
Text messages can be sent by radio link or over the internet through IGates – stations porting RF to the internet. messages are also transferred through IGates.

12. Live Data Via APRS Event Coordination – Grandma’s Marathon
Events requiring spatial coordination such as tracking progress of runners or location of resources is ideally suited to APRS. The Duluth amateurs provided communication services for Grandma’s Marathon tracking the position of lead and lag runners as well as dispatching medical assistance. Here a motorcycle outfitted with APRS is being tracked to provide information to the race coordinators on the position of the lead runner.

13. Live Data Via APRS DX Reporting
By requesting the station to identify the furthest station heard directly (DX), an idea of propagation conditions can be determined or a signal report of one’s own station.

14. Making Your Station APRS Capable
Technician Class or greater
2 Meter transceiver operating simplex on MHz
TNC or computer Sound Card
Mobile operation requires GPS
Computer or compatible radio
APRS Software or compatible radio
Making your station APRS capable is relatively easy. A GPS is only essential for mobile applications. The basic software can be obtained free.

15. N0AGX – 2 Mobile APRS Station
My mobile APRS station. A laptop computer running with a sound card, Radio Shack HTX202, and Garmin 45 GPS. A separate scanner radio is located below the computer. Transmitter keying is accomplished via a home brew MOSFET switch through the printer port.

16. APRS Implementation Tracking by Latitude & Longitude
Weather Conditions 
Object Location 
Text Messaging
A practical application of APRS’ capability to transmit live data is in the spotting of severe weather as part of the National Weather Service’s Skywarn program. This application of APRS utilizes the major features as previously discussed plus (hence the blue plus signs) enhancements that I will cover in this next section. This Skywarn program utilizes volunteer spotters to report weather conditions to NWS and is affiliated with the local amateur community. As you probably aware, locating the position of your spotters is crucial to both keeping track of who is out there and where they are as well as locating the precise position of weather observations. Which is done nicely with APRS’ tracking capability. Locating a spotter either automatically or by creating a stationary object to represent the spotter’s location is a task suited to APRS. Not only is the information useful to the net controller, but to NWS as well who is monitoring its APRS display.

17. APRS Implementation Weather Conditions 
Severe weather warnings are generated by the National Weather Service and are posted on the APRS internet servers. These area warnings are then decoded by an APRS station with graphic capabilities and the watch or warning area is displayed on the map showing the affected areas. This graphic display represents a severe thunderstorm watch associated with high winds and hail that moved through Northern Minnesota on May 9, Note the yellow bordered boxes. This information is IGated to RF and is available for display for spotters in the field. If the spotter is in the affected area, he/she should be highly observant or seek cover. As the storm moved through the area, periodic weather updates were issued effectively moving the areas of concern across the area in a easterly direction. I have this storm movement recorded and is available for a dynamic demonstration after the meeting.
Note the Citizen Weather Observer at the top of the screen identified by the CW in the blue dot.

18. APRS Implementation Weather Conditions 
The NWS bulletins are available for an area of concern bordered in red. Here a poke of the mouse brings up the associated weather bulletin providing details of the warning. During a recent watch in our area in which the weather net was activated, a spotter asked if the watch was still active and if he was in it. A quick glance of the watch border and the NWS bulleting allowed me to quickly respond to the spotter’s inquiry.

19. APRS Implementation Object Location 
The reason for weather spotters is to assist the NWS locate cells of strong activity that are otherwise invisible to radar. Earlier we had covered the ability of APRS to create objects. Here we create a “Skywarn Object” that represents a possible wall cloud by triangulating the sightings of two spotters whose location is known through the tracking feature of APRS. This object is then broadcast to the NWS with observations over the weather net.
The present status of the APRS implementation with NWS in our area does not fully utilize these features at the present time – due in part to the level of individual activity. However, it is anticipated that over time as APRS becomes more widely spread these features will be utilized to their full extent.

20. The future of APRS On the Range
Recent Additions
Bemidji
Thief River Falls
Atkin
Anticipated Additions to WD8RFS system
Mitrek 100W w/preamp - “A Hot Receiver”
Just in the six months I have been active in APRS, I have seen an increased number of APRS stations spring up in the area. One of the more heartening developments is the rapid growth out West along the ND/MN border. It also appears that Dave will be adding capability to his system to support APRS.

21. Further Information and Resources
Groups
Agassiz APRS Group
APRS Software
Internet APRS Maps / Weather
Additional information and links to downloadable software are available through the resources identified on this slide.