APRS in Wisconsin The Automated Packet Reporting System by: Michael Martens, KB9VBR and Mark Rasmussen, N9MEA
Overview • Introduction • Protocol and Implementation • Software • Hardware • Network
APRS is: • A one-to-many, unconnected packet protocol. • A tactical protocol designed for local RF use. • A protocol with many reporting capabilities. • A protocol with SMS capabilities. • A protocol also adapted to the Internet. • A protocol with extensive flexibility built-in. • A protocol still under development.
Introduction • APRS, the Automated Packet Reporting System, is an open system that uses unconnected AX.25 radio packets to transmit and collect data. This data is usually overlaid on a map
Uses of APRS • Using GPS data to track vehicle location • Sending short, tactical bulletins and messages between stations • Transmitting data collected by a weather station
The APRS Network • Home stations • Mobile and Portable GPS enabled stations (trackers) • Digipeaters (Wide-area and Fill-in) • Internet I-Gates • Automatic Weather Stations
What is needed to begin • Computer with APRS software installed • Terminal Node Controller (TNC) • VHF transceiver and antenna • GPS required for mobile stations only
APRS Frequencies • VHF 144.39 MHz • HF 10.151 MHz LSB • Experimental work is being done on other frequencies.
APRS Raw Packet Originator Path Application KB9DED>APW251,W9SM-10*,WIDE4-4,qAo, N9SDL:=4457.01N/08938.76W- WinAPRS 2.5.1 -WIMARWAUSAU -251- Location Status
APRS Paths • WIDEn-N (ex, WIDE3-3) • WIn-N (ex WI2-2, keeps packets within the state of Wisconsin) • Named Path (W9SM-10, KB9VBR) • Relay, Trace (Obsolete, Do Not Use)
WIDE and WIDEn-N • Digipeaters acknowledge WIDE paths • Home stations should not set myalias to Wide • WIDEn-N is not the same as WIDE (WIDE3-3 is not the same as WIDE,WIDE,WIDE)
Named Paths • Most efficient form of message propagation • Only the station with the matching Alias will digipeat the message • W9SM-1, N9QIP-10, K9ABC-1
WIn-N • Keeps APRS Packets within a geographic location, in this case Wisconsin • Reduces APRS overload as packets won’t propagate beyond their geographic confines • Great for public service event stations (eg walks, parades, races, etc)
Best Path to Use: • In the Wausau area: W9SM-10, WIDE2-2 • If you are mobile: WIDE1-1, WIDE2-2 • If you don’t want your packets to leave the state WI2-2
APRS Real Time Propagation http://www.mountainlake.k12.mn.us/ham/aprs
SSID • Special Station Identifier (SSID) allows multiple stations with the same callsign to coexist on the network. • Home stations have no SSID • Digipeaters may use the ID -1 (W9SM-1) • Mobile Stations may use the ID -9 (KB9VBR-9) • Kenwood APRS radios may use -7 (WA9NBC-7)
SSID Suggestions No SSID - Home Station, Home Station running I-Gate.-1 Digipeater, Home Station running a Wide1-1 Digi, WX Digipeater-2 Digipeater [#2 or] on 70CM-3 Digipeater [#3]-4 HF to VHF Gateway-5 I-Gate (Not home station) -6 is for Operations via Satellite-7 Kenwood D7 HH-8 is for boats, sailboats and ships (maybe 802.11 in the future)-9 is for Mobiles-10 is for operation via the internet only-11 is for APRS touch-tone users (and the occasional Balloons)-12 Portable Units such as Laptops, Camp Sites etc.-14 is for Truckers-15 is for HF
APRS Software • WinAPRS/MacAPRS • UI-View • APRSDOS • APRSpoint • Other platforms include: Palm, Linux, Java
WinAPRS/MacAPRS • www.winaprs.org • Very easy to use • Uses USGS Tiger maps and integrates with Precision Maps from Undertow Software • Also uses old style APRSDOS vector maps.
UI-View • www.uiview.org • Lots of features, more complex interface • Handles plug-ins. Vibrant developer network • Uses raster maps. Integrates with Precision maps. Plug-ins for Street Atlas, Mapblast, and Tiger Maps
APRSDos • web.usna.navy.mil/~bruninga/aprs.html • The original APRS application. Development going back to 1992 • Very rudimentary maps • Has satellite tracking features, network utilization analysis, and direction finding support
APRSpoint • www.aprspoint.com • Easy to use, familiar Microsoft style interface • Integrates with Microsoft Streets and Trips exclusively
APRS Software All APRS software applications are shareware and require a registration fee for continued use. Registration fees range in cost from charity donation to around $100. Some applications may also require you to purchase a map package.
APRS Hardware • VHF Transceiver • Terminal Node Controller (TNC) • GPS for mobile operation
VHF Transceiver • Any 2 meter radio will work as long as it will work on 144.390 csq. You will need to make a cable to connect mic and RX audio to the TNC.
APRS Enabled Radios • Some radios have built in TNCs for direct connection to a computer or APRS interaction right on the display. Alinco DR-135 Kenwood D-700A Kenwood TH-D7A
TNC • The TNC, also known as a radio modem converts the digital information from the computer and/or GPS into audio tones. • The APRS network runs at 1200 baud • The TNC communicates with the computer via the serial port.
TNC • The most common TNC is the Kantronics KPC-3+ • TNCs can be purchased used on EBay for about $40-50. Kantronics TNCs will be higher in price. • Older TNCs work great for home stations, ex: AEA PK-12, MFJ 1270 series, KPC-3 • Tiny Trak 3 and 4 - Open Tracker 1+ and 2
Kantronics KPC-3+ • About $230 retail • Has a dual port that allows simultaneous computer and GPS connection • Great TNC choice for running an APRS computer in a vehicle Kantronics KPC-3+
Tiny Trak 4 and Open Tracker 2 • About $65-$100 retail • Has a dual port that allows simultaneous computer and GPS connection • Cheaper than a regular TNC but has limitations Tiny Trak 4 Open Tracker 2
Tiny Trak 3 and Open Tracker 1+ • About $32 or $33 (kit) - $42 or $46 (built) retail • Has a single port that only allows connection to a GPS • Cheaper than a regular TNC but it only transmits data Tiny Trak 3 Open Tracker 1+
Global Positioning System (GPS) • A GPS unit is required for real time mobile tracking • GPSs come in many different forms • Any GPS with NMEA output will work with APRS Garmin Etrex Legend Garmin Streetpilot
Home Station Equipment • Watching on RF • Radio • TNC • Computer • Watching on the Internet • Computer
Tracker Station Equipment There are two ways to send out your position when mobile. • Dedicated APRS system • Mic-E system
Dedicated Tracker Station Equipment • With computer • Radio • TNC (High end unit) • Computer • GPS • Without computer • Radio • TNC (simple unit) • GPS
Dedicated Equipment Pros and Cons • Pros • Can watch other units on map and send messages • Position is sent out at predetermined intervals • Separate radio system in the car in case your 2M voice radio dies • Separate radio infrastructure in case your repeater goes down • Could also be used as Winlink or Packet station • Cons • Another radio in the car • More 2M RF to interfere with your local repeater traffic • Higher cost because of more equipment
Mic-E Station Equipment • GPS • Cheaper Encode only TNC • Uses you normal voice radio, no extra radio
Mic-E Pros and Cons • Pros • Don’t have to install another radio in the car • Cheaper than the dedicated equipment way • Can use the cheaper encode only TNC • Cons • Can not track other units on a map • Can not send messages to other units • Position only goes out when you talk on the radio • Position on map could be very old because you didn’t talk on the radio • More expensive for the repeater owners • Won’t work on all repeater systems • No back-up radio if your voice radio fails • If the repeater fails, no one sees your position
Putting it all together • Mobile tracking unit with integrated computer. GPS Computer running WinAPRS Transceiver tuned to 144.39 KPC-3+ TNC
Putting it all together • Portable tracker box Tracker GPS Antenna Radio
Bike Mobile APRS Putting it all together Who could this be? GPS Antenna Radio/Tracker
Putting it all together • APRS Home Station- notice no GPS TNC Radio Computer
Digipeaters Digipeaters extend the coverage of the portable and mobile units much like a repeater but operating on a simplex frequency. They are usually located at a high location on a tower but can also be located at someone’s home to help fill in a certain area.
APRS Network • I-Gates are internet gateways that expand the reach of APRS worldwide. • An I-Gate listens to the local RF channel and relays the information into an APRS Internet data stream. • I-Gates also relay information from the Internet data stream to a local RF station
Benefits of I-Gates • Reduces RF network congestion • Increases the trackability of mobile stations • Allows RF access of weather service bulletins and alerts • Can set up an APRS station without a radio and TNC • Any APRS station can be queried at www.findu.com (map.findu.com/kb9vbr)
Weather Service Messages • The National Weather EMWIN data stream is injected into the APRS data stream. • Alerts and messages can be color coded on the APRS maps.