APRS in Wisconsin

The Automated Packet Reporting System

by: Michael Martens, KB9VBR andMark 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 Data Flow

APRS Frequencies

• VHF 144.39 MHz

• HF 10.151 MHz LSB

• Experimental work is being done on other frequencies.

APRS Raw Packet

KB9DED>APW251,W9SM-10*,WIDE4-4,qAo,

N9SDL:=4457.01N/08938.76W- WinAPRS 2.5.1

-WIMARWAUSAU -251-

Originator Path

Location

Status

Application

APRS Paths

• WIDEn-N (ex, WIDE3-3)

• WIn-N (ex WI2-2, keeps packets within the state of Wisconsin)

• Named Path (KC9NW-10, KB9VBR)

• Relay and 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

• AB9PJ-4, 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-1, WIDE2-2

• If you are mobile: WIDE1-1, WIDE2-2

• If you don’t want your packets to leave the state WI2-2

How APRS Packets Propagate

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 audio, RX audio, and PTT 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 TH-D7AKenwood D-700A

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 Streetpilot Garmin Etrex Legend

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 your 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.

Computer running WinAPRS

Transceiver tuned to 144.390 csq

KPC-3+ TNC

GPS

Putting it all together

• Portable tracker box

GPS Antenna

Tracker

Radio

Putting it all together

• Bike Mobile APRSGPS Antenna

Who could this be?

Radio/Tracker

Putting it all together

• APRS Home Station- notice no GPS

RadioTNC

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.

Digipeaters in the NE District

Estimated APRS Coverage to a Mobile

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.

APRS and the Internet

• UI-View radar plug-in superimposes NWS radar data onto the APRS screen.

• WinAPRS has a similar feature.

Weather Stations

You can also send out your local weather information if you have the right equipment.

• 2M radio on 144.390

• TNC

• Weather Station

• Possibly a computer

Weather Information

APRS Satellites

• PCSAT2 is the second generation APRS satellite

• PCSAT1, launched in 2001, is no longer fully operational

• PCSAT2 launched August of 2005 has returned to earth with STS-115 in 2006

• The ISS is capable of digipeating APRS when the radio is not used for other activities.

APRS Books

• APRS, Moving hams on Radio and the Internet

• A good basic introduction to the mode

• OUT OF PRINT• ISBN 0-87259-916-7

APRS Books

• VHF Digital Handbook

• Covers APRS, Packet, D-STAR, and more

• 2008 printing, $19.95• ISBN 0-87259-122-0

For Additional Information

• Wisconsin APRS discussion group: groups.yahoo.com/group/wisconsinaprs

• web site: http://wisconsinaprs.net

• KB9VBR APRS page: www.kb9vbr.net

• Michael Martens: kb9vbr@wvraclub.org

• Mark Rasmussen: n9mea@wisconsinaprs.net