APRS

APRS (Automatic Packet Reporting System)

Table of Contents

What is APRS?

APRS (Automatic Packet Reporting System) is a digital communications system developed by Bob Bruninga (WB4APR) that uses amateur radio to transmit real-time tactical information. It combines GPS positioning, radio communication, and the internet to create a versatile information network.

Key Features

  • Real-time GPS tracking of stations, vehicles, and objects
  • Two-way messaging between stations
  • Weather station data transmission
  • Telemetry for remote monitoring
  • Internet gateway (APRS-IS) for global connectivity
  • Emergency communications during disasters
  • Event coordination for marathons, races, and public service events

APRS vs Traditional Packet Radio

FeatureAPRSTraditional Packet
PurposeTactical real-time informationMessage passing
NetworkConnectionless broadcastConnection-oriented
DataPosition, weather, statusGeneral data/messages
InternetIntegrated (APRS-IS)Limited
MapsBuilt-in visualizationNot standard

How APRS Works

Basic Components

  1. TNC (Terminal Node Controller) or Sound Card Interface

    • Converts digital data to audio tones (and vice versa)
    • Examples: TNC-X, Mobilinkd TNC, Direwolf (software TNC)

  2. VHF/UHF Radio Transceiver

    • Typically operates on 2-meter band (144-146 MHz)
    • FM mode with 1200 baud AFSK modulation

  3. GPS Receiver

    • Provides position information
    • Built into many modern radios and devices

  4. Computer or Mobile Device

    • Runs APRS software
    • Examples: APRSDroid (Android), APRSISCE/32, Xastir, Dire Wolf

Data Flow

GPS → Computer/Device → TNC → Radio → RF → Other Stations
                                            ↓
                                    Internet Gateway (IGate)
                                            ↓
                                        APRS-IS
                                            ↓
                                    Global APRS Network

APRS Packet Structure

A typical APRS position packet:

WB4APR>APRS,RELAY,WIDE:!3849.50N/07652.00W-PHG5132/W3,VA

Components:

  • Source callsign: WB4APR
  • Destination: APRS (APRS identifier)
  • Path: RELAY,WIDE (digipeater path)
  • Data: Position, symbol, comment

APRS Frequencies by Country

Americas

CountryFrequencyNotes
United States144.390 MHzPrimary national frequency
Canada144.390 MHzSame as USA
Mexico144.390 MHzAligned with North America
Brazil145.575 MHzNational frequency
Argentina144.930 MHzPrimary frequency
Chile144.930 MHzCoordinated with region
Colombia144.390 MHzFollowing North American standard
Peru144.390 MHzRegional coordination
Venezuela144.390 MHzNorth American alignment

Europe

CountryFrequencyNotes
Austria144.800 MHzÖVSV recommended
Belgium144.800 MHzEuropean standard
Czech Republic144.800 MHzCZ APRS frequency
Denmark144.800 MHzEDR coordination
Finland144.800 MHzSRAL approved
France144.800 MHzREF-Union frequency
Germany144.800 MHzDARC recommended
Greece144.800 MHzRAAG frequency
Hungary144.800 MHzMRASZ coordination
Ireland144.800 MHzIRTS frequency
Italy144.800 MHzARI recommended
Netherlands144.800 MHzVERON coordination
Norway144.800 MHzNRRL frequency
Poland144.800 MHzPZK recommended
Portugal144.800 MHzREP coordination
Russia144.800 MHzSRR frequency
Spain144.800 MHzURE recommended
Sweden144.800 MHzSSA frequency
Switzerland144.800 MHzUSKA coordination
United Kingdom144.800 MHzRSGB recommended

Asia-Pacific

CountryFrequencyNotes
Australia145.175 MHzWIA recommended
China144.640 MHzCRSA coordination
Hong Kong144.640 MHzHKARA frequency
India145.825 MHzNIAR recommended
Indonesia144.390 MHzORARI coordination
Japan144.640 MHzJARL recommended
Malaysia144.390 MHzMARTS frequency
New Zealand144.575 MHzNZART recommended
Philippines144.390 MHzPARA coordination
Singapore144.390 MHzSARTS frequency
South Korea144.620 MHzKARL recommended
Taiwan144.640 MHzCTARL frequency
Thailand145.525 MHzRAST coordination
Vietnam144.390 MHzVAST frequency

Africa

CountryFrequencyNotes
South Africa144.800 MHzSARL recommended
Egypt144.800 MHzRegional coordination
Kenya144.800 MHzARSK frequency
Morocco144.800 MHzARAM coordination
Nigeria144.800 MHzNARS frequency

Middle East

CountryFrequencyNotes
Israel144.800 MHzIARC recommended
Saudi Arabia144.800 MHzSARS coordination
United Arab Emirates144.800 MHzEARU frequency
Turkey144.800 MHzTRAC recommended

Space

ApplicationFrequencyNotes
ISS APRS145.825 MHzInternational Space Station
Satellite Uplink145.825 MHzVarious amateur satellites

APRS-IS Network

What is APRS-IS?

APRS-IS (APRS Internet Service) is the internet backbone of the APRS network. It allows APRS data from around the world to be shared in real-time.

Key Features

  • Global connectivity - Connect stations worldwide
  • Real-time synchronization - Instant data propagation
  • Multiple server network - Redundancy and reliability
  • Port access - Various ports for different purposes
  • Authentication - Passcode-based security

APRS-IS Server Ports

PortPurposeFilter
14580Full feedNo filter
8080HTTPWeb-based access
23TelnetLegacy access
10152UDPExperimental

Popular APRS-IS Servers

Tier 1 Servers (Core Network)

  • rotate.aprs.net
    - Load-balanced rotation
  • noam.aprs2.net
    - North America
  • euro.aprs2.net
    - Europe
  • asia.aprs2.net
    - Asia
  • soam.aprs2.net
    - South America
  • aunz.aprs2.net
    - Australia/New Zealand

Regional Servers

  • North America:

    • noam.aprs2.net:14580
    • second.aprs.net:14580

  • Europe:

    • euro.aprs2.net:14580
    • france.aprs2.net:14580
    • germany.aprs2.net:14580

  • Asia:

    • asia.aprs2.net:14580
    • japan.aprs2.net:14580

  • South America:

    • soam.aprs2.net:14580
    • brazil.aprs2.net:14580

Connection String Format

callsign pass passcode vers software version filter filter-specification

Example:

WB4APR pass 12345 vers APRSClient 1.0 filter r/38.00/-97.00/500

Passcode Generation

Algorithm

The APRS-IS passcode is generated using a specific algorithm to prevent unauthorized access while maintaining amateur radio's open nature.

Implementation

function generateAprsPasscode(callsign) {
  const cleanCallsign = callsign.toUpperCase().trim();
  let hash = 0x73e2;
  let i = 0;
  
  while (i < cleanCallsign.length) {
    hash ^= cleanCallsign.charCodeAt(i) << 8;
    hash ^= cleanCallsign.charCodeAt(i + 1);
    i += 2;
  }
  
  return hash & 0x7fff;
}

Key Points

  • Read-only access: Passcode 
    -1
    for receive-only
  • Full access: Generated passcode for transmit capability
  • Callsign specific: Each callsign has unique passcode
  • Not encryption: Security through amateur radio licensing
  • Verification: Validates amateur radio license

Example Passcodes

CallsignPasscode
WB4APR23515
N0CALL13023
TEST29939
KF5INZ12345

Use Cases

1. Vehicle Tracking

Track cars, trucks, boats, aircraft in real-time:

  • Fleet management for commercial operations
  • Search and rescue coordination
  • Race tracking for marathons and rallies
  • Personal tracking during road trips

2. Weather Stations

Automated weather reporting:

  • Temperature and humidity
  • Barometric pressure trends
  • Wind speed and direction
  • Rainfall measurements
  • Solar radiation monitoring

Example weather packet:

WX1ABC>APRS:!4028.51N/07506.67W_090/001g005t077r000p000h50b10120

3. Emergency Communications

Critical during disasters:

  • Shelter locations and capacity
  • Resource requests (water, food, medical)
  • Damage reports with GPS coordinates
  • Personnel tracking for safety
  • Communication when infrastructure fails

4. Event Coordination

Public service events:

  • Parade monitoring and coordination
  • Marathon SAG wagon tracking
  • Bicycle race support
  • Community events logistics
  • Ham radio field days

5. Maritime Applications

Boating and sailing:

  • AIS integration with marine traffic
  • Position reporting offshore
  • Weather buoy data
  • Distress signaling
  • Race coordination

6. Aviation

Aircraft tracking:

  • Glider tracking and safety
  • Balloon launches monitoring
  • Ultralight position reporting
  • Search patterns coordination

Equipment Requirements

Basic APRS Station

Minimum Requirements

  1. Amateur Radio License

    • Required for transmitting
    • Technician class minimum (USA)
    • Equivalent license in other countries

  2. VHF Radio

    • 2-meter FM transceiver
    • 5W minimum recommended
    • 25-50W for better range

  3. TNC or Sound Card Interface

    • Hardware TNC: $50-$300
    • Software TNC (Dire Wolf): Free
    • Built-in (some radios): Included

  4. GPS Receiver

    • USB GPS: $20-$50
    • Smartphone GPS: Built-in
    • Radio GPS: Varies

  5. Computer/Device

    • Laptop/PC
    • Smartphone
    • Raspberry Pi
    • Dedicated APRS device

Popular Equipment

All-in-One Solutions

DeviceTypePrice RangeFeatures
Kenwood TM-D710GAMobile$500-$600Built-in GPS, TNC, dual-band
Yaesu FTM-400XDRMobile$400-$500Touch screen, GPS, APRS
Kenwood TH-D74AHandheld$500-$600Tri-band, GPS, Bluetooth
Yaesu FT5DRHandheld$300-$400Dual-band, GPS, APRS

Trackers

DeviceTypePrice RangeFeatures
Byonics TinyTrak4Tracker$100-$150Compact, low power
Argent Data OT3mTracker$150-$200Micro-sized, versatile
APRS.fiMobile AppFreeSmartphone tracking

TNCs

DeviceTypePrice RangeFeatures
Mobilinkd TNC3Bluetooth TNC$80-$100Wireless, smartphone compatible
Dire WolfSoftware TNCFreePC/Raspberry Pi, excellent
Kantronics KPC-3+Hardware TNC$150-$200Classic, reliable

Budget Options

Under $100 Setup:

  • USB GPS receiver: $30
  • Baofeng UV-5R radio: $25
  • Sound card interface cable: $15
  • Dire Wolf software: Free
  • APRSdroid app: Free

Total: ~$70

Advanced Setup

Professional Station:

  • Kenwood TM-D710GA: $550
  • Diamond X50 antenna: $100
  • 50W power supply: $50
  • IGate equipment: $100
  • Weather station: $200

Total: ~$1,000

Getting Started

Step-by-Step Guide

1. Obtain Amateur Radio License

2. Choose Your Equipment

Start simple:

  • Mobile: Used radio with built-in APRS
  • Portable: Smartphone + Bluetooth TNC
  • Fixed: PC + software TNC + basic radio

3. Generate Your Passcode

Use this tool or alternatives:

4. Configure Your Software

Popular APRS software:

  • Windows: APRSISCE/32, UI-View32
  • Mac: Xastir, YAAC
  • Linux: Xastir, Dire Wolf
  • Android: APRSdroid
  • iOS: PocketPacket

5. Set Up Your Station

Basic configuration:

Callsign: YOUR-CALL
SSID: -9 (mobile), -5 (other), -10 (internet)
Symbol: /O (circle), /> (car), /- (house)
Comment: "Testing APRS"
Path: WIDE1-1,WIDE2-1 (recommended)

6. Test Your Setup

  • Transmit test beacon
  • Check on aprs.fi for your packets
  • Monitor local APRS traffic
  • Join local APRS net

7. Join the Community

  • Local ham club APRS group
  • Online forums: TAPR APRS
  • Facebook groups: APRS enthusiasts
  • Reddit: r/amateurradio

References

Official Resources

Documentation

Software

Online Tools

Communities

Books

  • "APRS Tracks, Maps and Mobiles" by Stan Horzepa, WA1LOU
  • "The APRS Handbook" by Mark Sproul, KB2ICI
  • ARRL Handbook - APRS section

Video Tutorials

  • Ham Radio Crash Course - APRS series on YouTube
  • K6UDA Radio - APRS tutorials
  • OH8STN - Portable APRS setups

Contributing to APRS

How to Help

  1. Run an IGate - Bridge RF to internet
  2. Run a Digipeater - Extend APRS coverage
  3. Maintain accuracy - Update your position/status
  4. Report issues - Help improve the network
  5. Educate others - Share APRS knowledge
  6. Develop software - Contribute to APRS tools

Best Practices

  • Use appropriate paths - Don't flood the network
  • Update position intelligently - Smart beaconing
  • Monitor before transmitting - Listen first
  • Use proper symbols - Standardized icons
  • Keep comments concise - Bandwidth efficiency
  • Respect the frequency - Share the resource

Troubleshooting

Common Issues

No packets received:

  • Check antenna connection
  • Verify frequency (144.390 MHz in USA)
  • Ensure squelch is open
  • Check TNC configuration

Packets not on APRS-IS:

  • Verify passcode is correct
  • Check internet connection
  • Confirm IGate coverage
  • Review filter settings

Poor coverage:

  • Improve antenna height
  • Increase transmit power
  • Check for RF interference
  • Verify path settings

GPS not working:

  • Check GPS antenna placement
  • Allow time for satellite lock
  • Verify GPS settings
  • Test GPS separately

Glossary

  • AFSK - Audio Frequency Shift Keying
  • Digipeater - Digital repeater for APRS
  • IGate - Internet Gateway
  • MIC-E - Microphone Encoder (compact position format)
  • SSID - Secondary Station Identifier (0-15)
  • TNC - Terminal Node Controller
  • WIDE1-1 - First-level wide area digipeater
  • WIDE2-1 - Second-level wide area digipeater

This documentation is maintained by the APRS community. For updates or corrections, please contribute to the project.

Last Updated: December 2025