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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

Feature APRS Traditional Packet
Purpose Tactical real-time information Message passing
Network Connectionless broadcast Connection-oriented
Data Position, weather, status General data/messages
Internet Integrated (APRS-IS) Limited
Maps Built-in visualization Not 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

Country Frequency Notes
United States 144.390 MHz Primary national frequency
Canada 144.390 MHz Same as USA
Mexico 144.390 MHz Aligned with North America
Brazil 145.575 MHz National frequency
Argentina 144.930 MHz Primary frequency
Chile 144.930 MHz Coordinated with region
Colombia 144.390 MHz Following North American standard
Peru 144.390 MHz Regional coordination
Venezuela 144.390 MHz North American alignment

Europe

Country Frequency Notes
Austria 144.800 MHz ÖVSV recommended
Belgium 144.800 MHz European standard
Czech Republic 144.800 MHz CZ APRS frequency
Denmark 144.800 MHz EDR coordination
Finland 144.800 MHz SRAL approved
France 144.800 MHz REF-Union frequency
Germany 144.800 MHz DARC recommended
Greece 144.800 MHz RAAG frequency
Hungary 144.800 MHz MRASZ coordination
Ireland 144.800 MHz IRTS frequency
Italy 144.800 MHz ARI recommended
Netherlands 144.800 MHz VERON coordination
Norway 144.800 MHz NRRL frequency
Poland 144.800 MHz PZK recommended
Portugal 144.800 MHz REP coordination
Russia 144.800 MHz SRR frequency
Spain 144.800 MHz URE recommended
Sweden 144.800 MHz SSA frequency
Switzerland 144.800 MHz USKA coordination
United Kingdom 144.800 MHz RSGB recommended

Asia-Pacific

Country Frequency Notes
Australia 145.175 MHz WIA recommended
China 144.640 MHz CRSA coordination
Hong Kong 144.640 MHz HKARA frequency
India 145.825 MHz NIAR recommended
Indonesia 144.390 MHz ORARI coordination
Japan 144.640 MHz JARL recommended
Malaysia 144.390 MHz MARTS frequency
New Zealand 144.575 MHz NZART recommended
Philippines 144.390 MHz PARA coordination
Singapore 144.390 MHz SARTS frequency
South Korea 144.620 MHz KARL recommended
Taiwan 144.640 MHz CTARL frequency
Thailand 145.525 MHz RAST coordination
Vietnam 144.390 MHz VAST frequency

Africa

Country Frequency Notes
South Africa 144.800 MHz SARL recommended
Egypt 144.800 MHz Regional coordination
Kenya 144.800 MHz ARSK frequency
Morocco 144.800 MHz ARAM coordination
Nigeria 144.800 MHz NARS frequency

Middle East

Country Frequency Notes
Israel 144.800 MHz IARC recommended
Saudi Arabia 144.800 MHz SARS coordination
United Arab Emirates 144.800 MHz EARU frequency
Turkey 144.800 MHz TRAC recommended

Space

Application Frequency Notes
ISS APRS 145.825 MHz International Space Station
Satellite Uplink 145.825 MHz Various 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

Port Purpose Filter
14580 Full feed No filter
8080 HTTP Web-based access
23 Telnet Legacy access
10152 UDP Experimental

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

Callsign Passcode
WB4APR 23515
N0CALL 13023
TEST 29939
KF5INZ 12345

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

Device Type Price Range Features
Kenwood TM-D710GA Mobile $500-$600 Built-in GPS, TNC, dual-band
Yaesu FTM-400XDR Mobile $400-$500 Touch screen, GPS, APRS
Kenwood TH-D74A Handheld $500-$600 Tri-band, GPS, Bluetooth
Yaesu FT5DR Handheld $300-$400 Dual-band, GPS, APRS

Trackers

Device Type Price Range Features
Byonics TinyTrak4 Tracker $100-$150 Compact, low power
Argent Data OT3m Tracker $150-$200 Micro-sized, versatile
APRS.fi Mobile App Free Smartphone tracking

TNCs

Device Type Price Range Features
Mobilinkd TNC3 Bluetooth TNC $80-$100 Wireless, smartphone compatible
Dire Wolf Software TNC Free PC/Raspberry Pi, excellent
Kantronics KPC-3+ Hardware TNC $150-$200 Classic, 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