Beginner’s Guide to Using APRS for Ham Radio

Amateur Packet Reporting System (APRS) is a digital communication system utilized by amateur radio operators to exchange messages and track locations utilizing GPS.

APRS is a well-known technology among hams, with numerous applications in emergency communications, tracking, and weather reporting. In this article, we will discuss what APRS is, how to set it up, how to use it, and the best practices for operating APRS.

What is APRS (Amateur Packet Reporting System)?

APRS is a digital communication system.  It functions by sending small packets of data via radio waves.  It’s designed for exchanging messages and information over short distances. It was initially developed in the 1990’s by Bob Bruninga, WB4APR (SK).  Since then, it is used extensively by amateur radio operators.

(Ham Speak: The term (SK) means “Silent Key” or a ham who has passed away.)

An APRS packet might only be a few data points.  They always have a call sign.  Sometimes in addition they have short, point-to-point text message.  Like “Meet me on 146.520 MHz at 10 AM.”   point-to-point message.  Sometimes they have position data, derived from  GPS coordinates.   Those packets get transmitted blindly, for reception by other radios within range.  Some hams operate radios that connect APRS to the Internet.   These radios are named  gateways and digipeaters.  On occasion, you’ll find APRS in use on the International Space Station.  When in use, it can be used to relay packets while overhead. 

Let’s explain a little more about gateways and digipeaters.  A gateway is used to receive APRS packages.  This provides them a “gateway” into the internet side of APRS.   A digipeater is a radio that receives the packets and sends them out to a wider area.  The ISS radio would be an example of a digipeater.   Yes, this function of digipeating and gateway can be combined into one unit. 

Based on this, you can see APRS has a wide range of applications. They include tracking the location of vehicles, people, and weather stations.

Its Founder: Bob Bruninga

APRS was pioneered by Bob Bruninga, WB4APR, a U.S. Navy officer and member of the U.S. Naval Academy, who initially developed the system on an Apple II platform in 2002. He originally created APRS to track ships using the AX.25 protocol, which eventually became popular in the ham radio community. Bob’s work laid the foundation for APRS, which remains a prominent protocol in amateur radio.

There’s also a common point of confusion: what does “APRS” stand for? Some refer to it as the “Automated Position Reporting System” while others say “Automated Packet Reporting System.” Both terms are acceptable.

The APRS Foundation: Carrying Bob’s Legacy Forward

Though Bob became a Silent Key in February 2022, his legacy endures through the APRS Foundation. About a year before his passing, Bob transferred the intellectual property and trademarks for APRS to TAPR (Tucson Amateur Packet Radio). TAPR later established the APRS Foundation to maintain and develop APRS resources.

The original APRS website, www.aprs.org, remains active, primarily as a historical archive. For those seeking current information and resources, the new website, how.aprs.works, provides modern guides, tips, and use cases for APRS.

How APRS Works and Where It’s Used

APRS operates over RF within a localized region but can connect to a global network through digipeaters and I-Gates, which amplify and relay transmissions. Jeff recommends checking out how.aprs.works and joining the APRS groups on groups.io and TAPR’s listserv to stay updated on the latest APRS developments.

Real-time data transmission is at the heart of APRS’s appeal. In contrast to Winlink, which stores and forwards messages, APRS packets are instantly received, making it invaluable in emergency and public service settings.

How to Setup APRS

You can participate in APRS with a variety of devices.  Some are hardware based, others are computer software.  Here are some options:

• A radio with built-in APRS capability.  These include handhelds and mobile rigs that will generate packets and receive them.   The radio typically operates on  144.390 MHz in North America.
• If your radio doesn’t have APRS built in, you can connect it to a computer. Then you generate APRS signals via special software.  Those signals get fed into your radio for transmission and reception of the APRS data. We call this a soundcard interface.
  • If you are using a Windows or Linux PC, including a Raspberry Pi, check out Dire Wolf.  That stands for “Decoded Information from Radio Emissions for Windows Or Linux Fans.” 
  • On Apple PC’s try MacAPRS.
• Some APRS users only use their Mobile Phone. There are apps for Apple and Android devices.  These don’t take advantage of the RF elements of APRS.  The phones GPS and data connections help here. The apps can be used to provide location information via APRS system packets online.

Steps to follow:

1. Configure the radio
   a. Radio with APRS capability:  Configure the software based on your radio’s instructions.
   b. Radio and computer design:  Install APRS software on your computer and create an audio interface between your PC and radio.  For simple receiving, a cable connecting the radio’s audio output to the PC’s line input will do.  Install one of the software versions mentioned above or one that fits your needs. 
2. Set the frequency for packets to 144.390 MHz in North America for the terrestrial network. (The ISS uses 145.825 MHz, other regions of the world use different frequencies).
3. Software configuration
   a.Radio with APRS capability: Your packet needs to include a “path.”  The path is used by receiving stations, particularly digipeaters.  WIDE2-2 is a typical terrestrial setting. It basically says, “send this packet through up to two digipeaters.”
   b. Radio and computer design: Configure the APRS software to work with your radio. Set the frequency, baud rate, and audio levels.  If you want your computer to be a gateway, set that up too.  Then it will send packet information it hears to the APRS-IS internet network.  To do that, check online to get a callsign passcode for your software.
4. Configure the APRS software to use your GPS device to send your location. The radio with APRS capability should track your location as you move.  For the static station, enter the location once in the software.
5. Test your setup.  Start by receiving and decoding APRS packets.   Then send a few APRS packets of your own to ensure that everything is working properly.  You can check online to see if your packet reached an APRS gateway.  Look at a site like https://aprs.fi/ to see if it was received by the terrestrial network.
6. Advanced
   a. Radio and computer design: Connect your PC’s output to the radio’s input to transmit your own packets.  A tool like a “Rigblaster” can be purchased or home brewed.

How to Use APRS

Once you have set up APRS, you can start using it to exchange messages and track locations.  APRS data messages go over RF between stations.  Many make it into the online APRS network, which can then show them on a real time map.

APRS is often used to track the location of vehicles or people.  That might include hikers or search and rescue teams. It can also be used to transmit weather data. Many APRS connected stations share weather data.  That includes temperature, pressure, and wind speed. Smart hams have figured out ways to interface that with the APRS network.

Advanced APRS Features

APRS has numerous advanced features that can be utilized to enhance its functionality.

• Automatic position reporting and tracking.  Follow stations that transmit their location automatically at regular intervals.  Very useful for tracking moving vehicles, such as ambulances or delivery trucks.  Frequently used for ham radio public service events like parades and marathons. 
• Digipeating to improve range.  When packets are relayed from one digipeater to another, APRS range is extended.
• Satellite Experimentation.  The International Space Station has an active APRS digipeater.  It’s managed by the ARISS team.  It operates on 145.825 MHz worldwide.  You can listen for it with any APRS capable device.  If you want to send packets through the ISS, it uses unique PATH designators.  Check for those settings before you operate.

• APRS can be used to report weather data, such as temperature, humidity, and wind speed.
• Weather stations can be connected to the APRS network to report weather data.
• Long Distance APRS:  Ambitious hams have events to try for packet distance records.   One is called the “Appalachian Trail Golden Packet event.”  In this July event, hams attempt to send an APRS packet via simplex over long distances.

Best Practices for APRS

To operate APRS effectively, it is critical to follow best practices.

1. Firstly, it is important to set the correct frequency and beacon rate for your station.  This will ensure that it is compatible with other APRS stations in your area.
2. Secondly, it is crucial to set up proper paths and filters. This will ensure that your APRS packets are being relayed to the correct stations.
3. Finally, it is important to follow good operating practices.  Those include avoiding excessive beaconing, avoiding using generic callsigns, and avoiding QRM.

APRS’s Future and Supporting the Foundation

Support for the APRS Foundation is greatly welcomed, and membership is open to everyone, with an annual fee of $20. “Joining doesn’t require being a ham,” Jeff mentioned during a short interview at the “Stone Mountain Hamfest 2024,” noting that the contributions are crucial for the progression of APRS and the support of new projects. The interview video is available for viewing.

Conclusion

APRS is a powerful and versatile digital communication system. It is used by amateur radio operators for a variety of applications. The small packet of detailed APRS data is special. It can be transmitted with GPS coordinates, weather data, and messages. That makes APRS a valuable tool for emergency communications, tracking, and weather reporting.

Hams can ensure that APRS is used effectively and efficiently.  This is driven by following best practices and operating responsibly. While the setup and configuration of APRS can be daunting. But, with a little practice, you can easily master this valuable technology.  Use APRS to take your communication capabilities to the next level.  Another way to expand your horizons in the world of amateur radio.