APRS — the Automatic Packet Reporting System — is one of the most versatile digital systems in amateur radio. It combines position reports, short messages, weather data and telemetry on a single frequency. In Austria there is a well-developed APRS network operating on 144.800 MHz.
What is APRS?
APRS was developed in the 1990s by Bob Bruninga (WB4APR) and uses AX.25 packets on 2 m (VHF). Unlike classic packet radio, APRS is not connection-oriented — it sends beacons that are heard by all stations within range. The data is relayed through digipeaters and fed into the worldwide APRS-IS network via internet gateways (IGates).
What makes it special: APRS is a real-time system. Positions, weather data and messages appear on maps like aprs.fi or aprsdirect.com within seconds.
APRS infrastructure in Austria
Austria has a dense network of APRS digipeaters and IGates. Most are operated by local amateur radio clubs or dedicated individuals. The key sites cover the main traffic routes and population centres.
The standard frequency in Europe is 144.800 MHz (FM, 1200 baud). All APRS traffic runs on this single frequency — position reports, messages, weather and telemetry share one channel. This works because APRS packets are very short (typically under one second of transmit time).
How does APRS work?
An APRS station transmits a position packet at regular intervals (typically every 2-5 minutes). The packet contains:
- Callsign with SSID (e.g. OE8XXX-9 for a mobile station)
- GPS coordinates
- Symbol (car, hiker, house, weather station, etc.)
- Optional comment or status
- Speed and heading (for mobile stations)
Digipeaters receive these packets and retransmit them, extending the range. IGates forward the packets to the internet, where they become visible on maps like aprs.fi.
Equipment for APRS
Classic approach: TNC + transceiver
The traditional way: a Terminal Node Controller (TNC) is connected between a GPS receiver and a 2 m transceiver. The TNC generates the AX.25 packets and controls the transceiver’s PTT. Popular TNCs include the TinyTrak4 and Mobilinkd TNC.
Modern radios with built-in APRS
Many current transceivers have APRS built in:
- Yaesu FTM-300/FTM-500: Mobile radios with full APRS functionality and SmartBeaconing.
- Yaesu FT-5D: Handheld with APRS and C4FM.
- Kenwood TH-D75: Handheld with built-in GPS, TNC and APRS — the reference device.
- Anytone AT-D878UV II Plus: DMR handheld with APRS capability.
DIY and trackers
For pure position reporting, there are affordable tracker solutions:
- Mobilinkd TNC4: Bluetooth TNC that works with any transceiver and uses a smartphone as the display.
- ESP32-based trackers: DIY projects like the LoRa APRS Tracker. Small, cheap, battery-powered.
- Raspberry Pi + Direwolf: Software TNC on a Raspberry Pi with a USB sound card. Ideal for home stations and IGates.
SmartBeaconing
SmartBeaconing is an intelligent algorithm that automatically adjusts the beacon rate. In turns or at high speed it transmits more frequently; when stationary, less often. This saves channel capacity and battery without compromising position tracking. Most modern APRS devices and software TNCs support SmartBeaconing.
APRS messaging
Besides position reports, APRS also supports text messages — a kind of SMS over radio. Messages are addressed to a specific callsign and repeated until an acknowledgement is received. This works without an internet connection, as long as both stations are reachable via digipeaters.
In emergencies, APRS messages can be a valuable communication tool — independent of mobile phone networks.
APRS weather stations
Many radio amateurs operate APRS weather stations that automatically transmit temperature, humidity, barometric pressure, wind speed and rainfall. This data feeds into the global APRS network and is visible on maps and weather aggregators.
A simple APRS weather station can be built with a Raspberry Pi, a Davis weather station (or a cheaper alternative) and Direwolf as the software TNC.
APRS and SOTA/POTA
For SOTA and POTA activators, APRS is especially useful. You can report your position automatically, so followers can track your ascent in real time on aprs.fi. Some activators also use APRS to post spots — an APRS message to the APRS2SOTA gateway automatically triggers a spot on SOTAwatch.
LoRa APRS
A newer development is LoRa APRS — transmitting APRS data via LoRa modulation on 433.775 MHz (70 cm band). LoRa offers significantly greater range than classic 1200-baud APRS while consuming less power. Ideal for trackers that need to run for days on a small battery.
In Austria, several LoRa APRS digipeaters are already supplementing the network. The data is fed via IGates into the standard APRS-IS network and appears on the same maps.
Software for APRS
- Direwolf: Open-source software TNC for Linux, Windows and macOS. The standard for IGates and digipeaters on Raspberry Pi.
- APRSdroid: Android app that turns a smartphone into an APRS tracker (via APRS-IS or Bluetooth TNC).
- YAAC (Yet Another APRS Client): Java-based APRS client with map display.
- PinPoint APRS: Windows software with comprehensive APRS features.
- aprs.fi: The best-known web platform for displaying APRS data worldwide.
Tips for getting started
- Listen first: Tune your 2 m radio to 144.800 MHz and listen. You will hear the short APRS bursts.
- Watch aprs.fi: Before transmitting, explore aprs.fi to see which stations are active in your area.
- Mind the SSID: The SSID after your callsign indicates the station type: -1 to -4 for digipeater, -5 for smartphone, -9 for mobile, -0 or no suffix for home station.
- Set the path correctly: In Austria, WIDE1-1,WIDE2-1 works well as the standard path. Longer paths generate unnecessary traffic.
- Adjust beacon rate: Do not transmit more often than necessary. Use SmartBeaconing if available.
- Transmit power: For APRS, 5-10 watts usually suffices. More power is rarely needed and loads the channel.
APRS is a fascinating system that goes far beyond simple position reports. From real-time tracking during outdoor activities to weather data to emergency communication — APRS adds value to nearly every area of amateur radio. And with modern LoRa trackers and smartphone apps, getting started is easier than ever.
73 – your oeradio.at editorial team
Transparency Notice
This article was researched and written with the assistance of AI (Claude, Anthropic). The editorial team has reviewed and edited all content. Despite careful review, occasional inaccuracies may occur — we welcome corrections via email to [email protected].
