The Automatic Packet Reporting System is a one-channel, unconnected packet network for short real-time data: where you are, weather from your station, a message to another call sign, or telemetry from a balloon.
How it works
Stations beacon 1200 baud AX.25 packets on a shared frequency — 144.390 MHz across North America, 144.800 MHz in most of Europe. Digipeaters repeat them, and internet gateways (igates) feed them to aprs.fi and similar sites, so a beacon from a car can appear on a public map seconds later.
What you need
- A radio with a built-in TNC (many Kenwood and Yaesu mobiles) — simplest.
- A handheld plus a small TNC such as a Mobilinkd or TinyTrak, driven by a phone app.
- A phone alone — APRSdroid or similar over the internet, which is fine for messaging but is
- A GPS source if you want to move; fixed stations beacon a set position.
not radio.
Paths and courtesy
The path setting decides how many digipeaters repeat you. WIDE1-1,WIDE2-1 is the sensible default for a mobile; anything longer clogs the channel across several states. Fixed stations should use WIDE1-1 or no path at all. Beacon every few minutes when moving, and much less often when parked — smart beaconing handles this automatically.
What people use it for
- Tracking club events, parades and marathons in real time.
- Sending short messages and SMS-style traffic where there is no cell coverage.
- Weather stations reporting into the public network.
- High-altitude balloon and rocket recovery.
- Local bulletins and objects, such as marking a net or an emergency operations centre.
Cautions
APRS is public. Every beacon you send, with your call sign and coordinates, is on a permanent public map — think about beaconing from home, and consider a fixed position offset or no home beacon at all. It is also a single shared channel: it degrades quickly when everyone uses long paths and fast beacon rates.