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APRS Radio Decoder

Decode APRS position, weather and message packets from raw frames.

Hardware, Radio & TelecomFree
INPUT
OUTPUT

The result appears here as you type.

Decoding runs in your browser. What you paste is not sent to a server.

APRS (Automatic Packet Reporting System) carries real-time position, weather and message data over amateur radio in AX.25 frames, and an APRS decoder parses those frames into callsign, coordinates, symbol and comment.

Example

Input
N0CALL-9>APRS,WIDE1-1,WIDE2-1:!4903.50N/07201.75W>088/036/A=001234 On the road
Output
Type            Position without timestamp
Source          N0CALL-9
Destination     APRS
Path            WIDE1-1,WIDE2-1
Format          Uncompressed position
Symbol          />
Course / speed  88° at 36 knots
Altitude        1234 ft
Comment         On the road
Position: 49.05833, -72.02917

What is the APRS Radio Decoder?

APRS packets ride inside AX.25 frames: a source callsign with an SSID, a destination that doubles as a software identifier, a digipeater path such as WIDE1-1,WIDE2-1, and an information field whose first character declares the packet type — ! or = for a position, / or @ for position with timestamp, : for a message, ; for an object, _ for weather.

Positions use a compact fixed-width format, ddmm.hhN/dddmm.hhW, with a symbol table and code selecting the icon that appears on a map. Between the coordinates and the symbol sits a course, speed or altitude field, and the rest of the line is free-text comment — often a station's power, antenna and gain in a compressed PHG code.

Nearly all of the world's APRS traffic is gatewayed into APRS-IS, which is why a packet heard on 144.800 MHz in Europe or 144.390 MHz in North America shows up on aprs.fi within seconds.

How to use the APRS Radio Decoder

  1. Paste the raw APRS frame, including the source, path and information field.
  2. Read the decoded callsign, packet type, coordinates and comment.
  3. Check the digipeater path to see how the packet reached you.

When to use it

  • Debugging a tracker that reports the wrong position or symbol.
  • Learning the APRS packet format while building a decoder.
  • Analysing captured amateur radio traffic offline.

APRS Radio Decoder at a glance

FrameAX.25 UI frame, callsign-SSID addressing
Frequencies144.390 MHz (NA) · 144.800 MHz (EU)
Type characterFirst byte of the information field
Position formatddmm.hhN/dddmm.hhW plus symbol code

Frequently asked questions

What does the SSID after a callsign mean?

A number 0–15 distinguishing multiple stations under one callsign. Conventionally -9 is a car, -7 a handheld, -1 a wide digipeater — a convention, not a rule.

What is WIDE1-1,WIDE2-1?

A digipeater path requesting one local repeat and then up to two wider ones. It is the standard path for mobile stations; longer paths flood the network and are discouraged.

Do I need a licence to transmit APRS?

Yes — APRS runs on amateur radio allocations, so transmitting requires an amateur licence. Receiving and decoding is unrestricted.

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