goadsb

A pure Go ADS-B decoder for RTL-SDR dongles. Listens to 1090 MHz Mode S/ADS-B transmissions and outputs decoded aircraft data in Beast binary format.

Ported from the dump1090 demodulator and decoder.

Features

RTL-SDR support via pure Go DLL binding (no CGo required)
2.4 MHz demodulator based on Oliver Jowett's demod-2400.c algorithm
ADS-B decoding: ICAO address, callsign, altitude, speed, heading, position (CPR), vertical rate, squawk
CRC checking with 1-bit error correction
Beast binary output on stdout (*<hex>;\n format) and TCP server
On-screen aircraft display on stderr
Aircraft tracking with Compact Position Reporting (CPR) decoding
Single binary - no dependencies beyond the RTL-SDR driver DLL

Requirements

Windows (uses syscall.NewLazyDLL for DLL loading)
RTL-SDR dongle with drivers installed (Zadig/WinUSB)
rtlsdr.dll on PATH or in one of:
- C:\Program Files\SDRangel\rtlsdr.dll
- C:\Program Files\SDR-Radio.com (V3)\rtlsdr.dll
- C:\Windows\System32\rtlsdr.dll

Quick Start

# Run with defaults (1090 MHz, 2.4 MS/s, AGC, 1-bit CRC fix)
.\goadsb.exe

# Custom settings
.\goadsb.exe -gain 496 -ppm 2 -freq 1090.0

# Quiet mode (no on-screen display, Beast output only)
.\goadsb.exe -quiet

# With TCP Beast server on custom port
.\goadsb.exe -beast-tcp ":30005"

Command Line Options

Flag	Default	Description
`--freq`	1090.0	Frequency in MHz
`--gain`	496	Tuner gain in tenths of dB (496=49.6dB, negative=AGC)
`--ppm`	0	Frequency correction in PPM
`--rate`	2.4	Sample rate in MHz
`--device`	0	RTL-SDR device index
`--beast`	true	Enable Beast binary output to stdout
`--beast-tcp`	:30005	TCP address for Beast output (empty to disable)
`--quiet`	false	Disable on-screen aircraft display
`--fix`	1	CRC error correction bits (0=none, 1=1-bit, 2=2-bit)
`--phase-enhance`	false	Enable phase enhancement (slower, more sensitive)

Building

go build -ldflags="-s -w" .

Requires Go 1.21+.

Output Formats

Beast Binary (stdout)

*8DA04641EA4C4864013C089A6425;
*8DA0464158C903ED06565F4315C6;

On-Screen Display (stderr)

--- goadsb  Aircraft:2  Msgs:45  Good:32  Bad:13 ---
ICAO    Callsign     Alt    Spd       Lat       Lon  Hdg    V/s   Msgs
------- --------- ------ ------ --------- --------- ---- ------  -----
A04641  DAL1234    36250    450   40.7128  -74.0060  270    -64     25
A1B2C3  --------   12000    220   40.6500  -73.7800   90      0     12

Architecture

RTL-SDR → rx callback → IQ→Mag LUT → Ring Buffer → Demodulator (2.4MHz)
  → Preamble Detect → Bit Slice → CRC Check → Message Decode
  → Aircraft Tracker (CPR) → Beast Output + Display

License

MIT