Modes & decoders — xng docs

Around 21 modes, every one of them a crate, every one feeding the same outputs. This page is honest about exactly how mature each decoder is — from production-validated to spec-anchored.

You select a decoder with --mode <name> on the CLI, or mode = "…"in a station file. Every multi-channel mode can decode any number of channels from a single capture.

Maturity, plainly

Decode cores are anchored to public specs or ported from reference implementations. What varies is how far the demodulator has been validated against real-world signals:

● live

Validated off-air. Decoded from real recordings or live radio and fenced by a CI regression gate. Safe to rely on.

◐ growing

Decode core validated, demod maturing. The frame/application decode is anchored to spec or oracle vectors; the demodulator may still be synthetic. Useful, but expect rough edges.

Flagship modes

The safe starting set. All are validated against real off-air captures and benchmarked against the established tools — frequently beating them.

--mode	Signal	Band	What you get
`acars`	VHF ACARS (ARINC 618)	118–137 MHz	Full application layer: ADS-C, CPDLC text, OOOI, MIAM, FEC bit-repair, many channels per capture	● live
`vdl2`	VDL Mode 2	136.6–137 MHz	ACARS-over-AVLC, full ATN-B1 (protected CPDLC, CM logon, X.25/CLNP)	● live
`hfdl`	HFDL (ARINC 635)	2.8–22 MHz	Squitters, logons, mapped positions, OTA system-table persistence	● live
`aero`	Inmarsat Aero L	1545–1547 MHz	P-channel 600/1200 bps + 10.5 kbps OQPSK; ACARS/ADS-C/CPDLC; C-channel voice	● live
`std-c`	Inmarsat STD-C / EGC	1537–1542 MHz	NCS TDM, EGC SafetyNET/FleetNET, geographic-area decode to coordinates	● live
`iridium`	Iridium	1616–1626.5 MHz	Ring alerts with sat positions, IBC/ITL, ACARS over SBD, pager, voice classification, IP frames	● live
`ais`	AIS (ITU-R M.1371)	161.975 / 162.025 MHz	NMEA AIVDM + field decode types 1–27, Inland-AIS, SART/MOB/EPIRB distress	● live
`adsb`	Mode S / ADS-B	1090 MHz	CPR positions, Comm-B, ACAS RA, TIS-B/ADS-R; SBS + Beast out; native 2.4 MS/s	● live

aero-c (Inmarsat Aero C bursts) is also available and RF-loopback validated. On the benchmarks: VDL2 reads more frames than dumpvdl2, HFDL hits 97% of dumphfdl, AIS 91% of AIS-catcher with zero false decodes, ADS-B 98–99% of readsb/dump1090-fa, and Iridium decodes 132% of gr-iridium’s frame count on a shared capture.

Newer modes

All wired to --mode and exercising the same runtime, outputs, and feeding. Demod validation ranges from live off-air to synthetic — each has a note in the repo’s docs/notes/.

--mode	Signal	Band	Decodes
`uat`	UAT 978 (DO-282B)	978 MHz	ADS-B downlink + FIS-B weather uplink, RS-FEC	● live
`sonde`	Radiosonde (Vaisala RS41)	~400–406 MHz	De-whiten + RS-FEC + STATUS/PTU/GPS	● live
`navtex`	NAVTEX (SITOR-B)	518 / 490 kHz	4-of-7 + FEC-B + ZCZC framing	● live
`flex`	FLEX paging	900 MHz	Auto rate-detect, BCH, alpha/numeric/tone	● live
`sarsat`	COSPAS-SARSAT 406	406 MHz	First-gen beacon ID + position (ELT/EPIRB/PLB)	◐ growing
`dsc`	DSC (GMDSS)	MF/HF/VHF	Distress / all-ships / individual / area	◐ growing
`ads-l`	ADS-L (EASA SRD860)	868 MHz	i-Conspicuity (CRC-24 + XXTEA)	◐ growing
`aprs`	APRS / AX.25	144.39 / 144.80 / 145.825 MHz	AFSK1200 + AX.25 UI; position/Mic-E/weather/telemetry; satellite tagging	◐ growing
`pocsag`	POCSAG paging	paging bands	2-FSK 512/1200/2400 + BCH; numeric/alpha/tone	◐ growing
`atcs`	ATCS (rail)	896 / 900 MHz	HDLC/LAPB + AAR Spec-200 header	◐ growing
`eot`	EOT/HOT (rail telemetry)	457.94 / 452.94 MHz	Manchester-FSK + AAR S-9152	◐ growing
`vdes`	VDES ASM	161.95 / 162.00 MHz	GMSK 9600 + ASM transport + spec payloads	◐ growing

The shared application layer

The reason a normalized message matters: ARINC 622 ADS-C positions and CPDLC render as readable text — like REQUEST CLIMB TO FL360 — the same way no matter whether the ACARS arrived over VHF, VDL2, HFDL, Aero, or Iridium SBD. Decode it once, get it everywhere.

Picking channels

Each mode ships a built-in frequency plan, so the simplest invocation is just a mode name:

bash

xng tui --sdr driver=rtlsdr --mode vdl2        # uses the VDL2 plan
xng listen --sdr driver=rtlsdr --mode ais \     # both AIS channels, one capture
    -r 2400000 -c 162.000M --channels 161.975,162.025

For hardware and antenna requirements per band, see Inputs & outputs; for full command lines per mode, see Recipes.