airspy-fmradion

• Version 20250929-0
• For macOS (Apple Silicon) and Linux

Contributing

See CONTRIBUTING.md for the details.

Known issues and changes

• Please read CHANGES.md before using the software.
• Refer to doc/old-README-until-2023.md for the other miscellaneous technical details.

What is airspy-fmradion?

• airspy-fmradion is software-defined radio receiver (SDR) software with command-line interface.

What does airspy-fmradion provide?

• Supported SDR frontends: Airspy R2/Mini, Airspy HF+, and RTL-SDR
• Playing back from I/Q WAV files
• Monaural/stereo decoding of FM broadcasting stations
• Monaural decoding of AM stations
• Decoding NBFM/DSB/USB/LSB/CW/WSPR station audio
• Playback to soundcard through PortAudio or saving to file through libsndfile
• Command-line interface

Usage

# Portaudio output
airspy-fmradion -t airspy -q \
    -c freq=82500k,srate=1000k,lgain=2,mgain=0,vgain=10 \
    -P -

# 16-bit signed integer WAV output (pipe is not supported)
airspy-fmradion -t airspyhf -q \
    -c freq=82500000,srate=384000 \
    -W output_s16_le.wav

# 32-bit float WAV output (pipe is not supported)
airspy-fmradion -m am -t airspyhf -q \
    -c freq=666k \
    -G output_f32_le.wav

airspy-fmradion requirements

• Linux / macOS
• C++20 (gcc, clang/llvm)
• Airspy library
• Airspy HF library
• RTL-SDR library
• libsndfile
• r8brain-free-src, a sample rate converter designed by Aleksey Vaneev of Voxengo
• VOLK
• PortAudio
• jj1bdx's fork of cmake-git-version-tracking
• {fmt}

Git branches and tags

• Official releases are tagged
• main is the "production" branch with the most stable release (often ahead of the latest release though)
• dev is the development branch that contains current developments that will be eventually released in the main branch
• Other branches are experimental (and presumably abandoned)

Prerequisites

Debian/Ubuntu Linux

sudo apt-get install cmake pkg-config \
    libusb-1.0-0-dev \
    libasound2-dev \
    libairspy-dev \
    libairspyhf-dev \
    librtlsdr-dev \
    libsndfile1-dev \
    portaudio19-dev \
    libvolk2-dev

macOS

• Install HomeBrew libraries as in the following shell script
• Use HEAD for airspy and airspyhf

brew update
brew install portaudio
brew install libsndfile
brew install rtl-sdr
brew install airspy --HEAD
brew install airspyhf --HEAD
brew install volk
brew install fmt

Install the supported libvolk

• Install libvolk as described in libvolk.md.
• Run volk_profile and save the configuration data for speed optimization.

Install the supported libsndfile for MP3 capability

• You may need to install libsndfile as described in libsndfile.md.

Install the supported libfmt

• You need to install libfmt as described in libfmt.md.

Installation

/bin/rm -rf build
mkdir build
git submodule update --init --recursive
cmake -S . -B build
cmake --build build --target all

Basic command options

• -m devtype is modulation type, one of fm, nbfm, am, dsb, usb, lsb, cw, wspr (default fm)
• -t devtype is mandatory and must be airspy for Airspy R2 / Airspy Mini, airspyhf for Airspy HF+, rtlsdr for RTL-SDR, and filesource for the File Source driver.
• -q Quiet mode.
• -c config Comma separated list of configuration options as key=value pairs or just key for switches. Depends on device type (see next paragraph).
• -d devidx Device index, 'list' to show device list (default 0)
• -M Disable stereo decoding
• -R filename Write audio data as raw S16_LE samples. Use filename - to write to stdout
• -F filename Write audio data as raw FLOAT_LE samples. Use filename - to write to stdout
• -W filename Write audio data as RF64/WAV S16_LE samples. Use filename - to write to stdout (pipe is not supported)
• -G filename Write audio data as RF64/WAV FLOAT_LE samples. Use filename - to write to stdout (pipe is not supported)
• -C filename Write audio data to MP3 file of VBR -V 1. Use filename '-' to write to stdout. (This function is available when linked with supported libsndfile only.)
• -P device_num Play audio via PortAudio device index number. Use string - to specify the default PortAudio device
• -T filename Write pulse-per-second timestamps. Use filename '-' to write to stdout
• -X Shift pilot phase (for Quadrature Multipath Monitor) (-X is ignored under mono mode (-M))
• -U Set deemphasis to 75 microseconds (default: 50)
• -f Set Filter type
  • for FM: wide and default: none, medium: +-156kHz, narrow: +-121kHz
  • for AM: wide: +-9kHz, default: +-6kHz, medium: +-4.5kHz, narrow: +-3kHz
  • for NBFM: wide: +-20kHz, default: +-10kHz, medium: +-8kHz, narrow: +-6.25kHz
• -l dB Enable IF squelch, set the level to minus given value of dB
• -E stages Enable multipath filter for FM (For stable reception only: turn off if reception becomes unstable)
• -r ppm Set IF offset in ppm (range: +-1000000ppm) (Note: this option affects output pitch and timing: use for the output timing compensation only!

Timestamp file format

• For FM: pps_index sample_index unix_time if_level
• For the other modes: block unix_time if_level
• if_level is in dB

Output audio specification

• Output maximum level is nominally -6dB (0.5) but may increase up to 0dB (1.0)
• Output audio sample rate is fixed to 48000Hz

FM multipath filter

• A Normalized LMS-based multipath filter can be enabled after IF AGC
• IF sample stages is defined by -E options
• Practical upper limit of -E value: 200
• Practical -E value: up to 50 for Raspberry Pi 4, approx. 100 for a modern computer

Airspy R2 / Mini configuration options

• freq=<int> Desired tune frequency in Hz. Valid range from 1M to 1.8G. (default 100M: 100000000)
• srate=<int> Device sample rate. list lists valid values and exits. (default 10000000). Valid values depend on the Airspy firmware. Airspy firmware and library must support dynamic sample rate query.
• lgain=<x> LNA gain in dB. Valid values are: 0, 1, 2, 3, 4, 5, 6, 7, 8 ,9 ,10, 11 12, 13, 14, list. list lists valid values and exits. (default 8)
• mgain=<x> Mixer gain in dB. Valid values are: 0, 1, 2, 3, 4, 5, 6, 7, 8 ,9 ,10, 11 12, 13, 14, 15, list. list lists valid values and exits. (default 8)
• vgain=<x> VGA gain in dB. Valid values are: 0, 1, 2, 3, 4, 5, 6, 7, 8 ,9 ,10, 11 12, 13, 14, 15, list. list lists valid values and exits. (default 0)
• antbias Turn on the antenna bias for remote LNA (default off)
• lagc Turn on the LNA AGC (default off)
• magc Turn on the mixer AGC (default off)

Airspy HF+ configuration options

• freq=<int> Desired tune frequency in Hz. Valid range from 0 to 31M, and from 60M to 240M. (default 100M: 100000000)
• srate=<int> Device sample rate. list lists valid values and exits. (default 384000). Valid values depend on the Airspy HF firmware. Airspy HF firmware and library must support dynamic sample rate query.
• hf_att=<int> HF attenuation level and AGC control.
  • 0: enable AGC, no attenuation
  • 1 - 8: disable AGC, apply attenuation of value * 6dB

RTL*SDR configuration options

• freq=<int> Desired tune frequency in Hz. Accepted range from 10M to 2.2G. (default 100M: 100000000)
• gain=<x> (default auto)
  • auto Selects gain automatically
  • list Lists available gains and exit
  • <float> gain in dB. Possible gains in dB are: 0.0, 0.9, 1.4, 2.7, 3.7, 7.7, 8.7, 12.5, 14.4, 15.7, 16.6, 19.7, 20.7, 22.9, 25.4, 28.0, 29.7, 32.8, 33.8 , 36.4, 37.2, 38.6, 40.2, 42.1, 43.4, 43.9, 44.5, 48.0, 49.6
• srate=<int> Device sample rate. valid values in the [900001, 3200000] range. (default 1152000)
• blklen=<int> Device block length in bytes (default RTL-SDR default i.e. 64k)
• agc Activates device AGC (default off)
• antbias Turn on the antenna bias for remote LNA (default off)

File Source driver configuration options

• freq=<int> Frequency of radio station in Hz.
• srate=<int> IF sample rate in Hz.
• filename=<string> Source file name. Supported encodings: FLOAT, S24_LE, S16_LE
• zero_offset Set if the source file is in zero offset, which requires Fs/4 IF shifting.
• blklen=<int> Set block length in samples.
• raw Set if the file is raw binary.
• format=<string> Set the file format for the raw binary file. Supported formats: U8_LE, S8_LE, S16_LE, S24_LE, FLOAT

Authors and contributors

• Joris van Rantwijk, primary author of SoftFM
• Edouard Griffiths, F4EXB, primary author of NGSoftFM (no longer involving in maintaining NGSoftFM)
• Kenji Rikitake, JJ1BDX, maintainer/developer/experimenter
• András Retzler, HA7ILM, for the former AF/IF AGC code in csdr
• Youssef Touil, Airspy Founder, aka Twitter @lambdaprog, for the intriguing exchange of Airspy product design details and the technical support
• Iowa Hills Software, for their FIR and IIR filter design tools
• Brian Beezley, K6STI, for his comprehensive Web site of FM broadcasting reception expertise and the idea of Quadrature Multipath Monitor
• Ryuji Suzuki, for reviewing the FM multipath filter coefficients and suggesting putting more weight on picking up more previous samples from the reference point than the samples after
• Teruhiko Hayashi, JA2SVZ, the creator of FM FPGA Tuner popular in Japan, for reviewing the measurement results of FM broadcast reception of airspy-fmradion, and various constructive suggestions
• Takehiro Sekine, for suggesting using GNU Radio's VOLK for faster calculation, and implementing Filesource device driver
• Takeru Ohta, for his Rust implementation of Tisserand-Berviller AGC algorithm
• Cameron Desrochers, for his readerwriterqueue implementation of a single-producer-single-consumer lock-free queue for C++
• Clayton Smith, for a bugfix pull request to airspy-fmradion to find an uninitialized variable and his help during bug tracking in VOLK.
• Andrew Hardin, for cmake-git-version-tracking

License

• As a whole package: GPLv3 (and later). See LICENSE.
• Each source code file might state a GPLv3-compatible license.

[End of README.md]