gr-frontends

GNUradio frontends that stream from different hardware to UDP

This repository is a collection of frontends that serve to stream from several different SDR hardware, recordings and other sources to UDP. The UDP data can be processed by another program.

The stream format is 1 channel 48kHz int16_t. It is the same format that gqrx uses to stream audio

The main goal of this repository is to be used with gr-satellites, but it can be used with many other pieces of software.

Branches

There are two branches:

• master. Supports GNU Radio 3.8
• maint-3.7. Supports GNU Radio 3.7

Usage

You can open the .grc file with gnuradio-companion and edit the parameters (they are on the upper part of the flowgraph). You can also run the .py script and specify the parameters on the command line. Use the -h flag to get help on how to specify the parameters.

Supported streamers

SDR hardware

The goal is to support as many different SDR hardware as possible. However, I can't test streamers for hardware I don't have. It is easy to modify an existing streamer to use with another SDR hardware supported by GNUradio. Then, it can be included in gr-frontends.

The streamers come in several different receive modes:

• usb This is like a normal USB receiver. The passband is 3kHz and the signal is tuned to 1.5kHz inside the passband. Use this for signals such as 1k2 BPSK or to record CW audio.
• usb_wide This is a wide USB receiver. The passband is 24kHz and the signal is tuned to 12kHz inside the passband. Use this for signals such as 9k6 BPSK.
• fm This is an FM demodulator. Use this for any kind of FSK signals.

All the hardware streamers support Doppler correction with Gpredict and gr-gpredict-doppler (you need to install this out-of-tree module if you want to use Doppler correction). To use this, you should set in Gpredict as downlink frequency the frequency of interest that you want to receive.

List of supported hardware:

• airspy Airspy devices.
• fcdpp FUNcube Dongle Pro+. It is necessary to install gr-fcdproplus.
• rtlsdr Receivers using an RTL-SDR chipset.

Recordings

WAV file streamers

The audio streamers are designed to play back and stream an audio wav file.

You have to choose the appropriate sampling rate. The available streamers are the following:

• wav_48kHz 48kHz WAV streamer
• wav_44kHz 44.1kHz WAV streamer

Hint: It is sometimes useful to play a WAV file repeatedly in loop. By default the streamers will only play the file once, but you can edit them with gnuradio-companion and set the WAV file to repeat.

Audio streamers

The audio streamers are designed to stream from the audio system: from a soundcard (to connect to a conventional receiver) or a virtual audio cable (to connect to another SDR program or software that doesn't support UDP streaming).

The available audio streamers are the following:

• audio_streamer It uses the Audio source block in GNUradio, so it will use whatever sound system is available for GNUradio in your machine.

  To stream from Linux pulseaudio, use ./audio_streamer.py --device=pulse. It might be necessary to configure the pulseaudio socket:

  $ id -u
  1001
  $ PULSE_SERVER=unix:/run/user/1001/pulse ./audio_streamer.py --device=pulse
  

Hint: In Linux you can use pulseaudio and pavucontrol or snd-aloop as a virtual audio cable between different applications.