No-SDR: A New Open Source Multi-User WebSDR for RTL-SDR

Thank you to George (gbozo), who has just released no-sdr (named from No(de)-sdr), a new open source multi-user WebSDR for the RTL-SDR written in Go and node JS. A WebSDR allows users to run an SDR remotely and access it over a local or internet network connection. This is useful for bringing an SDR closer to an antenna, instead of running a long, lossy coax cable, and for sharing SDRs among multiple networked users.

The no-SDR software runs on x86 or Raspberry Pi, is Dockerized, and supports multiple RTL-SDR dongles being connected at the same time. On the DSP side, it currently implements WFM (stereo + RDS), NFM, AM, AM Stereo (experimental stereo C-QUAM), USB, LSB, CW, and raw IQ, with digital decoders like ADS-B, AIS, APRS, POCSAG, FT8, and WSPR planned. There is also an "Identify Song" button that uses the Audd API to ID currently playing tracks on WFM, NFM, and AM.

George also points out that he's implemented an innovative lossless FFT codec with a very high ~10:1 compression ratio, as well as the Opus codec for audio. The result is a 12-15 kB/s transmission rate with a 12 FPS FFT with 8192 bins and AM demodulation compressed audio.