Web RTL-SDR

Access RTL-SDR devices and receive and demodulate radio signals from your web application.

What is this

This is a library that provides functions to access and operate an RTL-SDR device from a web application, receive radio signals, demodulate them, and play it through the computer's speakers or headphones.

It provides low-level access to the RTL-SDR stick, and also uses the Signals library to provide a full reception/demodulation pipeline.

This library powers Radio Receiver, my browser-based SDR application, which you can try at radio.ea1iti.es.

Compatible hardware and software

Web RTL-SDR was written to work with an RTL-2832U-based DVB-T (European digital TV) USB receiver with a R820/828/860 tuner chip. Support for other chips may be added as required.

Web RTL-SDR uses the WebUSB API, which is only available in Chromium-based browsers (Chrome, Edge, Opera) on computers and Android devices.

How to install

npm install @jtarrio/webrtlsdr

How to use

See the docs directory for the documentation, or check out the following examples.

High-level access to RTL-SDR (demodulate and play through the computer's speakers)

This program is a complete stereo FM radio receiver tuned for 88.5 MHz.

import { Demodulator } from "@jtarrio/signals/demod/demodulator.js";
import { getMode } from "@jtarrio/signals/demod/modes.js";
import { Radio, RtlProvider } from "@jtarrio/webrtlsdr/radio.js";

let demodulator = new Demodulator();
let radio = new Radio(new RtlProvider(), demodulator);

radio.setFrequency(88500000);
demodulator.setVolume(1);
demodulator.setMode(getMode("WBFM"));

document
  .getElementById("playButton")
  .addEventListener("click", () => radio.start());
document
  .getElementById("stopButton")
  .addEventListener("click", () => radio.stop());

You can also see a full example at examples/highlevel.

Low-level access (read samples straight from the stick)

This program connects to the RTL-SDR stick, tunes to 88.5 MHz, reads 65536 samples, and closes the connection.

import { RTL2832U_Provider } from "@jtarrio/webrtlsdr/rtlsdr.js";

let provider = new RTL2832U_Provider();
let device = await provider.get();
await device.setSampleRate(1024000);
await device.setCenterFrequency(88500000);
await device.setGain(null);
await device.resetBuffer();
let samples = await device.readSamples(65536);
await device.close();

You can also see a full example at examples/lowlevel.

Acknowledgements

This is a spinoff of https://github.com/jtarrio/radioreceiver, which is, in turn, a fork of https://github.com/google/radioreceiver. (I am the original author, but I was employed by Google at the time.)

Kudos and thanks to the RTL-SDR project for figuring out the magic numbers needed to drive the USB tuner.