Signals

Demodulate radio signals in real time from your JavaScript or TypeScript application.

What is this

This is a library that provides functions to receive or generate radio signals, demodulate them, and play the result through the computer's speakers or headphones.

How to install

npm install @jtarrio/signals

How to use

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

Demodulate and play through the computer's speakers

This program generates an AM signal, demodulates it, and plays it through the computer's speakers.

import { Demodulator } from "@jtarrio/signals/demod/demodulator.js";
import { getMode } from "@jtarrio/signals/demod/modes.js";
import { Radio } from "@jtarrio/signals/radio.js";
import { modulateAM, tone } from "@jtarrio/signals/sources/generators.js";
import { SimpleProvider } from "@jtarrio/signals/sources/provider.js";
import { GeneratedSource } from "@jtarrio/signals/sources/generated.js";

// Create the source, demodulator, and radio and connect them.
let source = new GeneratedSource(modulateAM(810000, 0.1, tone(600, 0.5)));
let demodulator = new Demodulator();
let radio = new Radio(new SimpleProvider(source), demodulator);

radio.setFrequency(810000);
demodulator.setVolume(1);
demodulator.setMode(getMode("AM"));

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

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

Acknowledgements

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