How to Get Started With Software-Defined Radio on Linux

​​​​​​Software-defined radio is a hobby enjoyed by millions of people worldwide. You can only receive radio signals on your Linux PC with software and a cheap USB dongle. You can listen to commercial radio stations as well as frequencies that are out of range of regular FM radios, and you can even receive complex data like images over the radio.

What is Software Defined Radio and how is it different from a regular radio?

Radio is one of the oldest communication technologies that allows people to send messages over long distances. Early radios were massive electromechanical devices with valves, tubes, oscillators, and dials that took time to heat up and were complex to operate.

Later radios could fit in your pocket but still required hardware controls to tune a radio to the correct frequency where a signal could be discerned.

Software-defined radios use software instead of physical hardware to receive analog radio signals, which are then converted to a digital signal.

What you need to start using software-defined radio on Linux

To start using SDR on Linux you will need:

1. A desktop or laptop running Linux – here’s how to install Linux on any PC or laptop.
2. A software defined radio USB dongle – we recommend the RTL SDR V3.
3. A suitable antenna
4. You will also install SDR drivers and GQRX on your Linux system

How to receive radio signals on Linux

Open a terminal with the keyboard shortcut ctrl + Old + T or by selecting Terminal from your menu system and then updating and updating all installed packages with APT:

sudo apt update
sudo apt upgrade

Install that rtl-sdr package and the software-defined GQRX radio receiver package:

sudo apt install rtl-sdr gqrx-sdr

This is a small command, but it results in a large download of around 700MB depending on what dependencies you already have installed. Before you start, you should make sure that you have enough free disk space on your Linux system.

Once you return to the command prompt, reboot your system.

reboot

Once your Linux system has booted up again, attach the antenna to your SDR USB stick and plug it into a free USB port. Now open another terminal and check if your system has the correct drivers and has successfully detected your SDR hardware.

rtl_test -t

The output should show the device name along with the supported gain values. Write down the device name and model number. In this case it is “Realtek, RTL2838UHIDIR”.

You have successfully installed the hardware you need to use your software-defined radio.

Using your software-defined radio on Linux

You have already installed the GQRX receiver software. Launch it from your start menu or from the terminal and in the window that appears select your model name from the drop down list and leave the other fields with their default values.

Once you’re on the main GQRX screen, you can start scanning the ethers by clicking the triangular “Play” button on the top left of the screen. You’re unlikely to get a strong signal right away, and if your computer speakers are on, all you’ll hear is static.

GQRX will display a random waveform on the top half of the screen (spectrum display) and the bottom half of the screen (the waterfall display) begins to fill in blue.

The current frequency is displayed at the top of the screen and you can change this value by clicking each digit or scrolling the mouse wheel. You can fine tune the frequency by dragging the red bar across the spectrum display to a strong signal.

Choose “input controls” on the right side of the screen and increase “LNA Boost”. This will boost the signal strength coming from the USB-SDR to the GQRX.

You should be able to see spikes in the spectrum display at frequencies where a strong signal is detected. You can tune into it by clicking on the tip.

You can now use GQRX and an SDR to receive radio signals on Linux

These were the basics for getting started with SDR on Linux. To continue your journey, examine strong signals and frequencies of interest in your area. You can hear police radio, taxi traffic and even air traffic control communications. Remember that you need a license to transmit radio signals.

If you don’t want to invest in the hardware required to set up an SDR, you can use your web browser to listen to the radio.