Software Defined Radio is a hobby enjoyed by millions of people around the world. With it, you can receive radio signals on your Linux PC using only software and a cheap USB dongle. You will be able to listen to commercial radio stations, as well as frequencies beyond the range of normal FM radios, and you will even receive complex data such as images by radio.
What is Software Defined Radio and how is it different from a normal radio?
Radio is one of the oldest communication technologies that allows humans to send messages over long distances. Early radios were massive electromechanical devices with valves, tubes, oscillators, and dials, which 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 transmitted.
Software-defined radios use software rather than physical hardware to receive analog radio signals, which are then converted to a digital signal.
What you need to start using Software Defined Radio in Linux
To start using SDR on Linux, you will need:
- A desktop or laptop running Linux: Here’s how to install Linux on any PC or laptop.
- A USB software defined radio – we recommend the RTL SDR V3.
- A suitable antenna
- You will also install the SDR and GQRX drivers on your Linux system
How to Receive Radio Signals in Linux
Open a terminal with the key combination CTRL + Other + J or by selecting terminal in your menu system, then update and upgrade all installed packages using APT:
sudo apt update
sudo apt upgradeInstall it rtl-sdr package and the GQRX software defined radio receiver package:
sudo apt install rtl-sdr gqrx-sdrThis is a small command but will result in a large download of around 700MB, depending on what dependencies you have already installed. Before you start, you need to make sure you have enough free space on your Linux system.
Once you return to the prompt, restart your system.
rebootOnce your Linux system has restarted, connect the antenna to your USB SDR and plug it into a free USB port. Now open another terminal and check if your system has the right drivers and successfully detected your SDR hardware.
rtl_test -tThe output should reveal 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 in 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, choose the name of your model from the drop-down list and leave the other fields with their default values.
Once on the main GQRX screen, you can begin scanning waves by pressing the triangular “Play” button in the top left of the screen. You’re unlikely to pick up a strong signal right away, and if your computer speakers are on, you’ll only hear static.
GQRX will display a random waveform in the upper half of the screen (spectrum display) and the lower half of the screen (the waterfall display) will begin to fill with blue.
The current frequency is displayed at the top of the screen and you can change this value by clicking on each digit or by scrolling with your mouse wheel. You can fine-tune the frequency by dragging the red bar on the spectrum display to a strong signal.
Select “Input commands” on the right side of the screen and increase the “LNA gain”. This will amplify the signal strength coming to GQRX from the USB SDR.
You should be able to see spikes in the spectrum display at frequencies where a strong signal is detected. You can listen to them by clicking on the pic.
You can now use GQRX and an SDR to receive radio signals in Linux
These are the basics for getting started with SDR on Linux. To continue your journey, investigate strong signals and frequencies of interest in your area. You will be able to hear police radios, taxi traffic and even air traffic control communications. Remember that to transmit radio signals you will need a license.
If you don’t want to invest in the hardware needed to set up an SDR, you can listen to the radio using your web browser.
