Software Defined Radio

Software-defined radio (SDR) is a technique for turning a computer into a radio. But not just an AM/FM radio - by using the computing power on your desktop you can listen and decode a wide variety of broadcasts. SDR can turn your computer into a weather-band receiver, a police/fire report scanner, a music listening station, and more! Instead of manually tuning inductors like a traditional piece of radio gear, it's all done in software by chips fast enough to pick up and decode radio waves on the fly.

If you've ever been curious about software defined radio (SDR), this USB stick is the easiest way possible to have fun with a powerful, configurable receiver. Packed with the powerful RTL2832U and R820T tuner, it can tune into signals from 24MHz to 1850MHz. That means you can use a computer (with Windows, Mac, or Linux) to tune into: FM Radio, AM signals (but not AM radio), CW (morse code!), unencrypted radio signals (such as those used by many police and fire departments), POCSAG pagers, and more.

1 x Software Defined Radio Receiver
USB stick and antenna

Getting Started

This tutorial will show you how to get your very first listening adventure underway - listening to FM radio and decoding the RDS/RBDS data signal that is sent along with many FM radio stations as well.

Freq Show: RPi RTL-SDR Scanner

Here's a more advanced tutorial for scanning the airwaves around you with an RTL-SDR radio receiver and a Raspberry Pi. It's a totally portable RF visualizer!

Fun SDR Projects To Try

Beyond listening to FM radio and generally exploring the RF spectrum, there are many other fun things to try out with software defined radio. Check out the list below for some ideas. NOTE: some of these projects require additional hardware or antennas, be sure to check the legality of these project in your local area.

TEMPEST- an SDR tool for eavesdropping on computer screens via unintentionally radiated RF

Airplanejs - Airplane Tracking with RTL-SDR for mac os 

Radio Reference Database In this incredibly thorough frequency database, you can check out your local region for interesting frequencies to try. Emergency services, vehicle dispatch, morse code stations, NOAA weather, ship tracking, aircraft/airport communications, there are all kinds of neat things to find!

POCSAG/Flex Pagers Believe it or not, there are still lots of organizations using pagers to send and receive alphanumeric text messages. They are sent in the clear, and with an added piece of decoding software, you can turn these radio waves into texts. This makes us appreciate modern, secure text messaging quite a bit more.

Digital Speech Decoding SDR on it's own can't act like a police scanner of old, because the law enforcement and public safety channels tend to be digital transmissions, not analog ones that we can easily listen to. This software can help you decode those digital transmissions! Here's more info on getting started with DSD+.

Satellite Imagery It's possible to download and view satellite imagery with SDR! It requires a more advanced antenna setup, but if you're interested, this tutorial shows you how!

Watch this video (you can scrub through if you like) to watch the image being downloaded in realtime.

Going Further

This just touched the tip of the SDR iceberg. If you'd like to get more involved, be sure to check out:

  • RTL-SDR.com for lots of great info, news, tutorials, and more
  • RTLSDR subreddit where interested users discuss SDR in great depth
  • SigIDWiki where people help one another identify mysterious signals!
  • Tire Pressure Monitor Systems this one is quite advanced, but a really fascinating bit of reverse engineering by Jared Boone to read the tire pressure on most modern cars over the air!
This guide was first published on Mar 20, 2018. It was last updated on Sep 18, 2018. This page (Software Defined Radio) was last updated on Mar 20, 2018.