Hardware

Explore Software Defined Radio — by Wolfram Donat (6 / 30)

👈 Chapter 1 Installing the Required Bits and Pieces | TOC | Software 👉

Let’s talk about the hardware that’s necessary for any software-defined radio experimentation. The first thing you’re going to need, obviously, is a radio — or its equivalent in the SDR world: a USB dongle. Most dongles in the SDR space have been originally designed as TV tuners, to allow the user to receive HD TV signals out of the air. As their popularity has grown (for both tuning into television signals and for software-defined radio enthusiasts) they’ve come down significantly in price, and many of them can be used to detect all sorts of signals, given the right antenna. Repurposing these dongles fits one definition of hacking: making a device do something it wasn’t built to do.

The most common SDR dongles you’re likely to see use the RTL28xx interface and the Realtek R82xx tuner chipsets, housed in a variety of different packages. The dongle I’m currently using (see the image that follows) is from NooElec and is available from your favorite online retailer for around $20 (https://www.amazon.com/gp/product/B009U7WZCA/).

Others are available, of course, from various retailers, so don’t feel any pressure to purchase one over another. That being said, however, remember my earlier warnings about getting different setups to work? If you’re completely new to the SDR world, it may behoove you to duplicate my efforts here exactly, starting with the hardware I’m using. I would hate for you to duplicate my steps exactly but have the project not work because of some vague mismatch between your hardware and your software, or because your USB device isn’t readable by your SDR software.

The next piece of hardware you’ll need is an antenna, to grab all of those beautiful signals out of the air and funnel them into your SDR dongle. Chapter 4 is all about antenna design and theory and which antennas will do the best job for particular projects and signals, but when you’re just getting started and getting familiar with the processes involved, you just need any old antenna.

The NooElec dongle in the previous link comes with an antenna; my experience is that the included antenna is worth about as much as a snowblower in the Mojave. Two hours spent trying to listen to the local radio station and failing to get anything convinced me to try another antenna I had picked up when I was still unsure as to what I needed. Don’t be afraid to switch antennas, as switching antennas can make all the difference, along with placement (which we’ll get into later as well). When you’re first getting started and are just trying to pick up some signals — any signals — you may have good luck with this one: https://www.amazon.com/1090Mhz-Antenna-Connector-2-5dbi-Adapter/dp/B013S8B234/ (see the following image). I certainly did. Out of all of the pieces in the SDR puzzle, the antenna may make the most difference. You may get your setup to work perfectly, but if your antenna is wrong (such as being the wrong design or having the wrong placement), you may have no luck picking up signals. Feel free to experiment.

We’ll be switching up our antenna for our later projects, but this is a good one to start with. Whichever one you choose, make sure that the connector matches the connector on your dongle, which is most likely an SMA (the first of the two images that follow) or an MCX (the second image). Happily, many add-on antennas come with an array of adapters to fit most any radio device.

You will most likely want to get a longer cable. The stand-alone antenna I bought, for instance, comes with a 1-meter cable, which is plenty for some simple experimentation — picking up your local radio station, for instance. However, success with SDR depends not only on the antenna but the antenna placement. Getting the antenna far away from your computer and other noisy devices is crucial, especially as the strength of the signal you’re trying to receive decreases. As I said, we’ll get into antenna design a bit later on, but a longer cable is almost guaranteed to be a necessity. Again, make sure the extension cable you choose fits not only the antenna but the connector on your USB dongle. Also make sure your genders are correct on each end of the cable; you may want to purchase a selection of gender-changing adapters to go with your SDR toolbox.

That’s the bare minimum of hardware you’ll need to start experimenting. Read on for an introduction to the software we’ll be using.

👈 Chapter 1 Installing the Required Bits and Pieces | TOC | Software 👉

Explore Software Defined Radio by Wolfram Donat can be purchased in other book formats directly from the Pragmatic Programmers. If you notice a code error or formatting mistake, please let us know here so that we can fix it.