SDR Buying guide

What is the best SDR?

There is no such thing as “The Best SDR”. It’s difficult to determine as it depends on the specific needs and preferences of the user. Every SDR has its advantages and disadvantages, depending on what you want to achieve. Also when you do a simple Google search for SDR these days, you will find an overwhelming number of possible choices out there. Each one is more appealing than the other. Moreover, to make matters worse, there are clones or copies of popular devices out there, which do not offer the same features or perform as intended as the original device but also they are more often than not indistinguishable from the original product. So unknowingly investing your hard-earned money in them would be a waste.

How to choose the correct SDR for you?

There are a few things to consider before buying a software-defined radio. Especially if you’re a newcomer and don’t have any idea where to start.

• Frequency Range 

The first thing to consider when buying an SDR is the frequency range. Different SDRs have different frequency ranges, and you must choose one that covers the frequencies you want to receive or transmit. For example, if you want to listen to FM radio, or general VHF/UHF traffic, a simple SDR like RTL-SDR V3 or Nooelec Nesdr would be enough. If you need to listen to HF transmissions, however, you’ll need something which covers HF frequencies like Airspy HF+ Discovery or SDRPlay RSPdx. Even though technically RTL-SDR type devices cover HF via direct sampling, performance is limited. On the other hand, if you want to experiment with cellular networks, WiFi, or Bluetooth networks, you’ll need a high-performance SDR like Hackrf or LimeSDR because they cover frequencies up to 6 GHz. However, there are additional components called Upconverters & Downconverters that can be used to extend the supported frequency range of an SDR or any other RF device by shifting higher or lower frequencies by a local oscillator to the supported frequency range of that device. We’ll discuss them in a future article in much more detail.

• Bandwidth

The bandwidth of an SDR determines how wide a frequency range it can process in real time. If you want to monitor trunk networks such as DMR/P25/TETRA, receive high-resolution weather satellite images from NOAA, Metop, or GOES satellites, or Decode local analog TV broadcasts, you’ll require an SDR that can process higher bandwidth in real-time. Hackrf is a great starting point for higher bandwidth applications since it’s quite a bit cheaper than the other high-performance SDRs.

• Sampling Rate

The sampling rate of an SDR determines how often it samples the incoming signal. A higher sampling rate means more accurate signal processing, but it also requires more processing power. If you plan to use your SDR for extensive signal analysis, demolition or decode, and conduct experiments with different modulations and modes, you should consider investing in something like BladeRF x40 or Ettus B210 since they are proven to be more accurate and precise in those use cases.

• Connectivity

The connectivity options of an SDR are also an essential thing to consider depending on your requirement. Most SDRs connect to a computer via USB, but some also have Ethernet Connectivity. If you plan to use your SDR remotely, you need an SDR with network connectivity. Granted, any SDR can be configured to operate remotely connected to a SBC like Raspberry Pi but having support for ethernet natively is more convenient and less complicated to set up. In that case, Adalm Pluto would be a great asset for you.

• Software compatibility

Software support is another key thing to consider when working with SDRs since not all software is compatible with every SDR and not all SDRs are compatible with every software. You may have to choose the SDR depending on the software you want to work with or choose the software depending on the SDR you want to use. Furthermore, some devices may not have proper drivers for Linux or macOS platforms but only for Windows. That being said, as of these days software support for most devices is improving rapidly so this may not be an issue in the future.

• Price

Finally, the price of an SDR is also an important consideration. SDRs range in price from less than $30 to several thousand dollars. The price depends on the features and capabilities of the SDR. If you are a beginner, it is best to start with a low-cost SDR and upgrade later as your needs grow.

Conclusion

Choosing the correct software-defined radio for you requires careful consideration of several factors and it can be especially tricky with all the fake and knockoff products on the market. It’s always a good idea to do some research online, read reviews and watch some credible youtube videos on the device you want to buy. When you finally decided on the device you want to buy, make sure you buy it from the manufactures official website or one of the authorized distributors. Hopefully, this guide will help you choose the best SDR for your need and clear out some of the confusion. I wish your SDR collection would grow with each passing year and eventually become an obsession (which is what happened to most of us🤭). Good luck.

Written by Dilusha Samarasekara – Associate Member, RSSL