The Best Software-defined Radios (SDR) for 2021 – A Radio Engineer reviews products

Updated August 2021

There are many software-defined radios on the market today and it’s not easy to pick one. We’ve tested SDRs, analyzed many confusing specifications and simplified the selection process to present you with our recommendations.

After extensively researching Software-defined Radios (SDR), we have concluded that the HackRF is the best product. HackRF is a transceiver that covers the most popular frequency range of 10 MHz to 6 GHz. The product can be used as both a transmitter and a receiver for a variety of real-world applications.

Here is our table of the best software-defined radios for 2021. Below we have also reviewed each of our top picks and outlined our research methodology.

  • 10 - 6000 MHz

  • Transmit & Receive

  • 10-bit ADC/DAC

  • 325 - 3800 MHz

  • Transmit & Receive

  • 12-bit ADC/DAC

  • 0.5 - 1700 MHz

  • Receive

  • 8-bit ADC

  • 0.001 - 2000 MHz

  • Receive

  • 14-bit ADC

  • 70 - 6000 MHz

  • Transmit & Receive

  • 12-bit ADC/DAC

         

         

The Research

         

The Best Software-defined Radio Transceiver  – HackRF One

The HackRF One covers a broad frequency range from 10 MHz to 6000 MHz to include the most popular bands of operation. It has both a transmitter and a receiver to enable true standalone operation as a radio system. The HackRF has a sampling rate of 20 million samples per second which allows the user to process waveforms that are 10 MHz wide. The product has a USB 2.0 interface which allows for high speed data throughput into a host processor. The antenna port can provide up to 50 mA of current at +3.3 V to enable the operation of a low noise amplifier for noise reduction and greater sensitivity.

The HackRF is fully open source with support for GNU Radio, SDR# and a large community of users with an active mailing list and support. The HackRF provides excellent value for money and is the best SDR on the market today.

PROS

  • Completely open source
  • Many online learning resources including how-to videos
  • Excellent accessories like the PortaPack
  • Frequency coverage and bandwidth

CONS

  • The maximum input signal power of -5 dBm.  Signals stronger than this will damage the HackRF
  • Half-duplex operation so you cannot transmit and receive simultaneously
  • The power amplifier in the transmitter is susceptible to damage

Read more reviews on Amazon

         

Runner-up software-defined radio transceiver – ADALM Pluto

Our pick for the runner up is the ADALM Pluto from Analog Devices. Like the HackRF this is a transceiver product so you can both transmit and receive signals with it. The ADALM was introduced in 2018 and even though it’s a relatively new product, it has excellent support from MATLAB for education and there’s an entire free education course that has been developed around this hardware. The price of the ADALM Pluto is lower than the HackRF, so it presents very compelling value.

PROS

  • Price
  • Full Duplex – transmitter and receiver can be operated simultaneously

CONS

  • Limited Frequency range
  • Lack of GNU Radio support

Read more reviews on Amazon

         

Best Budget Software-defined radio receiver – RTL-SDR

If you are looking for a low cost device to experiment with SDR and get your toes wet, look no further than the RTL-SDR. It is a small USB dongle that is packed with radio receiver electronics! On account of its low cost this is is truly the Arduino of the SDR world. The RTL-SDR is being used in thousands of applications as varied as Airplane tracking, Cellphone identification, Ham Radio and in schools to learn about communication signal processing.

PROS

  • Price
  • Large community of users
  • Extensive Software Support – pretty much every software works with this device from GNU Radio to MATLAB

CONS

  • Limited hardware specifications such as bandwidth and dynamic range

Read more reviews on Amazon

         

Best Software-defined Radio Receiver – SDRPlay RSP1A

The SDRPlay RSP1A is a powerful wideband full featured 14-bit SDR Receiver which covers the RF spectrum continuously from 1 kHz to 2 GHz. This product has a bandwidth of 10 MHz, large enough for most RF signals. It works with the Windows-based SDRuno software that is provided free of charge with the hardware. This is the only receiver product that actually has pre-select filtering built-into the hardware. As we have discussed here, preselect filters help with reducing the impact of interfering, strong out-of-band signals.

The SDRPlay RSP1A provides excellent controls for adjusting and trading off the linearity against the gain and noise figure. The benefit of this is that the user can adjust the receiver depending on the strength and frequency of the signal.

For a more advanced receiver option there is also a slightly more expensive version of this hardware with two software-selectable inputs called the RSPDx.

The RSP ships with a plastic case. For better immunity from RF interference, you can get this metal case.

PROS

  • Excellent receiver quality and specifications
  • Built-in filters and user controls for signal conditioning
  • Includes a well-designed bias tee feature for improving sensitivity
  • Price

CONS

  • Lack of software maturity and broader community support

Read more reviews on Amazon

         

Fastest SDR transceiver – USRP B205mini-i

The USRP B205mini-i is a new SDR platform introduced in December 2020. It has a wide frequency range (70 MHz to 6 GHz). The industrial grade Xilinx FPGA is user-programmable. The most significant differentiators of the USRP B205mini-i over others in this list are:

  1. 56 MHz of instantaneous bandwidth to process wideband LTE and Wi-Fi signals
  2. High-speed USB 3.0 connection for fast data streaming to the host computer
  3. Synchronization with a 10 MHz clock reference or PPS time reference input signal.

PROS

  • Fast throughput
  • Good integration with GNU Radio

CONS

  • Does not cover anything below 70 MHz which is an area of interest for many HF and VHF users
  • High Cost

Read more reviews on Amazon

         

FREQUENTLY ASKED QUESTIONS

         

What is the Best SDR Software?

Here is a list of the best software for Software-defined Radio. All of these are free.

1. SDR# or SDRsharp

SDR software for Airspy and RTL-SDR dongles. It includes a number of signal processing modules such as a High Performance ADS-B Decoder, A Fast Sweeping SDR Spectrum Analyzer and a Radio Astronomy Utility for Hydrogen Line Spectroscopy.

2. SDR-Radio

Windows software for Software Defined Radio (SDR) receivers and transceivers. Designed for the commercial, government, amateur radio and short-wave listener communities, this software provides a powerful interface for all SDR users. This software supports radios from most major manufacturers.

3. GQRX

Gqrx is an open source software defined radio receiver (SDR) powered by the GNU Radio and the Qt graphical toolkit. Some interesting features of GQRX include: AM, SSB, CW, FM-N and FM-W (mono and stereo) demodulators. Special FM mode for NOAA APT. The software also includes a variable band pass filter, Automatic Gain Control, Squelch and Noise blankers, FFT plot and waterfall and a number of other processing blocks.

4. SigDigger

SigDigger is a graphical, digital signal analyzer written in Qt5 for Unix systems like GNU/Linux or MacOS. Unlike existing alternatives, SigDigger is not based on GNU Radio. Instead, it uses its own DSP library (sigutils) and a realtime signal analysis library (Suscan) that exploits multicore CPUs to distribute load. SigDigger works in x86-64 CPUs running MacOS or GNU/Linux. In terms of performance, it can beat Gqrx by a factor of 20% (measured as saved CPU usage).

5. HDSDR

HDSDR is a freeware program for Windows 2000/XP/Vista/7/8/8.1/10. Typical applications are Radio listening, Ham Radio, SWL, Radio Astronomy, NDB-hunting and Spectrum analysis. The main features of this software are: separate large spectrum and waterfall display for input and output signals, AM, ECSS, FM, SSB and CW demodulation.

Sigdigger

         

How does Software-defined Radio work?

Software-defined radio (SDR) is a radio system where traditional analog components are replaced with digital components and software technologies. In traditional radio systems, a radio was designed entirely in analog and for a specific application. By contrast an SDR can be used to process a wide variety of signals from HF to Bluetooth thanks to the flexibility of software. One SDR to process any signal. This is what makes it so compelling! An important aspect of SDR is the host processor that is used to process the raw data that the SDR sends to it. A host processor like one of the single board computers that we have talked about in this post will take this raw data (ones and zeros) and process it further. For instance the binary data can be input to an FFT block so that you can see the spectrum of the signal. Alternatively it can be demodulated and turned to an audio or video signal for further analysis.

         

What are the Applications of SDR?

Software-defined Radios are used by Academics, Hobbyists and Professionals alike. They are used to track ships and planes, in radio astronomy, to track wild animals, ham radio and for a number of other interesting applications. We have written a longer article on applications here.

         

What is the Best SDR Dongle?

The best SDR dongle is the RTL-SDR. It’s affordable, has good hardware specifications, works with most SDR software out there and there’s a large community of users so you will always get the support you need.

         

How we Picked the Best Software-defined Radio

We looked for a wide range of SDRs in four different price ranges: $50, $100, $300 and $1000. While there are a number of factors that can be considered when picking an SDR, the three main considerations are Hardware specifications, Community support and Software support.

HARDWARE SPECIFICATIONS

Frequency Range: An SDR must cover a wide frequency range for it to be considered useful. Since most popular applications are limited to 6 GHz it is important that the SDR be able to operate to this maximum frequency.

Bandwidth and interface speed: Bandwidth which is largely determined by the analog design and digitizer sampling rate enables the SDR to process analog waveforms. The speed of the interface determines how much data can be moved to the host processor. Example interfaces include 10/100 Ethernet, USB 2.0 and USB 3.0.

Sensitivity and Dynamic range: Sometimes a strong signal from a nearby transmitter such as a cell tower can overwhelm a detector and prevent it from detecting a weak signal. As well, sometimes the detector generates a significant amount of internal noise and is therefore unable to detect a weak signal. The ability of the tracker to detect a weak signal in both the absence and presence of a stronger signal is a plus.

COMMUNITY SUPPORT

The larger the community of people using an SDR the better. This results in better support for hardware, more use cases and definitely more collaboration.

ACCESSORIES

We also considered accessories that were available with any particular SDR. Everything from the Portapack that turns the HackRF into a handheld SDR to external amplifiers that increase the range of HackRF or ADALM Pluto.

SOFTWARE SUPPORT

Software makes SDR useful. There is a large ecosystem of SDR software applications and toolkits in areas such as Test & Measurement, Signal Monitoring and R&D. GNU Radio is one example of a software development toolkit that provides signal processing blocks to implement SDRs. For an SDR to be useful it should interface with relevant software applications.

Once we came up with a preliminary list of all the SDRs on the market in our different price categories, we narrowed them down by studying data-sheets, performance for various practical applications, user documentation, Amazon user reviews and professional reviews from other sites focused on SDR. This left us with devices on this list.

         

The Future of SDR

There’s growing interest in SDR for RF Test, R&D, Education and many other applications. SDRs have been slowly replacing custom, application-specific chipsets with a move toward general-purpose radios and software processing. In the future most of the signal processing in a radio system will be done in software and at lower price points. Also radio hardware will move toward common platforms with a single radio being able to demodulate multiple standards. We’re already seeing this in many smartphones today.

         

Summary

We have studied a number of products to bring you the best SDRs. We recommend the HackRF as our top pick. Our top software-defined radios for 2021 are:

The field of SDR is changing very rapidly and there continues to be a lot of innovation in hardware chipsets and components. This in turn is driving the development of platforms with increasing capability and decreasing price. With products like the RTL-SDR we have truly entered Arduino-type accessibility. It will be interesting to see the wide range of applications that will emerge as a result of this.

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