After extensively researching Software-defined Radios (SDR), we think the HackRF is the best product. It covers the most popular frequency range of 10 MHz to 6 GHz which includes everything from FM radio, Smart phones to 5 GHz Wi-Fi. The product includes both transmitter and receiver and can be used for a variety of real-world applications.
With a growing community of users, interfaces to popular SDR frameworks such as GNU Radio and support for software like SDR# a user can be up and running in no time. At a price point of $300 the HackRF provides excellent value for money and is the best SDR on the market today.
The runner up is: ADALM Pluto from Analog Devices
Best budget pick: RTL-SDR
- How does Software-defined radio work and what are the applications?
- How we picked the best Software-defined Radio
- Our SDR pick: HackRF
- Flaws but not deal breakers
- The runner-up: ADALM Pluto
- The best budget SDR: RTL-SDR
- The future of SDR
- Notable mentions
How does Software-defined Radio work and what are the applications?
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 a 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! SDRs are used to track ships and planes, in radio astronomy, to track wild animals, ham radio and a number of other interesting applications.
How we picked the best Software-defined Radio
We looked for a wide range of SDRs in the under-$100 and under-$300 price brackets. While there are a number of factors that can be considered when picking an SDR, the three main considerations are Hardware specifications, Community support, Software support.
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 and USB.
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.
The larger the community of people using a SDR the better. This results in better support for hardware, more use cases and definitely more collaboration.
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 two 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 from HackRF, Lime SDR, BladeRF, AirSpy, Kiwi SDR, RTL-SDR and ADALM Pluto.
Our SDR pick
The HackRF One covers a broad frequency range from 10 MHz to 6000 MHz to cover 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 – MHz wide. The product has a USB interface which allows for high speed data throughput into a host processor. The antenna port can provide up to 50 mA of current at 3.3V 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.
Flaws but not deal breakers
Here are a few of the limitations of the HackRF:
- The dynamic range is limited to about 44 dB which is not high relative to at least a couple of the competitors. This limits HackRF’s applicability in real-world environments where it’s relatively common to come across wide variations in signal levels.
- The maximum input receive signal power of -5 dBm. Signals stronger than this will damage the HackRF.
- The power amplifier in the transmitter is susceptible to damage likely on account of its design
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 ADALM is priced at only $150 so it presents very compelling value and with a company like Analog Devices behind it, you can be sure there will be some exciting enhancements in the works.
The best budget 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 it 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.
The future of SDR
There’s growing interest in SDR for RF Test, R&D, Education and 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.
We considered a number of SDRs during our research and this is a short-list of the competition and summary of our research and the strengths and weaknesses of each of the products considered.
The AirSpy R2 is a receiver-only SDR which covers a frequency range of 24 MHz to 1700 MHz. We think of it as a more sophisticated RTL-SDR with a sampling rate of up to 80 million samples per second which allows the user to process waveforms that are 10 MHz wide. The Airspy has built-in tracking filters for interference suppression. The product has a USB interface which allows for high speed data throughput into a host processor. The antenna port can provide up to 50 mA of current at 4.5V to enable the operation of a low noise amplifier for noise reduction and greater sensitivity.
Unlike the HackRF, the Airspy is not open source and lacks the transmitter functionality that is very important for a number of applications. As well, the limited frequency range prevents its use in the very popular ISM bands. We would recommend buying this product if you are interested in a higher performance variant of the RTL-SDR.
The KiwiSDR is a receive-only SDR that operates over a very limited frequency range of 10 kHz to 30 MHz. This SDR will only be of interest to those conducting HF receive experiments. The KiwiSDR is different from other SDRs as it is a custom circuit board (cape) you connect to the BeagleBone Green (BBG) or Beagle Bone Black (link) computer. The KiwiSDR is available as a cape only or a complete kit that includes the BBG, enclosure and GPS antenna. Both versions include software supplied on a micro-SD card.
What makes this SDR unique? Since the KiwiSDR interfaces directly to the BBG, data can be processed locally on the host processor and the device can be connected to the internet. In fact there is a network of over 100 KiwiSDRs online and you can try them out on the sdr.hu website. An HTML5-capable browser and internet connection will let you listen to a public KiwiSDR anywhere in the world. Up to four people can listen simultaneously to one radio — each listener tunes independently.
Specifications of this SDR are probably the best of the ones we have researched with a 14-bit ADC providing in excess of 70 dB dynamic range. The only negative is the software features and support are relatively immature.
We have studied a number of products to bring you the three best SDRs. 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 points. 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.