When people consider upgrading from the RTL-SDR, there are three mid priced software defined radios that come to most peoples minds: The Airspy, the SDRplay RSP and the HackRF. These three are all in the price range of $150 to $300 USD. In this post we will review the three units and compare them against each other on various tests.

Note that this is a very long review. If you don’t want to read all of this very long post then just scroll down to the conclusions at the end.

What makes a good SDR?

In this review we will only consider RX performance. So first we will define some terminology, features and specifications that are required for a good RX SDR.

SNR – When receiving a signal the main metric we want to measure is the “Signal to Noise” (SNR) ratio. This is the peak signal strength minus the noise floor strength.

Bandwidth – A larger bandwidth means more signals on the screen at once, and more software decimation (better SNR). The downside is that greater CPU power is needed for higher bandwidths.

Alias Free Bandwidth – The bandwidth on SDR displays tends to roll off at the edges, and also display aliased or images of other signals. The alias free bandwidth is the actual usable bandwidth and is usually smaller than the advertised bandwidth.

Sensitivity – More sensitive radios will be able to hear weaker stations easier, and produce high SNR values.

ADC – Analogue to digital converter. The main component in an SDR. It samples an analogue signal and turns it into digital bits. The higher the bit size of the ADC the more accurate it can be when sampling.

Overloading – Overloading occurs when a signal is too strong and saturates the ADC, leaving no space for weak signals to be measured. When overloading occurs you’ll see effects like severely reduced sensitivity and signal images……

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