The Airspy Mini is a recently released $99 USD software defined radio with a tuning range of 24 MHz to 1800 MHz, 12-bit ADC and up to 6 MHz of bandwidth. The Mini is the younger brother of the $199 USD Airspy R2, but despite the $100 USD price difference, both units are very similar, which makes the Mini a very attractive option. The idea is that the Mini is the cheaper version for those who do not need the more advanced features of the R2.

In a previous review we compared the Airspy R2 with the SDRplay RSP and the HackRF. In those tests we found that the Airspy had the best overall RX performance out of the three as it experienced the least amount of overload and had the most dynamic range. The SDRplay RSP was the main competitor in performance to the Airspy R2, and was found to be more sensitive due to its built in LNA. But the RSP experienced overloading and imaging problems much easier. With an external LNA powered by its bias tee, the Airspy gained a similar sensitivity and still had very good dynamic range. The main downside to the Airspy R2 was its higher cost compared to the $149 USD SDRplay RSP, and needing to fork even more for the $50 USD SpyVerter if you want to listen to HF signals.

In this review we'll compare the difference between the R2 and Mini, and also see if the cheaper Airspy Mini ($99 USD), or Airspy Mini + SpyVerter combo ($149 USD) can compete in this lower price range.

Difference Between the Mini and R2

Airspy Mini Airspy R2 Price $99 USD $199 USD Tuning Range 24 - 1800 MHz 24 - 1800 MHz ADC Bits 12 12 Maximum Bandwidth (Alias Free Usable) 6 MHz (5 MHz) 10 MHz (9 MHz) Extras Bias Tee Bias Tee, External clock input, Multiple expansion headers Dimensions (Including USB and SMA ports) 7.7 x 2.6 x 1 cm 6.4 x 2.5 x 3.9 cm Weight 21 g 65 g

Right now the "early bird" price of the Mini is $99 USD. We are unsure if this price will go up in the future.

The external design between the two units is different. The Mini comes in a USB dongle form factor which is very similar to a standard RTL-SDR, whilst the R2 comes in a larger box with a female Micro USB input. In our tests this metal enclosure appears to provide good shielding from strong signals. One thing that was missing on the unit was a nut and washer on the SMA connector. Adding a nut helps the PCB ground make good contact with the aluminum enclosure. The Airspy team have said that future units will come with this nut provided.

Apart from the price and enclosure, the most noticeable feature difference between the two is the smaller bandwidth of the Airspy Mini. Unlike the Airspy R2, the Airspy Mini does not use a Si5351 clock generator chip. The lack of this chip limits the Mini's maximum bandwidth to 6 MHz and eliminates any ability to use an external clock. The main applications that you miss out on from the lack of an external clock input include: coherent clock, passive radar and direction finding experiments.

From the circuit photos below we can see that the Mini consists of mostly the same parts used in the Airspy R2. Missing is the Si5351 clock controller, expansion headers and the external clock input.

Setup

Like the Airspy R2, the Mini is very easy to set up. We simply plugged it into the PC, opened SDR#, selected the Airspy in the drop down menu and pressed play. And it worked.

With its 6 MHz lower sample rate the Mini works fine on our older first and second generation i5 PCs which can not smoothly run the R2 at its maximum bandwidth of 10 MHz. For PCs that struggle, there is also the option to turn on "packing" which will reduce the data transfer rate, or to reduce the bandwidth to the 3 MHz option. We have heard that the R2 now also supports the 6 and 3 MHz option too with the latest firmware.

Signal Performance

Here we tested the Airspy Mini in SDR#, the official software.

As expected the RX performance of the Mini is pretty much identical compared to the R2. As such, overloading in the Mini is rare and the spectrum always looks very clean, only showing real signals, and no images. See our previous review for more information on the Airspy signal performance.

The smaller bandwidth is still wide enough to look at several wide band signals, and is large enough for most general signal browsing purposes. However, whilst the bandwidth of the device is advertised as 6 MHz, in reality you are only likely to be able to use about 5 MHz as the edges have roll off and aliasing. SDR# automatically limits the visible bandwidth to 80%, which gives 4.8 MHz when run in 6 MSPS mode, and 2.4 MHz when run in 3 MSPS mode. Although the visible bandwidth is 80% lower, that unusable 20% still helps with decimation, resulting in better SNR.

Below we present some screenshots comparing the Airspy R2 and Mini on some trunking channels in their 10 MHz and 6 MHz modes. SNR and the spectrum is nearly identical, only difference is the bandwidth.

Again compared on L-band Inmarsat AERO signals using a decimation value of 16 for the Mini and 32 for the R2. Almost identical performance.

Airspy Mini vs R2 Lband

The Mini actually does unofficially support a 10 MSPS (10 MHz) mode, however because of the lack of the Si5351 clock controller, in this mode there are two fixed spurs visible, plus some other potential spurs at other locations in the frequency spectrum too. These spurs may or may not affect the usefulness of this unofficial mode for you. To use this mode edit the SDRsharp.config file and set the "airspy.debug" key to 1. Now in SDR# you can manually enter 10 MSPS into the sample rate selector and push enter. We must also warn that in this debug mode there are several additional buttons exposed that could cause the eeprom to be flashed incorrectly, thus damaging your device. Please take care not to press on these.

In the screenshot below notice the two spurs which show up on the Airspy Mini running in the unofficial 10 MHz mode.

Airspy Mini vs R2 Trunking Unofficial 10 MHz Mode

Spectrum Spy (Spectrum Analyzer) Performance

The SDR# download includes a program called Spectrum Spy. This program allows you to do a frequency scan on a large bandwidth between 24 - 1800 MHz. This essentially turns the device into a wide band spectrum analyzer. Spectrum Spy works well with the Airspy Mini, but the R2 works even better, scanning about twice as fast, since the bandwidth of the mini is almost halved. Still, the scan speed is incredibly fast. Scanning 1 GHz of bandwidth takes about 1 second on the Airspy R2, and 2 seconds on the Airspy Mini.

Airspy Mini GSM Band

Airspy R2 GSM Band

Airspy Mini 1 GHz Scan

Airspy R2 1 GHZ Scan

HF Reception

As the Airspy R2/Mini can only receive 24 MHz at it's lowest, an upconverter is required for the lower HF frequencies. The Airspy team recommend using the official SpyVerter upconverter which costs 49 USD. We reviewed the SpyVerter in a previous post and believe that the Spyverter is the best upconverter on the market at the moment. The Airspy Mini is fully compatible with the SpyVerter and it can be powered with its bias tee. Again, RX performance of the Airspy Mini + SpyVerter is pretty much identical to the R2. The main loss is that the smaller bandwidth reduces the amount of decimation used.

ADS-B

The Airspy software in the SDR# package comes with a good ADS-B decoder. For ADS-B decoding, both the Mini and R2 units are pushed up into a special 20 MSPS mode to improve decoding on the wideband ADS-B signals. This means that the Airspy R2 and Airspy Mini should have similar performance when decoding ADS-B.

(You might wonder why SDR# limits the sample rate of the Mini to 6 MSPS, when it is capable of running at 20 MSPS as we can see with ADS-B. The reason is that the Airspy ADS-B decoder runs in RAW mode, and as with the special debug 10 MSPS mode produces spurs resulting in a less clean spectrum, though these spurs have no effect on wideband noise tolerant signals like ADS-B.)

We compared the Airspy Mini and the R2 on ADS-B with a FlightAware ADS-B antenna, Habamp ADS-B LNA and 10m of coax cable fed into a 2-way signal splitter. One Airspy was used to power the habamp via its bias tee. Results show that the number of aircraft received and frame receive rate were almost identical.

Within the next few months we will test the Airspy against the SDRplay RSP and FlightAware ADS-B optimized RTL-SDR dongle on ADS-B reception.

Other Screenshots of the Mini

Airspy Mini or SDRplay RSP?

The SDRplay RSP already was a competitor to the Airspy R2, and now it appears that the Airspy Mini is even more of a competitor since they are so similarly priced. Because everyone will want to know, here is a quick summary of the SDRplay RSP vs Airspy Mini.

First, please read through our previous review to see the main differences between the Airspy R2 and RSP. Although the review was written for the Airspy R2, we believe that that review is still relevant to the Airspy Mini as well since performance between the R2 and Mini is almost identical. Below is a tabulated comparison.

SDRplay RSP Airspy Mini Notes Price (Direct) $149 USD + $15 - $35 $99 USD $148 USD (with SpyVerter) + $5 -$20 shipping The two units are similarly priced when the SpyVerter HF option is considered. Price (USA Distributor) $149 USD + Free shipping $99 USD $148 USD (with SpyVerter) + $12.50 shipping Airspy: Airspy.us RSP: hamradio.com Price (EU Distributor) £118.8 inc VAT + ~£10 - £20 shipping. Converted to euros: €154.7 incl. VAT + ~€13 - €26 shipping. No EU distributor yet. Estimated cost via China: €106 incl. est 20% VAT €169 incl. est 20% VAT (with SpyVerter) + €4.5 - €18 shipping Mini not yet available from a EU distributor at the time of this post, but seems to be on its way to ML&S at hamradio.co.uk and eurosdr.co.uk The RSP is produced in the UK. It can be bought from its official site at sdrplay.com. Freq Range 0.1 - 2000 MHz 24 - 1800 MHz 0 - 1800 MHz with SpyVerter. Max Usable Bandwidth 7 MHz 5 MHz Dynamic Range Good Excellent Dynamic range is one of the most important factors in a high performance radio. Better dynamic range means that strong signals will not block the reception of weaker signals, or cause the radio to overload. The lower dynamic range of the RSP can be alleviated by using external filters, though this may reduce sensitivity slightly depending on the type of filter used. Sensitivity Excellent Good The RSP has better sensitivity because of its built in front end LNA. The Airspy's sensitivity can be increased to the same level as the RSP whilst maintaining its high dynamic range by introducing a good high dynamic range LNA like one based on the PSA4-5043 or PGA103 chips. The LNA may be conveniently powered via the Airspy bias tee. Using an external LNA (as opposed to a built in one) also helps overcome losses from coax cable and other components in the signal path which can boost SNR by a significant amount. See the SNR test here for more information. Frequency Stability Average Excellent The RSP does not use a TCXO, whereas the Airspy uses a low phase noise 0.5 PPM TCXO. Software Official: Mirics DVB-T demodulator, Mirics FM/DAB player Unofficial: SDR#, HDSDR, SDR Console, SDR-J, SoDiRa, Spectrum Lab, dump1090, SDR Touch (beta). Official: SDR#, SpectrumSpy, AstroSpy, ADSBSpy. Unofficial: HDSDR, SDR Console, SDR-J, SoDiRa, Spectrum Lab, dump1090, Unitrunker, SDRTrunk There is no official general purpose software for the RSP, but they have recently acquired Studio 1, and may offer this to their customers at a reduced price in the future. Enclosure Plastic Metal A metal enclosure is desirable to keep out interfering signals. Extra Features None Bias Tee The bias tee allows you to easily power external components like upconverters and LNA's via the coax cable. Designed In UK France Manufactured In UK China

Conclusion

It is quite clear that the Airspy team have come out with an amazing SDR that is an excellent upgrade for those who are thinking of upgrading from an RTL-SDR but need to stick to a budget. Its RX performance is almost identical to its bigger brother the Airspy R2, but has a smaller maximum bandwidth and less ways to expand the unit in advanced experiments. If you are looking for something better than an RTL-SDR and don't need the advanced features offered by the Airspy R2, then we highly recommend the Airspy Mini.

More information about purchasing the Airspy Mini can be found at airspy.com.

Disclaimer: The Airspy Mini was provided to us for free by the Airspy team in exchange for an honest review.