New Magazine Reviews of the Airspy HF+ Discovery

Recently three new reviews of the Airspy HF+ Discovery have come out in various radio  enthusiast magazines from around the world. All three reviews have been released for free in PDF form over on the Airspy reviews page. Unsurprisingly each review praises the HF+ Discovery as it's clearly a great radio.

The first review comes from the September Edition of "The Spectrum Monitor" and is written by Larry Van Horn (N5FPW).

” Most the low-priced SDRs have never been preselected, mostly for cost reasons, and will suffer strong signal overload especially in high RF areas (urban/metro areas). Without exception, these devices usually have major problems with the antennas that radio hobbyist use. They overload very quickly, which makes serious reception on long, medium and shortwaves rather difficult. The HF+ Discovery is the big exception. Based on our testing, the Airspy HF+ Discovery has no equal at its price point. You will find world-class performance and an amazing piece of hardware wrapped up in a package smaller than a matchbox. The Airspy line has a very fine reputation in the radio hobby. In reviews published in Gayle Van Horn’s 2018 Global Radio Guide and the 2019 World Radio TV Handbook, the Airspy HF+ received high marks by the testers and a “Best Value” rating. ”

The second review is by Nils Schiffhauer (DK8OK) which was published in the October 2019 edition of "Radio User". For German readers, Nils also published a similar review written in German for the December edition of "Radio-Kurier".

Just another SDR? Wait, this beast is different – not only in size and price but also in terms of its concept and performance. In common with some former models of AirSpy SDRs, the new AirSpy HF+ Discovery model (henceforth: ‘Discovery’) is a joint venture of Youssef Touil and his team at the Chinese ITEAD studio and ST Microelectronics. This smart team has already developed, for example, the ground-breaking AirSpy HF+, which is widely considered to be the top performer in its class. The Discovery continues this success story.

The Discovery shines with less noise, and, astonishingly, less crackle. In at least 80% of these diffi cult cases, intelligibility with the Discovery is clearly better. With very few stations, this receiver will even make the difference between understanding the identification of a station and not copying it. In August, I also tested the Discovery with the most ‘demanding’ band, the Very Low Frequency range (VLF). Here most SDRs – and certainly the majority of budget SDRs – reach their limits, lacking sensitivity and filling up the band with internally-generated signals. Thanks to a newly developed input section to start at even 500Hz, this receiver shows outstanding strong and clean signals from as far as the US Navy in Australia.

Covers from the Spectrum Monitor and Radio User Airspy HF+ Discovery Reviews
Covers from the Spectrum Monitor and Radio User Airspy HF+ Discovery Reviews
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Ladislav OK1UNL

Hello All,
DC4KU measured some parameters of the Discovery:
here is a final report after objective measurement:
What to say:
Good receivers have parameter one of important NPR ( Noise Power Ratio) cca 70dB.
Here are 62dB. Not perfect, but what you want at price class???
The main problem is a hysterese AGC. Airspy guys at HQ experimented with firmware.
Experiments and latest varints of FW were targeted to improve AGC. (see change log)
The perfect parameter NPR has Perseus, better than Elad S2. On another site it is about 14 vs. 16 bits ADC.


This test doesn’t set the noise figure of the DUT before injecting the signals. Interestingly, the same website contains the review of the older HF+ where he used the manual gain correctly. Same for the other receivers he tested.
Looks like another test by an amateur who doesn’t know what he’s doing.


Also contains various flaws on the NPR measurement. For example, he uses the visual FFT level instead of the actual power level at 2.4 kHz to compare the distance between the notch and the upper level of the noise. Then he didn’t factor the FFT processing gain on his calculation. Instead, he fiddled with the smoothing to get the number he likes, which makes the whole estimation even more random.
Another funny comment in the doc is that he thinks IP3 doesn’t apply to SDRs, but went to measure it anyway but couldn’t interpret the results.



i need to correct your comments.
Schnorrenberg, a very experienced equipment test engineer did the NPR Measurement at 2,4 MHz, not 2,4 kHz.
An he applied the IP3 because the Discovery is a Hybrid Device: an analog Tuner Frontend with later digitization. An he explained in detail the measurement result, that the Discoveries Dynamic Range ist limited by the IP3 of the analog frontend and not by the A/D conversion

I appreciate Schnorrenbergs objective measurement report. There is no reason do try to disqualify his findings. The Discover is an good little device with an outstanding price-value relation. But it is not perfect. Therefore it should be allowed to mention the shortfalls of this device



“An he explained in detail the measurement result, that the Discoveries Dynamic Range ist limited by the IP3 of the analog frontend and not by the A/D conversion”
This is exactly the contradiction in his report. He says the Discovery operates at a very high sensitivity and he didn’t even attempt to reduce the gain. Just in case you don’t know, reducing the gain increases the IP3 by the same amount.
So, yeah. “Experts” … 😉


“Just in case you don’t know, reducing the gain increases the IP3 by the same amount.
So, yeah. “Experts” … ?”

This might be the case, if the gain is reduced by a passive – IM free – attenuator. But not with an AGC controlled amplifier with variable gain as in the Discovery Frontend.

Schnorrenberg is absolutely right.


Correct. The Discovery has an ATT setting, not a gain setting for obvious reasons.

Ladislav OK1UNL

Hello guys Fred, Garry and Co.
Discovery AGC hystereze problem is a known, widely discuss at group.
At objective report DC4KU missing one small detail, about release firmware installed in tested equipment.
Me saw changelog at airspy website and from FW 3.0 development staff experimented with AGC settings.Latest FW 3.06BB.
I must fully agree with DC4KU Mr. Schnorrenberg.
If you want a professional grade SDR receiver, me suggest Winradio G31DDC Excalibur or transceiver from Expert Electronics.


“small detail” 😉
The entire approach is flawed. AGC should be enabled for narrow band testing and fixed gain should be used for wide band.
For professional rig testing, refer to a discriminating scientist like Leif SM5BSZ, or the ARRL lab guys. They don’t miss this kind of “small details”.


So its “world class performance” must be equal to a 10k Icom flagship radio then? I think not.

Freebie for the review was it?


Yes, as usual. “Superb receiver” that I got to keep for free.


I could not find anything called a 10k icom, but I could find a ICOM IC-9700 which I’m going to guess is what you meant ? – and it costs about 2,000 euro/dollars, where as the above is $169 (excluding import duty/taxes and shipping).

So do you want a comparison with a radio that does RX (and TX) at frequencies of 144 to 148 MHz, 430 to 450 MHz and 1300.MHz. The doohickey in the review is RX only and covers frequency ranges from 0.5 kHz to 31 MHz and 60 to 260 MHz, so even though there is some overlap, probably not enough for a useful comparison.

Maybe I’m picking the wrong device (it was the closest ICOM product number I could find to 10k) , can you name the actual device that you mean.


The IC-7851 is 12k$, same for the IC-R9500. Other vendors have similarly priced high end transceivers, but we’re comparing apples to oranges. The point is that even if you’re such an high profile reviewer to be chosen for a review unit you don’t get to keep it for free, the price is not worth the publicity, not even Rob Sherwood NC0B gets those kind of perks.
Conversely, these affordable SDR receivers are sent out like candies to “influencers” (bloggers, youtubers, SWL/hams with a sizeable presence on social networks) that almost invariably shell out an enthusiastic review at a cost significantly lower than they would have to pay for traditional ad campaigns.


Thank you 🙂


Although the ip3 and BDR numbers aren’t as good, the MDS numbers of the Discovery are quite comparable, if not better, than the IC-7831. And that appears to be the “world class” spec that Airspy was chasing. Not bad given 2 orders of magnitude in price difference.


It’s quite hard to navigate through the specifications without doing some maths. The IC-7851 datasheet claims an IP3 of +40 dBm with preamp off. This corresponds to an MDS of -120 dBm according to the ARRL lab (link below).
The Airspy Discovery claims an IP3 +15 dBm at max gain, and an MDS at -141 dBm. These figures must be translated to the same noise figure of the 7851 in order to be comparable. If the math is correct, this gives IP3 15 + (-120) – (-141) = +36 dBm for -120 dBm.
Both receivers claim 110 dB of dynamic range, but it is limited by BDR, IMD DR or RM DR, whichever is reached first.


“+36 dBm”

That’s quite respectable for an SDR.