Airspy HF+ Discovery & Spurious Signals – Much Ado about Nothing

Worst case: Those very few and low-level spurious signals of the “Discovery” disappear completely in the atmospheric noise after you connect an antenna – leaving even faintest stations in the clear.

There had been some discussion about the “real” performance of the brand new Airspy HF+ “Discovery”. It is not only my experience that this great little SDR is a perfect performer at a ridiculous low price.

The discussion focuses on “spurious signals”. I measured them with the Winradio SIGMA as spectrum analyzer, compared it to the two past Airspy HF+ models, plus Discovery, and did some work on how this effect might touch reception.

The result is clear: this discussion in the Ivory Tower is “Much Ado about Nothing”. You may read more about method & findings, with many diagrams, in this PDF.


  • Pingback: Testing for Spurious Signals on the Airspy HF+ Discovery

  • Hi Nils, great article as usual. I suppose that band noise adds nature’s own dithering to any sdr, perhaps why some sdrs perform as well as they do on hf, better than their specs might suggest. Will have to look at the sdrs here and see how they fare as far as spurs.

  • Hi, Nils.

    I found your article very interesting and wanted to do something similar. I bought a Discovery recently, and it looks nice in SDR#, but won’t run with SpectrumSpy or RTL_Power. The SDR# is the only software that it runs with and that was a real pain.

    I pretty much only want to run scans over the full range of different SDRs. And to compare specific regions of the electromagnetic spectrum from multiple sensors. Is it too much to ask for a utility that dumps ALL the data to disk as is comes in? Or send it to my program to process? Oh well.

    Would you like another one? I can send it to you. It is worthless to me. $185 down the drain. Maybe you can put it to good use.


    • Hi, Richard – if I understood you right, you blame a software, not the Discovery, not being able to do some things (scanning) which neither the software, nor the hardware promised to do. Hmmmh. Software SDRC V3 by Simon Brown might be the multi-sensor, multi-instance software you have in mind. I use it successfully with many SDRs, among them also the Discovery. Alas, I don‘t know if it is already supporting the old fashioned art of scanning, because I don’t use this technique.
      73 Nils, DK8OK

      • Nils,

        No, I am blaming the disorganized state of the SDR community. People are wasting huge amounts of time just getting these things installed and working, let alone used for any purpose. I cannot condemn a group for how they relate socially or their inefficiency, but it seems a shame to have such intelligent and creative people spending weeks and months to do simple things.

        As for promises, the materials posted on the web to “sell” the device list software that you can use. They even say they are writing their own and making progress. But “Oh, this does not work in this case”, or “We don’t think it is very good at that, so did not bother”. So it is a false promise and misleading.

        I am just very tired. If it is any consolation, NASA and similar organizations are in worse shape. The Internet as a whole is in terrible shape because large groups cannot work together efficiently.

        It would be nice if all the software I see recommended would work with all the devices. I really don’t want to go back to writing device drivers and basic mathematics. I guess “Software Defined Radio ” still has a few decades to learn how to organize an industry.


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