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.
Morse Code or CW has become rare among professionals (in the West). But there is a busy net of small Japanese Fishery Stations literally pounding the brass. One of them is Kagoshima Radio, JFX. They are not daily heard in Europe, but a combination of receiver Winradio Sigma, active antenna MD300DX (2×2.5 m, vertical) and SDRC V3 software did the trick even under this grim summer propagation. See screenshot above, from 24 hours’ recording of 25 MHz HF. All channels clearly readable – as far as the expressive handwriting (see detailed screenshot at the bottom) of their CW allows for … Yeah: CQ CQ DE JFX JFX QRU QSX 6 / 8 /12 MHz K
From start, Airspy SDRs with their unique block diagram received an overwhelming reputation in the challenging HF bands. They feature a high dynamic range in a small case – and even match a small wallet, too. Now their new “Discovery” enters new dimensions in every respect. The photo on top shows the small black beauty in the foreground compared to the already known Airspy HF+ in the background.
It is already running here with e.g. SDR# and SDRC V3 software, see below. The very first impression is that of an SDR with an exceptionally low noise level and, thanks to its tracking filters, a matching dynamic range. Alas, being a bit short in time these days, I hope to come back with some more solid comments in due time.-
Specified to receive already from 0.5 kHz, it is a true performer also on VLF – see screenshot below with reception of US Navy Cutler/Maine on 24 kHz, about 35 dB down of Germany powerhouse DHO38 just 600 Hz below. Reception: August 2nd, 2019, 14:38 UTC in Germany with vertical active dipole (2×2.5 m) MD300DX.