Airspy HF+: Testing, testing, testing...

There was a thread in the Airspy groups.io reflector in early January concerning sensitivity in the LF (and especially VLF) part of the spectrum. There were also intermodulation products on the LF band. I didn't really pay much attention to it. It turned out however that the solutions (a firmware update and a hardware modification) had significant impact on the receiver's performance in general.

I had noted that sensitivity appeared to roll off much higher up than in the LF band, and Roelof Bakker kindly measured the 1000 kHz sensitivity and found -95 dBm (AM, 6 kHz, 30% modulation, 400 Hz tone). Which is good, but not outstanding. Roelof also confirmed that sensitivity was rolling off.

The solution to the LF problem was a simple "bypass operation" as illustrated below. It not only solved LF sensitivity, but sensitivity in general. Roelof noted an improvement to -110 dBm, which is truly outstanding in the SDR world. Together with a firmware update this seems to not have compromised performance in any way, probably the contrary as it seems that the intermod problems are gone.

I did the firmware update and R3 bypass on Saturday in less than half an hour. The improved sensitivity is indeed notable in my setup when noise levels and signal levels are low.

I'm mostly using HDSDR with the HF+ now, because it's easy on remote connections and to set up recordings. Works well with SDR Console V3 and SDR# too. More to come.

Original photo: Nils Schiffhauer