Sunday, January 28, 2018

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

There was a thread in the Airspy 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


Mark GM1004SWL said...

Hi Bjarne

Great to see you using the Airspy HF+ also, I got mine yesterday and am over the moon it is far better than my SDR Play RSP2.

I also did the R3 bypass and it certainly has improved the lower frequencies however I have to use a step attenuator inline to try and suppress what I think is noise and artifacts coming from the LORAN C at Anthorn about 50 miles away...on mw 5db takes it away but down on LW it needs 30db to completely remove it, at times it does go with less its not constant. So it makes me think will the firmware update help this.

I would be very surprised if it cant handle the Loran C its barely 20db over 9 and other users including yourself are not reporting this. As so far my mini whip antenna has shown no signs of overload except from this phenomenon after I did the bypass.

I wonder Bjarne can you outline the procedure for updating the firmware...on the group some are talking about using metal clips to short out and erase the flash memory...surly not ! So Im wondering how you did it so that when the new firmware files are back up in the group I know what to do :) Also others talk about checking and changing calibration settings is this so and how did you do it?

Cheers Mark GM1004SWL
Hawick Scottish Borders

Bjarne Mjelde said...

Hi Mark, send me an email to bjarne dot mjelde at gmail dot com and I'll explain.