Initially, this was quite a problem with version 1 of the AirSpy. I opened it up, scraped paint on the inside at both the USB and SMA connectors and copper taped/soldered (where I could) bridges from each connector to the now bare aluminum (no solder there) and from each connector to the PCB ground plane. I also installed ferrite with two to three turns through each bead on the USB and RF input cables located at the AirSpy, itself. I found that even the non-ferrited antenna input cable picked up USB noise and coupled it into the AirSpy. A lot of that has changed with Version 2 which I now have and especially the HF+, but still have trouble with my ISP (Rise Broadband/ Jab Broadband) getting into the receiver. I have very aggressively (and I do mean aggressively!!) loaded the RiseBroadband cable with large heavy ferrites with multiple turns through each. When I'm serious about radio astronomy, especially with the ham - it - up, I turn power OFF on the ISP hardware. My AirSpys have locked as low as 17 MHz. I believe because I'm pushing that, I get more vertical lines, but I've learned to live with that. I can comment that the AirSpys are head-over-heals better than the 'competition', SDRPlay which I also have. It is absolutely miserable for vertical lines, overload, and just 'garbage responses' in the lower frequency ranges and does NOT respond in a dB manner. I will NOT be spending any more $$$ on the SDRPlay products ! ! ! Besides, I vehemently dislike SDRuno ! ! ! !
I presently have the AirSpy set up on a crude interferometer (two antennas) on 432.050 MHz (for Cygnus A). Here (and attached) is a screen capture of my present condition with the AirSpy terminated at the AirSpy with a 6 dB pad (12 dB return loss or better than a 2:1 SWR).
This is an AirSpy 2. You will also find the density and number of vertical lines is a function of FFT display resolution. The above and first attachment are at 524288 samples. If I drop that to 4096, the following results:
Outside of the obvious addressing EMC/RFI, play with the settings. I like the finer results as I'm feeding the output of SDR# to other applications through VBCable for radio astronomy.
Regarding the USB noise, just be thankful Firewire died. It was TERRIBLE for radiating RF noise.
Dave - WØLEVJust Let Darwin Work