For some time I’ve had this really nasty drifty wide spurious noise which affected both 6 and 2 meter bands.
You can see it here on the MAP65 waterfall. This thing made it impossible to work stations within a 2-4KHz region of the band. Worst of all it was constantly drifting from one end to the other.
Using a small portable antenna, I “sniffed” the cables to see what might be the cause. It turns out it was a Prolific RS232 USB adapter. Further not just one Prolific USB adapter, but three of them, each throwing their own nasty spurs.
I don’t know if this is a systemic problem with all Prolific USB RS232 Adapters, but it certainly is with all of the ones I have. This was an easy fix, I ordered a PCIe RS232 board and installed it in the computer.
Now now more nasty drifty spurious blobs…