Wow, that's awful. But I'm pretty sure this is a serious power supply, grounding or some sort of RFI/EMI problem. Look at the screenshots below. Typical terrible SMPS RFI starting at 43 kHz with harmonics running up through LF (and probably higher).
But then there is this absolutely awful broadband junk all the way down at 0 Hz!! S9+10!! And in AM mode it sounds exactly like the hum that is cross-modulated on all your other signals. The Kiwi has no RF response below about 7 kHz. So this can't be an RF signal. It's got to be from the power supply or a ground loop or something getting into the ADC and/or ADC preamp somehow.
I assume you're running an antenna that uses a powered amplifier, given you say "Indoor Active Loops" for the antenna. Check the power supply for that antenna. Unplug the power supply for your antenna replace it with a simple wire antenna while tuned to a strong local signal. If the hum on the signal goes away, it's possible that's your problem.
I've had this happen to me when selecting a wallwart power supply from my junk box for a homemade active loop. It worked, but all the signals were modulated with a 60Hz hum. Selecting a different power supply with better filtering solved the problem.
Capacitors can fail in power supplies, so a once clean power supply can begin generating noise at any time.
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John, I've got a sudden problem with reception: Seems the LO is modulated, resulting in a hum like modulation on all received signals, even CW.
See https://sdr.sixvpn.net/
Is this likely a software or hardware problem?
Wow, that's awful. But I'm pretty sure this is a serious power supply, grounding or some sort of RFI/EMI problem. Look at the screenshots below. Typical terrible SMPS RFI starting at 43 kHz with harmonics running up through LF (and probably higher).
But then there is this absolutely awful broadband junk all the way down at 0 Hz!! S9+10!! And in AM mode it sounds exactly like the hum that is cross-modulated on all your other signals. The Kiwi has no RF response below about 7 kHz. So this can't be an RF signal. It's got to be from the power supply or a ground loop or something getting into the ADC and/or ADC preamp somehow.
I assume you're running an antenna that uses a powered amplifier, given you say "Indoor Active Loops" for the antenna. Check the power supply for that antenna. Unplug the power supply for your antenna replace it with a simple wire antenna while tuned to a strong local signal. If the hum on the signal goes away, it's possible that's your problem.
I've had this happen to me when selecting a wallwart power supply from my junk box for a homemade active loop. It worked, but all the signals were modulated with a 60Hz hum. Selecting a different power supply with better filtering solved the problem.
Capacitors can fail in power supplies, so a once clean power supply can begin generating noise at any time.