Strange Interference Issue with SDR

[mfn002]

I don't exactly know where to post this, but because it involves HF, I guess I'll post it here.
After Hurricane Beryl moved through my area (40-50 MPH winds, not much rain), I seemed to have developed some sort of weird interference on HF, mainly from 7 MHz to around 12 MHz. The screenshots I've included are what's been showing up on my SDR for the past week or so. I've replaced antennas and cables, but I still can't seem to get it to go away. I'm using an RTL-SDR COM BlogV4 with SDR Sharp. I listened to one of the "spikes" and it seems to be a jumble of voices from various commercial shortwave broadcast stations.

 

[TAC4]

That is fascinating. I am sure someone on here can figure it out.
Does sharp software have a reset button to original settings ?
Those look like classic SDR spurs usually from to high a gain
setting which causes (intermod) or strong RFI nearby like monitors etc getting through the USB cables and dongle or a bad USB cable.

Since you changed antenna's that should rule out anything to
do with the storm or outside as I was thinking water in the coax
but you said not much rain.

Any new modern electronic devices added to the shack lately?

 

[W5KK]

You, most likely, have a high level RF source nearby (like a broadcast transmitter) and it is overloading the SDR. The “tell” is that you hear a jumble of stations. Look for something in the 540 kHz to 1700 kHz. and the 88.1 MHz. to 107.9 MHz. bands that is 20 dB or more above the other surrounding signals in level. It is possible that it could be a television transmitter but not likely. A radio broadcast station transmitter site may have been damaged by the hurricane and they are transmitting from a backup site close to your location. There are several filters available to solve this issue.

 

[Ubbe]

It's 40KHz between spikes. Change the sample rate in SDR# and see if those spikes change, then it's probably an internal issue in the RTL-SDR. You don't have another SDR to swap with and check? When I see that kind of a forrest of spikes it's from an electronic device, my sat TV box or my computer or a computer display. But you heard broadcast audio in those spikes so that's weird.

/Ubbe

 

[mfn002]

There is an AM transmitter (1150AM) about 5 or 6 miles from my house, but that's never caused me any problems before. I also hooked the antenna up to an ICOM R9000 that I have, and the issue didn't show up on the signal graph on that. Oddly, there isn't much bleed-over from the spikes to adjacent frequencies. What signals I do get on nearby frequencies come in perfectly clear. I have another SDR (a NOOELEC NESDR Smart V5), but I got intense AM broadcast interference when I last used it. I maxed out the gain on the BlogV4 SDR and the spikes seemed to get shorter. I still find it strange that it's only showing up in a small slice of the HF spectrum.

Just FYI, I'm using an MLA-30+ active loop antenna.

The only new thing that I've added recently was a UPS power strip, but that was added before the storm.

 

[Ubbe]

I have another SDR (a NOOELEC NESDR Smart V5), but I got intense AM broadcast interference when I last used it. I maxed out the gain on the BlogV4 SDR and the spikes seemed to get shorter. I still find it strange that it's only showing up in a small slice of the HF spectrum.

Interferences from my other devices only show up as in your picture, 10-20 spikes in a limited frequency range.
If you got AM overload issues using another dongle then you probably have a high AM interference level.
Spikes get weaker at a higher gain, as you are using AGC in AM mode that operates on the strongest signal and reduce the overall level for all other signals.

/Ubbe

 

[mfn002]

Okay, this is weird. I just checked and the interference is gone. Completely. Nothing. I didn't unplug anything, although I did briefly swap out SDRs to see if that was the issue. As I suspected, I got intense AM broadcast interference (and the RF spikes) on my NOOELEC. When I plugged my SDR Blog back in, the spikes were gone.