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I've notice a couple of times over the past couple of weeks that the noise floor, particularly on 40 and 80, is exceptionally high as the grayline passes me into night. I'm looking at the general band conditions right now from qrz/spaceweather and they are showing as good for both day and night on 40/80m.

I'm unsure if it's something in my area or something to do with my equipment? I have a Flex 3000 connected to a Comet 250Bx and a homemade 20/40m fan dipole I made through a fairly cheap antenna switch. I was working 20/30/40M on the comet earlier today but then I returned about 30 minutes later and the noise floor had jumped. Normally I'm down around S1 but it's up at S4 and above on the waterfall and s7 on the signal meter.

I just want to ensure something isn't awry on my equipment. There are ice crystals in the air. Not sure if that is a factor? Also when I switch to my fan dipole the noise drops but I still see the interferance (the big bit of noise on the right.)

If I switch to my fan dipole that noise is significantly worse on 40m. It's better on 80m. I'm guessing this is because my dipole is tuned for 20/40m.

Also in a couple of days I expect this noise to slowly fall away.

Here's a picture of my 40m signal first and then 20m and finally 160m...

40M 20M 160M

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    $\begingroup$ I notice this also. The 6m band did it also until I fixed a malfunctioning LED light. What you see is, I think, normal, but some may be due to local interference which coincidentally turns on as grey line approaches. $\endgroup$ – Chris K8NVH Nov 17 '18 at 12:27
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I'm unsure if it's something in my area or something to do with my equipment?

Since the effect is time dependent, it is most likely RFI caused by a timed electrical device. Based on the time of day, it could be related to a lighting device such as a mercury vapor lamp, an LED light, holiday decorations or similar. It could also be some type of industrial process that is starting up at that time of day.

Given the spectra of the signal, you may be able to track it down with a portable radio and a short whip or loop. Before setting out in the neighborhood, turn off your main breaker and shutdown battery operated devices in your own home to make certain it is not a locally grown noise. When you are out searching for the source keep your situational awareness elevated and be cognizant of your appearance to any observers.

Good luck with the hunt!

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