[RFI] What would cause noise like this?

[Frank O'Donnell]

Hi all, new to this list, hoping to learn enough to chase down some of 
my yet-unsolved RFI issues.

As a start, I'm wondering if the way that RFI I saw the other morning 
appeared in the receiver's waterfall might suggest anything about what 
the source of noise could be.

Here are two brief video clips from SDR Console, displaying a waterfall 
covering the LF/MF spectrum with input from an Elad FDM-S2 SDR and 
broadband vertical antenna.

The first clip is at 6:08 a.m. PDT, exactly one hour before local sunrise:

https://vimeo.com/370416556/e3cf9bcb09

At 00:23 of that clip, a pattern of heavy RFI starts, with lines in the 
waterfall spaced ~16 kHz apart (approx 6 lines per 100 kHz).

A couple of minutes later, I noticed that the RFI started toggling, with 
the pattern changing for a second or two, and then the RFI disappearing 
briefly before restarting. In the following clip this pattern starts at 
00:09:

https://vimeo.com/370418392/afb0a0c4ef

Any thoughts? We live in a suburban neighborhood where lots are all 
approx 50 x 200 feet. There are at least two houses with solar panels 
within ~200 feet of us, and more down the block. I gather that RFI from 
solar panels can vary, based on the type of system and the deficiency 
responsible for the RFI. Do these clips show any kind of visual 
signature that might suggest the source?

Thanks and 73,

Frank K6FOD