[RFI] Mystery signal on 40M

[N4ZR]

I've run across a signal on 40M that has me puzzled.  Because this 
reflector doesn't accept images, I have put an HDSDR image in Dropbox 
with a link address of 
https://www.dropbox.com/s/zgat3frt70zhrgg/wide.png?dl=0.  As you'll see, 
it definitely has 120Hz major intervals, as well as minor signals at 60 
Hz in between.  They look like "sidebands" of the central signal  That 
tempts me to think it must be some sort of powerline-driven device, like 
a switching power supply. but there's only one of it, so far as I can 
tell, across the HF spectrum here, and it was not there this morning 
when I got up.

Before I start running around killing breakers, does this look familiar?

-- 
73, Pete N4ZR
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