[RFI] FM modulated RFI on 3.885 and more

WHYTE radiotrade at rogers.com
Sun Feb 14 14:58:03 EST 2021

FM RFI on 75m; 
I recently have been hit with 24/7 RFI on  frequencies from AM BC band up to 20m. The worst of it (S-9) seems to be in the 75m band, with a very “digital” sounding, wide band “hash” on 3.885. It sounds FM modulated. It certainly, most clearly demodulates when listening in FM mode. (On Yaesu FT-857d) . Example of RFI groupings; 3.585, 3.620 to 3.665, 3.770, 3.880 to 3.905, 4.120 to 4.157 etc etc..

As it increases and decrease from these frequencies, it’s strength gets weaker. (S-7 to S-5) 
I have eliminated sources from my own home per usual AC / battery cuts etc. 
It is certainly coming-in off my 80m dipole (Fed with RG-6,  with coax choke- only at feed point).  Shield is certainly picking up much of it . Coax runs close to property line of abutting house.

Bottom line;  I can’t find any typical household consumer devices etc.,  that may use the 3.5 to 4.5 MHz, that almost certainly transmit in FM and digital in nature. I have not yet found a “fundamental” frequency outside the HF band..suspect is may be  the 4.120-4.157 frequency.

Any ideas on which devices are suspect? ( e.g wireless thermometer, wifi AC line extenders etc) ? I have a new neighbour who recently moved in and suspect it’s from his home...but I have yet to DF (using FM mode- portable HF receiver).  AM receiver will work for tracking it, but it’s far less distinguished from my normally very high RFI smog, so will take the FT 857 “backpack mobile” for Its FM. 

Any source ideas ? I have never before encountered an FM modulated HF “Spectrum killer” ...and right on The AM window :-( 
Tnx for permitting my chatter...

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