I recently encountered RFI at about the worst spot on 160 meters for DXing
(a 5 KHz wide signal that would wander slightly between 1.820 and 1.830
MHz). Turns out the RFI was from a Hi-Fi Digital Amplifier MN180BT or its
power supply located 0.27 miles from my house. I just uploaded a video
documenting this case for those interested, and here is the YouTube link:
https://youtu.be/l0kCW2dzhC0
I called this case the Poltergeist case because I could sometimes hear
very gentle piano music playing way down in the white noise of the RFI
signal, and there was never any audio announcement, just music playing.
The RFI was not on 24 hours a day so I set my SDR receiver to record 10
seconds at the hour and half hour points so I could go back and fill in a
tracking log to see when the RFI was present. I did this to better
understand when the RFI was on in order to have the highest probability of
it being on when working with the homeowner where I suspected the RFI was
originating. Turns out the homeowner knew exactly what was causing the RFI
after looking at my log even before I mentioned the piano music, and she
did confirm they had been streaming piano music on the system (we both got
a big laugh out of this).
I would really like to know if the RFI is being generated by the power
supply or the Amp but the homeowner has a lot on her plate right now and
wants to hold off on figuring that out until her schedule frees up a bit.
I suspect the signal was being radiated by the house wiring, and I really
suspect the problem is the power supply but that's just a wild guess at
this point in time.
P.S. I live in a subdivision of 205 homes, and it turns out that I had met
this homeowner back in 2014 when her young son was riding his bicycle next
to his dad who was jogging. My wife and I were gardening out front and saw
the boy crash his bicycle as he went face first onto the sidewalk. I
loaded his bicycle into my car and drove them back home. I did not put 2
and 2 together until after I contacted the homeowner about the RFI they
were generating. It really is a small world.
Just FYI, and 73.
Don (wd8dsb)
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