[RFI] RFI on 160 meters at WD8DSB from Hi-Fi Amp or its power supply 0.27 miles away.

[James Jordan]

Interesting story Don!
I’d start with the easy stuff first. Toroids on the speaker lines, toroids or a brute force filter on the AC line. If you’re a quarter mile away just doing that should drop it to about nothing. I’ve had great success with the Schaffner (from Mouser) line filters specified for the current draw of the offending source. Knocked the buzz from a variable speed 1 HP pool pump right down. 
Good luck. 
73,
Jim K4QPL 

Sent from my iPhone

> On Apr 8, 2022, at 8:52 PM, Don Kirk <wd8dsb at gmail.com> wrote:
> 
> 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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