Hi Jim,
Yep, I normally first try a common mode choke using 31 material as well as
a commercial differential mode filter on the power supply power cord to see
which one works or if both are required. Often both are required to fully
address RFI. I normally use Delta Electronic filters which are also from
Mouser, etc.
73,
Don wd8dsb
On Fri, Apr 8, 2022 at 10:23 PM James Jordan <k4qpl2@gmail.com> wrote:
> 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@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)
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
>
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