[RFI] RFI from small indoor Xmas tree lighting 0.22 miles away.

Don Kirk wd8dsb at gmail.com
Wed Jan 5 13:55:57 EST 2022


Hi Dave,

You can see details on this loop at the 3:08 mark of this youtube video:
https://youtu.be/vDB8rAwVt5Y
The video also shows how I use it.


73,
Don (wd8dsb)

On Wed, Jan 5, 2022 at 12:27 PM Dave <dave at nk7z.net> wrote:

> How about a photo of your small loop...
>
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist, RFI
> ARRL Asst. Director, NW Division, Technical Resources
>
> On 1/4/22 20:07, Don Kirk wrote:
> > I work hard keeping my noise floor on 160 meters low and hopefully equal
> > between my 3 different pennant RX antennas that point 40, 160, and 300
> > degrees from my QTH.  This winter I've struggled with an increased noise
> > floor on my 40 degree pennant, and a few weeks ago I located a power pole
> > that was arcing badly and this pole was subsequently repaired as I
> > mentioned in a previous post.  The noise level on my 40 degree pennant
> came
> > down substantially after repair of the pole, but I noticed it was still
> > higher than my 160 and 300 degree pennants as well as its historical
> level
> > by about 3 or 4 dB.  Yesterday I tracked the cause of the 3 to 4 dB
> > increase in my noise floor to a home 0.22 miles away, and this afternoon
> I
> > worked with the homeowner to quickly identify the root cause of the
> problem
> > which turned out to be a power supply running the lights on his small
> > indoor Xmas tree located on the second floor of his home.
> >
> > I once again used a very small loop to sniff each circuit breaker in his
> > circuit breaker panel to identify the suspect circuit, and when we shut
> off
> > the suspect circuit breaker the RFI vanished.  The homeowner then
> unplugged
> > one device at a time from the circuit until we found what device was
> > generating the RFI.  Finding the suspect circuit took about 30 seconds
> > using my sniffing loop, and then it took about 10 minutes to figure out
> > what device on the circuit was the root cause of the problem.
> >
> > I can't stress enough how important it is to not try and guess what
> device
> > is causing the RFI because the homeowner was pretty certain it was due to
> > his recent addition of a blower fan that he installed on his fireplace,
> and
> > he even had me worrying about how difficult of a fix it would be if that
> > was indeed the case as the wiring was within his walls.  I told the
> > homeowner I never guess what device is causing the RFI because the
> problem
> > is almost always different from case to case, and after we were done he
> > fully appreciated my comment.  I use my laptop SDR receiver a lot to
> > visually see what's going on (behavior of the RFI), but I don't use it to
> > guess what the guilty device might be except for trying to determine if
> the
> > RFI might be power line related RFI.
> >
> > Using my small loop to sniff the circuit breaker panel is definitely a
> game
> > changer for me, and it sure makes working with homeowners a much
> > simpler task (very efficient, and least intrusive to the homeowner).
> >
> > Here is a link to a video documenting this case for those interested:
> > https://youtu.be/J6OjwTRNIvY
> >
> > 73, and Happy New Year.
> > Don (wd8dsb)
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