Lesson learned on my part (year back now) - the higher frequency also means
shorter wavelengths yielding 'plane waves'/freely radiating wave from a source
closer in, having E and H fields normal to each other and then a DF apparatus
will indicate correctly WHILE it is in the "far field" region" and outside the
influence of noise coupling via magnetic of electric fields only in the near
field ...
My DF apparatus consisting of a marine direction finder using both a ferrite
loop and a 'sense' antenna work well when respecting the near vs the far fields
.. and going up in frequency sometimes I can see the direction indicated
change, if I am not quite far enough away from the near field and into the
plane-wave far field.
Like you I've located down to a choice of two houses on the lower bands (160
meters in particular). Fortunately my noise went away after awhile so I didn't
have the opportunity of going deeper. One of those sources was a (presumed)
wireless dog collar that used a low freq but created wandering 'dirty' carriers
below and in the 80 meter band.
Good to know the results of your RFI-xpedition, Don.
de AA5CT Jim
-------------------------------
On Thursday, November 2, 2023, 12:01:36 PM GMT-5, Don Kirk
<wd8dsb@gmail.com> wrote:
I had a very interesting case involving RFI on 160 and 80 meters and
actually a little bit on 40 meters at my QTH which I was able to resolve
yesterday. For those interested here is a link to a youtube video I just
uploaded that documents the case:
https://youtu.be/Ktl-GNxq1C8?si=uUue8aG5asoC7_1B
*Details*
While I hate to admit mistakes I did make one while tracking down the RFI.
Originally I tracked the RFI down using a frequency high in the AM
broadcast band and all of my MF antennas (portable flag, tuned loop, and
untuned loop) agreed on what house the RFI was coming from. Well I was
wrong by one house and when I later switched to higher frequencies (2 MHz
and above) all of my antennas now indicated the RFI was actually coming
from one house North of the first house I suspected.
The two houses and their electric meters are only 14 feet apart from each
other and their underground utility feeds run right between the two
properties and it appears they get fed from the same ground mounted
pedestal. The first homeowner was kind enough to work with me and her
house wiring was swamped with RFI even when we killed the main breaker to
her house. She then gave me permission to access her backyard during
daylight hours so I could get better headings on the RFI. I came back over
with all my gear and quickly determined I was off by one house.
Yesterday I worked with the second homeowner and within minutes of sniffing
his circuit breaker panel with my sniffer loop we determined the RFI was
originating from his garage circuit breaker circuit and that the source of
the RFI was his indoor garage 3 panel LED light fixture that had been in
service for a very long time (many years). We replaced the LED light
fixture with a new one he just happened to have still in its box and this
cured the RFI problem (same light fixture manufacturer but different
model). I suspect something had failed in the old fixture that caused the
RFI to suddenly appear this year.
What was interesting about this entire case is that the RFI would typically
come on around 8 or 9am and stay on until around 8pm but occasionally the
RFI would not turn off at night. It turns out that the homeowner's wife
likes to leave the garage light on continuously during the day so it's not
dark when she goes in the garage as the garage has no windows but sometimes
they forget to turn the light switch off at night (light switch is in the
hall that leads to the garage). Initially I had to cancel a couple of
visits to the house because for some reason the RFI was magically not
present on the first 2 days I was scheduled to go there, but after we
cancelled my visits due to lack of RFI the RFI would magically appear
(within a half hour both times) and this had me thinking the homeowner was
playing games with me. I started to think I was dealing with a grow light
because of the typical 12 hour on time of the RFI. *What this experience
once again taught me is to keep an open mind and don't jump to conclusions.*
Well it's now time for me to bake a couple of batches of brownies and
deliver them to both houses.
Just FYI, and 73.
Don (wd8dsb)
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