Recently I posted a note about a buzz noise that had been plaguing me on
160. This buzz was on for 55 seconds and then off for 55 seconds, at S9
levels. It mostly was there some time after sunset and sometime before
sunrise. While it covered Top Band and a bit beyond, there was no
apparent harmonic on 80 meters. I received numerous helpful tips for
tracking from several of you on the reflector.
Tracking became difficult, because while it first was there with some
regularity, it became quite irregular. It might be several days till I
would hear it. This change in frequency corresponded with a recent
change in temperature -- it's been much colder -- and at first I thought
it was temperature related. But then after several more days it came
back on our coldest nights. And while the "on" time remained constant at
55 seconds, the "off" time often became much greater. This morning over
the course of 3 hours listening, it came up only twice, with perhaps an
hour between them.
Adding to the difficulty in tracing was that my usual RFI tool, my
IC706Mk2G, was in the midst of a shift to a new vehicle. I finally got
it temporarily hooked up, using just a 2-meter mag-mount for an antenna.
This way-out-of resonance antenna actually proved to be very good for
this job, since the signal level was much weaker than it would have been
on the low band screwdriver -- I knew I was closing in when I could hear
it; peak was about S7.
Tonight the noise was back with the original regularity -- 55 on, 55 off
-- for an extended time, and I left the shack just after the sun came
up in BD7 to attempt to locate the buzz source. I used a stopwatch so
I'd know when to expect it to come back on, and slowly drove up and down
the road, watching street and other lights as the noise came on and off,
and watching the S meter. Within a few minutes I finally spotted the
culprit! It was a light mounted at the peak of a neighbor's pole barn,
about 2000 feet or so from my nearest Beverages. I remembered seeing it
on my first pass down the road, but now it was almost off -- it still
glowed dimly. I watched it cycle through several times -- it would reach
full brilliance and the noise would disappear. Then in 55 seconds the
light would go very dim and the noise would begin a few seconds later,
until it again reached full brilliance.
This may be a mercury-vapor light, or perhaps another type -- it seemed
to have a slightly more orange color than a mercury vapor, but that may
just have been reflection from the steel pole barn.
I'm on good terms with this neighbor, so I'm hopeful of working out a
solution. He was away this evening so we haven't discussed yet.
My numerous Beverages were not of great help in tracking this down --
the buzz was loudest on a new 5-degree Beverage that is furthest from
the noise and broadside to it. But the power line that runs down our
road is only 35 feet off the back of that Beverage and no doubt there
was some coupling. The metal pole barn also may have shielded the noise
in some directions.
73/Jon AA1K
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