My QTH is in an older residential area, surrounded by overhead power
lines. Line noise is a constant problem. We recently had a major power
outage, so I measured the noise levels to get a baseline with little
line noise. (See below, assuming it comes through.) The outage was
pretty large: there was no power within a kilometer or so, perhaps
further to the west. The levels I measured shortly after power was
restored the next morning are fairly typical lately. To the NE, it
wasn't so bad, only increasing 5-8 dB when the power came on. West was
much worse, 7-19 dB. I've long known there was a major noise source to
the west. I guess it's time to track it down.
I suspect these levels are fairly typical of a residential area with
overhead lines. They would probably be worse if I hadn't been doing
battle with the utility for the past 30 years to get the worst of the
sources fixed. One thing this data shows, which I've long suspected, is
that the distribution lines are the major source of noise. There are
some transmission lines just a few hundred meters away, but I've never
traced any significant noise to them.
It may say something about the sad state of our utility's
infrastructure: A car knocked down a pole about 1 km from my QTH, and it
took out the power up to 2 km away, with power surges causing extensive
damage to appliances, etc. (None at my place.) Just down the street, far
from the downed pole, we had a major fireworks show and nearby a
transformer exploded. Apparently, similar things happened throughout the
affected area. Did they forget the fuses?
73,
Scott K9MA
--
Scott Ellington
Madison, Wisconsin, USA
scott@sdellington.us
K9MA
23.01.28 Noise Levels
Major power outage
MT, K4, 10 kHz span, 7 dB rx path loss
Resolution bandwidth 11 Hz
Frequency Bearing Power Out Power On
14 45 -135 -130 dBm
270 -139 -120
21 45 -141 -133
270 -140 -127
28 45 -148 -141
270 -146 -139
--
Scott K9MA
k9ma@sdellington.us
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