OK, a bit of apples and oranges. I have two powerline sources, and when
both are active my noise level is ~s8-9 on 10 meters in AM bandwidth.
I am less than 100 yards from a very high voltage line, but to my
knowledge it has never caused any RFI problems. Years ago, it was
explained to me as "if they have a leak it costs them real money."
73, Pete N4ZR
On 2/1/2023 10:32 AM, K9MA wrote:
Don't be too envious, Pete. Those levels are from the K4 panadapter
with a 10 kHz span, which means a noise bandwidth of about 20 Hz.
(Resolution bandwidth 11 Hz.) Besides, I have a power splitter and
some other stuff between the receiver and the antenna, about 7 dB of
loss, though I don't know where 4 of those dB come from. In any case,
my "good" noise level on 20 of -130 dBm corresponds to about -110 dBm
in a 400 Hz bandwidth, about S-3 at 6 dB per S unit.
Pete is very close to a big transmission line. I have one of those a
couple hundred meters away, but whatever noise it causes is always
overwhelmed by noise from the distribution lines with which I'm
surrounded.
73,
Scott
On 2/1/2023 8:25 AM, Pete Smith N4ZR wrote:
I am green with envy - my local line noise is currently "only" S5
73, Pete N4ZR
On 2/1/2023 12:26 AM, K9MA wrote:
That table didn't come out very well at all. Here's a link to the pdf:
https://sdellington.us/hr/RFI/Power%20Outage.pdf
73,
Scott K9MA
On 1/31/2023 11:21 PM, K9MA wrote:
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
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