<div dir="auto">Hi all,</div><div dir="auto"><br></div><div dir="auto"> We should also emphasize that power line radiation is not just local. In case you hadn’t seen it, power line harmonics have also been detected in near-Earth space right out to the edge of the ‘VLF bubble’ and beyond (bubble extent = the plasmasphere boundary layer, 14000 - 20000+ km altitude) essentially out to the extent of VLF transmissions and those latitudes where humans live. This was discovered long ago by the Stanford group (Don Carpenter, Chung Park, etc.) using ground based VLF whistler observations in the Antarctic and Arctic (e.g. Roberval in Canada). </div><div dir="auto"><br></div><div dir="auto"><div><a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA080i031p04249">https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA080i031p04249</a></div><br></div><div dir="auto"><div><a href="https://link.springer.com/article/10.1007/BF00173690">https://link.springer.com/article/10.1007/BF00173690</a></div></div><div dir="auto"><br></div><div dir="auto"> DEMETER satellite data, at 600 km altitude, has also clearly detected power line harmonics in the topside ionosphere in its data. See this article and related ones:</div><div dir="auto"><br></div><div dir="auto"><div><a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006JA012134">https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006JA012134</a></div></div><div dir="auto"><br></div><div dir="auto"> So it is truly everywhere.</div><div dir="auto"><br></div><div dir="auto">73</div><div dir="auto">Phil W1PJE</div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Dec 6, 2023 at 06:29 Jonathan <<a href="mailto:emuman100@gmail.com">emuman100@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)"><div dir="ltr"><div><div dir="ltr"><div><div><div dir="auto">Mike,</div></div><div dir="auto"><br></div><div dir="auto">At ELF, ULF, and VLF, powerline hum (including harmonics) is omnipresent and comes from many different sources, meaning the VLF receiver detects power line emissions from the house, surrounding houses, surrounding power lines, both access, distribution, and transmission lines, and anything else supplied by mains within hundreds of miles. There is never any “one source” of powerline hum and it will always be present on a VLF receiver. In many VLF applications, power line hum is filtered so as long as it’s not at high enough levels that it causes clipping at the data acquisition input. I filter in my signal processing chain, but before I do, I continually monitor levels of 60Hz and 180 Hz</div></div><div dir="auto"><br></div><div dir="auto">Steve,</div><div dir="auto"><br></div><div dir="auto">I’ve heard of many cases where solar panel inverters create lots of noise at HF, but few have been characterized at VLF. I would imagine making these inverters VLF quiet will take much more legwork, as it always does with VLF. </div><div dir="auto"><br></div><div dir="auto">With vlfrx-tools and Spectrum Lab, an adaptive mains filter is included and is very effective. <a href="http://www.abelian.org/vlfrx-tools/hum.mp3" target="_blank">Here</a> is a sample containing 50 Hz hum and harmonics with the adaptive mains filter in vlfrx-tools. After a few seconds, it locates the fundamental and odd/even harmonics and adaptively notches them out. It tracks them as the line frequency changes throughout the day. Once it kicks in, you can hear sferics and the VLF spectrum quite easily. It notches harmonics up to 6 kHz by default, but can notch up to 8 or 10 kHz in mains-heavy environments. Using it, you can easily hear natural radio events and amateur radio transmissions in the VLF band.</div><div dir="auto"><br></div><div>Dana,</div><div><br></div><div>Mains harmonics usually extend up to ~6 kHz but could extend much higher in heavy harmonic environments. Those noises you hear are not usually related to power line emission, but could be synchronous to 60 Hz because they originate from power converters synchronous to power line frequencies.</div></div></div><div><div dir="ltr"><div><br></div><div>Jonathan</div><div>KC3EEY</div></div></div></div><div dir="ltr"><div><div><div dir="auto"><br></div><div dir="auto"><br></div><div><div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Dec 5, 2023 at 1:01 PM Eric Nichols <<a href="mailto:kl7aj72@gmail.com" target="_blank">kl7aj72@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)"><u></u>
<div>
<p>Golden Valley Electric association up here has always been very
competent and eager to solve noise problems. Probably because
the head of engineering for many decades was a ham. I believe he
also trained his underlings well...the systems seems to be
incredibly clean. This may not be the case elsewhere, but I'm
very grateful for our power folks up here.</p>
<p>73!</p>
<p>Eric<br>
</p></div><div>
<div>On 12/5/23 06:45, Dana Whitlow wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">David,
<div><br>
</div>
<div>As I've tried to emphasize above, all i've looked at so far
is the "raspy buzz"</div>
<div>impulsive form of noise, which I've normally tended to
regard as the most</div>
<div>objectionable. However, I do recognize that the "fuzzy
hum" form would</div>
<div>likely turn out to be more of a problem for very narrowband
analyses, which</div>
<div>is my usual case, if a harmonic should land too close to
the signal band of</div>
<div>interest.</div>
<div><br>
</div>
<div>Many of my experiments have involved a final measurement
bandwidth of</div>
<div>less than 1 Hz, so I should be alert to this possibility.</div>
<div><br>
</div>
<div>Dana</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Dec 5, 2023 at 9:38 AM
David G. McGaw <<a href="mailto:david.g.mcgaw@dartmouth.edu" target="_blank">david.g.mcgaw@dartmouth.edu</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">
<div> Generally, transformers do not make noise. All the
electronic loads in the neighborhood on the line will create
a certain amount of harmonics, though the larger loads are
required to include power factor control to minimize this.
Defective insulators or branches and such across the wires
do create pulse noise.<br>
<br>
You are correct, if you can localize the source of the
interference, the power company will fix it. They do not
have the capability of finding it themselves so rely on us
to find and report it. In New England, we have created a
task force under ARRL to help, see <a href="https://nediv.arrl.org/spectrum-protection-utilization/" target="_blank"><https://nediv.arrl.org/spectrum-protection-utilization/></a>,
"Noise Identification".<br>
<br>
73,<br>
<br>
David N1HAC<br>
<br>
<div>On 12/5/23 10:34 AM, Dana Whitlow wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Michael,
<div><br>
</div>
<div>Since there is no electrical connection to the top
end of the pipe,</div>
<div>basic EM theory says that the pipe is actually
irrelevant to common-</div>
<div>mode current flows. Whether or not the pipe
provides any shielding</div>
<div>for E-fields is another matter, of course. I have
not looked at the</div>
<div>E-field issue, because even if the pipe is <i>not</i>
grounded, the 40 ft of</div>
<div>unshielded wiring from the pole to the top of the
pipe would by far</div>
<div>be the dominant radiator, and there is nothing I
could do about it.</div>
<div><br>
</div>
<div>Your mention of the transformer itself being noisy
is scary, because</div>
<div>the ultrasonic test would almost certainly fail to
detect such a</div>
<div>problem, probably making it rather difficult to
persuade the power</div>
<div>company to change out the transformer "on
speculation".</div>
<div><br>
</div>
<div>As far as power outages are concerned, I'd love to
see a county-wide</div>
<div>outage at night in clear WX, just so I could enjoy
a dark sky for a</div>
<div>change. But preferably in the summer, you
understand.</div>
<div><br>
</div>
<div>Dana</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Dec 5, 2023 at
9:01 AM 'Black Michael' via HamSCI <<a href="mailto:hamsci@googlegroups.com" target="_blank">hamsci@googlegroups.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">Make
sure your metal pipe is grounded to the ground rod at
your breaker panel.<br>
You should see almost 0 Ohms between the pipe and
ground connection.<br>
<br>
It may be more likely coming in the wiring. Do you
have an oscope you can use to see what's on the
wires/pipes?<br>
<br>
The power outage is a good clue and you may be able to
get the power company to come out based on that
observation.<br>
Noisy transformers are common and they are required to
replace them.<br>
<br>
Mike W9MDB<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
On Tuesday, December 5, 2023 at 08:55:58 AM CST, Dana
Whitlow <<a href="mailto:k8yumdoober@gmail.com" target="_blank">k8yumdoober@gmail.com</a>>
wrote: <br>
<br>
<br>
<br>
<br>
<br>
Michael,<br>
<br>
I've only tried that once, during an episode of the
raspy buzz form<br>
of the problem. I used a battery-powered AM radio in
the AM BC<br>
band so that I could use the ferrite bar antenna.<br>
<br>
The breaker panel is located on the outside of the
house, and the<br>
incoming power comes down through a metal pipe which
extends<br>
up through the eave, with the wiring from the pole
entering said<br>
pipe through the usual arrangement used to keep rain
out.<br>
<br>
Anyway, before I turned off any breakers I moved the
radio around<br>
and concluded that the noise was manifested (at least
primarily) as<br>
a common-mode current through the metal pipe.<br>
<br>
Next I began turning off individual breakers to see if
the problem<br>
was confined to a single circuit, but apparently it
was not. <br>
<br>
Then, with all the individual breakers back on, I
opened the master<br>
breaker, with the same result. The noise remained in
all its glory.<br>
<br>
I suspect a problem with the pole about 40 ft from the
house, but <br>
did not have an ultrasonic snooper at the time. I
acquired one of<br>
those only very recently, but have not yet put it to
the acid test.<br>
<br>
I have not yet found anybody selling giant clamp-on
ferrite chokes<br>
for "cables" about 4 inches in diameter :-)<br>
<br>
Also, I have not yet investigated the fuzzy hum form
of interference.<br>
<br>
Dana<br>
<br>
<br>
<br>
<br>
On Tue, Dec 5, 2023 at 8:25 AM 'Black Michael' via
HamSCI <<a href="mailto:hamsci@googlegroups.com" target="_blank">hamsci@googlegroups.com</a>>
wrote:<br>
> Can we assume you've tested cutting power to your
house so you can determine if it's YOUR house causing
any of the hum?<br>
> <br>
> Mike W9MDB<br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> On Tuesday, December 5, 2023 at 05:34:33 AM CST,
Jonathan <<a href="mailto:emuman100@gmail.com" target="_blank">emuman100@gmail.com</a>>
wrote: <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> A benefit to powerline hum (radio emissions of
60Hz and harmonics radiated by power lines) being
omnipresent even in the most RF quiet locations is
that you can monitor local and regional power outages
very closely with a VLF receiver. A local power outage
occurred around the vicinity of the VLF receiver at
Spring Brook Township, PA. Here is a plot of the
amplitude level of 180 Hz, a harmonic of 60 Hz,
showing some power loss at ~2030UT and completely at
~2100UT:<br>
> <br>
> <br>
> Here you can see the hum level in greater
temporal detail. What is so impressive about this
power outage is how low the hum levels got. I will be
pulling the audio file and listening to this period.
Unfortunately, there were no whistlers or dawn chorus,
but hum levels this low are quite a treat:<br>
> <br>
> <br>
> After the power outage ended, there were some
interesting spikes, possibly due to inductive inrush,
then hum levels returned to normal:<br>
> <br>
> The VLF system was on a UPS during the power
outage, so there definitely is benefit to keep the
system up and running during local power outages,
especially if the magnetosphere decides to be
generous. Power grid studies are often done using VLF
receivers and the benefit is that no attachment to the
power lines are required. <br>
> <br>
> Jonathan<br>
> KC3EEY<br>
> <br>
> <br>
> <br>
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</blockquote>
</div><div><pre cols="72" style="font-family:monospace">--
Eric P. Nichols, KL7AJ
AlasKit Educational and Scientific Resources
<a href="https://www.google.com/maps/search/138+Shenandoah+Drive%0D%0AFairbanks,+AK+99712?entry=gmail&source=g" target="_blank" style="font-family:monospace">138 Shenandoah Drive
Fairbanks, AK 99712</a>
(907)371-7120
<a href="http://www.alaskit.net" target="_blank" style="font-family:monospace">www.alaskit.net</a>
<a href="mailto:kl7aj72@gmail.com" target="_blank" style="font-family:monospace">kl7aj72@gmail.com</a></pre>
</div>
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