[TangerineSDR] [hamsci-grape] Re: [HamSCI] Power Outage Detected by VLF System

Tue Dec 12 08:59:11 EST 2023

Mike,

The amplitude level of mains hum is so loud, especially harmonics, that
most of the noise is drowned out by the signal. Mains hum can account for
up to 50 or 60% of the soundcard's scale on my system. There is some noise
out of the FM demodulator, but that's in the uHz range or less of frequency
deviation. The FM demodulator may not be utilizing any fftw functions, but
I will have to check.

Jonathan
KC3EEY

On Tue, Dec 12, 2023 at 8:39 AM 'Black Michael' via HamSCI <
hamsci at googlegroups.com> wrote:

> Remember you aren't just measuring 180Hz -- you're also seeing the noise
> level in your amplitudes.  One of the weaknesses of an FFT.
>
> If you want the 180HZ level you have to subtract the noise level.
>
> Mike W9MDB
>
>
>
>
>
>
>
>
> On Tuesday, December 12, 2023 at 05:50:45 AM CST, Jonathan <
> emuman100 at gmail.com> wrote:
>
>
>
>
>
> One of the benefits of vlfrx-tools is how powerful its signal processing
> tools are. I wanted to investigate the power line frequency over time to
> understand how it varies throughout the day. With GPS timestamped and
> sampled aligned data, I can see how the 180 Hz harmonic varies over time.
> To do so, I feed the stream into a brick wall filter centered at 180 Hz
> that is 2 Hz wide. Then, after downsampling, I feed it into an FM
> demodulator, which gives me a frequency deviation output. This frequency
> deviation output gives me the frequency variation that I'm looking for. I
> downsample some more to a rate of 1 Hz/sec to decimate and plot the data.
>
> Here is a plot of the 180 Hz harmonic over a span of 4 hours showing the
> deviations in hundreds of mHz:
>
> The vertical scale is in mHz and the horizontal scale is in
> seconds, spanning 4 hours. You can see the deviation spanning ±200mHz which
> is really interesting! This might represent the variations in load on the
> local and regional grid.
>
> Jonathan
> KC3EEY
>
> On Sun, Dec 10, 2023 at 9:59 PM Jonathan <emuman100 at gmail.com> wrote:
> > Here on the day of the annular eclipse, powerline hum levels were low
> enough that the 180 Hz harmonic seemed to have exhibited ionospheric
> propagation. Notice the drop in amplitude at dawn. To me, this shows
> daytime D layer absorption as seen in other signals:
> >
> > You'll also notice a slight decrease in absorption during eclipse time
> which is expected.
> >
> > As time went on, background hum levels increased, so this ionospheric
> propagation can't be seen on those days. Here is a plot of the last 60 days
> since the eclipse showing an increase in power levels of the 180 Hz
> harmonic:
> >
> > Despite this, you can still see some cyclic nature from diurnal to
> diurnal that could indicate ionospheric propagation. The break in the data
> was when there was an issue with the system.
> >
> > Jonathan
> > KC3EEY
> >
> > On Wed, Dec 6, 2023 at 7:38 AM Phil Erickson <phil.erickson at gmail.com>
> wrote:
> >> Hi all,
> >>
> >>   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).
> >>
> >> https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA080i031p04249
> >>
> >> https://link.springer.com/article/10.1007/BF00173690
> >>
> >>   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:
> >>
> >> https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006JA012134
> >>
> >>   So it is truly everywhere.
> >>
> >> 73
> >> Phil W1PJE
> >>
> >> On Wed, Dec 6, 2023 at 06:29 Jonathan <emuman100 at gmail.com> wrote:
> >>> Mike,
> >>>
> >>> 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
> >>>
> >>> Steve,
> >>>
> >>> 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.
> >>>
> >>> With vlfrx-tools and Spectrum Lab, an adaptive mains filter is
> included and is very effective. Here 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.
> >>>
> >>> Dana,
> >>>
> >>> 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.
> >>>
> >>> Jonathan
> >>> KC3EEY
> >>>
> >>>
> >>>
> >>> On Tue, Dec 5, 2023 at 1:01 PM Eric Nichols <kl7aj72 at gmail.com> wrote:
> >>>>
> >>>>
> >>>> 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.
> >>>>
> >>>> 73!
> >>>>
> >>>> Eric
> >>>>
> >>>>
> >>>> On 12/5/23 06:45, Dana Whitlow wrote:
> >>>>
> >>>>
> >>>>>
> >>>>> David,
> >>>>>
> >>>>>
> >>>>>
> >>>>> As I've tried to emphasize above, all i've looked at so far is the
> "raspy buzz"
> >>>>>
> >>>>> impulsive form of noise, which I've normally tended to regard as the
> most
> >>>>>
> >>>>> objectionable.  However, I do recognize that the "fuzzy hum" form
> would
> >>>>>
> >>>>> likely turn out to be more of a problem for very narrowband
> analyses, which
> >>>>>
> >>>>> is my usual case, if a harmonic should land too close to the signal
> band of
> >>>>>
> >>>>> interest.
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> Many of my experiments have involved a final measurement bandwidth of
> >>>>>
> >>>>> less than 1 Hz, so I should be alert to this possibility.
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> Dana
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Tue, Dec 5, 2023 at 9:38 AM David G. McGaw <
> david.g.mcgaw at dartmouth.edu> wrote:
> >>>>>
> >>>>>
> >>>>>>
> >>>>>>  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.
> >>>>>>
> >>>>>> 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 <
> https://nediv.arrl.org/spectrum-protection-utilization/>, "Noise
> Identification".
> >>>>>>
> >>>>>> 73,
> >>>>>>
> >>>>>> David N1HAC
> >>>>>>
> >>>>>>
> >>>>>> On 12/5/23 10:34 AM, Dana Whitlow wrote:
> >>>>>>
> >>>>>>
> >>>>>>>
> >>>>>>> Michael,
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Since there is no electrical connection to the top end of the pipe,
> >>>>>>>
> >>>>>>> basic EM theory says that the pipe is actually irrelevant to
> common-
> >>>>>>>
> >>>>>>> mode current flows.  Whether or not the pipe provides any shielding
> >>>>>>>
> >>>>>>> for E-fields is another matter, of course.  I have not looked at
> the
> >>>>>>>
> >>>>>>> E-field issue, because even if the pipe is not grounded, the 40 ft
> of
> >>>>>>>
> >>>>>>> unshielded wiring from the pole to the top of the pipe would by far
> >>>>>>>
> >>>>>>> be the dominant radiator, and there is nothing I could do about it.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Your mention of the transformer itself being noisy is scary,
> because
> >>>>>>>
> >>>>>>> the ultrasonic test would almost certainly fail to detect such a
> >>>>>>>
> >>>>>>> problem, probably making it rather difficult to persuade the power
> >>>>>>>
> >>>>>>> company to change out the transformer "on speculation".
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> As far as power outages are concerned, I'd love to see a
> county-wide
> >>>>>>>
> >>>>>>> outage at night in clear WX, just so I could enjoy a dark sky for a
> >>>>>>>
> >>>>>>> change.  But preferably in the summer, you understand.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Dana
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Tue, Dec 5, 2023 at 9:01 AM 'Black Michael' via HamSCI <
> hamsci at googlegroups.com> wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>>> Make sure your metal pipe is grounded to the ground rod at your
> breaker panel.
> >>>>>>>> You should see almost 0 Ohms between the pipe and ground
> connection.
> >>>>>>>>
> >>>>>>>> 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?
> >>>>>>>>
> >>>>>>>> The power outage is a good clue and you may be able to get the
> power company to come out based on that observation.
> >>>>>>>> Noisy transformers are common and they are required to replace
> them.
> >>>>>>>>
> >>>>>>>> Mike W9MDB
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Tuesday, December 5, 2023 at 08:55:58 AM CST, Dana Whitlow <
> k8yumdoober at gmail.com> wrote:
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Michael,
> >>>>>>>>
> >>>>>>>> I've only tried that once, during an episode of the raspy buzz
> form
> >>>>>>>> of the problem.  I used a battery-powered AM radio in the AM BC
> >>>>>>>> band so that I could use the ferrite bar antenna.
> >>>>>>>>
> >>>>>>>> The breaker panel is located on the outside of the house, and the
> >>>>>>>> incoming power comes down through a metal pipe which extends
> >>>>>>>> up through the eave, with the wiring from the pole entering said
> >>>>>>>> pipe through the usual arrangement used to keep rain out.
> >>>>>>>>
> >>>>>>>> Anyway, before I turned off any breakers I moved the radio around
> >>>>>>>> and concluded that the noise was manifested (at least primarily)
> as
> >>>>>>>> a common-mode current through the metal pipe.
> >>>>>>>>
> >>>>>>>> Next I began turning off individual breakers to see if the problem
> >>>>>>>> was confined to a single circuit, but apparently it was not.
> >>>>>>>>
> >>>>>>>> Then, with all the individual breakers back on, I opened the
> master
> >>>>>>>> breaker, with the same result.  The noise remained in all its
> glory.
> >>>>>>>>
> >>>>>>>> I suspect a problem with the pole about 40 ft from the house, but
> >>>>>>>> did not have an ultrasonic snooper at the time.  I acquired one of
> >>>>>>>> those only very recently, but have not yet put it to the acid
> test.
> >>>>>>>>
> >>>>>>>> I have not yet found anybody selling giant clamp-on ferrite chokes
> >>>>>>>> for  "cables" about 4 inches in diameter  :-)
> >>>>>>>>
> >>>>>>>> Also, I have not yet investigated the fuzzy hum form of
> interference.
> >>>>>>>>
> >>>>>>>> Dana
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Tue, Dec 5, 2023 at 8:25 AM 'Black Michael' via HamSCI <
> hamsci at googlegroups.com> wrote:
> >>>>>>>>> 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?
> >>>>>>>>>
> >>>>>>>>> Mike W9MDB
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> On Tuesday, December 5, 2023 at 05:34:33 AM CST, Jonathan <
> emuman100 at gmail.com> wrote:
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> 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:
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> 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:
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> After the power outage ended, there were some interesting
> spikes, possibly due to inductive inrush, then hum levels returned to
> normal:
> >>>>>>>>>
> >>>>>>>>> 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.
> >>>>>>>>>
> >>>>>>>>> Jonathan
> >>>>>>>>> KC3EEY
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> --
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> .
> >>>>>>>>>
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> .
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> --
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> .
> >>>>>>>>
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> .
> >>>>>>>>
> >>>>>>>
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> >>>>>>
> >>>>>>
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> >>>>>>
> >>>>>
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> .
> >>>>>
> >>>>
> >>>> --
> >>>> Eric P. Nichols, KL7AJ
> >>>> AlasKit Educational and Scientific Resources
> >>>> 138 Shenandoah Drive
> >>>> Fairbanks, AK 99712
> >>>> (907)371-7120
> >>>> www.alaskit.net
> >>>> kl7aj72 at gmail.com
> >>>>
> >>>>
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> .
> >>>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
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> .
> >>>
> >>
> >
>
>
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