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

Tue Dec 12 06:50:28 EST 2023

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:
[image: Screen Shot 2023-12-11 at 5.52.29 PM.png]
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:
> [image: Screen Shot 2023-12-10 at 9.41.07 PM.png]
> 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:
> [image: Screen Shot 2023-12-10 at 9.49.02 PM.png]
> 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 <http://www.abelian.org/vlfrx-tools/hum.mp3> 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/>
>>>>> <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
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> > --
>>>>>> > Please follow the HamSCI Community Participation Guidelines at
>>>>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>>>>> > ---
>>>>>> > You received this message because you are subscribed to the Google
>>>>>> Groups "HamSCI" group.
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>>>>>> send an email to hamsci+unsubscribe at googlegroups.com.
>>>>>> > To view this discussion on the web visit
>>>>>> https://groups.google.com/d/msgid/hamsci/CAOY0kB1bH8_cOqH0diQ7vBBaCHzuZo0h2FNRkGDkfHvA2YK23Q%40mail.gmail.com
>>>>>> .
>>>>>> >
>>>>>> > --
>>>>>> > Please follow the HamSCI Community Participation Guidelines at
>>>>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>>>>> > ---
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>>>>>> > To view this discussion on the web visit
>>>>>> https://groups.google.com/d/msgid/hamsci/2099478555.158709.1701786348336%40mail.yahoo.com
>>>>>> .
>>>>>> >
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Please follow the HamSCI Community Participation Guidelines at
>>>>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>>>>> ---
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>>>>>> To unsubscribe from this group and stop receiving emails from it,
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>>>>>> To view this discussion on the web visit
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>>>>>> .
>>>>>>
>>>>>> --
>>>>>> Please follow the HamSCI Community Participation Guidelines at
>>>>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>>>>> ---
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>>>>>> Groups "HamSCI" group.
>>>>>> To unsubscribe from this group and stop receiving emails from it,
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>>>>>> To view this discussion on the web visit
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>>>>>> .
>>>>>>
>>>>> --
>>>>> Please follow the HamSCI Community Participation Guidelines at
>>>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>>>> ---
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>>>>> Groups "HamSCI" group.
>>>>> To unsubscribe from this group and stop receiving emails from it, send
>>>>> an email to hamsci+unsubscribe at googlegroups.com.
>>>>> To view this discussion on the web visit
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>>>>> <https://groups.google.com/d/msgid/hamsci/CADHrwpeHA9SDaKf_hUY1rKt-aDeJJrh-P-ZOhcEZuLgRNr1h%2Bg%40mail.gmail.com?utm_medium=email&utm_source=footer>
>>>>> .
>>>>>
>>>>>
>>>>> --
>>>>> Please follow the HamSCI Community Participation Guidelines at
>>>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>>>> ---
>>>>> You received this message because you are subscribed to the Google
>>>>> Groups "HamSCI" group.
>>>>> To unsubscribe from this group and stop receiving emails from it, send
>>>>> an email to hamsci+unsubscribe at googlegroups.com.
>>>>> To view this discussion on the web visit
>>>>> https://groups.google.com/d/msgid/hamsci/7fba57a4-23ad-48c3-b245-34e874f1c86e%40dartmouth.edu
>>>>> <https://groups.google.com/d/msgid/hamsci/7fba57a4-23ad-48c3-b245-34e874f1c86e%40dartmouth.edu?utm_medium=email&utm_source=footer>
>>>>> .
>>>>>
>>>> --
>>>> Please follow the HamSCI Community Participation Guidelines at
>>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>>> ---
>>>> You received this message because you are subscribed to the Google
>>>> Groups "HamSCI" group.
>>>> To unsubscribe from this group and stop receiving emails from it, send
>>>> an email to hamsci+unsubscribe at googlegroups.com.
>>>> To view this discussion on the web visit
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>>>> <https://groups.google.com/d/msgid/hamsci/CADHrwpeP7tZvK8Q1zjP_8JA_wtPwBCr5g4m%2BiKfR9UtjyLrYdg%40mail.gmail.com?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>>> --
>>>> Eric P. Nichols, KL7AJ
>>>> AlasKit Educational and Scientific Resources138 Shenandoah Drive
>>>> Fairbanks, AK 99712 <https://www.google.com/maps/search/138+Shenandoah+Drive%0D%0AFairbanks,+AK+99712?entry=gmail&source=g>
>>>> (907)371-7120www.alaskit.netkl7aj72 at gmail.com
>>>>
>>>> --
>>>> Please follow the HamSCI Community Participation Guidelines at
>>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>>> ---
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>>>> <https://groups.google.com/d/msgid/hamsci/af7ffc79-f5cd-4c6c-a14b-b568ed0b12ac%40gmail.com?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>> --
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>>> .
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>>
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