[TangerineSDR] [HamSCI] Power Outage Detected by VLF System

Wed Dec 6 06:29:41 EST 2023

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
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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 Resources138 Shenandoah Drive
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> (907)371-7120www.alaskit.netkl7aj72 at gmail.com
>
> --
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