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title = "Sferics"
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description = "On a hunt for the Voice of the out there"
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description = "Hunting for the voice of lightning from thousands of kilometers away"
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date = 2024-06-20
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authors = ["Aron Petau"]
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[taxonomies]
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tags = [
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"antenna",
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"electronics",
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"magnetism",
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"fm",
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"geosensing",
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"lightning",
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"radio",
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"sferics",
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"vlf",
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"university of the arts berlin"
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]
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show_shares = true
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## What the hell are Sferics?
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## What the Hell are Sferics?
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>A radio atmospheric signal or sferic (sometimes also spelled "spheric") is a broadband electromagnetic impulse that occurs as a result of natural atmospheric lightning discharges. Sferics may propagate from their lightning source without major attenuation in the Earth–ionosphere waveguide, and can be received thousands of kilometres from their source.
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> A radio atmospheric signal or sferic (sometimes also spelled "spheric") is
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> a broadband electromagnetic impulse that occurs as a result of natural
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> atmospheric lightning discharges. Sferics may propagate from their lightning
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> source without major attenuation in the Earth–ionosphere waveguide, and can
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> be received thousands of kilometres from their source.
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- [Wikipedia](https://en.wikipedia.org/wiki/Radio_atmospheric_signal)
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*Source: [Wikipedia](https://en.wikipedia.org/wiki/Radio_atmospheric_signal)*
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## Why catch them?
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## Why Catch Them?
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[Microsferics](microsferics.com) is a nice reference Project, which is a network of Sferics antennas, which are used to detect lightning strikes. Through triangulation not unlike the Maths happening in GPS, the (more or less) exact location of the strike can be determined. This is useful for weather prediction, but also for the detection of forest fires, which are often caused by lightning strikes.
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[Microsferics](https://microsferics.com) is a fascinating reference project—a
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network of sferics antennas used to detect lightning strikes. Through
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triangulation (not unlike GPS mathematics), they can determine the
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more-or-less exact location of each strike. This proves useful for weather
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prediction and detecting forest fires, which are often caused by lightning.
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Because the Frequency of the Sferics is, when converted to audio, still in the audible range, it is possible to listen to the strikes. This usually sounds a bit like a crackling noise, but can also be quite melodic. I was a bit reminded by a Geiger Counter.
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When converted to audio, sferics frequencies fall within the audible range,
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making it possible to actually *listen* to lightning strikes. The sound is
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usually a crackling noise, though sometimes surprisingly melodic—reminiscent
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of a Geiger counter.
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Sferics are in the VLF (Very Low Frequency) range, sitting roughly at 10kHz, which is a bit of a problem for most radios, as they are not designed to pick up such low frequencies. This is why we built our own antenna.
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At 10kHz, we are talking about insanely large waves. a single wavelength there is roughly 30 Kilometers. This is why the antenna needs to be quite large. A special property of waves this large is, that they get easily reflected by the Ionosphere and the Earth's surface. Effectively, a wave like this can bounce around the globe several times before it is absorbed by the ground. This is why we can pick up Sferics from all over the world and even listen to Australian Lightning strikes. Of course, without the maths, we cannot attribute directions, but the so called "Tweeks" we picked up, usually come from at least 2000km distance.
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### The Technical Challenge
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Sferics live in the VLF (Very Low Frequency) range, around 10 kHz—a problem
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for most radios not designed for such low frequencies. That's why we built our
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own antenna.
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At 10 kHz, we're dealing with *insanely* large waves: a single wavelength
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stretches roughly 30 kilometers. This scale demands a sizable antenna. A
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special property of such massive waves is their tendency to reflect between
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the ionosphere and Earth's surface—effectively bouncing around the globe
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several times before absorption. This means we can pick up sferics from all
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over the world, even Australian lightning strikes!
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Without proper triangulation math, we can't determine exact directions, but
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the "tweeks" we captured typically originate from at least 2,000 km away.
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## The Build
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We built several so-called "Long-Loop" antennas, which are essentially a coil of wire with a capacitor at the end. Further, a specific balun is needed, depending on the length of the wire. this can then directly output an electric signal on an XLR cable.
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We constructed several "long-loop" antennas—essentially a coil of wire with a
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capacitor at the end. A specific balun is needed (depending on wire length) to
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output an electrical signal via XLR cable.
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Loosely based on instructions from [Calvin R. Graf](https://archive.org/details/exploringlightra00graf), We built a 26m long antenna, looped several times around a wooden frame.
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Loosely following instructions from
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[Calvin R. Graf](https://archive.org/details/exploringlightra00graf), we built
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a 26-meter antenna looped multiple times around a wooden frame.
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## The Result
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We have several hour-long recordings of the Sferics, which we are currently investigating for further potential.
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We captured several hours of sferics recordings, which we're currently
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investigating for further potential.
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Have a listen to a recording of the Sferics here:
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### Listen to the Lightning
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{{ youtube(id="2YYPg_K3dI4") }}
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As you can hear, there is quite a bit of 60 hz ground buzz in the recording.
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This is either due to the fact that the antenna was not properly grounded or we simply were still too close to the bustling city.
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I think it is already surprising that we got such a clear impression so close to Berlin. Let's see what we can get in the countryside!
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As you can hear, there's a noticeable 60 Hz ground buzz in the recording.
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This likely stems from improper grounding or our proximity to the bustling
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city. Still, it's surprising we achieved such clear results so close to
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Berlin. Let's see what the countryside yields!
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{% gallery() %}
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[
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{
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"file": "./sferics1.jpg",
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"alt": "Listening to sferics at night",
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"title": "Night session capturing atmospheric signals"
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},
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{
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"file": "./sferics2.jpg",
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"alt": "The Drachenberg location",
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"title": "Recording location at Drachenberg"
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},
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{
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"file": "./sferics3.jpg",
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"alt": "The long-loop antenna",
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"title": "Our 26-meter VLF antenna setup"
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}
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]
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{% end %}
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