
Plasma Antenna - bcaa7f3a8bbc
https://en.wikipedia.org/wiki/Plasma_antenna
======
Zenst
Had a dig around for some pictures of such antennas and found this:
[https://www.researchgate.net/figure/A-model-4068-MHz-ac-
plas...](https://www.researchgate.net/figure/A-model-4068-MHz-ac-plasma-
antenna_fig4_286640009)

Find myself wishing such tech was prevalent during the early days of mobile
phones and massive external aerials, but that's just the inner Jedi in me.

~~~
segfaultbuserr
Imagine a Sci-Fi title with this scene: At the last moment, some critical
battlefield information is transmitted by a huge, bright and colorful beam of
plasma antenna that shines the ground like Sun at night. It would make a
spectacular and impressive scene of SFX and CGI, just like the SFX of the
wrapped engine in the new Star Trek..

> _during the early days of mobile phones_

Probably not a good idea, in its original form, it requires a lot of power
from the mains to maintain its arc discharge, which is what turns it into an
antenna, kind of like a vacuum tube that needs a constant heating power. But
Wikipedia says antenna-on-chip is possible, which is quite interesting.

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the8472
Early mobile phones were car-mounted. So if you had a nuclear-powered car a
plasma antenna would fit right in.

~~~
segfaultbuserr
And a tube transmitter, of course!

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davidklemke
One of my university lecturers, John Rayner, worked on developing these back
in the day. Managed to track down a paper he published on it which is quite
interesting:
[https://ieeexplore.ieee.org/document/1291644](https://ieeexplore.ieee.org/document/1291644)

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danepowell
Does anyone know how stealth fighter aircraft are able to incorporate radar
hardware that doesn't act like a giant retro reflector? Putting a radar array
on the front of a stealth fighter just seems like painting a giant bullseye on
it, even if it's not emitting.

I wonder if something like this could already be in use, since it becomes
invisible to radar as soon as the plasma generator is turned off?

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syphilis2
[https://aviation.stackexchange.com/questions/25368/how-
are-a...](https://aviation.stackexchange.com/questions/25368/how-are-antennas-
integrated-into-stealth-aircraft)

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hawski
Going further with the idea it could be possible to make an antenna from
ionized air.

As it turns out someone already patented "Antenna of ionized air":
[https://patents.google.com/patent/US2760055](https://patents.google.com/patent/US2760055)
The patent expired in 1973.

~~~
topspin
Meteor burst communications

[https://en.wikipedia.org/wiki/Meteor_burst_communications](https://en.wikipedia.org/wiki/Meteor_burst_communications)

Meteors punch ion trails through the atmosphere that serve as antennas for
various purposes.

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duxup
I'm not antenna knowledgeable nor plasma knowledgeable.

Is there a layman's explanation about what the advantages / why there are
advantages here?

It talks about turning off the plasma antenna, is that any different than
simply not using a regular antenna? ... or what they mean by stealth or
"resistance to electronic warfare and cyber attack".

~~~
logfromblammo
Hard-wired antennas can be detected by their shadows and reflections in the RF
bands. Additionally, unless they are hardened against it, extreme RF energy,
as might be generated by an EMP or by a highly-directional attacking antenna,
can damage circuits connected to the receiving antenna.

When the plasma antenna is turned off, it stops existing. There's nothing
there to attack or detect.

A possible future advantage would be shaping the plasma with magnetic fields,
to create customizable antenna geometries, or geometries that electrically
extend beyond the physical bounds of the equipment. Imagine using a laser
small enough to fit in a backpack to create a 1/4 wave antenna long enough to
transmit or receive at 30 kHz, with length 2.5 km .

You could create a plasma antenna 2500m long, send a message to a submarine
150 m below the surface, then it just disappears when you turn it off.

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lachlan-sneff
What a cool visual. Setting up a small beacon like object on the ground,
standing back a couple hundred feet, and then a beam of bright blue light
bursts several kilometers into the air, sending a quick burst of data while
the capacitors powering it can keep it alive.

~~~
logfromblammo
If using multiple converging lasers, the antenna need not be connected to the
equipment. Two lasers could ionize the air in a line 2500m long, and a third
could excite the center of it in a modulated fashion. That would be transmit
only, unless you had some way to measure the energy levels at that center
point from a distance.

It would be unlikely to glow brightly enough in the visual spectrum to see in
the daytime, but it would be pretty cool at night.

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saghm
Slightly OT, but there was no image in the page, so I scrolled down to the
bottom and clicked a link in the "See also" section labeled "Article with
image". The article had no image of a plasma antenna. What gives, Wikipedia?

~~~
segfaultbuserr
The picture was there [0], but later livescience.com updated the website and
it's gone due to link rotting. Even worse, archive.org didn't have the image
archived (but the "zoom picture" text can be seen). Wikipedia is one of the
most affected website by link rotting.

What gives, the Web? Donate to archive.org today!

[0]
[https://web.archive.org/web/20081010224347/http://www.livesc...](https://web.archive.org/web/20081010224347/http://www.livescience.com/technology/071205-plasma-
antenna.html)

~~~
testtesttest
Another article [0] (2007) featuring the image.

[0]
[http://www.nbcnews.com/id/22113395/ns/technology_and_science...](http://www.nbcnews.com/id/22113395/ns/technology_and_science-
innovation/t/new-radio-antenna-made-star-material/)

EDIT: Presentation from Igor Alexeff and Theodore Anderson (University of
Tennessee):

[https://www.ysc.org.ua/2011/data/i.alexeff_presentation.pdf](https://www.ysc.org.ua/2011/data/i.alexeff_presentation.pdf)

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madengr
I’m betting this will have horrible noise temperature. Not good for receiving.

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Zardoz84
Did you really read it ?

> At satellite frequencies, they exhibit much less thermal noise and are
> capable of faster data rates.

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madengr
Yes I did. This is the main presentation from the reference web site.

[http://nebula.wsimg.com/d0cadaec2cf44c9682cebb1610ce1a91?Acc...](http://nebula.wsimg.com/d0cadaec2cf44c9682cebb1610ce1a91?AccessKeyId=3DA8D5B43ACC4E9632E1&disposition=0&alloworigin=1)

If you look at the thermal analysis, it is incomplete. They are only
considering the thermal noise of the reflector. The noise temperature of an
antenna is a function of temperature AND aperture efficiency, with the latter
set by the conductivity of the reflector. Plasma is not a great conductor
(compared to metal), as is shown by the nested antennas. High performance
satcom (e.g. NASA DSN) not only cool the electronics, they cool the feeds
also.

There is another paper where they show a tube covering a LNB. Looks like some
BS. I don’t see any actual measurements of noise temperature (which are very
easy to do).

[http://nebula.wsimg.com/48f10bd80f702313a1d8d094fc7d6b01?Acc...](http://nebula.wsimg.com/48f10bd80f702313a1d8d094fc7d6b01?AccessKeyId=3DA8D5B43ACC4E9632E1&disposition=0&alloworigin=1)

I didn’t see any of the papers published in IEEE APS.

I design antennas for a living, and this sets my BS detector off, and it did
10 years ago too. They look fine for TX (the patterns look good), but the
noise data is conspicuously absent.

Here is another noise analysis, but again it is incomplete. Just show some
measurements.

[http://nebula.wsimg.com/754ac5460a5e1531953c79dd1c4863b7?Acc...](http://nebula.wsimg.com/754ac5460a5e1531953c79dd1c4863b7?AccessKeyId=3DA8D5B43ACC4E9632E1&disposition=0&alloworigin=1)

~~~
ganzuul
I thought plasma was a near-perfect conductor... Is that wrong?

You don't need high temperature for plasma; just low pressure. There is a big
difference between glow discharge and arc discharge.

~~~
madengr
If you look at plasma attenuation of a reentry body, it’s about 30 dB. Even a
thin sheet of foil or perforated screen is way more (> 100 dB).

They just need to hook an antenna to a spectrum analyzer (with low noise path)
and measure the noise density. If it is anywhere slightly above -174 dBm/Hz,
then it is not going to function well as a satcom antenna.

That picture they show of the tube taped onto the LNB feed, they say it
“intercepted” the signal. Do they mean it blocked it? Sure, it will if the
plasma is conductive enough, but it should also drop the noise coming out of
the receiver. Maybe it swamped the receiver with noise. Can’t tell. If they
can pattern the lower frequency antennas, they can certainly take the time to
do some noise measurements.

Maybe the issue is exciting the plasma, and that is noisy. I’d think you
couldn’t do it with pulse excitation unless you limited the rise time. You
could do it with CW, say a magnetron, way outside your operating band.

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inflatableDodo
Can someone wire one to a guitar and pair it with a rydberg vapour cell as the
recieving antenna, so the audiophile community can finally have something to
justify their pricing.

[https://aip.scitation.org/doi/10.1063/1.5099036](https://aip.scitation.org/doi/10.1063/1.5099036)

~~~
jacobush
On the other end we have :
[https://en.wikipedia.org/wiki/Plasma_speaker](https://en.wikipedia.org/wiki/Plasma_speaker)

~~~
inflatableDodo
Good call. Since they demonstrated 2 channel already, maybe drive that with a
standard electric guitar and then have a Tesla coil driven by a bass.

~~~
godelski
People just do it with Tesla coils [https://youtu.be/JH-
YmzZgZ-Q](https://youtu.be/JH-YmzZgZ-Q)

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peter_d_sherman
Fascinating!

Did not know you could make an antenna out of a plasma; this is fascinating;
thank you for expanding what I thought was possible!

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mjfl
Your microwave has a plasma antenna in it - it makes microwaves. It’s called a
magnetron

~~~
willis936
Or a gyrotron if you eat really big hot pockets.

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Razengan
Technologies like this suddenly make a lot of science fiction seem outdated.
:)

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DoctorOetker
people interested in this may also be interested in GDD Gas Discharge
Detectors, they can also be used for mixing / heterodyning

~~~
bcaa7f3a8bbc
Wow, a gas discharge mixer! I couldn't believe it exists...

~~~
DoctorOetker
I think I have seen projects using miniature neon indicator lamps tubes as
GDD's / mixers

I have often toyed with the idea of making oscilloscopes, and spectrum
analyzers with them, but that would take a long time to explain...

Also, I miswrote it's _Glow_ Discharge Detector

Another idea is repurpousing plasma display panels as a grid of GDD detectors,
as an imaging array.

For an example circuit using a neon indicator lamp see figure 1 of the 2010
article:

[http://www.academia.edu/download/44461415/Heterodyne_Detecti...](http://www.academia.edu/download/44461415/Heterodyne_Detection_by_Miniature_Neon_I20160405-1310-1do4wyg.pdf)

This 2016 article measures the light emitted from the neon indicator lamp
instead (with FMCW scheme to detect distance as well)

[https://www.osapublishing.org/viewmedia.cfm?uri=prj-4-6-306&...](https://www.osapublishing.org/viewmedia.cfm?uri=prj-4-6-306&seq=0)

This setup improves response time (bandwidth) of the output signal.

