[HN Gopher] Lightweight woven helical antenna could replace fiel...
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Lightweight woven helical antenna could replace field-deployed
dishes
Author : westurner
Score : 90 points
Date : 2024-01-24 16:28 UTC (1 days ago)
(HTM) web link (newatlas.com)
(TXT) w3m dump (newatlas.com)
| titaniumtown wrote:
| Is this still able to be directed/pointed in the same way as a
| satellite dish? Very cool if so, the article says that it can be
| used in lieu of satellite dishes, but I'm wondering if there's
| any downsides due to the geometry of the solution.
| _whiteCaps_ wrote:
| Yes, QFH antennas are directional. But the other benefit is
| they're circularly polarized which is a benefit in satellite
| communication because you don't know how the satellite is
| oriented in space.
|
| The innovation here is the antenna that's normally static and
| somewhat fragile is now collapsible and part of the woven
| structure. Really neat idea.
|
| https://www.instructables.com/NOAA-Satellite-Signals-with-a-...
| xhkkffbf wrote:
| In many cases, the geometry of antennae matter. I would worry
| that a flexible antenna like this might be bent or stretched
| enough to degrade performance. Am I right?
| NikkiA wrote:
| It's just strips of thin metal and thin 'plastic', insanely
| cheap to produce and replace if they get damaged.
|
| Dishes are also fairly easy to damage, especially if they're
| torn down and moved.
|
| That said, what's shown isn't 100% of the antennae, you need
| a ground plane disc that the helix is attached to and acts as
| a reflector.
| slow_typist wrote:
| Ground planes are not really necessary for helix antennae
| IMHO.
| PaulHoule wrote:
| Yes.
| willy_k wrote:
| I think the "bi-stable" part of this somewhat addresses this,
| it's designed to snap into either a tall or flat
| configuration, so it should at least be harder to distort
| than a freely moving version would be.
| gary_0 wrote:
| [deleted]
| vpribish wrote:
| it's just a helical antenna - where are you seeing any
| reference to phased-array?
| gary_0 wrote:
| [deleted]
| RecycledEle wrote:
| The dish antennas I am thinking of use parabolic
| reflectors.
| bagels wrote:
| You can build a phased array of any kind of antenna...
| Patch, helical, dish, etc.
| peter_d_sherman wrote:
| >"Importantly, that cylinder can be pulled out into a long skinny
| configuration about one foot tall (305 mm), or pushed down to
| form a ring about one inch tall by five inches across (25 by 127
| mm).
|
| In its long state - and when connected to electronics such as a
| transceiver, ground plane and battery - the antenna emits a low-
| power signal in all directions, allowing for radio communications
| with ground-based team members. In its short state, it sends a
| high-power signal in a specific direction, allowing for satellite
| communications.
|
| _The frequencies utilized in either state are determined by the
| exact dimensions of each individual antenna._ "
|
| Isn't that weird and interesting?
|
| An antenna which can transmit in two distinct "dispersion modes"
| depending on shape and frequency...
|
| In "wide-dispersion mode" (for lack of a better term), it is a
| standard transmitting antenna, probably subject to the inverse
| square law (https://en.wikipedia.org/wiki/Inverse-square_law),
| that is, not unlike the radio frequency analogue of incandescent
| light -- as might be emitted from an incandescent light bulb...
|
| In "narrow-dispersion" (AKA "focused" AKA "beam") mode -- it is
| no longer subject to the inverse square law(!) -- and is not
| unlike the radio frequency analogue of a _laser beam_!
|
| What's amazing (to me!) is that apparently (if this article is
| true!) _frequency makes all of the difference between dispersion
| modes -- relative to size and shape_.
|
| In other words, perhaps it is possible to get a laser to act more
| like an incandescent light soruce if its frequency is changed,
| and conversely, perhaps it is possible to get an incandescent
| light source to act more like a laser, again, if its frequency is
| changed. (Of course, in the latter case, we'd need to start with
| a single frequency since incandescent/white light is by
| definition multiple frequencies...).
|
| And perhaps this same effect is possible across all frequencies
| (RF, infrared, ultraviolet, etc., etc.)...
|
| This antenna/coil design seems very similar to something called a
| "Caduceus Coil", which I first read about on the now defunct
| Keelynet BBS/website, a copy of one such file is here:
| https://www.newphysics.se/archives/keelynet/energy/caduceus....
|
| Related (future) question: Under what conditions, exactly
| (exceedingly rigorous definition required!) is a _coil_ (AKA
| "inductor") in a circuit _also_ an _antenna_ -- and conversely,
| when exactly is an _antenna_ in a circuit _also_ a _coil_?
|
| The "Hopf Fibration" -- might be related to all of this:
|
| https://www.google.com/search?q=hopf+fibration&tbm=isch
|
| As might the ancient notion of the "Norse World Tree":
|
| https://www.google.com/search?q=norse+world+tree&tbm=isch
|
| Related:
|
| https://www.mail-archive.com/ctrl@listserv.aol.com/msg31218....
|
| Anyway, a very interesting article!
| PaulHoule wrote:
| The intensity of the beam still falls off by the inverse square
| law but it covers a cone instead of a pattern like
|
| https://en.wikipedia.org/wiki/Dipole_antenna
| peter_d_sherman wrote:
| Why does the intensity of the light emitted by an
| incandescent light bulb fall off with the square of the
| distance (the inverse square law) -- but the light of a laser
| beam does not?
|
| ?
|
| ???
| PaulHoule wrote:
| The laser beam spreads over distance, it's just the cone is
| really narrow so you have to get far away to notice.
| datadrivenangel wrote:
| coherence.
|
| Light from a bulb is not coherent, so it interferes with
| itself and spreads out.
| peter_d_sherman wrote:
| OK, so if it is coherence -- then what's the generalized
| method to make a given EM wavelength or frequency band
| (light specifically, all EM wavelengths generally)
| coherent?
|
| That is, in Physics, how would one take an EM
| wavelength/set of wavelengths/frequency/set of
| frequencies (or even more broadly speaking, "energy") --
| and make it coherent?
| PaulHoule wrote:
| The antenna is already coherent because it is driven by a
| single signal. The lightbulb isn't because individual
| electrons are being shaken randomly by thermal noise. The
| laser is coherent because it is taking advantage of
| stimulated emission which makes the output photons
| coherent with the environmental field.
|
| https://en.wikipedia.org/wiki/Coherence_(physics)
|
| See https://www.eso.org/sci/facilities/paranal/telescopes
| /vlti/t...
|
| (I wish I could find a better writeup of the spatial
| interferometer, it's actually a pretty simple concept and
| a simple experiment but I've never seen it explained very
| well, even in print, when I was studying physics.)
| peter_d_sherman wrote:
| >"The antenna is already coherent because it is driven by
| a single signal.
|
| 1) Did you mean laser or antenna?
|
| 2) By single signal, did you mean single frequency? (If
| so, I get it. If not, please elaborate...)
|
| >"The lightbulb isn't because individual electrons are
| being shaken randomly by thermal noise. The laser is
| coherent because it is taking advantage of stimulated
| emission which makes the output photons coherent with the
| environmental field."
|
| 3) If thermal noise is the reason that a lightbulb's
| light cannot be made coherent -- then could you suggest a
| method whereby the thermal noise in the lightbulb could
| be removed such that the light emitted could be made
| coherent?
|
| 4) What do you mean exactly by "environmental field"? (A
| Google search for that term in the context of Physics --
| seems not to yield any results -- but then again I lay no
| claim to being the best Google searcher out there...)
| PaulHoule wrote:
| (1) antenna
|
| (2) the signal of a radio transmitter is (usually) more
| or less a sine wave that is either modulated by varying
| the amplitude or the frequency. You could feed the same
| signal to multiple antennas. For instance in this photo
|
| https://mastodon.social/@UP8/111780254496170231
|
| there is a radio antenna used for emergency responder
| comms. Note that there are several arrays of antennas
| stacked on top of each other. If you feed the same signal
| into an array like that the radiation pattern becomes
| focused around the horizontal plane so that energy is not
| thrown into the ground and the sky.
|
| (3) It is the shaking by random vibrations that makes the
| black body radiation of a light bulb. If you stopped that
| shaking there wouldn't be any light.
|
| (4) By "environmental field" I mean the electromagnetic
| field inside the laser that an active molecule or atom
| inside the laser experiences.
|
| Note if I hooked up 50 antennas to the same oscillator
| that would be coherent, but if I hooked up 50 antennas to
| 50 different oscillators that would be incoherent.
|
| Take a look at
|
| https://en.wikipedia.org/wiki/Phased_array
|
| there are two ways to build a phased array. A passive
| phased array has one transmitter and an collection of
| phase shifters that delay the signal to create a
| controlled wavefront. In the first case the emissions of
| all the antennas are coherent because they come from the
| same oscillator, in the second case the antennas are
| coherent because the oscillators are synchronized to a
| common timebase and controlled by a computer.
|
| Note the "magic" of that kind of phased array is similar
| to the "magic" of a hologram (they do similar things to
| wavefronts.) Light other than laser light has a certain
| amount of coherence though it is a complicated subject,
| see
|
| https://www.nature.com/articles/s41598-017-06215-x
|
| Note in Figure 10 they show that you can get enough
| coherence out of an LED to make a hologram. When they use
| a real laser the picture is really sharp but you see a
| speckle pattern that's caused by interference of the
| light with surface roughness. The LED image is blurry but
| doesn't have the speckle.
| insapio wrote:
| Absorb; and then re-emit coherently, accepting conversion
| losses.
| colanderman wrote:
| Coherence is not a necessary property of collimated
| (nondiverging) light (and doesn't cause it to "spread
| out"). You can produce noncoherent collimated light from
| any point source using e.g. a parabolic mirror.
| sp332 wrote:
| Photons from a laser are generated from amplification in a
| particular direction, so they point the same way from the
| beginning.
| projektfu wrote:
| The light of a laser does diminish at the square of the
| distance but the cone is very, very narrow. This is because
| laser light is collimated. The production of laser light
| occurs in an optical cavity that where uncollimated light
| is reflected back into the cavity. I would really just be
| quoting wikipedia so I included the link.
|
| A parabolic antenna also collimates the energy, reducing
| the size of the cone that the energy is spread over. This
| allows things like point-to-point communication and narrow-
| field radio telescopy.
|
| The "power" of a transmitter is the effective radiated
| power so a transmitter using 1 watt might spread that out
| over a wide area, but with low power in each direction, or
| collimate it to a narrow area but with relatively high
| power in that one direction.
|
| https://en.wikipedia.org/wiki/Collimated_beam
|
| https://en.wikipedia.org/wiki/Optical_cavity
|
| https://en.wikipedia.org/wiki/Parabolic_antenna
|
| https://en.wikipedia.org/wiki/Effective_radiated_power
| colanderman wrote:
| Cones are still subject to inverse square. What matters
| more is that the focal length is much longer (effectively
| infinite) with a collimated beam -- that is, the
| (virtual) tip of the cone is very far behind the light
| generating element. Inverse square only applies at
| distances from the source much greater than the focal
| length.
| mlyle wrote:
| And just to add a little more--
|
| Laser beams at short distances don't fall off inverse
| square and may even _increase_ in intensity (decrease in
| spot size) with distance.
|
| But in the end, beam dispersion/the diffraction limit
| wins and the power density is inverse square.
|
| (I can focus a big light down to a smaller spot; but
| ultimately the light is going to be spreading out. This
| can be true for radio, too, with weird things happening
| close).
| mlyle wrote:
| > Isn't that weird and interesting?
|
| I think it's very neat! There's calculators online to design
| your own QFH antennas and they're popular for amateur use to
| e.g. receive images from weather satellites. And the
| calculators can tell you that if you make it more squat, it's
| more directional.
|
| But I don't think anyone had had the idea before to let you
| vary those parameters by pinning/scissoring it.
| PaulHoule wrote:
| Makes me think of electric fence tape
|
| https://store.am.gallagher.com/am/us/en_US/animal-management...
|
| which has metal fibers woven into a mesh of plastic fibers. Even
| though the structure is mostly non-metallic I think it gives a
| better shock than a plain wire. I think I'm going to try making a
| ham radio antenna using that stuff.
| cadr wrote:
| This guy recently made a neat roll-up antenna for 2m using
| "faraday cloth"
|
| https://www.youtube.com/watch?v=X7K6DNLD9Wo
| estiaan wrote:
| I once threw a weight with a transformer wire and some string
| attached to it over a high tree branch in my yard to see if it
| would make a decent antenna for my SDR, it worked! It was an
| extremely inexpensive ~5m antenna
| dtx1 wrote:
| This could be really cool for drone/fpv application.
| 83 wrote:
| We already have helical antennas and most fpv is done at a high
| enough frequency that the antennas fit in your hand. Might be
| nice for 1.2ghz or lower but even there I can't see it folding
| down much lower than a VAS crosshair or pepperbox.
| schiffern wrote:
| A long-range directional base station that automatically tracks
| the drone (and can switch to omni at short range) would be
| cool.
| 83 wrote:
| As I understand it this new antenna changes frequencies in
| the collapsed/omni states so you would then need multiple
| transmitters/antennas on the drone which would be weight
| prohibitive.
|
| Antenna tracking ground stations and diversity receivers have
| been around since the early fpv days, although tracking isn't
| very mainstream because its challenging to set it all up. I'd
| still prefer my dual antenna / diversity RX setup since it
| provides some redundancy.
| schiffern wrote:
| Ahh thanks, I hadn't seen that detail.
|
| I thought the tracking could be mostly automated between
| GPS (outdoor) and direction finding + dBm (indoor/canyon),
| but I guess not.
| tamimio wrote:
| This is a very cool invention that could have many applications.
| It reminds me of the origami-inspired robots that can fold and
| unfold themselves to perform different tasks. I wonder how
| durable and reliable the antenna is, and how easy it is to deploy
| and control. It would be interesting to see some experimental
| results and comparisons with conventional antennas.
| _whiteCaps_ wrote:
| Would be interesting to see this antenna modelled in MMANA-GAL
| westurner wrote:
| Astrophysical jets produce helically and circularly-polarized
| emissions, too FWIU.
|
| Presumably helical jets reach earth coherently over such
| distances because of the stability of helical signals.
|
| 1. Could a space agency harvest energy from a (helically and/or
| circularly-polarised) natural jet, for deep space and/or local
| system exploration? Can a spacecraft pull against a jet for
| relativistic motion?
|
| 2. Is helical the best way to beam power wirelessly; without
| heating columns of atmospheric water in the collapsing jet
| stream?
|
| 3. Is there a (hydrodynamic) theory of superfluid quantum gravity
| that better describes the apparent _vorticity_ and _curl_ of such
| signals and their effects?
| itishappy wrote:
| > Presumably helical jets reach earth coherently over such
| distances because of the stability of helical signals.
|
| I don't think this is correct.
|
| 1. Sure, but I doubt they're energetic enough to power a
| spacecraft. I don't think you can "pull" against radiation.
|
| 2. Not really. Atmospheric gasses are going to be aligned too
| randomly for polarization to matter much. Circular polarization
| can be trivially decomposed into linear polarization (with a
| 90deg phase offset) so it can still interact as such.
|
| 3. Above my paygrade, but "superfluid quantum gravity" sounds
| like it's likely be firmly in the theoretical realm of physics.
| Maybe superfluid vacuum theory may be what you have in mind?
|
| https://en.wikipedia.org/wiki/Superfluid_vacuum_theory
| FredPret wrote:
| I'm getting into a new hobby: amateur radio astronomy.
|
| From what I understand you need an dish with d > 1m to pick up
| hydrogen line emission well.
|
| I'd be interested to know if I can just build a wide wire helix
| like this instead of investing in a big dish. It'd have to look
| nice and be weather-proof to be wife-approved though.
| petschge wrote:
| To get sensitivity you actually need collection area.
| FredPret wrote:
| Fair point. I'm trying all kinds of backflips to avoid buying
| a huge dish
| strangattractor wrote:
| I have a similar interest. One way to avoid the large
| antennas is to have multiple separated small antennas -
| like the VLA [1] - using an SDR receiver like Kraken [2]
|
| [1] https://www.vla.nrao.edu/ [2]
| https://www.crowdsupply.com/krakenrf/krakensdr
| FredPret wrote:
| That is so cool. I'd call mine the Very Small Array.
|
| I was always under the impression that it's super hard to
| pull off interferometery due to precise positioning and
| timing requirements, but looks like the Kraken multi-
| antenna you linked has that figured out in a simple way.
| bgnn wrote:
| I never done sth like this but you can lock the clocks of
| each of the samplers I guess. Simplest solution might be
| using a single source clock and distributing it to each
| board with equal length of cables. You can calibrate the
| lenght of the cable precisely if you have access to a
| pulse generator and a scope. Though, alternative would be
| shifting the sample times in post-processing the data by
| searching for a high correlation. I believe both are used
| in practice.
| pizza wrote:
| ...wonder if you could make something similar to this starting
| from a slinky? Chop it up into 4 bits, stretch them, give them
| some diy cladding/enframing of some kind, etc?
| samstave wrote:
| Since the frequency can be adjusted based on the amount its
| stretched - such that in the 'short-squshed state its better for
| 'ground' users - and stretched for satellite comms -- could one
| of these be 'Funnel-shaped' so that you have a wide, but squished
| 'ground'section - and then it funnels to a stretched out length
| for satts?
|
| Or can you only have one frequency per form?
| wildzzz wrote:
| It's not the frequency of the antenna that changes, it's the
| directivity of the emitted power. The resonant frequency is
| determined by the length of the metallic strips of the helix
| which determines how thick and tall the helix is. The angle of
| the helix when the strip lengths are fixed is what determines
| the directivity pattern, which is what they are adjusting here
| by squashing it down.
|
| If you tried to design an antenna that was good at both
| directions, you'd end up with an omnidirectional antenna which
| is exactly what the extended helical does. If you don't know
| where the receiver is, you build an omnidirectional antenna
| that will send power out in all directions. When you do know
| where the receiver is, you build a directional antenna that
| puts most of the power in a specific direction (and make sure
| the antenna is pointed that way). You can see the polar plots
| in Figure 8 in the article that shows two different plots, one
| with a flat shape that puts most power in the horizontal
| direction with little being directed backwards (extended
| helix). The next plot shows nearly all the power being directed
| to 0deg, meaning straight up (squashed helix). The next plots
| show that at 1.1GHz, the extended helix has a pretty flat gain
| between -100 and +100deg but the squashed helix has nearly 10dB
| gain at 0deg. There are other directional antennas that can get
| better gain at 0deg but they aren't flexible like this design.
|
| I could see this kind of design used for cellular modems
| mounted on vehicles. If you are within range of a tower, the
| antenna is in the extended state. If you are out of range, the
| antenna moves to a flattened state to try to reach a satellite
| capable of receiving cell communications.
|
| It could also be used in other applications where the extended
| state and is used to locate a signal but then once it's been
| detected, the antenna morphs to the flattened state and is
| pointed at the signal source. Extra gain means you can increase
| bandwidth of a digital signal.
| samstave wrote:
| >>>*"the antenna moves to a flattened state to try to reach a
| satellite capable of receiving cell communications."
|
| Sounds just like what Starlink is going to need for the
| direct to cell service they just tested!
|
| But your point of mobile mounting this sounds pretty great,
| and obvious when its pointed out, actually.
|
| I hope this does good things.
|
| Hopefully its something that anyone can make and doesnt need
| to pay some high fee to benefit from.
| ChrisMarshallNY wrote:
| That looks very cool!
|
| Antenna science is a deep pond. I worked for a defense contractor
| that did microwave stuff, and the antenna scientists were a breed
| unto themselves (frequently "odd").
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