6 ms·

Lightweight woven helical antenna could replace field-deployed dishes

128 points by westurner 3y ago

aaron695 3y ago
[dead]
titaniumtown 3y ago
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_ 3y ago
  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-PVC-QFH-Antenna-and-/ https://www.instructables.com/NOAA-Satellite-Signals-with-a-...
- xhkkffbf 3y ago
  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?
  - MR4D 3y ago
    Put it in a plastic cylinder to protect it, with an easily removable lid and you'll fix that issue for many situations. Unless there is something weird about plastic that impacts the signal, it might even be able to stay in the container when running. Might be as simple as carrying around a device about the size of a Pringles can. Will be interesting space to watch, ass this could truly disrupt many things. Attached to a drone or ballon, and the possibilities multiply versus a static location. Side note: I wonder if future wifi hubs will be cylindrical. Much better than the spiders today.
  - NikkiA 3y ago
    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 3y ago
      Ground planes are not really necessary for helix antennae IMHO.
  - PaulHoule 3y ago
    Yes.
  - willy_k 3y ago
    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 3y ago
[deleted]
- vpribish 3y ago
  it's just a helical antenna - where are you seeing any reference to phased-array?
  - gary_0 3y ago
    [deleted]
    - RecycledEle 3y ago
      The dish antennas I am thinking of use parabolic reflectors.
    - bagels 3y ago
      You can build a phased array of any kind of antenna... Patch, helical, dish, etc.
peter_d_sherman 3y ago
>"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 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.txt 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 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 https://www.google.com/search?q=norse+world+tree&tbm=isch Related: https://www.mail-archive.com/ctrl@listserv.aol.com/msg31218.html https://www.mail-archive.com/ctrl@listserv.aol.com/msg31218.... Anyway, a very interesting article!
PaulHoule 3y ago
Makes me think of electric fence tape https://store.am.gallagher.com/am/us/en_US/animal-management/electric-fencing/portable-fencing/tapes%2C-wires%2C-braids/c/tapes-wires-and-braids-pf 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 3y ago
  This guy recently made a neat roll-up antenna for 2m using "faraday cloth" https://www.youtube.com/watch?v=X7K6DNLD9Wo https://www.youtube.com/watch?v=X7K6DNLD9Wo
  - benbojangles 3y ago
    This guy has been making fabric antennas for a few years and selling them cheap on ebay: https://www.ebay.co.uk/itm/204232411345 https://www.ebay.co.uk/itm/204232411345 He also makes flatpack helical antennas: https://www.ebay.co.uk/itm/196095158881 https://www.ebay.co.uk/itm/196095158881 I think everyone from hollywood to big corporate companies have been buying his backyard inventions. He should feel really proud getting in there before the academics, youtubers, and opportunists jump on board! I bought this set back in 2019 and have had some really nice chats with the guy.
    - benbojangles 3y ago
      Just to add, he writes up on his stuff too: He made an SBand antenna out of a Beachball: https://dalybulge.blogspot.com/2023/09/diy-gatr-ball-antenna-for-qo100.html https://dalybulge.blogspot.com/2023/09/diy-gatr-ball-antenna... Before that a Fabric Parabolic Antenna: https://dalybulge.blogspot.com/2022/11/updates-on-portable-parabola-antenna.html https://dalybulge.blogspot.com/2022/11/updates-on-portable-p... Explaining how he did the design: https://dalybulge.blogspot.com/2022/10/parabola-design.html https://dalybulge.blogspot.com/2022/10/parabola-design.html
dtx1 3y ago
This could be really cool for drone/fpv application.
- 83 3y ago
  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 3y ago
  A long-range directional base station that automatically tracks the drone (and can switch to omni at short range) would be cool.
  - 83 3y ago
    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 3y ago
      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 3y ago
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_ 3y ago
Would be interesting to see this antenna modelled in MMANA-GAL
westurner 3y ago
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 3y ago
  > 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 90° 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 https://en.wikipedia.org/wiki/Superfluid_vacuum_theory
  - westurner 3y ago
    1. /? energy harvesting (and PV and TPV) /? inverse tractor beam https://www.google.com/search?q=inverse+tractor+beam https://www.google.com/search?q=inverse+tractor+beam 2. Perhaps helical is advantageous over distance (and through plasma). Given efficiency of a power transmission channel, what is the estimated loss due to scattering / heating intermediate mass over what volume of atmosphere. 3. Mass warps spacetime (in Lorentzian GR). Plasma have nonuniform mass. Plasma are apparently fluidic. Fluidic nonuniform plasma mass warps spacetime probably fluidically. There are various conjectures about quantum n-body gravity, which GR does not solve for. Recently, many additional solutions to [perpetual] non-quantum n-body gravity were posted. https://news.ycombinator.com/item?id=37960035 https://news.ycombinator.com/item?id=37960035 To model a path of [a quasar jet] through such turbulence as empty space, curl and viscosity very probably matter. Is empty space empty? The CMB Cosmological Microwave Background shows nonuniform distribution of mass/energy in the observable universe. Due to Dirac (before "Dirac sea" and e.g. Godel's Dust solutions), many have attempted to estimate where dark matter must be; though there are no confirmations of the existence of dark matter which is hypothesized to explanation discrepancies between predicted gravitational force distributions and also expansion constants like the Hubble constant. A sufficient Superfluid Quantum Relativity must predict the behavior of particles in superfluids like Bose-Einstein condensates and superconductors, and SHOULD or MUST also predict n-body gravity. Electrons appear to behave fluidically in superconductors. Photons / Polaritons appear to behave fluidically in superfluids; "liquid light" "Room-temperature superfluidity in a polariton condensate" (2017) https://www.nature.com/articles/nphys4147 https://www.nature.com/articles/nphys4147 https://news.ycombinator.com/item?id=38871054 https://news.ycombinator.com/item?id=38871054 https://news.ycombinator.com/item?id=38785433 https://news.ycombinator.com/item?id=38785433 https://news.ycombinator.com/item?id=38500760 https://news.ycombinator.com/item?id=38500760 : >>> "Gravity as a fluid dynamic phenomenon in a superfluid quantum space. Fluid quantum gravity and relativity." (2015) https://hal.science/hal-01248015/ https://hal.science/hal-01248015/ : >>> [...] Vorticity is interpreted as spin (a particle's internal motion). Due to non-zero, positive viscosity of the SQS, and to Bernoulli pressure, these vortices attract the surrounding quanta, pressure decreases and the consequent incoming flow of quanta lets arise a gravitational potential. This is called superfluid quantum gravity And in this superfluid quantum gravity, there is no dark matter. It's more like a "Dirac sea" of quantum foam with pressure FWIU; and does this correspond to black hole topologies of particle affect.
FredPret 3y ago
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 3y ago
  To get sensitivity you actually need collection area.
  - FredPret 3y ago
    Fair point. I’m trying all kinds of backflips to avoid buying a huge dish
    - strangattractor 3y ago
      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/ https://www.vla.nrao.edu/ [2] https://www.crowdsupply.com/krakenrf/krakensdr https://www.crowdsupply.com/krakenrf/krakensdr
      - FredPret 3y ago
        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 3y ago
        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 3y ago
...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 3y ago
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 3y ago
  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 3y ago
ChrisMarshallNY 3y ago
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").
Sporktacular 3y ago
"(Dish antennas) require a lot of power to operate". "Our antenna is lightweight, low-power..." What does she mean power to operate? When steering the dish with motors? Or is it in some special category for efficiency.
- klyrs 3y ago
  My guess is that they're talking about the radiation efficiency -- the strength of signal you get for a unit of power. I would interpret that sentence to mean that communicating with a satellite over a dish antenna will take more power than using this helical antenna in its short state. https://en.wikipedia.org/wiki/Radiation_efficiency https://en.wikipedia.org/wiki/Radiation_efficiency

128 points by westurner 3y ago

[dead]

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_ 3y ago
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-PVC-QFH-Antenna-and-/ https://www.instructables.com/NOAA-Satellite-Signals-with-a-...
xhkkffbf 3y ago
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?
- MR4D 3y ago
  Put it in a plastic cylinder to protect it, with an easily removable lid and you'll fix that issue for many situations. Unless there is something weird about plastic that impacts the signal, it might even be able to stay in the container when running. Might be as simple as carrying around a device about the size of a Pringles can. Will be interesting space to watch, ass this could truly disrupt many things. Attached to a drone or ballon, and the possibilities multiply versus a static location. Side note: I wonder if future wifi hubs will be cylindrical. Much better than the spiders today.
- NikkiA 3y ago
  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 3y ago
    Ground planes are not really necessary for helix antennae IMHO.
- PaulHoule 3y ago
  Yes.
- willy_k 3y ago
  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 3y ago

[deleted]

vpribish 3y ago
it's just a helical antenna - where are you seeing any reference to phased-array?
- gary_0 3y ago
  [deleted]
  - RecycledEle 3y ago
    The dish antennas I am thinking of use parabolic reflectors.
  - bagels 3y ago
    You can build a phased array of any kind of antenna... Patch, helical, dish, etc.

peter_d_sherman 3y ago

>"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 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.txt 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 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 https://www.google.com/search?q=norse+world+tree&tbm=isch Related: https://www.mail-archive.com/ctrl@listserv.aol.com/msg31218.html https://www.mail-archive.com/ctrl@listserv.aol.com/msg31218.... Anyway, a very interesting article!

PaulHoule 3y ago

Makes me think of electric fence tape https://store.am.gallagher.com/am/us/en_US/animal-management/electric-fencing/portable-fencing/tapes%2C-wires%2C-braids/c/tapes-wires-and-braids-pf 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 3y ago
This guy recently made a neat roll-up antenna for 2m using "faraday cloth" https://www.youtube.com/watch?v=X7K6DNLD9Wo https://www.youtube.com/watch?v=X7K6DNLD9Wo
- benbojangles 3y ago
  This guy has been making fabric antennas for a few years and selling them cheap on ebay: https://www.ebay.co.uk/itm/204232411345 https://www.ebay.co.uk/itm/204232411345 He also makes flatpack helical antennas: https://www.ebay.co.uk/itm/196095158881 https://www.ebay.co.uk/itm/196095158881 I think everyone from hollywood to big corporate companies have been buying his backyard inventions. He should feel really proud getting in there before the academics, youtubers, and opportunists jump on board! I bought this set back in 2019 and have had some really nice chats with the guy.
  - benbojangles 3y ago
    Just to add, he writes up on his stuff too: He made an SBand antenna out of a Beachball: https://dalybulge.blogspot.com/2023/09/diy-gatr-ball-antenna-for-qo100.html https://dalybulge.blogspot.com/2023/09/diy-gatr-ball-antenna... Before that a Fabric Parabolic Antenna: https://dalybulge.blogspot.com/2022/11/updates-on-portable-parabola-antenna.html https://dalybulge.blogspot.com/2022/11/updates-on-portable-p... Explaining how he did the design: https://dalybulge.blogspot.com/2022/10/parabola-design.html https://dalybulge.blogspot.com/2022/10/parabola-design.html

dtx1 3y ago

This could be really cool for drone/fpv application.

83 3y ago
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 3y ago
A long-range directional base station that automatically tracks the drone (and can switch to omni at short range) would be cool.
- 83 3y ago
  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 3y ago
    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 3y ago

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_ 3y ago

Would be interesting to see this antenna modelled in MMANA-GAL

westurner 3y ago

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 3y ago
> 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 90° 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 https://en.wikipedia.org/wiki/Superfluid_vacuum_theory
- westurner 3y ago
  1. /? energy harvesting (and PV and TPV) /? inverse tractor beam https://www.google.com/search?q=inverse+tractor+beam https://www.google.com/search?q=inverse+tractor+beam 2. Perhaps helical is advantageous over distance (and through plasma). Given efficiency of a power transmission channel, what is the estimated loss due to scattering / heating intermediate mass over what volume of atmosphere. 3. Mass warps spacetime (in Lorentzian GR). Plasma have nonuniform mass. Plasma are apparently fluidic. Fluidic nonuniform plasma mass warps spacetime probably fluidically. There are various conjectures about quantum n-body gravity, which GR does not solve for. Recently, many additional solutions to [perpetual] non-quantum n-body gravity were posted. https://news.ycombinator.com/item?id=37960035 https://news.ycombinator.com/item?id=37960035 To model a path of [a quasar jet] through such turbulence as empty space, curl and viscosity very probably matter. Is empty space empty? The CMB Cosmological Microwave Background shows nonuniform distribution of mass/energy in the observable universe. Due to Dirac (before "Dirac sea" and e.g. Godel's Dust solutions), many have attempted to estimate where dark matter must be; though there are no confirmations of the existence of dark matter which is hypothesized to explanation discrepancies between predicted gravitational force distributions and also expansion constants like the Hubble constant. A sufficient Superfluid Quantum Relativity must predict the behavior of particles in superfluids like Bose-Einstein condensates and superconductors, and SHOULD or MUST also predict n-body gravity. Electrons appear to behave fluidically in superconductors. Photons / Polaritons appear to behave fluidically in superfluids; "liquid light" "Room-temperature superfluidity in a polariton condensate" (2017) https://www.nature.com/articles/nphys4147 https://www.nature.com/articles/nphys4147 https://news.ycombinator.com/item?id=38871054 https://news.ycombinator.com/item?id=38871054 https://news.ycombinator.com/item?id=38785433 https://news.ycombinator.com/item?id=38785433 https://news.ycombinator.com/item?id=38500760 https://news.ycombinator.com/item?id=38500760 : >>> "Gravity as a fluid dynamic phenomenon in a superfluid quantum space. Fluid quantum gravity and relativity." (2015) https://hal.science/hal-01248015/ https://hal.science/hal-01248015/ : >>> [...] Vorticity is interpreted as spin (a particle's internal motion). Due to non-zero, positive viscosity of the SQS, and to Bernoulli pressure, these vortices attract the surrounding quanta, pressure decreases and the consequent incoming flow of quanta lets arise a gravitational potential. This is called superfluid quantum gravity And in this superfluid quantum gravity, there is no dark matter. It's more like a "Dirac sea" of quantum foam with pressure FWIU; and does this correspond to black hole topologies of particle affect.

FredPret 3y ago

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 3y ago
To get sensitivity you actually need collection area.
- FredPret 3y ago
  Fair point. I’m trying all kinds of backflips to avoid buying a huge dish
  - strangattractor 3y ago
    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/ https://www.vla.nrao.edu/ [2] https://www.crowdsupply.com/krakenrf/krakensdr https://www.crowdsupply.com/krakenrf/krakensdr
    - FredPret 3y ago
      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 3y ago
        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 3y ago

...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 3y ago

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 3y ago
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 3y ago

ChrisMarshallNY 3y ago

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").

Sporktacular 3y ago

"(Dish antennas) require a lot of power to operate". "Our antenna is lightweight, low-power..." What does she mean power to operate? When steering the dish with motors? Or is it in some special category for efficiency.

klyrs 3y ago
My guess is that they're talking about the radiation efficiency -- the strength of signal you get for a unit of power. I would interpret that sentence to mean that communicating with a satellite over a dish antenna will take more power than using this helical antenna in its short state. https://en.wikipedia.org/wiki/Radiation_efficiency https://en.wikipedia.org/wiki/Radiation_efficiency