8 ms·
>"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 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 agoThe 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 https://en.wikipedia.org/wiki/Dipole_antenna
- peter_d_sherman 3y agoWhy 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 3y agoThe laser beam spreads over distance, it's just the cone is really narrow so you have to get far away to notice.
- datadrivenangel 3y agocoherence. Light from a bulb is not coherent, so it interferes with itself and spreads out.
- colanderman 3y agoCoherence 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.
- peter_d_sherman 3y agoOK, 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?
- 3y ago