A wave traveling between two parabolic antennas

[@A-Milkdromeda-Laniakea-Hominid]

I am reminded of one of my biggest aha moments as a child: at a big budget science fair they set up two (now extinct) 8 foot diameter satellite dishes facing each other across an enormous gymnasium, end to end. The receiver had been stripped and in its place was a simple piece of PVC pipe. Now the gymnasium was full of other exhibits, and hundreds of people were wandering around, playing with noisy gadgets, and laughing and talking. It was a cacophony of sound, like you can imagine. One person could stand at a dish at each end and YELL across the room, and the other person simply wouldn't hear it. I doubt even a bullhorn could cut through the din at that distance. HOWEVER! One person puts their ear to a tube, and the other person talks into the other tube, and with a slight delay you can have a clean conversation - and none of the "interference" from the noisy room mattered. Because the dishes were perfectly aligned (like in this video) only the 2 people at the foci were of significance.

[@aratof18]

that's so cool

[@faland0069]

Thats awesome

[@phutureproof]

They have something like this at Jodrell Bank a large astrophysics centre in the UK, I went there on a school trip many many years back and it's pretty much the same setup, except this is outside and the distance between the two dishes is maybe 200 meters, so cool!

[@mal2ksc]

The Oval Office of the White House actually is elliptical, and sounds made at one focus are clearly audible at the other focus. This is clearly intentional, although I'm not entirely sure what purpose it was intended to serve other than being impressive in the days before amplification.

[@A-Milkdromeda-Laniakea-Hominid]

@@mal2ksc You think that would be intentional? Seems a bit of a security risk. *Whispers quietly to veep. Guy on other end: "I can hear you..."

[@RaymondThePainter]

I’m now gonna call parenthesis “parabolic antennas”

[@Rojomanzana438]

I don't know why but your comment made me laugh really hard brah

[@onepunchman1953]

I'm now going to call curved brackets as "parenthesis".

[@TheDantheman12121]

@@onepunchman1953 lmao

[@gaypreator8547]

Hark, what men are these, that wear their legs in parentheses. 🙂

[@Rh0mbus]

Antennae are for animals, antennas are for communication

[@sparking023]

It's nice that the simulation also demonstrates signal loss as part of the wave doesn't bounce off the antenna, and how external noise influences the signal quality

[@MatteoGalet]

Only if the feeder is omnidirectional :) If the feeder is directional and pointed towards the parabolic reflector, all the energy goes reflected to destination. That's why in some broadcast dishes, you find a small reflector in front of the feeder antenna, so to reflect all the signal to the main dish

[@저스트라구]

I thought the same one 👍

[@darkracer1252]

@@MatteoGalet except that has nothing to do with what the op was commenting about. this was not a demonstration of the situation you described. and so it did infact demonstrate the signal loss.

[@MatteoGalet]

@@darkracer1252 what he wrote is applicable both in case of the emitted signal (which I commented on), and the received signal. But in the latter, there is HUGE percentage of signal not bouncing off the antenna reflector... Much more than shown in the video

[@OneBiasedOpinion]

That was the part that interested me the most. I can easily visualize the focusing effect, but seeing how clutter repeatedly interrupted, distorted, and weakened the core signal was fascinating!

[@redcrafterlppa303]

It shows really nicely how parabolic antennas keep a signal crisp between the antennas focal points.

[@HuckleberryHim]

It looks like a little ray gun shooting a beam directly at the foci

[@realcalebrome]

truly one of the best uses of three minutes ever

[@andrebartels1690]

I don't have the education to see the benefits of this simulation, but it is beautiful.

[@ToastyMozart]

See how the primary "flat" wave from the antenna on the left winds up hitting the little dot on the right all at once after it's reflected? That dot's the receiver, meaning it got a vastly more powerful signal than if the transmitter (left dot) had sent the wave in free space without the reflectors. That way transmissions can be sent and received from much greater distances.

[@memebandit]

Bro easily I can beat you in a foot race to 20 yards.

[@louislouis7258]

@André Bartels You are clearly educated enough to recognize the limits of your knowledge. With a mind open enough to assimilate new information. Congratulations 🎊 👏

[@fregtz735]

@@ToastyMozart this is also how brittain made theyre first Way of detecting german bombers

[@nikolab.4264]

@@fregtz735 those big ass antenas that would pick up the sound of i coming bombers?? Is that what you meant

[@NikKappa]

Wave around a circle to show that the brightest point in a Shadow Is the centre

[@NilsBerglund]

Thanks, I'll have to see if I can find parameter values allowing to demonstrate that...

[@HISEROD]

@@NilsBerglund That'd be awesome

[@NikKappa]

@@NilsBerglund It would be awesome

[@toriknorth3324]

In 2D a circle analogue would just be a line segment blocking the wave. I'm not sure, but I think the center spot would be brighter in 3D than 2D because in 3D the wave would have the entire circumference of the circle to diffract around compared to just the two ends of the line segment in 2D.

[@msaciek1234]

You notice that if you have more than 2iq

[@TheMattg345]

You should do one showing waves going through different kinds of filter gates that effect different wavelengths to show the mechanics of hi-pass, lo-pass, noise cancelling, stuff like that.

[@atirutwattanamongkol8806]

you know those are different waves, right? Those filters deal with waves as a signal, not as physical waves.

[@MrMegaMetroid]

@@atirutwattanamongkol8806 signal waves are physical waves.

[@atirutwattanamongkol8806]

@@MrMegaMetroid No? Physical waves travel through the air in 3d but signal waves are just fluctuations in the current

[@ilyamanyakin8241]

@@atirutwattanamongkol8806 Signal waves you mean electrical signals? - If so then they are also waves, electromagnetic waves - either in medium or on surface of conductors...

[@gabrielxavier2676]

Are there physical filters? Or do you mean the ones we do with electronic components?

[@5mmTech]

Please forgive my ignorance on the subject as I'm brand new. Regarding the part of the initial wave that didn't touch the first parabola, once it arrives at the second parabola (around 0:33) is it received simply as noise? Would the other antenna, generally speaking, have a threshold filter that would filter it out? Thank you for making this.

[@NilsBerglund]

That part of the wave would be received as a fainter and unfocused version of the signal. The longer the distance between the parabolic reflectors, the fainter this part would be. Real dishes use a directional emitter, to avoid this part of the wave altogether.

[@5mmTech]

​@@NilsBerglundthank you so much for the reply. That's extremely helpful. I really enjoyed your video. Have a great day!

[@prodigalsonresurrection]

I remember making my first parabolic antenna out of cardstock, glue, and aluminum foil. This was back when wifi routers had external antennas, it would really beef up the signal but it's highly directional.

[@chadblechinger5746]

Aw the old pringle can days.

[@rstous7691]

Thought this was a Bill Wurtz video when I clicked on it Still enjoyed it!

[@pinngg6907]

( )

[@mage4083]

My thoughts exactly lmao

[@zurkozajebant9783]

Same lol

[@kristyandesouza5980]

YES me too

[@kristyandesouza5980]

Idk there is something so iconic on Bill wurtz style

[@Unmannedair]

That's really cool. The refraction pattern is like watching a macro scale double slit experiment.

[@Synthwave89]

Kind of like power being generated by the relative motion of conductors and fluxes, produced by the modial interaction of magneto-reluctance and capacitive diractance.

[@silas0403]

@@Synthwave89 Exactly! Gotta be careful though to prevent side-fumbling of the unsynchronised gramm-meter..

[@zombieregime]

@@silas0403 moreover whenever fluorescence score motion is required it may also be employed in conjunction with a drawn reciprocation Dingle arm to reduce sinusoidal deplanaration. Which, goes without saying, is vital in the operation of Milford trunnions.

[@archise3191]

@@zombieregime you forgot about the malleable logarithmic casing Because without it the two main spurving bearings wouldn't be in a direct line with the panametric fan.

[@VXVirtuoso]

Ya what he said in ten years when I understand it

[@dariugrinov9472]

2:19 put it on x2 speed and the music becomes drum and bass

[@deusexaethera]

Seeing how messy that is gives me a new appreciation for what radio engineers have to deal with.

[@Echo_the_half_glitch]

Messy but also controlled and predictable

[@ArthurTavares]

And this is how we send and receiv information by waves... It is amazing that we can modulate the waves so the signal can transport information in detail to be recgnized and reconstructed on the other side. Science is amazing!

[@AleksyGrabovski]

Nice simulation, the best way to experience it is to travel to some place that has an acoustic mirror installed. It is crazy how loud it can get near the focal point of a destination dish.

[@NilsBerglund]

Thanks! You also have that in some old buildings, such as the dome of St-Paul's cathedral in London, UK.

[@superscatboy]

There's a theme park I used to go to as a kid that has those on either side of this huge hall. You could easily talk to a mate over all the other noise going on, they're proper trippy.

[@rustyaxelrod]

There is a set of parabolic acoustic reflectors on the side of a large hill at the space museum in Alamogordo NM. Surprisingly effective.

[@jasonjacoby]

They are a lot of fun. I've never seen a good visualization of it before!

[@Dmaher1111]

Science works melbourne has this very cool you can almost whisper into the dish and you mate on the other side hears it clear as a bell

[@mathyoooo2]

a lot more beautiful than I was expecting. The interference pattern at 1:50 almost looks like some sort of plant growing

[@Mikelica69]

Wow yes

[@AlessioSangalli]

Is that actual interference pattern or an artifact of the simulation?

[@mewintle]

The human brain loves fractal patterns. Clouds, trees, water, moiré, doesn’t matter where it comes from. Fractals are brain food. Or at least yummy spice.

[@MrOvipare]

​@@AlessioSangalli I would say it's somewhere in between, but mostly due to the size of the mirror and the fact that they diffract the wavefront. 1) There are some artifacts visible, for instance if you look at 0:13 you see that after the reflection on the left parabolic mirror, there are multiple dim circles present. This looks like it's coming from the sharp edges of the pixelated mirror, reflections coming from those should look like light emerging from point sources. It reminds me of the huygens principle stating that any wavefront can be described as the sum of distributed point sources. In our case the distribution is not 100% optimal, otherwise you wouldn't even see any residual circles. 2) The shape you are asking about looks to me like it's the resulting diffraction pattern of the mirror itself. The mirror is finite and the wavefront "sees" this a diffracting object (like an aperture/slit). In the simulation if the size of the mirror was much bigger but with the same curvature you would surely an interference pattern that is a lot less complex. In optics we have to think about this when using a lens to focus a beam. If the lens is too small compared to the beam, the lens will diffract the beam you will not obtain a nice focal spot.

[@SabahAlSabahs]

At the two minute mark It kind of looks like the interference pattern seen in the double slit experiment.

[@JxH]

The scale of your colour coding apparently covers an immense dynamic range, because that repeated back-and-forth multiple reflections is never actually seen in practice (at least in radio communications). The dynamic range of radio communications is such that the secondary and tertiary reflections are lost in the thermal noise. If it were not, then the passband would show frequency dependant effects. Thankfully it's not actually a real world thing.

[@NilsBerglund]

I think the colors cover about 40 to 50 dB. In a couple days there will be a simulation showing a log plot of the energy along a color plot like here, for a different geometry.

[@SimonBuchanNz]

I wouldn't be surprised to see the effects shown when the antennae are this close?

[@JxH]

@@SimonBuchanNz They're not close !! Based on ~46s travel time at 'c', they're almost 14 million km apart. Of course this implies that they're each about 7 million km in diameter... ;-) !!

[@JxH]

@@NilsBerglund Hmmmm... The colour starts out red, and strangely stays red - even as the initial circular wavefront from the feed point spreads out. Just spreading loss alone should have the wavefront changing colour in the first 10s of the video. Perhaps the colour scale has a flat-top section where it's constant colour over at least a magnitude of dynamic range. If the present colour is not log, then it's linear? If it was linear, then it would even more so fade away if the colour scale was distributed linearly. Beware Radio Communications vice Physics (especially Optics), as there can sometimes be confusion and/or miscommunication between 10*Log... and 20*Log... (power density vice field amplitude); almost if they're sometimes speaking a different language. :-)

[@NilsBerglund]

You're right, I feed the energy into a flattening tanh() function because I don't know the range beforehand. Maybe I should decrease the contrast to get more range, or use a log scale. There will be a log plot for a different geometry in a couple of days.

[@Sp1der44]

That's a pretty cool simulation - I like how you can see right where the focal point is and why the feedhorn / sensor sits in that exact position. This is also relevant to how a parabolic microphone would gather and amplify a wave. Great Stuff!

[@NilsBerglund]

Thank you very much! You may want to check out the new version kzbin.info/www/bejne/hqGuooGhlKxlftk as well

[@lordandrewiesq.8825]

If you put play back speed to 2x and skip to 2:30 the music is absolutely fire

[@dekk_kko]

Definitely my favorite one so far!

[@NilsBerglund]

Yay! Thank you!

[@goddessdeedeebubblesofimag7789]

I never heard parentheses be called something as fancy as _parabolic antenna._

[@lucasc5622]

I never heard brackets being called something as fancy as parentheses

[@WiseMasterNinja]

@@lucasc5622 I never heard curve bois be called anything as fancy as brackets.

[@ElectricGun100]

@@WiseMasterNinja sideway eyebrows

[@MiScusi69]

@@WiseMasterNinja I never heard lines be called as fancy as curvy bois.

[@average-neco-arc-enjoyer]

@@WiseMasterNinja I've never heard "c" be called something as fancy as curved bois.

[@shrub4248]

Would love to see a graph of the received power over time alongside it

[@mistathenicepersonthatwont2546]

what power

[@Wadmd]

@@mistathenicepersonthatwont2546 received power in milliwatts or dBm. Basically the strength of your signal, think of it like how many "bars" your cell phone has to a tower. Those bars on your phone translate to rssi or rsrq or received signal strength. This visualization shows color range, red meaning strong signal, to green to blue weak signal. The red strength could be something like -50 or better dBM, where the green in the -60's, and blue in the -80's. Closer to 0 is stronger, further from 0 is weaker. Not all wireless is same range. LTE or cell phones, -80 dBm is good, and -120 dBm is poor.

[@mistathenicepersonthatwont2546]

@@Wadmd bro its me downloading 1 megabyte of big chungus meme

[@alxuria]

@@mistathenicepersonthatwont2546 lmfao

[@RGaming108]

@@Wadmd I work with satellite communication and in our feild -120 is like the silence of space lol. -80 is hardly anything at all if there's something we work within an acceptable range of like -60 up to -5 or -4 depending on whats being measured. Edited for spelling error

[@irresponsibledad]

From the thumbnail, I thought there was a new Bill Wurtz video

[@kartiks1039]

Writing fea code for over 25 years for magnetics, I've never seen anything so beautiful. Thank you for the great work.

[@SaraWolffs]

Awesome, better than I hoped! Thank you for all the demonstrations you've been putting up. It's interesting how the wave doesn't seem to do any wrapping around the edges, is that due to them being sharp?

[@NilsBerglund]

I think so, yes. There should be some diffraction on any edge, but it will depend on the angle at the edge. Also, I lowered the contrast a bit compared to some previous simulations.

[@TheNapalmFTW]

Radio engineers sometimes use the edge effect to diffract radio signals to the other side of mountains.

[@witoldgrabowski9263]

This is hypnotic ! Thank you ! I want to see it in a ten-hour looped version !

[@NilsBerglund]

Maybe one day!

[@phutureproof]

No you dont

[@Max_Marz]

I have been interested in point to point microwave for a long time and never has this connected with me in such an intuitive way. the color grading and seeing everything hit the focal point at the receiving end really did it for me.

[@doctorspin8085]

and in phase too!

[@savva.1427]

Here are the timecodes: 0:00 (• ) 0:04 (о ) 0:12 (D ) 0:23 ( I ) ) 0:54 ( € Э 1:11 ( | € ) 1:25 ( {:- ) 1:40 €« ) ) 1:46 €

[@noeyesee1]

should some of the reflecting waves be cancelled out and/or bifurcate ? (1:30 onwards )

[@TheBigLou13]

These animations have something so soothing and satisfying 💕

[@iwaited90daystochangemynam55]

The music makes me feel like the king of the world.

[@tonymintz8537]

For real, the fact that we can understand something as simple as this is a such a beautiful concept. Hope we all can find peace in our minds with our understanding of the universe.

[@au5music]

What’s the medium here?

[@NilsBerglund]

It can be several kinds of medium, but is most realistic for sound (pressure) waves in air.

[@FalloutUrMum]

For anyone wondering, this is why satellite receivers are usually shaped like a shallow bowl. That bit sticking out in the middle is where the magic happens. Do not touch that bit, it gets insanely hot. Now if you want to see something really mind blowing, you should see a cross section of one of those middle bits. Different ones for different wavelengths have different amounts of spacing.

[@kevinchen8325]

I love how the waves get the smallest exactly at the focus of the antennas

[@professordanfurmanek3732]

University Astronomy Professor: Fluid Dynamics in all its magnificent splendor! The applications and implications of this beautiful simulation are Beyond far-reaching!! From the macroscopic universe to the world of quantum mechanics!!

[@KitagumaIgen]

Is the light-blue trailing pattern at ~0.15 s due to interference from the distcretized parabolic surface?

[@NilsBerglund]

I think so, although I'm not completely sure. I'm using here a simple discretization on a square grid, which does not fit the parabolas. It would probably be better to use a finite elements discretization adapted to the parabolas, but that would be harder to code...

[@Topspeedcraft]

@@NilsBerglund i actually thought this was a finite element simulation, although the straigt line formed after the first bounce made me doubt it for a bit. This is great!! Thanks a lot!

[@easy99ish]

Oh you sneaky B. I just thought I was clicking on a Tom Scott video because of your red shirt in the profile picture xD

[@c4b0ombazzist90]

Best screen saver ever

[@dummyaccount.k]

watching this on double speed while super stoned was a visceral experience. the swelling of the music sounded like throat singing to witness the perishing wave

[@Linuxdirk]

This video needs 5x to 10x speed.

[@islandcave8738]

@@Linuxdirk you can go up to 16x on KZbin.

[@Linuxdirk]

@@islandcave8738 It shows 2x as maximum speed here.

[@butstough]

Thank you so much for posting the C code. I've been thinking recently about simulating wave propagation and interference/beam forming from various speaker drivers, while simulating cone break-up in 2D, among other things. Then this video gets randomly suggested... the mind boggles at the algorithm.

[@NilsBerglund]

You're welcome! Keep in mind I used the simplest possible algorithm, so depending on what you want to simulate, it may be necessary to use an improved version.

[@butstough]

@@NilsBerglund Yes, I will probably have to stare blankly at it for some time to even have a faint idea what its doing. Then figure out how to make a rough approximation of a driver...

[@LonnyH]

This is one of those videos you wish they had 3x speed for.

[@Rafael-pi4md]

you actually can speed any youtube video to any value up to 16, if you are on computer type Ctrl + Shift + J, in the tab that opened copy and paste document.getElementsByTagName("video")[0].playbackRate = x where x is the speed you want, for example 3, then press enter, you can close the tab and play the video

[@LonnyH]

@@Rafael-pi4md *cries in mobile app*

[@tripodgamer]

@@LonnyH just press the 3 dots

[@GillAndBurtTheCop]

Am I supposed to be cheering for something like this the way I am right now?

[@ghlscitel6714]

I did not expect what I saw. Really thought-provoking video!

[@bomblii]

me when i am a wave and i'm travelling between 2 parabolic antennas

[@MeltedMask]

I just wonder what will happened if you have this same configuration, but antennas are closer and shares same focus point.

[@NilsBerglund]

See my reply to Kram1032.

[@timwhite7127]

Damn, I wish we had graphics like this back in the '60's when I was doing acid...

[@NoosaHeads]

This is one of the most beautiful things I have ever laid eyes on. The interference patterns are beyond my conception and cognitive abilities (the maths behind this are astonishingly complicated and could only ever be done with a sophisticated computer algorithm) but I, at least appreciate the work and thought that has gone into this glorious animation. Thank you for the effort you've put into this.

[@camerapasteurize7215]

Beautiful demonstration of the effectiveness of parabolic reflectors with recievers/transmitters

[@AChippendale]

Funny how it looks like an eye from different perspectives at different times.

[@Rick_Mave]

From a different point of view, this video is a remarkalble proof of how science and digital art can coexist.

[@lolerskatez]

Is there a suggestion that they couldn't or don't already?

[@Rick_Mave]

@@lolerskatez My photographic eye is always looking for simmetries and reflections or for any geometric patterns and textures that can be spotted in natural or less natural landscapes. This is what motivated my comment. I love the human ability of generating works of art, either on purpose or not.

[@Kram1032]

what if the two mirrors share a focal point?

[@NilsBerglund]

Then the wave should keep alternating between planar and circular. It could be fun to try it, thanks!

[@VolcanoVistaXC]

@@NilsBerglund This sounds like an example of an optical resonator. Lots of interesting math and physics to be visualized there with different configurations and stability conditions!

[@gabemerritt3139]

If the wave origin was also the focal point would it not have destructive interference with itself after the first reflection?

[@titan1235813]

Those two focal points on each side of the parabolic antennas make it for a richer experience. Brilliant.

[@lelsewherelelsewhere9435]

What is that immediate rightward wave at 1:36? How??? Very fascinating!

[@spore573]

I love the esthetics and the music choice to your videos. I love how much you simplify the understanding of quantum wave to quite comprehensive animations. I imagine it takes quite a bit of effort for the code to work out. Your chanell could be used as an good example, and explantion in quite a few Univerities. I have a question for you tho: 1.Are you maybe planing to expand to 3D at some point? 2.Can you make a "presentation" on polarization? Keep up the good work, sadly your chanell is quite a nieche...

[@NilsBerglund]

Thanks! Feel free to recommend this channel to any math/physics teachers/professors you think may be interested... 1. Solving real 3d wave equations would take too long at this point, roughly 1000 times longer to compute. What seems possible is to do 3d plots of the 2d wave equation, that is, the wave height z as a function of x and y. I'll have to refresh my knowledge of 3d OpenGL, though. 2. I'll have to look into what could be interesting and possible to do with polarization. I assume it would require a vectorial, 2d wave equation, e.g. a version of Maxwell's equations.

[@spore573]

@@NilsBerglund I was thinking abbout that 3d thing. I'm no quantum scientist, nor programmer. BUT I was thinking about making two separate animations one for vertical axis, and one for horizontal. It seems like you could "hide" some of the data in the colour values, and maybe it would be possible to make the whole thing using just two separate animations... you would have to have some kind of dedicated compiler of some sorts to transpose the data to 3d... It propabbly would work if you would stick to "simple shapes" like well parabolic mirrors for example :x ... spheres, walls, cubes etc... like I said I'm no computer scientist but maybe some kind of X-Y axis shenanigans is possible if you could menage to use the colour values as some kind of medium, and since you already use it to represent the strength, phases, and other values... maybe that ain't that far off... dunno just thinking out loud :) Have a nice day and please do continue your good work

[@spore573]

@@NilsBerglund Oh and also, a "time took to render" could be a nice touch for US THE INTERNET NERDS 🤓

[@NilsBerglund]

Okay, I'll try doing it in future simulations!

[@XOXO-tg1yv]

Me to my gf: what you want?? Her: 0:12

[@ZetsKai]

This video is so motivational and inspiring

[@mipmip4575]

lol

[@billgiles3261]

I recall at school in science the teacher setting up two parabolas and creating a spark in one with a battery and that spark being copied in the other parabola although there was no power there. This was a great demonstration of how that could refocus the energy of the spark. Of course it is the basis of radio, and these days microwave transmission.

[@Rush_Fun]

I had a friend that made these two parabolic antennas in real life (around 2 meters high each) 10 meters from one another. When you whispered towards one of them, the person in the front of the other one could hear what you said. It was amazing and bizarre at the same time.

[@leksluthor3]

1:05 it’s Wednesday my dudes.

[@DreadEnder]

Indeed it is

[@CoolDeveloperOnBalance]

it's saturday

[@USERNAME1-x5u]

It's Sunday

[@spacechannel8798]

2024 on a Wednesday

[@raynic1173]

I felt like god was going to show his face...

[@Astinel]

( 🌊 )

[@joels7605]

This is an excellent visualization. That got a subscribe. Thank you.

[@laurensvanhelvoort3921]

From the thumbnail i thought this was gonna be a bill wurtz video

[@magnesjberg24]

1:11 lemon wedge

[@jneal4154]

Sometimes in your wave propagation videos, I see echoes or reflections that I'm pretty sure are artifacts. In this case, right around 0:17, you can see the exiting wave, top and bottom, get reflected back a bit, where I would expect the evolution of the wave to be unaffected by exiting the frame. Could this be caused by how you're calculating boundary conditions?

[@NilsBerglund]

It is not that easy to get absorbing boundary conditions right. If you just set the wave equal to zero outside the simulated domain, the waves will get fully reflected on the boundaries. Thus you need a form of what is called perfectly matched layer boundary conditions. This is a rather old video. I later managed to improve the plm boundary conditions, see for instance kzbin.info/www/bejne/hqGuooGhlKxlftk

[@jneal4154]

@@NilsBerglund Awesome. That was what my intuition was telling me. Thanks for the insight. To handle the boundary condition in the case of EM waves then, is the technique similar to impedance matching? I realized after it was an older video. 😄

[@NilsBerglund]

I'm no expert on impedance matching, but there may be some similarity. What you basically try is to predict what the derivative of the wave will look like at the boundary, based on its value, and use that as a type of mixed ("Robin") boundary condition.

[@quietsamurai1998]

I noticed that just before the wave hits the first mirror (0:05) , the inside of the wave looks more like a squircle than a circle, with flatter faces in the cardinal directions. Is this a simulation artifact?

[@NilsBerglund]

Yes, this is most likely due to the relatively low resolution of the simulation mesh. I later improved the resolution, see for instance kzbin.info/www/bejne/hqGuooGhlKxlftk

[@miketate3445]

It is striking and beautiful to see the waves focus on the receiver antennas like that.

[@theelephantintheroom69]

Changed my life forever.

[@Maxym-sk4zq]

This is actually very helpful for better understanding of radio waves. I would absolutely love to see more on the topic

[@NilsBerglund]

There are many more like this in the playlist kzbin.info/aero/PLAZp3rbgWLo3VO2rqVKyL1T6DUmnDAaEN

[@omj5149]

Looks like math problem with infinite mathematical iterations

[@Cnupoc]

Awesome! It shows why the dot with the sensor in front of both dishes is SO important.

[@anson7064]

Explanation: The node where the wave starts is at the parabola’s foci, a specific point where the wave can bounce perfectly to form a straight line coming out. When it hits the other parabola, it bounces directly into the opposite foci.

[@therfnoob7697]

Great video! What is causing the reflections (from bottom to top below, and from top to bottom, above) at 0:17 ?

[@NilsBerglund]

I'm using a form of absorbing (perfectly matched layer) boundary condition, but in this simulation the resolution is probably too low. Later versions such as kzbin.info/www/bejne/hqGuooGhlKxlftk use a higher resolution, and the reflections are reduced.

[@therfnoob7697]

@@NilsBerglund thanks, subscribed !

[@frikyouall]

This actually cleared a few things up for me, thank you.

[@NilsBerglund]

Glad it helped!

[@woahdudeitsme9742]

Woah, I want this on a T-shirt!

[@hubercats]

Your simulation results are really interesting. I’d be quite interested to see similar images for a microwave cavity resonator field as I’ve long tried to visualize such. Thanks much!

[@NilsBerglund]

Thanks! While I have not simulated microwave cavities as such, I have several sims of "parabolic resonators" that may interest you, they are in the playlist kzbin.info/aero/PLAZp3rbgWLo3VO2rqVKyL1T6DUmnDAaEN

[@caryccharlson]

The placement of the receiver transmitter in the parabolic formula escapes me right now but I completely understand why the emplacement is so important I knew that it worked I didn't know why it worked

[@NilsBerglund]

This particular point is known as the focal point, or focus of the parabola.

[@freshdumbi999]

This knowledge doesn‘t give me any advice or help for my life, yet i am sitting here in the middle of the night thinking „mm yes very interesting“

[@ianklanfer4887]

The timings incredible and it's cool how it comes off flat with the curved surface hitting the curved surface and it seems to do something in the exact same spot at the dot on the other side and then it seems to terminate backwards started Pretty cool

[@TheDaggwood]

That's a LDE. Long Delay Echos are pretty sweet.

[@me14ch]

As a student who never listen and gets bored in science class, just watching this made me question my existence. Its too beautiful

[@andyowens5494]

A lovely demonstration of focus, dispersion and attenuation.

[@Yoraiz3rt]

". O D I C" I don't know if I'm crazy seeing letters and symbols

[@NeedlesSweetToothKaneTheClown]

This is like one of those things I see when I'm sleep-deprived and hallucinating in a dark room.

[@codemechanic2024]

never Admired my calculus lessons related to focal point of parabola until my teacher explained its usage in dish antenas.

[@anmoldeepsingh9281]

signal loss would be theoretically zero if the antennnas had their foci at the same point.

[@NilsBerglund]

Indeed. In practice, small errors in alignment and imperfections in the parabolic shapes will degrade the signal, but it remains much better than without the dishes.

[@jevirandio]

This is what I am watching instead of studying

[@yardy88]

Electrodynamic simulations are hard af. Props man.

[@NilsBerglund]

Thx!

[@walterpcjr]

Interesting simulation. However, it is worth mentioning that, in most parabolic antennas, the primary source of the fields (in the transmitting antenna feeder) is not omnidirectional, but directive. Therefore, the part of the energy that is radiated directly from the primary source to the receiving antenna (without being reflected on the transmitting parabola) is much smaller. However, there are some antennas whose primary source is a dipole (and therefore omnidirectional). In this case, the simulation is more realistic.

[@ArtForSwans]

idk why this showed up in my recommended but it just made me realize how we're able to pick up and send signals from and to spacecraft located as far away as the edge of the solar system. The beams spread out by the time they get to their destination, but you don't need to capture all of the radio waves to interpret the data, only a small portion. As long as the wave wasn't distorted too badly, the sequence of the bits will be preserved.

[@ignatiolu863]

It's an unstable resonator. Could you add an amplifier in the middle and pull the mirrors closer? It would be a video about how a laser works :D

[@NilsBerglund]

The question is how to simulate the amplifier. One would have to add some active wave sources, that react to incoming waves.

[@Ganjalf_the_Green]

I NEED my advanced antenna engineering lectures to start as soon as possible. After RF circuits and microwaves I really want to understand how antennas work!

[@barnyardbrio7597]

so cool. I have stood at the receiving end of a parabolic antenna and it is unreal the smallest sounds from a large distance that you can hear clearly

[@williamruzicka2073]

Very cool! Did a simulation of GPR in college bouncing off an object in a medium and could see the evanescent waves in the simulation.

[@trapkat8213]

What is the shape of the pulse in the time domain? Back in the nineties I did a simulation of the acoustic scattering from a rigid sphere, showing what happens when it is hit by the spherical wave emitted by a monopole source. After much experimentation I settled on a Hanning pulse as input to the monopole source. The main energy content was concentrated below 3kHz. It took ages to make the animations but they served us well. We had them put on to VHS tape (no s***, we even had a version in the format used in the US) and showed them at conferences around the world!

[@NilsBerglund]

The initial state is radial, with a radial dependence given by a Gaussian times a cosine. I have not tried using a Hanning pulse.

[@Aswin-qk5nl]

The music is out of this world

[@bojangles2492]

I remember in school when they would draw a parabolic curve and these perfect reflection lines.

[@BillFlann9]

Hi! Thanks for posting this. Great concept for a KZbin channel.