- 5 months ago
Category
🤖
TechTranscript
00:00Beaming internet from the middle of the woods, using an extra-large pizza-sized satellite dish placed on top of your house,
00:07up to a satellite orbiting 550 kilometers outside Earth's atmosphere, well, let's be honest, is technologically mind-blowing.
00:18What's even crazier is that the Starlink satellites move incredibly fast, around 27,000 kilometers per hour,
00:26and data is being sent back and forth between them at hundreds of megabits per second,
00:31all while the dish and satellite are continuously angling or steering the beam of data pointed directly between them.
00:39On top of that, the dish switches between different satellites every four or so minutes,
00:44because they move out of the dish's field of view rather quickly.
00:48If you have no clue as to how this is possible, stick around,
00:52because we're going to dive into the multiple key technologies which enable satellite internet to magically work.
00:59First, we'll explore inside the satellite dish and see how it generates a beam of data that is able to reach space.
01:07Second, we'll see how this dish continuously steers the beam so that it points directly at a satellite moving across the sky.
01:15And third, we'll dive into what exactly the dish and satellite are sending inside the beam
01:21that results in your ability to stream five HD movies or shows simultaneously.
01:28This video is quite long as it's full of in-depth details.
01:32We recommend watching it first at 1.25x speed and then a second time at 1.5x speed
01:38to understand it as a complete technology.
01:41So stick around and let's jump right in.
01:45First, let's start by clarifying the difference between a television satellite dish such as this one
01:52and the Starlink ground dish, which Elon Musk dubbed Dishy McFlatface, or Dishy for short.
02:00TV dishes use a parabolic reflector to focus the electromagnetic waves
02:05which are the TV signals sent from broadcast satellites orbiting the Earth at an altitude of 35,000 kilometers.
02:12TV satellite dishes only receive TV signals from space.
02:16They can't send data.
02:19Dishy, however, both sends and receives internet data from a Starlink satellite orbiting 550 kilometers away.
02:28While the Starlink satellite is 60 times closer than TV satellites,
02:32it's still an incredible distance to wirelessly send a signal,
02:36and thus the beams between Dishy and the Starlink satellite need to be focused into tight, powerful beams
02:43that are continuously angled or steered to point at one another.
02:47Compare this to TV broadcast signals which come from a satellite the size of a van
02:53and whose signals propagate in a wide fan that covers land masses larger than North America.
02:59Table-sized Starlink satellites, however, need to be in a low Earth orbit to provide for 20 millisecond latencies,
03:07which is critical for smoothly playing internet games or surfing the web,
03:11and as a result, their coverage is much smaller.
03:15Thus, 10,000 or more Starlink satellites, all orbiting at incredibly fast speeds in a low Earth orbit,
03:23are required to provide satellite internet to the entire Earth.
03:27Let's now open up Dishy McFlatface.
03:30At the back, we have a pair of motors and an Ethernet cable that connects to the router.
03:35Note that these motors don't continuously move Dishy to point directly at the Starlink satellite.
03:41They're used only for initial setup to get the dish pointed in the proper general direction.
03:47Opening up Dishy, we find an aluminum structural backplate,
03:51and on the other side, we find a massive printed circuit board, or PCB.
03:55One side has 640 small microchips and 20 larger microchips organized in a pattern with very intricate traces,
04:05fanning out from the larger to smaller microchips,
04:08along with additional chips including the main CPU and GPS module on the edge of the PCB.
04:15On the other side are 1400-ish copper circles with a grid of squares between the circles.
04:21On the next layer, there's a rubber honeycomb pattern with small, notched copper circles,
04:27and behind that, we find another honeycomb pattern, and then the front side of Dishy.
04:32So, what are we looking at?
04:34Well, in essence, we have 1,280 antennas arranged in a hexagonal honeycomb pattern,
04:42with each stack of copper circles being a single antenna controlled by the microchips on the PCB.
04:49This massive array works together in what's called a phased array
04:53in order to send and receive electromagnetic waves
04:56that are angled to and from a Starlink satellite orbiting 550 kilometers above.
05:03Let's zoom in and see how a single antenna operates.
05:07Here, we have an aperture-coupled patch antenna composed of six layers,
05:12most of which are inside the PCB.
05:14It looks very different from the antenna of an old-school radio
05:18and is honestly incredibly complicated.
05:22So, let's simplify it.
05:24We'll remove a few of the layers for now
05:26and step through the basic principles of how we generate an electromagnetic wave
05:32that propagates out from this antenna.
05:34To start, at the bottom, we have a microstrip transmission line feed
05:39coming from one of the small microchips.
05:41This transmission line feed is just a copper PCB trace or wire
05:46that abruptly ends under the antenna stack.
05:49We send a 12 gigahertz high-frequency voltage or signal to the feed wire,
05:54which is a voltage that goes up and down in a sinusoidal fashion,
05:58going from positive to negative and back to positive once every 83 picoseconds,
06:0412 billion times a second, or 12 gigahertz.
06:08Note that high-frequency electricity works differently from direct current
06:13or low-frequency 50 or 60 hertz household electricity.
06:18For example, above the copper feed wire,
06:21we have a copper circle with notches cut into it called an antenna patch.
06:26With DC or low-frequency alternating current,
06:29there wouldn't be much happening because the patch is isolated.
06:32But with a high-frequency signal,
06:35the power sent to the feed wire is coupled or sent to the patch.
06:39How exactly does this happen?
06:41Well, as mentioned earlier,
06:43a 12 gigahertz signal is applied to the copper feed wire.
06:47When the voltage is at the bottom of its sinusoidal or trough,
06:51we have a concentration of electrons pushed to the end of the feed wire,
06:56thus creating a zone of negative charge,
06:58which corresponds to the maximum negative voltage.
07:02This concentration of electrons on the tip of the wire repels all electrons away,
07:08including the electrons on the top of the patch.
07:11And as a result,
07:12these electrons are pushed to the other side of the circular patch.
07:17Thus, one side of the patch becomes positively charged,
07:20while the other becomes negatively charged,
07:23thereby creating electric fields between the patch and feed wire, like so.
07:27However, when we reverse the voltage to the copper feed wire 42 picoseconds later,
07:34we have a concentration of positive charges,
07:36or a lack of electrons at the end of the wire,
07:39and thus the electrons in the patch flow to the other side.
07:43The voltage in the patch is flipped,
07:45and the direction of the electric fields are also flipped.
07:49Because the feed wire voltage oscillates back and forth,
07:5242 picoseconds between one peak and trough,
07:56the electric fields in the patch will also oscillate
07:59as the electrons, or current, flows back and forth.
08:03If we pause the oscillation,
08:05we can see some of these electric field vectors,
08:08or arrows from the patch, are vertical.
08:10And because they're equal and opposite,
08:13they cancel out.
08:14However, other electric fields are horizontal in the same plane of the patch,
08:19and are called fringing fields.
08:21These fringing fields are in the same direction,
08:24and thus they add to each other,
08:26resulting in a combined electric field pointing in this direction.
08:30At the same time,
08:32electrons flowing from one side of the disk to the other,
08:35which is an electric current,
08:36generate a magnetic field with a strength and direction,
08:40or vector,
08:41perpendicular to the fringing electric field vector.
08:44As a result,
08:45we have an electric field pointing one way,
08:48and a magnetic field pointing perpendicular to that.
08:51Let's move forward in time
08:53to where the voltage on the feed line becomes positive.
08:56And now we're at the peak of the sinusoid,
08:5942 picoseconds later.
09:01The charge concentrations, or voltage,
09:04as well as the current,
09:05is all flipped,
09:07and thus the electric and magnetic fields
09:09point in the opposite directions.
09:11Electric and magnetic fields propagate in all directions,
09:15and by creating these oscillating fields,
09:18we've generated an electromagnetic wave,
09:21which travels in the direction perpendicular
09:23to both the electric and magnetic field vectors.
09:27Because the two sets of field vectors
09:29are not all in the same plane,
09:31but rather are curved,
09:33the propagating electromagnetic wave
09:35travels outwards in an expanding shell
09:39or balloon-like fashion.
09:40Kind of like a light bulb on the ceiling.
09:44Let's simplify the visual
09:45so we can see the peak and trough,
09:47or top and bottom,
09:49of each wave,
09:50and note that the trough
09:51is just a vector
09:52pointed in the opposite direction.
09:54Additionally,
09:55the strengths of these field vectors
09:57directly relate back to the voltage and signal
10:00that we originally sent
10:01to the copper microstrip feed wire
10:03at the bottom of the stack.
10:05Which means,
10:06if we want to make these electric
10:08and magnetic fields stronger,
10:09we just have to increase the voltage
10:12sent to the feed line.
10:13It's like a dimmer on a light switch.
10:16More power equals a brighter light.
10:18Thus far,
10:19we've been talking about this
10:21aperture-coupled patch antenna
10:22as transmitting.
10:24However,
10:24it can also be used
10:25for receiving a signal.
10:27In this microchip,
10:28called a front-end module,
10:30we switch the antenna
10:31from transmit to receive
10:33and turn off
10:34the 12 gigahertz signal.
10:36When an electromagnetic wave
10:38from the satellite
10:38is directed towards DISHI,
10:40the electric fields
10:41from this incoming signal
10:43will influence the electrons
10:45in the copper patch,
10:46thus generating
10:47an oscillating flow of electrons.
10:49This received high-frequency signal
10:52is then coupled
10:53to the feed line
10:54where it's sent
10:54to the front-end module chip
10:56which amplifies the signal.
10:58Thus,
10:59these antennas
11:00can be used
11:00to both transmit
11:02and receive
11:02electromagnetic waves,
11:04but not at the same time.
11:07Two quick things to note.
11:08First,
11:09as seen earlier,
11:10this antenna
11:10has many more layers
11:12and is more complicated
11:14than we've discussed.
11:15For example,
11:16here are two circular patches.
11:18The bottom is used
11:19to transmit at 13 gigahertz,
11:22while the top
11:23to receive at 11.7 gigahertz.
11:26Additionally,
11:26there are two H-slots
11:28and two feed wires
11:29to support circular polarization,
11:32a reflective plane
11:33in the back,
11:34and also there are
11:35multiple features
11:36for isolating
11:37the operation
11:37of one antenna
11:38from the adjacent antennas.
11:40We've included these
11:41and many more details
11:43in the creator's comments,
11:44which you can find
11:45in the English-Canadian subtitles.
11:48The second note
11:49is that there are
11:50electromagnetic waves
11:51of all different frequencies
11:52from thousands
11:53of different sources,
11:55passing through
11:56every point on Earth,
11:58whether it be
11:58visible light
11:59from the sun,
12:00radio waves
12:01from radio or cell towers,
12:03or TV signals
12:04from satellites or towers.
12:06Therefore,
12:07in order to block out
12:08all other frequencies
12:09of electromagnetic waves,
12:11these antenna patches
12:12are designed
12:13with very exact dimensions
12:15so that they receive
12:16and transmit
12:17only a very narrow
12:18range of frequencies.
12:20and all the other frequencies
12:21outside this range
12:23are essentially ignored
12:24by the antenna.
12:26Let's move on
12:26and see how a single antenna
12:28can be combined
12:29with others
12:29in order to amplify
12:31the beam
12:31to reach outer space.
12:33This single antenna
12:34is only a centimeter
12:36or so in diameter,
12:37and using only it
12:39would be like
12:39turning on and off
12:41one light bulb
12:42and trying to see it
12:43from the International
12:44Space Station.
12:45What we need
12:46is a way to make
12:47the light
12:47a few thousand times brighter
12:49and then focus
12:50all the electromagnetic waves
12:52into a single,
12:54powerful beam.
12:55Enter the massive
12:56Mr. McFlatface PCB,
12:5955 centimeters wide,
13:01with a total of
13:021,280 identical antennas
13:05in a hexagonal array.
13:07The technique of combining
13:08all the antennas' power together
13:10is called beamforming.
13:13So, how does it work?
13:14Well, let's first see
13:16what happens
13:16when we have
13:17two simplified antennas
13:18spaced a short distance away.
13:21As mentioned before,
13:22one antenna generates
13:23an electromagnetic wave
13:25that propagates
13:26outwards
13:26in a balloon shape.
13:28At every single point
13:29in space,
13:30there's only one
13:31electric field vector
13:32with a strength
13:33in direction,
13:34and thus,
13:34the two antennas'
13:36oscillating electric field vectors
13:37combine together
13:39at all points in space.
13:41In some areas,
13:42the electric fields
13:43from the antennas
13:44are pointing
13:45in the same direction
13:46with overlapping peaks
13:47and thus,
13:48add together
13:49via constructive interference
13:51and,
13:51in other locations,
13:53they're opposite
13:54with one peak
13:55on one trough
13:56and thus,
13:57they cancel each other
13:58via destructive interference.
13:59We can now see that the zone
14:01where they add together
14:02constructively
14:03is far tighter
14:05or more focused
14:06than a single antenna alone.
14:08When we add even more antennas,
14:10the zone of constructive interference
14:12becomes even more focused
14:14in what is called
14:15a beam front.
14:16Thus,
14:17by adding 1280 antennas together,
14:20we can form a beam
14:21with so much intensity
14:23and directionality
14:24that it can reach outer space.
14:26Now,
14:27you might be thinking
14:28that the strength
14:29of one antenna
14:30duplicated 1280 times over
14:32would result
14:33in a combined power
14:34of,
14:35well,
14:361280 times
14:37a single antenna,
14:38but you'd be mistaken.
14:40The effective power
14:41and range
14:42of the main beam
14:43from all these antennas combined
14:45is actually closer
14:47to 3,500 times
14:49that of a single antenna.
14:51The quick explanation
14:51is that by having
14:53these patterns
14:54of constructive
14:54and destructive interference,
14:56it's as if we took
14:57a single antenna,
14:58multiplied it by 1280,
15:00and then placed
15:01a whole bunch
15:02of mirrors around it
15:03and left only
15:04a single hole
15:05for the main beam
15:06to exit through.
15:07The long explanation
15:09requires a ton
15:10of math and physics,
15:11so let's move on.
15:15Dishy McFlatface
15:16and the Starling satellites
15:18undoubtedly have
15:19some rather complicated
15:20science and engineering
15:21inside,
15:22and to fully comprehend
15:23it all.
15:24You have to be
15:25a multidisciplinary student.
15:27To help you do that,
15:28check out Brilliant,
15:30which is sponsoring
15:30this video.
15:32Brilliant is an amazing
15:33tool for learning.
15:34They teach a wide range
15:36of STEM topics
15:37in hands-on,
15:38interactive ways,
15:39many of which
15:40directly relate
15:41to Starlink
15:42and other cutting-edge
15:43technologies,
15:44such as electric cars,
15:46quantum computers,
15:48rocketry,
15:49or neural networks.
15:51For example,
15:52they have an entire course
15:53dedicated to waves
15:55and light,
15:55and another one
15:56on gravitational physics,
15:58which will greatly help
15:59in understanding
16:00Starlink and SpaceX rockets.
16:02Brilliant is nothing
16:03like a boring textbook,
16:05but rather,
16:06all the courses
16:06use interactive modules
16:08to make the lessons
16:09entertaining
16:10and to help the concepts
16:12stick in your head.
16:13To really understand
16:14today's frontier technologies,
16:16and to help you become
16:17a revolutionary engineer
16:18and entrepreneur
16:19like Elon Musk,
16:21you have to be versed
16:22in a wide range of fields
16:23in science and engineering.
16:25We recommend you sign up.
16:27Try out some of the lessons
16:28for free,
16:29and if you like them,
16:30which we're sure you will,
16:32sign up for an annual subscription.
16:35To the viewers of this channel,
16:36Brilliant is offering
16:3720% off an annual subscription
16:39to the first 200 people
16:41who sign up.
16:42Just go to
16:43brilliant.org
16:44slash branch education.
16:46You can find that link
16:47in the description below.
16:50Now, let's continue exploring
16:52how a powerful beam
16:53can be continuously swept
16:55across the sky,
16:56and then how we fill it
16:58with hundreds of megabits
16:59of data every second.
17:01As a quick refresher
17:03from before,
17:03here's an array
17:04of 1280 antennas,
17:06and we fed them all
17:07with the same 12 gigahertz signal
17:10in order to create
17:11a laser-like beam
17:12propagating perpendicular
17:13to DISHI.
17:14However, as mentioned earlier,
17:16we need to be able
17:17to angle this beam
17:19so that it points directly
17:20at the Starlink satellite
17:21zooming across the sky
17:23at 27,000 kilometers per hour.
17:26Using the motors
17:27isn't feasible
17:28because they would break
17:29within a month
17:30and aren't accurate enough.
17:31So the solution
17:32is to use what's called
17:34phased array beam steering.
17:37Well, let's go back
17:38to our two antenna example.
17:39Before, we were feeding
17:41the same signal
17:42to the two antennas,
17:43and thus the antennas
17:44were in phase
17:45with one another.
17:47Understanding phase
17:48is critical.
17:49So, quickly,
17:50changing the height
17:51or amplitude
17:52of the signal
17:53is done by changing
17:55the power sent
17:56to the antenna,
17:57thus making the signal
17:58stronger or weaker.
18:00The frequency
18:00is how many peaks
18:02and troughs
18:03or wavelengths
18:04there are in one second,
18:05and changing the phase
18:07is shifting the signal
18:08left or right.
18:09Phase shifting
18:10is measured in degrees
18:12between 0 and 359
18:14because if we shift
18:16the signal 360 degrees
18:18or one full wavelength,
18:20then we're back
18:21at the beginning,
18:22exactly as if we were
18:23to loop around a circle.
18:25For example,
18:26here's a signal
18:26with a 45-degree phase shift.
18:29Here's another
18:29with a 180-degree shift,
18:32and then another
18:33with a 315-degree shift.
18:36Your eyes can't see differences
18:37in phase-shifted visible light.
18:39However,
18:40high-tech circuitry
18:41such as what's inside DISHI
18:43is really good
18:44at detecting
18:45and working with phase shifts.
18:47So then,
18:47how do we use phase shifting
18:49to angle the beam
18:50and have it point
18:51directly at the satellite?
18:53The solution
18:53is to phase shift
18:55the signal sent
18:56to one antenna
18:57with respect
18:58to the other antenna,
18:59and as a result,
19:00the timing of the peaks
19:01and troughs
19:02emitted from one antenna
19:04is different from the other.
19:05These peaks and troughs
19:07propagate outwards,
19:08and the location
19:09of the constructive interference
19:11is now angled to the left
19:13with destructive interference
19:14everywhere else.
19:16If we change the phase
19:17of the antennas again,
19:19the zone of constructive interference
19:21is angled to the right.
19:22Therefore,
19:23by continuously changing
19:24the phase of the signal
19:25sent to the antennas,
19:27we can create a sweeping zone
19:29of constructive interference.
19:31Let's bring in
19:32six more antennas
19:33and simplify the visual
19:34so that we only see
19:36a section of the peaks
19:37from each wave.
19:38Far away from the antennas,
19:40the waves join
19:42to form a wavefront
19:43that is a planar wave,
19:45kind of like ocean waves
19:46crashing on a shoreline.
19:48Just as before,
19:50by continuously changing
19:52the timing
19:52of when each wave peak
19:54is emitted
19:54by each antenna,
19:56we can change the angle
19:57at which the wavefront
19:59is formed,
20:00essentially steering the beam
20:02in one direction or another.
20:04And if we bring in
20:05more antennas
20:06in a two-dimensional array,
20:08we can now steer the beam
20:09in any direction
20:10within a 100-degree field of view.
20:14Let's move back
20:15to view all 1280 antennas
20:17in DISHI.
20:18In order to know
20:18the exact angle
20:19the beam needs
20:20to be pointed or steered,
20:22we use the GPS coordinates
20:24of DISHI from this chip
20:26over here,
20:27along with the orbital position
20:28of the Starlink satellite,
20:30which is known
20:30in DISHI software.
20:32The software computes
20:33the exact set
20:34of 3D angles
20:35in the required phase shift
20:37for each of the antennas.
20:39These phase shift results
20:40are then sent
20:41to the 20 larger chips
20:43called beamformers,
20:45and each beamformer
20:46coordinates between
20:4732 smaller chips
20:49called front-end modules,
20:50each of which controls
20:52two antennas.
20:53Every few microseconds,
20:55these computations
20:56are recalculated
20:57and disseminated
20:59to all the microchips
21:00in order to perfectly aim
21:02the beam at the satellite.
21:04As a result,
21:05the beam can be steered
21:06anywhere in a 100-degree
21:07field of view.
21:09There are a few quick notes.
21:11First, the main beam,
21:13also called the main lobe,
21:14looks like this.
21:16However,
21:16constructive and destructive
21:18interference isn't perfect,
21:20and as a result,
21:20there are additional
21:22side lobes of lesser power.
21:24Third,
21:25Mr. McFlatface
21:26holds a single phased array.
21:28However,
21:29on the Starlink satellite,
21:31there are, in fact,
21:32four phased array antennas.
21:34Two are used to communicate
21:35with multiple dishes,
21:37and two are used to communicate
21:38with the ground stations
21:40to relay the internet traffic.
21:42And fourth,
21:43phased arrays
21:44are used in many applications,
21:46and interestingly,
21:47they're used on commercial airlines
21:49to allow for mid-flight internet.
21:51So, this video also tangentially explains
21:55how mid-flight internet works.
21:57Before we explore how actual data is sent,
22:00we want to mention that this video
22:02took a month to research,
22:04two dozen script revisions,
22:06and two months to model and animate.
22:08If your mind is blown
22:10by the complexity of this technology
22:12and the depth of this video,
22:14click the subscribe button,
22:16like this video,
22:18write a comment below,
22:19and we'll be sure to create
22:20more videos like this one.
22:23The third topic
22:24we're going to dive into
22:25is how information gets sent
22:27between DISHI
22:28and the Starlink satellite.
22:30For example,
22:31we've talked about
22:32high-frequency sinusoid-shaped
22:34electromagnetic waves,
22:35but that doesn't look anything
22:37like binary,
22:38and even less like
22:39your favorite TV show.
22:41So, what's happening?
22:43Well, DISHI and the satellite
22:45indeed send a signal
22:46that looks like this.
22:47However,
22:48they vary the amplitude
22:49and the phase
22:51of the transmitted signal,
22:52and then assign or encode
22:54six-bit binary values
22:56to each different combination
22:58or permutation
22:59of amplitude and phase.
23:01With six bits,
23:02there are 64 different values,
23:05and thus we need
23:0664 different permutations
23:07of amplitude and phase.
23:09However,
23:10instead of listing
23:11all the permutations,
23:12it's more easily visualized
23:14by arranging
23:15the 64 different values
23:17in a graph
23:18called a constellation diagram
23:20as shown.
23:21Let's look at the point
23:22011101
23:24and draw a line
23:26from the origin
23:26to this point.
23:28The distance from the origin
23:29is the amplitude
23:30of the signal,
23:31and the angle
23:32from the positive x-axis
23:34is the phase.
23:35It's a bit like
23:36using polar coordinates.
23:38Thus,
23:38for DISHI to send
23:39these six bits,
23:41it transmits a signal
23:42with an amplitude
23:43of 59%
23:44and a phase shift
23:46of 121 degrees.
23:48Then,
23:49if the next value
23:50being sent
23:51is 101000,
23:54the signal switches
23:56to an 87% amplitude
23:58or brightness
23:59and a 305 degree
24:01phase shift.
24:03After that,
24:03it sends the next value
24:05with a different amplitude
24:06and phase shift.
24:07Each of these six-bit groupings
24:09are called symbols,
24:10and they last
24:11for only 10 or so nanoseconds
24:13before the next symbol
24:15is sent.
24:15Lots of times,
24:16you see the signal
24:17scrunched up like this,
24:19however,
24:19because the frequency
24:20of the signal
24:21is just once
24:22every 83 picoseconds
24:24or 12 gigahertz.
24:26And since a symbol
24:27lasts 10 nanoseconds,
24:29it's more accurate
24:30to have around
24:31120 wavelengths
24:32per symbol
24:33before the next symbol
24:35is sent.
24:36Because we're dealing
24:37on the order of
24:38pico and nanoseconds,
24:40that means that
24:41we can fit
24:4190 million
24:42six-bit groups
24:43or symbols,
24:44resulting in
24:45540 million bits
24:47per second.
24:48However,
24:49note that this data transfer
24:51is shared between
24:52download and upload.
24:54Since this particular
24:55antenna can't transmit
24:56and receive data
24:57at the same time,
24:59about 74 milliseconds
25:01of every second
25:02is used to send data
25:03from DISHI
25:04to the Starlink satellite,
25:05and 926 milliseconds
25:08is used to send data
25:09from the satellite
25:10down to DISHI.
25:11And for the sake
25:12of reducing latency,
25:14these time slots
25:15get distributed
25:16throughout a single second
25:17instead of grouping
25:18them all together.
25:19This technique
25:20of sending 6-bit values
25:22using different variations
25:23of amplitude and phase
25:25is called 64-QAM,
25:28or Quadrature Amplitude Modulation,
25:31and is more complicated
25:32than we discussed.
25:34But let's not get sidetracked.
25:36Now that we have a stream
25:38of millions of 6-bit symbols
25:40yielding hundreds of megabits
25:42of data per second,
25:43in order to turn it
25:44into your favorite TV show,
25:46we use the Advanced Video Codec,
25:49or H.264 format.
25:52You can learn more about that
25:54in our video
25:54that explores image compression,
25:57shown here.
25:58I'm sure you have many questions,
26:01and by all means,
26:02put them in the comments below.
26:04But before we finish,
26:05let's clarify two things.
26:08First, the scale of practically
26:10everything in this video is off.
26:12Here's the correct scale
26:14of DISHI and the Starlink satellite.
26:17However, DISHI is 550 kilometers away,
26:21which we can't correctly show.
26:23In stark contrast,
26:24the emitted electromagnetic waves
26:27are only around 2.5 centimeters apart.
26:30And thus, between DISHI and the satellite,
26:33there are around 22 million wavelengths,
26:36which is many more than the few waves
26:39that you see here.
26:40Additionally, in this animation,
26:42we're showing the wavelengths
26:44slowly making their way up and down,
26:47when actually,
26:48it only takes around 2 milliseconds
26:50for an electromagnetic wave
26:51emitted from DISHI
26:53or the Starlink satellite
26:54to reach the other.
26:56The second clarification
26:57is that we disproportionately show DISHI
27:01emitting electromagnetic waves
27:03and sending them to the satellite.
27:05In reality,
27:06the satellite DISH is more frequently
27:08in receive mode,
27:09and the steps and physics
27:10of receiving an electromagnetic wave
27:12are similar to emitting one,
27:15just in reverse.
27:16That's pretty much it
27:20for how Starlink and DISHI
27:22send data to each other.
27:23The original script for this video
27:25was over 45 minutes long,
27:27so all the details that were cut
27:29got thrown in the creator's comments
27:31found in the English Canada subtitles.
27:33Thank you to all of our Patreon
27:36and YouTube membership sponsors
27:38for helping to make this video.
27:40Also, thank you to Colin O'Flynn
27:42at New A.E. Technology
27:43for lending us a Starlink DISHI PCB
27:46for imaging and research.
27:48This is Branch Education,
27:50and we create 3D animations
27:52that dive deep into the technology
27:55that drives our modern world.
27:57Watch another Branch video
27:58by clicking one of these cards,
28:00or click here to subscribe.
28:01Thanks for watching to the end.
Comments