How the First Transatlantic Submarine Cable in 1858 led to Transmission Line Theory as we know it
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- Опубликовано: 17 май 2024
- The key to understanding modern transmission line theory is to first understand its history. This is the story of how the first Transatlantic Telegraph Cable in 1858 led to the birth of Transmission Line Theory. Professor William Thomson (later Lord Kelvin) was the genius who developed the initial breakthrough that led to the first accurate model of a long cable. Although it would be left to Oliver Heaviside some decades later to introduce inductance, Kelvin's idea to distribute the resistance and capacitance evenly along the line led to a powerful mathematical analysis with enough predictive power to explain the failure of the first transatlantic cable.
The mathematics of Lord Kelvin's analysis is fascinating - and crucial to understanding how modern transmission theory was developed.
00:00 Introduction
00:39 Motivation
01:53 A primitive starting point
02:58 Description of Kelvin's model
09:41 The first transatlantic cable
11:32 Lord Kelvin rises 
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For those who ponder, "Why study calculus?" this presentation gives a clear answer. Also, the EE concepts that seem obvious to today's diligent EE student (and which mystify those who lack either diligence or proper preparation) earlier mystified the best minds, even Faraday. A hint to those who "don't quite get" some aspect of the material here: Go back and learn the fundamentals. Somewhere you missed a step or learned an incorrect shortcut.
"But what about inductance?" as some have noted. Yes, it had not yet been folded into the theory.
This is where Heaviside comes in...
Right, once someone else figures it out, it's relatively easy to understand!
Today people don't need to know calculus to send a message over the Internet. Never encourage anybody to study. The more uneducated people the less competition on the job market.
@@miroslaw5615 Sorry, but you'll wind up working for a boss who should know calculus, and even thinks he knows it, but who is directing you based on faulty understandings. I was there, busy trying to tell PhD EE guys why their naive computer programs were failing. (This was 50 years ago.) They did not want to hear me tell them that any "real" number in their Fortran programs was only a representation of an approximation to a real number, and that limits as understood in calculus did not map onto the limited precision supplied by the computer. (You are guaranteed at least one more real number between any two others, but the computer's "floating point" engine lacks continuity and thus does not give you that guarantee.) Those EE guys did not want to listen because I only have a bachelor's degree. How could I possibly be right?
The issue is now better known, and is explained well in this Wikipedia article. en.wikipedia.org/wiki/Floating-point_error_mitigation but knowledge of calculus (particularly /limits/) is still needed so the programmer doing intricate stuff like geophysics can avoid the errors.
Fundamentals: Pushing, stopping, kick-turning. In both stances and for both front and back sides. My switch stance, certainly needs some revisiting.
I was in a baseball card shop in the early 90's and they had a NY Times from 1858 for sale. It had a box score for a few games in the NY/NJ area, including Hoboken. I thought that was very cool and bought it. When I got home and read the whole paper it was obvious why it was saved. It was because it was from the day after the first cable was completed. The entire front page was dedicated to it. It's fascinating.
Not mentioned in the video, but they actually found the damaged spot on the original, pulled it up and fixed it.
Well researched, well written, and beautifully produced. Thank you for your labors !
Vastly more informative than other videos on transatlantic cables.
Geez, back in the 20th century I struggled with transmission line theory. Now nearly 24% into the 21st century watching how you illustrate the properties of cables, the equations, I get a better intuitive feeling for transmission lines.
I strike gold on YT every now and then. This being one of them.
Teaching is a skill like any other, but we pretend that any shmuck can do it.
It's a low-pass filter where the break frequency drops the longer the line gets. I note (and the video notes) that Lord Kelvin didn't know about the series inductance, which makes it an even steeper filter (and much more "ringy"), a classic RLC tank circuit.
Shut up you with your 24% into the century because I've never looked at it that way and now l suddenly feel really old.
yes, a chapter in my undergrad electromagnetics text could have been replaced by this video.
A lot of effort went into making these videos. Thank you sir for the joy that you put into making them.
Hidden gem of a channel
The distortion affected early telephone signals over wires.
A lot of effort was put into developing filters to reduce this distortion.
Eight words a minute is not so bad.
It's really amazing when you consider the benefit of going from Zero to something that is useful.
Pupinize much?
@@sashimanu Ha ha. Thanks for making me learn about Pupin coils.
Slick. I never went to school to be an Electrical Engineer. But I do have a little background in Math, so I could follow along a little. Thanks. Elegant. I remember reading what about the fuss that Ohm's Law raised.
Top notch production quality. Hugely underrated channel
That's a very well-made video. I had imagined his knighthood was for something related to temperature. This is quite a relevant problem for the time and a brillant approach.
Lord Kelvin is not obscure, he's a legend. He pushed classical physics to its absolute limits. Transmission lines are one contribution but thermodynamics was his real forte leaving his name on the absolute temperature scale to this day. Yep, he's why it's d̶e̶g̶r̶e̶e̶s̶ Kelvin. Obscure?
no, it's just Kelvin not deg Kelvin :)
@@davenelson413 I appreciate the correction, you're right of course.
Loved the video, this deserves a sequel with heaviside.
YT has come a long way thanks to high quality content like this one. Amazing work.
Thank You for this Amazing Video! It explained everything so clearly! Ever since I watched the documentary "The Story Of Electricity" by Jim Al Khalili, I have been looking for an in-depth explanation of this event. After watching your video it felt like something just clicked inside of me, It's the same feeling you get after putting all the pieces of a puzzle together. I feel so happy now. Thank You for making me feel like this!
Glad it was helpful!
02:27 What about the inductance of the transmission line? when did they start to consider the inductance of the transmission path?
The puzzle of inductance and its effect on transmission line theory was solved by Oliver Heaviside a few decades later in 1876.
@@VisualElectric_any chance you are going to make a video on this?😊😊
Watching this again, I think of diving back into those equations I struggled with in college. I also think while most of us struggle learning the math, but these guys like Faraday, Clark, Thompson, and others had to learn it from scratch! Though 16 hours to send a message across the Atlantic but it must have been totally awesome to pick up the pulses like seeing the first video transmission from the moon.
Very well done and informative. Remember me as one of your OG fans when this channel blows up
When ham operators (amateur radio) had to be able to morse, the minimum requirement was 5 words pr minute (wpm). The limit for the traditional morse key is 15 wpm. With machine or computer generated morse it is possible to understand up to 40-50 wpm.
Very nice and informative video. Thank you!
This presentation is awesome!
When people try to tell me about how awesome lord Kevin was, it gets absolutely zero reaction out of me. I'm just like 0 K.
Well told. It's amusing that the solution was to increase the voltage, a choice made by a man who did not understand theory. In my career as a EE in mill controls I would encounter frequently people who would argue or give orders to use setting that would fail or would damage the equipment. It happened way too often actually.
Excellent Video! This deserves way way more views
Thanks!
Wowww, what a content, wonderful 👏 , enjoyed the way you guys have presented complicated topics in a manner that we can relate, thank you 😀
Fabulous content! Well done! Greatly appreciated. Thank you!
Beautiful production in every way. Wow.
This channel is undermined.
you have gained a new subscriber , sir.
thank you so much for this amazing video 😇🎓
The genius of these men.
very very very nice video....thank you.
Continue with your videos . They are very informative
Thank you, I will
Wow!! Great job at explaining ! Subscribed
Masterfully done! I have subscribed
Thank you very much!
Superb content.
Kelvin read Fourier's treatise on heat when he was 14. He was adept in its use. Nice presentation of the technical issues.
Outstanding production quality.
May I ask what software was used for the animations?
Thanks - I use a combination of things - after effects for animations, some blender and manim for equations.
Beautiful video
Check out "The Forgotten Genius of Oliver Heaviside: A Maverick of Electrical Science" ~ Basil Mahon
My dad told me that, in his Cambridge degree exam in 1934 there was a question on heat transmission. He said that he wrote as his answer "Using the telegraph equation, well known to electrical engineers, we have as the solution xyz" and moved on to the next question.
Love this. A great following could be the story of the Great Eastern.
well done!
Great Video
Thanks!
Nice video
Thank you!!!
What's amazing to me is how Fourier solved the differential equation
This are great videos! As a non english speaker i need the use of headphones to follow the script of the video. Funny to hear the balancing on the chair of the author! 😅
Small correction. Thomson was raised to a peerage to become Lord Kelvin not 'knighted'.
I don’t understand all of this but I do understand the concept of carrying power across large distances with smaller wires by sending them at a high voltage and then you can step the voltage down and increase the current to get the same power. So essentially you can carry many loads with a small wire, but once the voltage is reduced, large wires are required to carry even a small portion of that load. This makes sense to me if voltage is a force like I was taught in college but if voltage is not a force then it doesn’t make sense at all.
sir i have some doubts in adc control using fpga how could i contact u please reply .
Lord Kelvin was a genius.
The video is 60fps, which can't play correctly on my Chromecast. It's a pity. Why don't you upload videos at 1080p x 30fps ? 😮
leave it to old men w/ too much time on their hands to 'misunderstand' the concept and start buying super expensive 10ft speaker cables that don't smear the upper octaves of the audio fq spectrum :)
jokes aside, this was a great production, thanks and wish you all the best!
And what was the carecterstic impedance "Zo" of the transatlantic telegraph cable?
Nice job. Great video. Thanks. I look forward to checking out your channel. Subscribed ... Cheers ...
11:15 Both cables had multiple strands forming the center conductor, which increase the surface area of the conductor and the distributed capacitance. It seems as though a single center conductor would be better, perhaps with an electrically isolated shield between the center and outer conductors as this would divide the capacitance into two in series and reduce the reactive current.
re: "multiple strands forming the center conductor, which increase the surface area of the conductor and the distributed capacitance. "
Um, it does not work that way, stranded RG58 for instance has pretty much the same capacitance per foot as solid conductor RG58 cable ... see, the rough area exposed to the shield (the other capacitor plate) is roughly the same for both cases. Very small difference. Very. Small.
What is the book referenced in the video?
GREAT! The problems of resistance and capacitance are very well explained. If you had included induction (L), you would have covered the Big Three. Question: I'm assuming that R, C and L are irrelevant in a fiber optic cable. Is this so?????
it is I believe and that is because fiber optic uses light rather than electricity(blah blah blah photons electricity blah blah)
Fiber works to 'guide a wave' (light wave) versus carry a current (like a coax cable or twisted pair does.) Then there is 'wave guide' which is bigger and traditionally carries microwaves (and Great Britain did at one time try a cross country WG system) BUT it is physically a lot larger.
This has me wondering if I could explain the need for thicker cables to the scientists and engineers of the time (prior to Thomson's revelations) in a way that would at least seem plausible. Is there a more conventional physical model I could use to demonstrate why the cable they had used was inadequate, aside from the mistaken use of higher voltage?
They had no comprehension of cable impedance matching at that time, so, they were baseband 'switching' a voltage to actuate a coil at the far end .. this made for 'echos' that interfered and would propagate back and forth. Land cables didn't have the low impedances that shielded under sea cables did, and the echo was manageable over shorter land runs.
Another two smaller details 1. "Ohm's law" is not a law despite of names, in fact we call Ohmic conductors those that obey Ohm's law (a law that is only valid to those that obey this law is not a law at all or we would have billions of edge case "laws"), and even those only obey it in very small ranges as as conductors heat their "resistance " (the quotes use is explained further ahead) gets higher. But if Ohm's law defines resistance this is a circular reasoning, just like using Newton's second law as a definition of force (it is not).
It is an empirical law, not a fundamental law.
2. The approach using only capacitance is valid for very low frequencies, for higher frequencies the inductance is not negligible (like audio or radio frequencies). But the same idea of calculating it can be used. In fact this approach is not different to the propagation of light on a dispersive medium, as the speed of each frequency component depends on the frequency (not surprising as Fourier created this method hat involves series of sines and cosines to solve heat equation). That is why when we learn that at college we learn to use a series involving the L and C and taking the limit to infinitesimal parts (there are two different ways to approach the slicing of the line in parts but when you take the limit bot converge to the same solution), this way is the first step that is more intuitive to students before you attack the differential equation and even calculation the distribution of energy around the line using the Poynting vector (that should silence sterile false polemics created by Veritasium but no one seems to have made their homework even those that pointed it like ElectroBoom ignored this part).
Heaviside was a great scientist and mathematician -- read about him. He struggled through adversity and was largely self-taught. Lord Kelvin was of course a great man also. with some advantages Heaviside did not have.
A math problem;
With the cost of the cable, divided by the expected lifetime or the wanted break even time, what should the price per minute for a telegram be?
Since they used 'codes' for common words (an early form of compression), do you charge per character sent, or the full letter count of the original message?
Give it up for Heaviside!
How many people knew this but never thought about the transmission time per word...? Half way round the planet. Me.
Good vid.
It's interesting how the predicted problems in the first cable were ignore, and only corrected in the second cable after the wretched performance of the first one were clearly demonstrated. The same thing happened more than a hundred years later when AOL bought Time Warner, expecting that someone would quickly figure out how to send 10 MHz videos through T1 voice grade telephone lines... as if the laws of physics truly were as "elastic" as Star Trek episodes portrayed them. As for pulse dispersion, an acoustic example of this was exploited to make sound effects for Photon torpedoes in Star Trek, and blaster sounds in Star Wars. In both cases, those sounds were recorded by striking a steel guy wire for a radio tower, and recording the resulting audio pulse, reverberating through the cable... One can clearly hear the rapid decay of high frequency components, as predicted in the math, yielding the prolonged metallic "twang" sound that screams "DISPERSION !" to anyone who understands this stuff. An example is here : ruclips.net/video/fl0wIdGxfbQ/видео.htmlsi=eGCJv8ikpXjRv1gk
re: " how to send 10 MHz videos through T1 voice grade telephone lines"
Apples and oranges; A "T1 line" is a 1.544 Megabit per second digital line, and it cares not whether analog or digital 'data' is being carried. There is no such thing as a "T1 voice grade telephone line", unless you consider a T1 (still a digital trunk) used as a voice 'trunk' with robbed bit signalling in use. Robbed bit signalling can (should be!) only used with 'voice' transport (where distortion from random missing, change bit will not materially affect the phone call.)
Signal Source impedance has to equal Transmission Line impedance HAS TO EQUAL Terminating Resistor impedance. Failure to establish these conditions results in unwanted Signal Reflections.
Willium Tompson is still a Giant in physics.
I still find RxC=t stunning
One thing missing is the inductance that makes it even worse. The inductance is in series with the resistance and as this is worse for higher frequencies it smears out the signal. it rises and falls slower.
As the video noted, with this RC transmission line model, the higher frequencies travel faster than the lower frequencies, smearing the pulses. One of the contributions Heaviside made was that to compensate for this, inductance needs to be added the the transmission line. This was in fact done for the long voice land line and telegraphy runs of the past.
@@bobkitchin8346 I am sorry but I have never heard about that higher frequencies travel faster on a transmission line than lower frequencies. I saw the video once more and yes it is said to be the case but is has always been my understanding that all frequencies travel at speed of light c speed but reduced according to the environment. Higher frequencies are dampened faster than lower frequencies and as any pulse consists of it's base frequency and some higher harmonics (as sine waves) so the front will always be rounded of.
If a cable like a coax cable with a set impedance should however work as a pure resistor at all frequencies if the impedance is correct in both ends. That is why we can obtain quite high transmission speeds on such transmission lines I believe.
I have learned some thing about it when I studied to become an electronic engineer but I am not a transmission line specialist so maybe you are right. I also don't dispute that I might have been thought wrong. It wouldn't have been the only thing that we where thought wrongly. One should only believe what one is thought until one knows better (not believe to know better but truly do know better).
In your diagrams people could misunderstand the flow of electrons this is the flow of electric charges.
Electrons do not flow from source to load.
This is exactly what the transmission line demonstrates.
Electron valence drift is so small that no electron from your power grid gets to your home.
The Ohm's law is a lumped some model they are simplified explanations of what's going on underneath an object of abstraction.
I can prove this to you. The common everyday product like a electric toothbrush pause the Wireless cell phone charger has no physical connection to your device.
The power grid is the same, with capacitors and Transformers and isolators the basics of a transmission line there is no physical connection.
The electromagnetic field is propelled around the wires through the air to your load which could be something at your house and it seems like magic.
This is called electrodynamix which comes from the Maxwell-Havyside , which came later.
Although electrons do not move from source to load, they do move slowly in the general direction of the field. Otherwise, the analysis of Kelvin would not make sense and it would be difficult to show visually how the equations and underlying theory originated.
Amazing how such huge capital projects were embarked upon apparently without any practical modelling to prove the theory.
Practical, as in make miles and miles of cable and test it on land first? There's always room for a POC, but when the money folks are looking at least expense, I can see anything not essential to putting copper on the sea floor being cut from the budget (and they lost their money, ultimately). From a more macro view of model, Thompson/Kelvin was doing exactly that - predicting the behavior of a cable based on resistance and capacitance - and the final results matched up with his predictions. Kind of an OG moment in the emerging field of electrical engineering. And doing it on the floor of the Atlantic ocean, 160 years ago, represents its own achievement. What was learned from all of these became the basis of future engineering projects.
I’ve never seen voltage represented by V. It was always E when I was in school. But how can voltage be present without current? If current is zero then the other side of the equation must also equal zero and therefore voltage cannot exist but is does. And I recently learned that electromotive force is not a force at all and I really don’t understood that. Back in the 80s and 90s, voltage was the force that pushed the electron flow. A lot has changed about the way we think but electricity hasn’t changed. It makes me wonder how much we really understand it.
WOW, it's pretty much all I saw since the 1970's. E was used only occasionally. Of course voltage can be present without current. Your assumption is incorrect. Voltage represents a potential difference between 2 points ... eg either terminal of a battery. Using your reasoning it would mean there is no water in the water tank on the tower. But of course, there is, and it is a potential difference between the top of the tank and ground. Just the same for any battery or pair of wires with a voltage ( potential difference) across them.
oh I agree 100% that voltage can be present without electron flow. A receptacle with nothing plugged into it is a good example. And a battery. But let’s say current is zero. E=IR right? If I=0 then IR=0. If IR=0 then E(or V)=0 also.
Let’s apply that same logic to P which we can both agree that if there is no current, there is no power. P=IE. If I=0 then IE=0. If IE=0 then P must = 0 as well and we would probably agree that it does.
So why does the math work in one instance and not the other?
And I remember it as I=E/R and P=IE.
V is pretty much standard nomenclature. V is often used for DC voltages, while v is used for time varying voltages e.g. AC. On the other hand in physics, E is almost exclusively used for the Electric Field strength. Voltage is the integral of the Electric Field over distance between 2 points in space
And the foundation for the network you are watching this on!
Subbed.
Anyone watching this would appreciate reading "the world is one" , a non fiction book by Arthur C Clarke about the history of the transatlantic cable.
who's got the skinny on the western route across the Bering Strait during Field's Atlantic attempts?
From an 85 year old electronic technician, WOW!
4:07 : there should not be ' I = ..' in the first eqn. but " dI = ..'
is this a typo? Ri = -dv/dx, should be idR/dx = -dv/dx
cmon everyone knows Lord Kelvin
You can't call Lord Kelvin obscure! Not as long as we meansure in degrees Kelvin and use the first two laws of thermodynamics.
Someday a video on this subject will made that all understand. Otherwise this made for insiders who already know the formulas and what they represent. Unless it is clear, this is as dry a bone in the desert.
We are still with cables
Indeed! We now have optical cables that can carry much more data using much less energy.
But the transmission theory is still very similar to electric cables.
So it shows one line is carried like that
And now we have 'twisted Pair' cables ...
Mejor imposible
@ 0:58 SCHEVENINGEN
Good thing fiber optic cables don't suffer from the same problem...
...oh, right. They do after all, just not to a degree that's measurable over 14,000 miles.
Fine content, but what's with the odd rhythm?
Faraday saw the transportation of energy
I have a system with transmission lines and a sub! 😅
It's not theory it's science.
Being made a knight is not the same as being made a lord. They are distinct honours and he was awarded both (not simultaneously, though).
similar to
different from
Get it?
It's called English.
So they tried to overclock the first trans-Atlantic cable and blew it up....
Is out the electricity
Kelvin was clever but he blew it when he attempted to compute the earth's age with heat flow theory. His answer was 200000 years.
Doesn't electricity travel instantaneously? Why did the messages take long to arrive?
Unfortunately it travels at most the speed of light, and usually slower depending on the surrounding media.
@@VisualElectric_ But still, in the speed of light it could travel trough the atlantic in less than a second. Why did it take so long? I dont comprehend
@@VisualElectric_ Thanks for answering
It takes time to charge up the huge capacitor the cable is through the significant resistance the cable has, so a pulse is smeared and delayed by the resulting RC filter network. If you work the key too fast, the other end will not be able to discern the separate pulses but will see just fluctuations in DC voltage, not unlike a blurred out of focus image of a page of text consisting of unintelligible grayscale blobs.
Also, electromagnetic wave (electricity or light) doesn’t travel instantaneously. It travels at the speed of light in the given media which is below the ultimate limit of speed of light in vacuum. For example, the speed of light in optical fiber is 2/3 the speed of light in vacuum
@@sashimanu Correct but also the inductance which is forgotten (or possibly not known at the time) makes a big influence too. What is said to be resistance is part reactance (induction) and part resistance only. Capacitance shows reactance too. Reactance is worse at higher frequencies and as a square wave that we are trying to transmit transmitting Morse code demands a lot of high frequencies to make it rise fast.
Land lines are affected too but as the capacitance between the wires is much smaller (or wire and ground if single wire is used) then it makes a much smaller influence.
It didn't work. It took 9 hours to transmit a few words.
Any student here ?