AT&T Archives: Similiarities of Wave Behavior (Bonus Edition)
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- čas přidán 19. 05. 2024
- For more from the AT&T Archives, visit techchannel.att.com/archives
On an elementary conceptual level, this film reflects the multifaceted scientific hyperthinking that was typical of a Bell Labs approach. Host Dr. J.N. Shive's presence as a lecturer is excellent - it's understandable by a layperson even when he branches into equations, because he uses copious amounts of real-world examples to bolster the material.
Shive's role at Bell Labs was more than just a great lecturer: he worked on early transistor technology, inventing the phototransistor in 1950, and the machine he uses in the film is his invention, now called the Shive Wave Machine in college classrooms.
Dr. J.N. Shive of Bell Labs demonstrates and discusses the following aspects of wave behavior:
Reflection of waves from free and clamped ends
Superposition
Standing waves and resonance
Energy loss by impedance mismatching
Reduction of energy loss by quarter-wave and tapered-section transformers
Original audience: college students
Produced at Bell Labs
Footage courtesy of AT&T Archives and History Center, Warren, NJ - Věda a technologie
This video acts as an impedance matching network between this topic and my brain. Perfect!
Good one!!!!!
well said... same for mee too☺️
Works better with tapered glasses
I have no clue what you just said.
Gold
This film is a real gem. I'm an engineer (and used to be a professor) and the clarity of explanation in this film is exceptional. It is the best explanation of SWR that I've come across to date. This man would have been a favorite teacher had I had the opportunity to sit under him.
indeed, this was very well done
This dude has a very slightly evident grin that appears when he knows he's explaining something enlightening. You can tell he loves what he's teaching.
Yes! his love of the material is extremely engaging, at least I found it so.
agree- probably was a very nice guy -- it is obvious he loved to teach.
made me smile
You can tell from his expressions that this guy is having a blast talking about this.
Right? Like he knew we'd get it!
I couldnt help but think this the entire video. such a great thing he knows he's been able to do here
I have learned more about waveform in this 30 minute video than 7 years of being an amateur radio operator. Great explanation and video.
What an utterly gifted teacher Dr. Shive was, and what a gift Bell Labs gave us by preserving his work on film.
My dad worked at Bell Lsbs and I had a basement full of test gear and jars of vintage transistors to toy with as a kid, and consequently have always had electronics and radio close to my heart and am still learning the deeper aspects of those subjects.
Bell Labs was an amazing place, there were actually two, one in Murry Hill, NJ, where the transistor was invented, and one in Holmdel, NJ, where my father had worked and did quite a bit of transmission cable work and later fiber work.
There was a white water tower there at the campus in Holmdel with 3 support columns, which oooked suspiciously like an oversized transistor; the joke was someday someone would paint E, B, and C for emitter, base, and collector on the bottom of the tower to properly label the “leads” of the water tower.
That kind of research is where it’s at, we need to get back to that collaborative multidisciplinary approach with a big center and a big budget to push the technology frontiers hard again. For example, the west needs workable fusion power, and the fragmented approach is perhaps costing more in lost time, than it is saving in dollars.
I wish I would have had someone like him when I was studying to get my Amateur Radio license, I might have accidentally learned something instead of just memorizing the correct answer.
As an old-school extra-class amateur radio operator, I recommend this video as an aid to understanding feedline/antenna matching.
Maybe this has been commented earlier in this thread…
About 5:30 into the film, John Shive talks about the termination of an electrical transmission line. At first, I thought John Shive was wrong, since I have truly seen the opposite in our lab. What I have seen on an oscilloscope is a wave that returns “upside down” from a short circuit termination, while an open circuit termination gives a reflected wave with the same phase as the incoming wave.
But John Shive talks about a current while an oscilloscope measures voltage. At an open end, the law of conservation of energy results in the pulse having to return to where it came from (since it has nowhere else to go). Going back, a current would have to pass through an imaginary amperemeter in the opposite direction compared to its original direction, thus giving a current with the opposite sign.
So, John Shive was right about the current. Why doesn’t the voltage change polarity as well? This also has to do with energy. The termination and the ideal wires do not “steal” (convert) or store any energy. Therefore, the sum of energy from the forward and the return wave must be zero, E(forward) + E(return) = 0 and E(forward) = -E(return). The minus-sign comes from the inverted current, therefor the voltage can’t be inverted.
Anyone who agree with me?
I had the same initial thought, about shorts vs opens, but just figured I had misremembered my EM classes, since the professor must be right.
Thank you so much for explaining the mental disconnect. I'll sleep better, now that Dr shive and I agree.
I'm glad I'm not the only one who noticed this. Thought maybe I was missing something.
I have been getting into ham radio over the past three years and this video is one of the most helpful things I've found in my learning journey.
Amazing. So clear and direct. I find the further I go back in history, recorded science lectures seem to just make way more sense than today's classes. I'm not sure why. Maybe they weren't trying to teach so much at once then, and they had a script, so the material was presented in a very logical order, but this is definitely easier to understand for me than a lot of more modern videos that seem to just "wing it".
Agree. These basic videos are explained step-by-step with the goal of understanding.... Today's videos seem to focus on flashy presentations but lack clear instruction...
because nobody teaching those classes knows it from the ground up unless you go to MIT.
A lot of them (military analog computers comes to mind) had a very interesting non academic, non ceremonious yet charmingly vintage in style.
Probably as good as a MOOC :p
I was wondering the same thing. It is more to the point and informative than most videos.
The explanation's rather simple I believe: it's laziness. It takes real effort - persistence, thoroughness, time - to produce instruction of this quality. That's been replaced all too widely by superficiality, glitz and the desire to be considered clever without the requisite work to become clever. What's one of the most common complaints about CZcams tutorials? Too much attention paid to background music. Dr Shive's teaching is devoid of such frills - and brimming with evidence that he really knew what he was talking about and went to considerable lengths to communicate it effectively. The same's true, for example, of w2aew's CZcams videos and content from the Khan Academy. There are no shortcuts to excellence.
This film is precious! The mechanical analogue equivalent is the perfect medium to explain concepts like impedance mismatch and standing waves. It is easy to see the mechanics by which a high SWR can destroy the output stage of a transmitter.
Information is sliding so pleasantly and efficiently into my brain! So much respect for this era of engineering.
look at the smile on his face when he talks through the megaphone.
WHO WOULD DISLIKE THIS!?
7:30 is the visual demonstration of how a standing wave forms that I’ve been wanting for so long
We just don't have awesome professors like this anymore.
I could listen to this guy for hours.
Multiple "aha!" moments, absolutley Priceless!!!!!!
As I get into amateur radio, CZcams brings up these beautiful old educational shorts that demonstrate concepts so succinctly and accessibly. I'm so lucky to live in this age for the accumulation of information that's been possible with the internet.
This is so much more than clear, concise education: It's poetic. Absolutely amazing.
Yes! It's truly a thing of beauty like a priceless piece of art.
A picture is worth a thousand words, it is said. This demo of SWR is worth a million. I am an amateur radio operator, and thought I understood SWR in transmission lines. I certainly understand it a lot better now.
This a great video .Truly a treasure. A slight correction would be that the free end of the mechanical system is analogous to an open circuit in an electrical system. While the restrained end in a mechanical system is analogous to a short circuit in an electrical system.
@John King Thanks for clarifying
This is so much better than any explanation I've encountered in many textbooks.
The reflection formula at 18:15 made my head blow up. I am unable to continue learning wave behavior as my... well..... my head is gone.
This is gold. I am amazed how the concept of impedance can be applied to so many things at once and how waves are all similar in their nature. I went from having no deep understanding of waves to seieng patterns between different physics areas in one video.
I've known about most of these concepts for decades, but now I have a real understanding! This is an amazing film, and Shive is absolutely brilliant in his capacity for imparting knowledge.
Absolutely fantastic description of waves, impedance matching and SWR! As a radio amateur, this explanation is wonderful. Thanks for sharing!
This has to be one of the greatest lectures of any kind that there can be.
This is such a wonderful and very visual explanation of the basics of waves. Thank you for preserving this awsome content and making it accessible!
this video is so addictive, the more you watch, the more you like
This is a great video. Clear and well organized and the physical machine really shows off the concepts easily.
Exceptional tuition and understanding by a most clever man.
Wow-- what a terrific explanation. Every instructor could learn from his relaxed but deliberate pacing-- gives the student a moment to reflect on what he's saying. For anyone wanting to learn more about what an amazing place Bell Labs was, I really enjoyed Jon Gertner's book.
It's a fantastic presentation - very clear, concise and to the point -
Best demonstration of wave behavior that I have seen so far.
Genius is making the complex simple. What an amazing guy. We are very fortunate a small piece of his knowledge was captured on film.
this channel has become one of my favorites on all of CZcams, and why youtube is so amazing. i'm one of those math-challenged liberal arts majors (lol right) but i found the UNIX video *really* cool as a backgrounder on computer science in general as well as UNIX, coding etc etc. this vid is incredibly educational as well. awesome stuff, ATT.
Watching this in 2022 and it's still extremely useful and clear with building an intuition of transmission lines.
One of the best videos /films I have ever seen in my life !
This video is gem. The best explanation of standing waves I've ever seen
I remember teachers like this as a child, pleasant, refined, disciplined, and often very conservative. They did not suffer fools lightly. It is a sad reality that the ability to calculate in mathematical terms is extremely difficult for so many people. The best way to counter this condition is through constant repetition. Practice practice practice from a young age, as soon as possible. The torture of that exercise will pay huge dividends later in school. So many geniuses become lost in this struggle, the old left brain right brain argument. Matching the imaginative dreamy brain with the analytical is another form of impedance resulting in miraculous new innovation. Happens every time.
Repetition may help to memorize but what's generally missing in the first place is meaning. There is a generalized use of mathematics in a meaningless approach. That may be the bigger problem. Meaning may though depend on earlier non symbolic early experiences... Diffcult subject! They are many discussion in this direction in Education in Mathematics but this subject of research is not in an very advanced stage.
Its funny how entitled Incels who think they're better than everyone else spread to every corner of the internet event the education part 🙄 This comment shows a clear lack of understanding how social systems generate behavior.
I don't know what you're talking about, but it has little to do with this video beyond the one minute or so where he's working at the blackboard.
@@Gladiva19
Entitled incel?
This video is one of the best that mankind has to offer.
Amazing Amazing Amazing !!! The examples by Dr. Shive are way better than today's 3D & digital simulations !
Old True school of amazing physics it must be incredible to have such a fantastic teacher at least once a time in life, this can change the mind and the way of thinking physically for ever.
this is a superb demonstration and lecture on the general topic
Very informative and well presented. But I think I noticed something possibly incorrect. At about 5:48, the speaker mentioned that in an electric transmission line, an open end results in a reversed polarity returning wave, and a short circuit end results in a same polarity returning wave. In another CZcams video I viewed, "Tektronix - Transmission Lines", the opposite was demonstrated to be true using an oscilloscope. Which is correct?
You are indeed correct - the short inverts the wave. Would be a neat trick if it was the other way.
This is so amazingly clear and easy to understand!
Wish I had this guy as my teacher! Great video!
thanks a lot for the perfect analogy. For years I was struggling to understand the propagation of highspeed currents in the circuit boards with different loads.
I wish I'd seen this a few times at college! I could have progressed a lot farther a lot quicker in my career with this Gentleman teaching.
Absolute genius. Masterpiece
surfs up Waves awesome dude.
Maximum shear occurs at nodes in structural analysis. FEM today makes this much easier to calculate. Awesome film Thanks.Shalom
At 5:58, there is a mistake on the chalkboard. If the transmission line is shorted, the voltage reflected will be inverted. This is because the current will flow on the minus terminal momentarily during the return propagation time before the output is zero due to short circuit condition. Otherwise, this is a very informative video.
I thought that too. I don't understand how they made this mistake though?
Incredibly good explanation for how SWR works!
A great explanation and a stylish presentation! Really enjoyed this.
Excellent point about studying an area that deals with waves extensively allowing you to understand any other area that where waves are fundamental to the field; absolutely agreed. Particles and waves are what everything eventually comes down to.
Really enjoyed !
Impedance matching looks so simple and effortless...
Thank you for posting this.
Remarkable outstanding presentation! imho Very Thanks and Very Well Done to this exceptional teacher (to his memory of course).
Nice demonstrations of mechanical 1/4 wave and taper matching elements.
Thanks a lot for this amazing video. I love that wave model! Very creative idea.
Really thought provoking. Excellent.
physics always enlightening me.
Simply Brilliant.
This video is a true gem
amazing. great job wherever you are man
I remember seeing this film ... High School electronics class I think. Great subject .... Goo d presentation!
Beautiful handwriting and drawing.
Thank You AT&T Channel
May you rest in peace. I deeply appreciate all the knowldge and the laugh. I needed both.
(May 2023) - This professor is a passionate GENIUS!! Why have I never heard of this teacher/clever demonstrator before?!
Very informative. Thanks for posting this!
Plz add such type of videos on voltage, current etc.
Brings back memories of the Newton's Cradle I had on my dresser as a kid. A visual reference of the physical characteristics of things that occur and can be seen throughout the natural world around us.
I want to build one of these machines. It would be great at parties. BRILLIANT!
BEST VIDEO EVER teaches alot which universities cant teach in 6 months
Excellent demonstration.
Such films are very useful for everyone
Love the use of big fractions fractions at around 18:35. When I was in school, oh so long ago it seemed perfectly intuitive for me to use =>1 fractions.
I was told that this was wrong, somehow -- though my work was accurate, correct, documented, and mostly legible, I tended to skip the needless reduction of fractions at every step that they expected it of me. Conferences were held, admonishment was dolled. I now feel vindicated by this verification that there is no shame in expressing a number as "seven halves," as everything presented in this film is perfectly cromulent and expertly explained.
Thank you.
What did they want you to use, mixed fractions? Mixed fractions are almost never used in math and science because they make arithmetic harder.
@@tarmil Know this is old, but your observation makes sense. We Americans use the imperial system, so ''improper'' fractions have a good deal of practical use to us.
Ditto, Adam Perry...loads of arguments and discussions with mathematics teachers in high school. But the methods taught to me by my engineer father worked best for me! As long as my answers were correct in the end....
Best explanation of swr I've ever seen!
good advice! This is ehat I did as I work on shortwave frequency that I can only mesure with my oscilloscope I decided to experiment also with light and audible frequency as they all behave in the same way but it is easier to understand them when actually we can experience them by hearing or seeing (like sound or visible light) .
I love this. It's so awesome I have no words.
This is great. Thanks for sharing.
Wow, that was the best explanation of resonance and SWR I’ve ever seen or heard. Where’s the subscribe button.......
really great, thanks for sharing
10:51 "impedance" being the ratio of "cause" to "effect" 21:00 It's true, our world is abound with these examples! 26:57 was an insightful remark from Dr. J.N. Shive, "Waves of all types behave alike."
A guitar string has a standing wave ratio of infinity, and gears and levers are impedance transformers promoting the transmission of the energy of motion . Just two of the many things I've learnt in 26 minutes watching this lecture.
Very good demonstration !
Damn, this guy is good. He did this all in one take?!?
What an incredible video!!!!
Best ever seen wave tutoriral
Excellent explanation that gives a lot of insights.
At 05:09, I think that load impedance is not correct: positive reflection happens on open circuit (not short circuit), and negative reflection happens on short circuit (not open circuit).
He should explain it with regards to Voltage (not Current). I.e a short circuits does not allow the voltage to change (fixed side), whereas the open circuit allows the voltage to change (open side).
I noticed that too.
Excellent talk.. Very interesting... Thanks for posting.
Marvelous!
Wow, Thank you, Perfect demonstration ( Beautiful handwriting btw. )
Thank you John N. Shive
Excellent. Hi is so enthusiastic :) That's how knowledge should be shared.
This is awesome
Excellent lecture!
Obrigado! Esse vídeo vale ouro!