#143
ฝัง
- เผยแพร่เมื่อ 23 พ.ย. 2024
- An introduction to why and when terminations are needed for transmission lines in both high speed digital applications and RF applications. 50 ohm termination examples are given, but the principles apply for other line impedances as well. The basic operating principles of signal propagation down a transmission line and the effects of reflections coming from improperly terminated are covered. Examples for digital-like signals as well as RF signals are given. A description and examples of what is meant by Standing Waves is also given. As a bonus, the properties of quarter wavelength transmission lines in RF applications is also presented. Notes from the video can be found here:
www.qsl.net/w/w...
I'd been looking for a tutorial that I could recommend to audio engineers who need to understand word clock distribution but don't want to be buried in math. This is it! Your explanations and demonstrations are simply superb!
Using that transparent sheet to explain superposition of traveling waves to produce standing waves is GENIUS.
You sir never cease to amaze with your ability to explain things lucidly.
Absolutely!! That transparent reflection was indeed sheer genius!!
I think that video is a 100 years of RF experience packed into 19.14 minutes.
I was underestimated how deep you going with transmission termination from the title of this video, this is a great video!!
Alan's ability to explain phenomenon is unequaled. I learned so much that I have been hazy about for years. Thanks, Alan.
No words can describe the high educational content of this video, even for experienced RF engineers!!!! So good to visualize the effects of the transmission line (and not imagining the equations)
Late to the game here - building a homebrew CPU - old man hobby - and was looking for some insight into transmission line theory - thank you so very much for this. Full of beer right now, I'm looking forward to watching again tomorrow and fully appreciating it.
now THIS is why I had to plug in those little shiny terminators when I helped to build a coaxial ethernet network back in school. now, 25 years later, I finally learned it.
I've been had a ham radio license for 43 years and until I watched this video transmission lines were a 'bit of magic' to me. Brilliant explanation and superb practical demonstrations. I'm going to try some experiments with my new understanding......Thank you!
I like how this principle applies to all kinds of waves, be it acoustic, mechanical, light or whatever wave you can imagine.
Oui, meme pour supprimer un bruit parasite dans un conduit de fumée. Avec un tube raccordé avec un T et un bouchon reglable.
Now why didn't my instructor in EE 101 lab make us perform this experiment. This is the best description of standing waves I have ever seen!
Really helpful to see what is happening with the explanation! Thanks
Software/electrical engineer here. When I'm trying to brush up on a topic and stumble on your videos, I always take time to watch. You have a real knack for explaining things in simple terms. Thanks for sharing the knowledge!
I'm glad you're enjoying my videos and find them useful.
This has confused me for years, After watching this video it all makes perfect sense.
Matt Heilman Studying for my HAM Test on May 17th. Every word he said made sense. In fact, I just read about "standing waves" in the HAM study material. I went back and watched all his HAM related stuff.
Nice visualization of standing waves! Great video all around!
omg applied science!!
The reflection in the piece of plastic is absolutely brilliant. I'm busy watching all your videos, incredible wealth of knowledge.
Best scope-based explanation and demonstration of standing waves since the term was defined. +100 points. Another 100 points for the demonstration of how reflection creates constructive and destructive interference with that piece of glass. Clever!
I am of the opinion that the world is a better place with you on it.
+RenanzinhoSP Thank you!
Agreed. We need more w2aew's running around.
RSP I agree! :-)
Totally agree with you. Best explanation among I've ever learned in universities for over 10 years
Of course!
For over 20 years, I got away with RF builds without fully understanding transmission lines. With this single video, only now, was I able to completely wrap my brain around the concept. Thumbs up!
Excellent tutorial. It is interesting to apply the L/C digital waveform distortion demonstration as applied to say Cat-6e cable and then think of exceeded radius bends and improperly terminated cable. Makes one realize the forward error correction in IP communication is actually saving the very data you are trying to get. All I.T. professionals should be required to learn these transmission line properties as fundimentals at the physical layer of IP.
Great video. Terminators are also needed to terminate signal leakage and ingress points. Open connections and impairments in the line allow for the line to act like an antenna itself. This unbalances the actual antenna that is hooked up. A simple terminator tricks the system into thinking equipment is hooked up by means of a resistor inside the terminator.
By FAR the clearest explanation I've seen about line termination, wave reflection, standing waves, etc.
Your videos are all outstanding.
Thanks for sharing your knowledge!
watching this video again after seeing it a year ago and it never ceases to amaze me how well you explain complicated topics. I greatly appreciate your efforts in making these great quality videos and sharing them with everyone! Thank you and please know a lot of people have benefited from your knowledge and teaching abilities!
Fantastic demonstration. Explanation with that reflective plastic was just wow.
Thank you Alan for this informative video lesson. I've been a General Class ham for nearly 38 years and worked in the commercial antenna industry for decades and I've never had these principles explained so well. It gives the viewer a deep understanding of things that are hard to visualize. 73, Tony WB9UZY
Spring 2021 THANK YOU! You just explained the hows and whys of the first 3 weeks of my EMAG class! Now all the math makes sense!
You are a premium resource for electronics on par with the best . I have seen this a few times for both electronic review and non electronic purposes .ty
Great video. This helped me troubleshoot a problem. I recently purchased an HP 3589A off ebay. I bought it to learn more about network analysis. I watched your video on dBm, bBu, etc., but my results were way off. I was afraid the analyzer was out of calibration, but when I ran the test from this video, I noticed my terminator had no effect. I measured the terminator and found it open. Replacing it, I was able to observe the results you show in this video, and found my 3589A measures correctly with the proper termination. I also learned that buying cheap terminators off Amazon.com is a mistake. Thanks for the good work.
You Sir, deserve at least a cookie, one of the most beneficial 20 minutes I have seen regarding this topic. May your transmission lines be free of null points, unless self-induced for various reasons.
If I could, I'd give you not one, but one million likes for every single video that you've made.
Excellent video and the best explanations on SWR graphically...
Wow! Finally someone that can teach! God bless you!
Super.
I always assumed that it was good to have a large impedance load. (Much larger than output impedance going in.) So as not to drag the input down.
Things change at high frequencies. A wire is not always a wire.
Ac is a bit more complicated that dc. For sure.
Great video. Nicely explained.
Wow what a great series! Many moons ago a job I had taught me the ins and out of RF signal tuning in a lab environment. I was fortunate enough to learn the whole process. Of course these were mechanical rigs we were tuning but same idea. Kudos for you for taking the time.!
Enjoyed IMMENSELY. Answered a number of questions I had. Many ah-ha light bulb moments... TEACHING: The most honorable, invaluable professions next to a ER doctor saving my life 😉 Thanks so much 👍😁
Excellent as allways. The old teaching; fitting impedans to impedans from end to end or output to input.
I’m very lucky to come across your channel at early stage of my career....thanks for the videos
I can't stop watching your vidoes. So good that I can learn something even when I'm familiar with it.
What a beautiful explanation! How many of us have been told that 'energy is reflected' but have never understood *how* it's reflected? What causes the electrons to travel back to the source? I've searched but have never seen an explanation--until now... Now I understand!! Excellent presentation!!
Love this video, i am a curious hvac technician and i am sure nothing is useless in knowing in how the things work.
When you have a no wanted noise in a boiler exhaust pipe, you make a T with an adjustable cap to change the lengh of the pipe without issue. And adjust the lengh at the frequency you want short circuit.
I am very bad in english, learning since 35 years 😭😭😭
Very usefull, I have not studied this field well in my tech life and I learn every day, thanks
Much better explanation than my professor gave us for a lab we did a few weeks ago! By explaining the application of this technique it becomes crystal clear. Thank you!
First time I ever heard a rational explanation for the impedance of a cable. Delta V over Delta I as the signal moves down the wire. Heard that and all-of-a-sudden everything clicked. Don't get me wrong. I've known about and accepted the concept of cable impedance for years and understood the model inductance and capacitance per unit length of cable. I could run the numbers and knew to match impedance of the cable to the source impedance and load impedance. But never before really "got" at a visceral level what the impedance of a cable was until I heard you say what you did at the 3:00 mark.
Very happy to hear that I helped you get that "ah-hah" moment!
More like an epiphany. I still haven't mastered Maxwell's Equations. But baby steps. Baby Steps.
If I may have one more question: You must have lived through at least two generations of RF connectors. Have you done (or considered doing) a video contrasting modern RF connectors to their 40s, 60s, 80s counterparts? I see some oddball stuff come up for sale on eBay every now and then, equipped with connectors that seem so primitive (one was threadless, with four petals that would mate in an androgynous sense with an identical connector). I imagine improvements were necessary as RF carrier frequencies have skyrocketed. But there must have been some logical progression for these new connectors to have found acceptance as standards when (I strongly suspect) certain companies (say HP or GenRad) probably promoted their own designs in the 80s/90s that (maybe) didn't become accepted. Point is that I'm guessing you know all about connectors. Is this a fair topic to request?
@@TheCondoInRedondo Ha - books could probably be written... The 4-petal connector you see on eBay is often called a GR connector, after General Radio. It is more accurately called the type 874 connector. It is hermaphroditic as you've noticed, and works up to about 4.5 to 5GHz. Performance degrades as they wear, or if they are repeatedly mating "sloppily" and the pedals/leaves get bent. Frequency range, size and durability considerations are generally the driving factors for new and different coaxial connector designs. The most common these days are BNC (generally rated to 4GHz, but precision types can go >8GHz), N-type and the SMA variants (3.5mm, 2.92mm). MMCX and and GPO are popular due to their tiny size, and find themselves in small RF devices (GPS, cell phones, etc.). A real good reference can be found here: www.microwaves101.com/encyclopedias/microwave-coaxial-connectors
My hero.
WOW, thank you for sharing your wealth of knowledge with us again, but more over your ability to transfer this wealth is amazing. Thank you.
Nice one. A much better explanation than any of my tutors ever gave who solely relied on the mathematical explanation.
Best explanation ever. Where were you when I needed you 30 years ago?
Hmmm - 30 years ago... ....I was working, learning a lot of this stuff in the "school of hard knocks".
I don't know if you teach for a living but you're quite skilled at it (i would say gifted but that doesn't pay proper respect to the level of effort you put into it). I've been tinkering with amateur radio for a while now and I know for a fact that i have learned and relearned what impedance matching is and how it can affect signals...but until now I've never really had more than a tenuous grasp of the concept.
Somehow just watching you walk through the propagation on paper in the first couple of minutes is what really did it for me (impedance matched lesson i suppose, lol). Seeing it all play out so clearly on the scope is such a modern luxury and just drove the point home that mind-boggling speeds and inconceivably short timescales don't somehow give you license to ignore the details...they still matter greatly.
I guess all this is just a verbose thank you, but i didn't want to cut any of it out. :)
Thanks!
Thanks! Great explanation and demonstration. My first transmitter (a little FM bug circuit) transmitted well at 89mhz.....and 92.....and 94.....and 105.... Now I get it! Thanks.
I am studying for my ticket, and now I know about why SWR works in coax transmission lines.
Thanks, Alan!.
This has to be one of the most valuable videos I have ever watched. Fantastic job!
Amazing teaching skills. I loved the explanation with the "sheet of plastic". Very visual. Thanks a lot for your time and efforts in making this video.
I Appreciate your efforts put into making this video
It is wonderful explanation ,
You used a simple transparent plastic to explain standing wave that’s a nice technique
thanks
Great to actually see what standing waves actually look like on an actual wire!
Great tutorial.
Best presentation of this topic I've seen. Awesome, thanks.
Your vids are just stellar, clearly presented, well thought-out, without tons of editing ”chops”. Thank you for what you do.
Very good explanation, I finally understood what needs to be perfect matches between the transmitter antenna, and what should be Balun end of the transmission line! Thanks
Very interesting and very understandable for everyone! Electronic education should become mandatory to show these videos.
I will treasure this channel. Absolute love.
My favorite channel w2aew. Thank you very much for wonderfull videos/lectures.
Appreciate the demonstration that the signal at the midpoint of the line goes to near zero as the length of that line equals is equal to 1/4 wavelength but the length of the cable can be determined at any frequency by looking at the delay between the signal onset at the midpoint compared to the end of the line. So, eg, at 6:19 since channel 1 is delayed by 8.4 ns compared channel 2, the length of the line (in meters) is then 300*0.0084*0.66 = 1.66 meters (in this formula when the speed of light is expressed in mega meters/sec the time delay is expressed in microseconds). Also I generally don't need an oscilloscope to help me find the length of a coax that I'm holding in my hand but rather this technique is more useful by turning it around and determining the velocity factor given the time delay ie,
velocity factor = length (meters)/(300*delay (microsec)).
Another great lesson! You never cease to amaze and inform me.
Thx
Another excellent explanation of a difficult to grasp subject. Alan's
my go-to guru.
Thank you so much for your videos! Seeing a visual representation really makes things much easier to understand.
Im going to tech college in the fall so all of these lessons are awsome! Thank you
Just a Great explanation of transmission termination and a little brain exercise regarding RF 🙂 I will watch this video once again for sure. By the way, love the scope 👌I hope I will run across one like that on the second hand market. The B version even better. They hold the price though. .. I see a lot on e-bay but in US. Shipping to Europe too costly...
This was very enlightening. Thank you for your thorough explanations. You're always constructive, not destructive. :D (had to say it)
This is GOLD.
wow again you are so great and accurate. I have termination resistors on can bus lines and i never knew why but now i do for sure. you are amazing with all you details. i really liked the math that proves the distance of your tapping point. i am such a rookie that this is mind blwing stuff right now. you have this stuff down to a science.
Nice video. I like the way shown the concept of standing wave created with the reflection of a plastic. Also the TDR is useful.
A very interesting and down-to-earth explanation Allan. I found it very useful. Thank you
thanks one of the best explainations i have seen
Wow. Ask you you shall recieve. I requested a video on this subject last week and we all got a very clear, understandable and well demonstrated summation. Thanks Alan
Transmission lines are so fundamental.
It should be more emphasized in school the way you've done it here
To all hams out there, what would you have given to have "standing waves" explained this way the first time you asked?? I was a kid and was told "loss", which left a lot of questions unanswered. Another awesome video from Alan. 73.
In total agreement with you. This man has teaching skills and the knowledge to back up.
This is the best explanation I've ever seen.
it was an annoying question asking to myself since years , now i have the answers thanks to you
Excellent explanation, now I finally understand how this all works.
One of the best videos on TH-cam
Brilliant. Extremely clear and coherent explanation. Thank you again Alan for a fantastic video!!
That was the best explanation for termination and reflection I have ever seen.
You rock ..!!
Thanks for the video Alan, takes me back to using SWR meters back in the CB days.
Really aswome explanation... thank u very much dude. Make more videos for these termination. ..I didn't understand in college but now it was clear...
A fountain of well presented knowledge, first class as always.
Excellent video and best explanation I have ever seen
Very good and visual explanation. I love watching your unique videos.
Very good video. Describes the behavior very well. Thank you.
Sir, this is the best explanation I saw in my life ;)
Your videos are pure gold. Thank you very much!
Wow. Best video ever. This is how to teach properly
you are amazing really
you are the best teacher in all youtube
long healthy life for you
thanks
Great video!!! Thanks for making this!! I'm a digital guy and these videos are really helpful!!
Well done and well explained. You obviously spent considerable time planning this one.
11:40 Appreciable Demonstration
Very clear and interesting video. Really well done, congratulations!
Thanks Alan for a great explanation! Michael VE3TKI
wow, one of the best videos seen on youtube! thank you for the good videos!!!
Can't thank you enough for all of your videos. Great information, thoroughly explained.
Really enjoyed it and understood so much more from your teaching, thank you.
Thanks Alan AGAIN! Perfectly well explained in simple terms, perfect! Keep them coming and thanks again!
This video is truely amazing !!! HUGE THANKS ! Moreover, at the end of this video I thought it would be cool to visualize the standing wave by gliding a probe on an open cable and.. Quickly found out the #208 vid where you exactly do that ! I couldn't have dreamed better to study my TL course which was really confusing. And you made it cristal clear in 19min... Really awesome. I'm subscribing right now :D