#276

Building upon the lessons in videos #274 and #275, this video describes how to design a 2-element L-Network to create an impedance match to the desired system impedance using series and shunt (parallel) inductors and capacitors. The design process is described, and then actual matching results are measured using a Smith Chart on a VNA. PDF of the show notes:
www.qsl.net/w2a...
Previous Smith Chart videos:
#274: Basics of Smith Chart - Impedance and Admittance:
• #274: Smith Chart Basi...
#275: VSWR and Transmission Line Effects:
• #275: Smith Chart: Z, ...

[@rodericksibelius8472]

I took a Microwave Electronics Technician Class for 9 months at Microwave Training Institute taught by Alan Scott who owned the school in Mt. View, SILICON Valley, California, way back in 1985, and we had PhD's and practicing employed Electrical engineers as was our INSTRUCTORS from companies in the Silicon Valley designing MICROWAVE microstrip amplifiers and learned the use of the Smith Chart, Vector Network Analyzers, antennas, klystrons, magnetrons, etc... etc.. and many other unique subjects about the history and current state of the art of Microwave Engineering. I am now retired and watching this VIDEO made me have great admiration and RESPECT that this SHORT video less than 12 minutes has given be QUICK REFRESHER COURSE of the the applied knowledge and practical computational skills that can be applied in the REAL WORLD of Design. THANK YOU for a WELL THOUGHT OUT Presentation, SIR!, You deserve a MILLION SUBSCRIBERS FOR THIS! ~ Retired Engineering Technician.

[@davidcohen5938]

There are instructors and there are teachers. You Alan are a gifted teacher, and you make the world a better place. Your ability to convey knowledge and understanding is truly a gift. Please keep it up.

[@hankhamner3671]

Very gifted man !

[@ottoomen5076]

I agree.

[@ashishderhgawen]

I just designed an L match network using a Smith chart. Seeing the impedance move to the center seemed like magic. This is such a powerful tool. Your video is excellent. Can't thank you enough.

[@denelson83]

Ohm my goodness... I think I am starting to understand Smith charts a lot more, giving me a lot more insight when it comes to impedance matching.

[@CuriouslyWatching]

You've rescued my semester with your videos. I am forever grateful to you. Thank you so so much

[@w2aew]

You're welcome! Please share my videos/channel with your classmates and professors. Do you mind telling me what school you're attending?

[@saberx77]

Thank you so much for sharing your knowledge Alan! You are an excellent teacher!

[@sraiken]

Very impressive. I wish I had seen this about 10 years during an antenna design and testing project. I did all you did but much more trial and error. At least I had a VNA and a good supply of passive components. One thing I learned is: RF system design is all about impedance matching!

[@johnthompson5034]

As a Radio Amateur (in more than one sense) this is the first time I've seen such a straightforward and practical explanation of impedance matching using a Smith Chart. No doubt these days there are ways of computing the values of components required but this method is just so satisfying and helps gain an understanding of what is actually involved in the process.

[@TheMorningbirdFoundation]

Thank you for a very clear and concise explanation and example.

[@ws6802]

Alan first of all: best wishes for 2025. A very clear video, thank you. I will first try to work out your explanation on paper myself.Then measure my magloop with a nanoVNA (for a wspr frequency) and use this to create an matching network.

[@southernexposure123]

Thank you. I've been looking for this information for days.

[@johnwest7993]

This is EXACTLY what I wanted to know, and now I know it. And in under 11 minutes. That was wonderfully clear. Thank you.

[@wk2w]

I spent a considerable amount of time poring through Caron's Impedance Matching book, but never quite understood it as well as I did after watching this short video. Seeing the initial problem with a complex load impedance, the calculations, the Smith chart plots, and the immediate results on the VNA made all the difference in the world. There is enough information in these videos to work through any matching problem. This Smith Chart series is invaluable. So glad you were willing to devote time to making the videos. I imagine the prep time to create these was very substantial. Thank you once again, Alan.

[@w2aew]

I"m glad that this series of videos helped to shed some light on the subject for you!

[@George-gz5zm]

Brilliant series on practical applications of the Smith chart. Better than university.

[@prajeeshdev_poonkulanji]

Excellent... he simply does a 'copy paste' to your mind..!

[@PixelSchnitzel]

Thank you a thousand times! The light has clicked on and I finally get it. Now to sit down with my VNA and do some hands-on to really sink the lesson in . . .

[@acestudioscouk-Ace-G0ACE]

Really well and clearly explained. You have a great gift for teaching. Your calm way of talking the student through, works really well for me. Thank-you!

[@boonedockjourneyman7979]

I am amazed. Someone got the whole thing right in less than 20 minutes. Thank you.

[@Luzt.]

Enjoy? Sir, you a rock star! I'm afraid I'll have to watch all you videos ;-). Thank you and good luck.

[@alanwolke6253]

Thank you!

[@maxk4324]

I study mechanical engineering, so you can imagine I am starting from scratch when it comes to RF circuitry. Yours is the first video out of SOOOOOOOOOOOOOOOOOOOOOOO many that I have watched about impedance matching that actually helped me understand the a practical approach to designing matching networks without getting bogged down with a textbook's worth of electrical engineering terms that a mech such as myself has no schooling in. Thank you so much for your hard work, and looking forward to watching more of your stuff :)

[@ernieschatz3783]

This stuff is captivating to me. The graphical representation makes it so much easier to stay 'pointed in the right direction' when you are solving problems related to this.

[@jeffomundson8761]

Thank you for putting this series together! You have clarified working with the smith chart, a subject I never really understood completely. It is really helpful to watch you work through an example. You are an Elmer to many...

[@ruvalcabagonzalezgerardo6316]

De verdad disfruto aprender con tus vídeos Haces que temas aparentemente complicados luzcan tal cual son Muchas gracias y saludos desde México 🇲🇽

[@DavePKW]

I really enjoy this presentation. I come back and watch it ever so often just to refresh. Such an eloquent job. Thank you so much for all the fine work that you do.

[@DarkNemesis25]

incredible video. two things that would be great to elaborate on, you mentioned you CAN do it with two caps or two inductors but you say you dont want to, i dont think you ever mentioned why you wouldn't want to if you could. also, it would be nice to know what specific component and spec for those components would be key to look out for, when searching for inductors i see many notes on the components Q value and q frequency, self resonant frequency and dc resistance, all of which im scratching my head at. incredible video once again helped so much

[@smgvbest]

Wow, that was great. the RF and Smith Charts are new to me and I've had a major problem understanding them. while I won't say things are crystal clear this certainly moved me in that direction. Love your teaching style very much.

[@shidharthoroy4402]

Your videos are great to follow! And the touch you give with the practical approach really helps along the way. Nice!

[@아크3]

I didn't know about L circuit before i watch this video But now, thanks to ur explanation, i understood thanks for helping me :) From south korea

[@apostolosgeorgiadis]

Your capacity in delivering such well-structured and detailed tutorials, covering both the theoretical and experimental aspects is truly amazing. We are really grateful. Would you consider making a video on demonstrating and measuring the characteristic impedance of a transmission line and/or coax cable and its dependence on frequency?

[@idontseeit]

Hey there, I know this is an older video but your teaching methodology is brilliant. Clear, encouraging, patient, deliberate, etc. You ever thought about writing an RF textbook?

[@w2aew]

I've thought about it, and have even been asked about writing several times (RF, basic electronics, etc.), but just don't have the time.

[@JackZimmermann]

I'll probably sound like a parrot, but your videos always keeps me amazed! Deep into RF now, and I'm actually thinking of getting a HAM license thanks to you. I find that I go back to your videos as reference again and again. If you're ever in Sweden, I'll buy you a beer.

[@garethm5kvk802]

I've only just found this channel, Alan, and I'm very glad I did. I was looking for some videos to refresh my 40+ EE education on Smith Charts and came across it. As others have said on here, learning about Smith Charts at university or to pass Ham exams tends to be mainly theoretical, though I did design a couple of fixtures for early ham antennas, but your approach has the benefits of being theoretically sound and very engaging. I will be looking for others and have subscribed.

[@derosram9333]

Wow, as a german electrical engineering student I enjoy your perfect practical-orientated Videos. Would be great to have a Video about RF-Oscillator design, especially good quality VCOs with low harmonics for QRP projects.

[@Nobody-ld7mk]

AEW's video tutorials keep the knot's off your head. This one helps put the L/C icing on the cake. "Crazy Good" Circa 1939" Wow !

[@abrahamkennedy3016]

you are a magician, you are a magician. you saved me in midterm.

[@siamakdadras3825]

Very informative and comprehensive video on impedance matching of a network. Thanks a million!

[@vonzigle]

The best instructional video I’ve seen on the Smith chart-thanks!

[@ThereskaJanee]

Hey, this was SO helpful. So glad I found it! But, quick question, at 6:44, your Zload I think is a little off. It looks like you drew it along -j, not along -.51j. I'm confused, is that on puporse?

[@w2aew]

It was a typo on my handwritten normalized impedance. It should read 0.66 - j1.02. The PDF copy of the notes has this corrected. See page 5 of the PDF: www.qsl.net/w2aew/youtube/Smith_Chart_L-Network.pdf

[@Cptnbond]

Fantastic channel, really enjoy your clear and instructive style of presentations. I do have an electrical engineering exam, but boy I wished my teachers have been as good as you!

[@MichaelLloyd]

Outstanding! I've needed this series for years. Smith Chart sales probably spiked when you released this video :o)

[@soajpg]

you are wonderful man. you found the truth in this world, you helped many people. may you find the truth in the afterworld, thats the least advice/help i can give to you in return...

[@josegermanparra6064]

Thanks again for a brilliant video! Using your video on the RF bridge and this I successfully tune my RandomWire antenna. Thanks!

[@twong689]

The video says a lot about impedance matching. Excellent!

[@Scuba_Bro]

Really great practical explanation of the topic. Wish I had more videos like this when I started grad school. Thanks for sharing the knowledge!

[@CuriousMarc]

Fantastic series of crystal clear Smith chart videos (I’m binge watching). So now all of the power of the transmitter goes into the nicely matched line, but I suppose there is no miracle, it still does not all go to your mismatched load after the L adapter at the end. Is this correct? The extra power not going into the load is then dissipated by the matching network components I suppose? Being returned to ground by the inductor?

[@w2aew]

power can only be dissipated by resistance (line resistance, antenna/structure resistance, resistance in the tuner components, and radiation resistance). Thus, the bulk of it is indeed going to the radiation resistance (thus being radiated).

[@martinusher1]

Outstanding video. All this stuff is very obvious -- once its explained.

[@JimNicholsMotorManiaGarage]

That was awesome! I could never find any information on how to build a matching network. Haha now I know why no one knows... It's math!! This was very informative and really something I've searched for many times. Thank you for the time you put into these videos. I'm a fan and new subscriber! 73, ke0eyh

[@zoolkhan]

greetings from Finland. i am very grateful for your teachings. i am a big fan and i hope you will never stop with your videos. 73 de oh8xat.

[@rlamb51]

Great Smithchart video series. I will invariably play through them often

[@bunman2353]

you are a legend!

[@philipyoung9002]

Beautifully done! Love the presentation with actual hardware being used for me to get a feel of what's going on. Thumbs up, up , up.

[@octavmandru9219]

It is indeed magical how wonderful theory works. Thanks Alan

[@diy-projects]

thank you * 1000. best video out there. this really helps me during my fields and waves class at college

[@gustavomatos7428]

Your videos are a fantastic supplement material for transmission lines courses!

[@danielzdanowicz6899]

Wow! Awesome! I NOW understand Smith Charts a bit better! Thanks.

[@DavidScarecrow]

Great stuff! Gonna look up more of your videos on Smith Charts! Do you have a more in depth Back to Basics video on why impedance matching is so important and the theory behind it? Could not find anything

[@tohopes]

Absolutely great demonstration, Alan.

[@rcberry]

Alan, very nice. I just purchased a NanoVNA. They are only $80.00 at Amazon and look pretty accurate for ham use. Check them out. Every ham can afford a VNA now. Amazing!

[@volkerblock]

"Where were you when I was in school 30 years ago?? Excellent job! Keep the channel going. There is so much cool stuff to learn!!" Ha, 50 years ago and now I understand it. Age 75.

[@alfredocrn]

Awesome videos!!! keep making them. Very clear, concise and to the point!

[@shabeesatsangi]

I wish you were my teacher. i would have been at some good places designing some crazy stuff by now

[@tcarney57]

Thanks, Alan. It's never been clear to me why transformers--in particular, Ruthroff 1:4 transmission-line types--are used in place of simpler L-networks when matching, say, 50 ohm IF amps to each end of a crystal filter. I think I understand why a transmission-line transformer is preferred over a conventional one, but why does one see almost no use of L-networks in that application? For use in an IF chain, impedance matching doesn't need to be broadband, and with an L-network the match can be fine tuned and not a fixed ratio. --Todd K7TFC

[@manishbarnwal9342]

Really helpful videos to understand practical implementation.. Thanks..!!

[@tutortobey2139]

Quick comment, At around the 6:30 mark you have Z_l = 0.66-j0.51 but it should be Z_l ~0.66-1j since 51/50~1. This is also where you put your starting point on the smith chart. Good video though!

[@w2aew]

Thank you - that error was noted a while back, and the downloadable PDF notes have been corrected.

[@supyrow]

Alan you outdid yourself yet again, talk to you soon!

[@stefanosmakris5641]

Thank you for explaining with such clarity !

[@EvgeniX.]

nice and detailed video! wonder what's the cons and pros of LC vs LL in this case?

[@johnwoodcock5090]

Very nice. I prefer clockwise/counter-clockwise for adding reactances.

[@TheRadioShop]

As always Alan very nice presentation. Thanks for doing these tutorials.

[@leonardpeters3266]

Thank you for this. Greatly appreciated.

[@bblod4896]

Great explanation. You should be an instructor. Thanks.

[@trollshavesouls]

Great video! Helped me understand these concepts I’m learning in school! Thanks!

[@dus777]

I just happen to be working on a project in the 20m ham band, and the load just happens to look similar. And, now I understand what to do and why.

[@michaellove7912]

your videos are always helpful. thanks a bunch

[@grantfullen9559]

GREAT video. Thanks for taking the time to make and share these videos

[@CH_Pechiar]

Excelente video como siempre! Gracias.

[@Andreasonline3]

you are a bloody legend

[@indigoskywalker]

Excellent video Alan, always wondered what these charts were called and what they represented

[@ericthielking262]

This could be used to help predict settings for a transmatch, if one knows the antenna impeadance.

[@장상현-p8s]

I appreciate your good explanation.

[@battyroy3894]

Only thing I don't get is @ 6:17 Zload/50 is 33 -j51/50 which would be .66-j1.02 no?

[@sabahhadhood603]

Excellent lecture.Thank you so so much.

[@patrickohara9901]

Great job Alan! It would be nice to see how to match over a bandwidth rather than a single frequency.

[@w2aew]

Maybe in future videos. That's one of the downsides of an L-network. The Q of the tuned circuit is pre-determined by the Z0 and load impedance. Other tuned circuit types (PI and T, and others) allow you to adjust for Q (bandwidth) somewhat.

[@PelDaddy]

Great series. Thank you for all your hard work.

[@rekhakunnathu]

Dear Alan, thanku so much for this wonderful demonstration. I am new to RF. I would like to ask you some doubts. You showed impedance matching for a single frequency(single point). How will we do impedance matching for a band of frequencies? Say I want to connect an antenna to a power amplifier board which operates for frequencies from 100 -200 MHz. Output impedance of my board is 50 ohm and I want to design a matching network to connect this amplifier output to an antenna ( impedance is not 50 ohms). What are the parameters that help me choose which configuration should i use? ( single LC section or multiple lc section, Lowpass or band pass). Like in a filter design we specify parameters like passband frequency, stop band frequency, passband stop band attenuation, how much variation we can afford in passband and stop band, with these paramaters we choose filter order and type of filter. Like this, which are the parameters that influence a matching circuit design. Can you suggest me any reference ( article or video)?

[@bloodedge]

Nice, i can finally understand and user Smith Chart. Thanks you.

[@buffplums]

This is fabtantsitic given me the confidence to do some expirembtation

[@PatAutrey]

I understand the schematic diagrams and what they mean and how they work but where I'm confused is to how to apply this theoretical knowledge to an actual antenna system. Do you have any videos or books that you could recommend of how to actually attach a parallel inductor or capacitor to an antenna or it series inductor or resistor to an antenna or combinations thereof would appreciate any recommendations that you have

[@DavidGillooly]

Nice explanation and thanks for the mnemonics!

[@CodeJeffo]

@w2aew Alan, I would love if you could make a video about the complex impedance curve. Some practical applications. I believe there should be a way to do something like complex impedance fitting to equivalent circuit. Another topic would be how to do impedance matching to a range of frequencies. I can't find much information about this nor anyone covering this topic. Maybe it's an old art already forgotten. Thank you very much for any hints where one can find more information about this.

[@pratwurschtgulasch6662]

if the impedance is perfectly matched at the frequency of interest, that also implies that the frequency of interest is not being filtered out correct? nobody ever talks about the fact that there are technically an infinite number of matching solutions and depending on which you pick it is going to do some filtering. i know you touched on this subject very briefly, the way i see it is that impedance matching and filtering are basically the same thing and should be thought of as such.

[@ws6802]

Alan at 6:45 in your video you hit the constant resistance circle with the parallel inductor. If that inductor was in series it must hit the constant conductance circle as in your video #278 @3:55. But why is this? And is there a general rule when constant resistance or constant conductance circle should be hit? Many thanks in advance.

[@w2aew]

Multiple circuit configurations will often be able to achieve a match, so you generally pick the one that gives you the most convenient component values.

[@TheGmr140]

Smith charts, I use online calculator or simple equation coded up in excel or matlab. Good to see this using microstrip traces

[@KD0CAC]

Allan , a thought came up while watching , a display on tuner , that would show a Smith Chart with a marker showing where the load / antenna starts , then follows the adjustments of the matcher / tuner . You know how hams like to get tech-y ;)

[@w2aew]

You've seen this video (that almost does that), right? kzbin.info/www/bejne/nGnae2OfpJ5oiKc

[@KD0CAC]

Yes & gave a like back then . I was thinking about a device that could show a Smith Chart , that would not require a full blown VNA , I do have a couple of antenna tuners that do show smith charts , Timewave TZ-900 , MiniVNA Pro & Sark 110 . But maybe something that could be added to a tuner / display . Just a thought - toys for hams to look at with hamming around ;) Thanks again John

[@w2aew]

Interesting idea. I would think that using something like this: rigexpert.com/products/kits-analyzers/aa-30-zero/ from RigExpert could be something that could be incorporated inside a tuner with a display and arduino based controller.

[@californiakayaker]

Very good groundwork theory . I'm trying to tell my friends that the VNA (NanoVNA) will remove a ton of fuzzy logic when trying to match something. The DYNAMIC NATURE of these smith charts when shown on a VNA is the secret sauce. I have a special smith chart labeled "RADIO TRANSMISSION LINE CALCULATOR" with instructions on the back , probably rather old, seems to only have what might be resistance circles. On the left side it is labeled on the top Positive reactance component , on left on bottom below resistance line it says negative reactance component. Around the outside of the primary circle it says Angle of Reflective Coefficient in Degrees. But, the unusual thing about my plastic smith chart is what I'm ceiling the primary chart is "mounted" on top of another plastic piece, and it has labeled numbers (ON THE OUTSIDE) , and near ZERO it says with arrows pointing to left "wavelengths toward load" and on the right of Zero it says "Wavelengths toward Generator". The two pieces of plastic can be rotated. It has a piece on top of everything , a straight plastic piece, which is labled on the outside on left "voltage or current" and on right "attenuation /dissipation reflection" and is pinned on the center of the entire chart. I've heard it called a Transmission Line Slide Rule. If I knew how to use it I would make a video, but at this time I'm studying from a beginners level. I think the theory was produced by Bell Telephone Laboratories. Manufactured by The Emeloid Company in N.J.

[@jonboro2000]

Can you do a video explaining conjugate matching? I haven't seen a good one on youtube explaining why, when, how. Just "this is the math of conjugate matching."

[@eugene7922]

Hello Alan, This is a great tutorial, with a unique approach I have not seen before, thank you for sharing! According to "RF Microelectronics" book, by Behzad Razavi, shunt element facing ZL can only be chosen when Zin < ZL. In the case of the chose example in this tutorial, RL(33 Ohm) < Rin(50 Ohm), which according to Razavi, should follow shunt at the input and series at the load. Please, comment on the above and how do you explain your reasoning. Regards, Eugene

[@w2aew]

Razavi's statement is correct, but is not the only way to go. The Ying-Yang diagrams give a more complete picture of which networks can be used. Often times there are two or three different options you can choose.

[@NeedleBender785]

Does the Smith Chart have anything in common with a Nyquist plot? I sort of understand the basics of a nyquist plot but only use a bode plot in practical applications.

[@user-su5sq5ib3i]

A big thumbs up as usual Allan, do you have any tutorials on how to figure out the operating range of an unknown toroid with tests and some math?

[@w2aew]

Not yet...

[@wlk1757]

Really good explanation, thanks Alan