#208: Visualizing RF Standing Waves on Transmission Lines

This video illustrates how RF (radio frequency) standing waves are created in transmission lines - through the addition of the forward (transmitted) wave and the reflected wave that results from improperly terminating the line or matching the load or antenna to the transmission line impedance. I have done several videos that relate to transmission lines, terminations and reflections - all of which tell a piece of the story. This video is another piece, and I hope it helps you to understand how standing waves are formed and what the "look" like. This wikipedia link has some great graphics (shown in my video):
Here's my video on transmission lines and terminations:
Measuring the length and impedance of coax:
How a directional coupler works:
Measure velocity factor of coax:
RF Detector Probe used in this video:
*Brilliant* mechanical explanation and demonstration of wave propagation and reflections, courtesy of Bell Labs:
...and if you read this far, here's a challenge...
Brownie points to you if you can tell me how I created the "sliding" waveforms and displayed the static standing wave in the first half of the video.

Update: This video got posted on Hackaday!

[softwarephil]

Outstanding demonstration of standing waves!

[AppliedScience]

That is so cool!  I've never seen RF power measured at different positions along a transmission line like that.  I guess it's no surprise that it works, but it's always nice to see theory shown with an oscilloscope probe and a steady hand.

[Thesignalpath]

Thanks Allen. I remember when we did this experiments when I was an undergrad during one of my courses in the lab, I had a "WOW!" moment which changed my perspective forever. :)

[bryceroberts]

This video is the absolute gold standard for demonstrating standing waves. A wiki page is one thing, but seeing the RF power minima and maxima being measured on an actual transmission line is quite another. Fantastic work W2AEW! 73 de W6PGS.

[MichaelLloyd]

You are very good at explaining somewhat hard to understand "things" in a way that makes them understandable. Thank you.

[ernieschatz]

Your organized thought, visual aids and practical application is spot-on to me. So many You Tubers want to race through a subject without coming up for air. Also, you don't seem to have the tendency of diving down rabbit holes to the point where I feel I've been through a spin cycle! I rarely have to pause your videos either. I revisited this vid because memory is always the first thing to go!

[rameshbabu]

Greetings from India, Alan you are my greatest RF guru

[RocketRoberts]

So great to see someone who knows the material explaining it well!

[Parirash]

Wow, I never thought that I'll ever witness RF Standing wave so practically.

[paulp]

That was a terrific visualisation of an effect I understand, but had never witnessed so clearly. I've watched many of your fabulous videos, Alan, but this one has somehow eluded me. Glad to see it today.
Thank you.

[daic]

Best demonstration of standing waves so far, and a useful function of persistence on a digital scope. Thank you.

[jmartin]

This was fascinating. As a newish ham I never really got SWR until watching this. Thanks!!

[wakzy]

Fantastic presentation. Back in the day, we saw similar demos using "Letcher" wires. Nothing can be more informative than actually seeing the reality of the electric waves in their natural habitat, so to speak. Well done. In all of your videos, you have proven yourself to be a great teacher.

[grantgiesbrecht]

Wow, I've never been able to see the effects of impedance matching as directly as you measured it here. It's very cool that you were able to measure the nodes and antinodes. Time to break out some PCBs and give it a try!

[Avionics]

I dont think any body can explain this any better and any clearer than you have Alain. You've nailed it.

[DonzLockz]

Amazing to actually see it in action! TY

[hineko_]

I'm starting to think that utube is much better form of education than the universities. They never explained it this good at my U. In my case it was like here take this bunch of formulas, plug in numbers, calculate, congrats here's your bachelor's.

[borayurt]

Great video! SWR explained without getting drowned in formulas and theory etc. Loved every moment of it. Thanks!

[MichaelShaw_vkhms]

This an excellent demonstration of VSWR. Thank you!

[RedlabsTV]

Wow, your visualization methods help a lot to understand. Thank you!