r/amateurradio • u/stoichiophile • 1d ago
General What does "impedance matching" actually look like? (electricity waves)
https://www.youtube.com/watch?v=RkAF3X6cJa411
u/erlendse 1d ago
Check this: https://www.youtube.com/watch?v=DovunOxlY1k
AT&T Archives: Similiarities of Wave Behavior (Bonus Edition)
Probably the single video you need to check out to get an idea about how it all behaves!
It does cover what you ask, nice and visual.
No math in the video as far as I recall.
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u/stoichiophile 1d ago
This is fantastic. It has that old school, straight to the point using elegant hardware to convey concepts. Thanks!
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u/flannobrien1900 1d ago
When this makes sense, then take a look at the various videos on youtube showing that magnetism is an illusion, it's actually electric force but viewed from two different frames of reference in special relativity. Indeed, I believe that's how Einstein came up with special relativity because whilst electric charge has monopoles (positive charge without negative and negative charge without positive) there is no magnetic equivalent, you can't have a North pole without also having a South. Makes transmission lines look simple.
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u/stoichiophile 1d ago
Oh yeah. I did a deep dive into magnetism about fifteen years ago. It's relatively straightforward if a bit mysterious on the surface. Take some properties, do the equations and you get useful results. But once you start peeling back the layers it gets hella weird haha.
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u/oh5nxo KP30 1d ago
Alpha-Phoenix is great. Working thru problems enthusiastically, damned any production values, often without prior knowledge. Or maybe he just plays it like he skipped Physics at school :)
Some other similar youtubers are too slick or just jaded (if it's the right term).
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u/Professional_Wing381 1d ago edited 1d ago
Conductor has physical and electrical length.
Maximum power transfer occurs when impedance is matched between each side of the transfer.
You can prove maximum power transfer occurs this way.
Trying to create pictures in your mind of what things look like besides math is pointless because at the deepest level the stuff is literally made of math.
Example maybe in your mind inductor and capacitor make wire longer or shorter but is that what's happening not really...
Maybe the wave hits a boundary and if it hits out of phase then some of it bounces back and power is lost. If there is no boundary (matched impedance) then that can't happen.
Maybe it's not even a wave inside the conductor, my point.
Most people will hit this exact problem of 'what does it look like? are there little billiard balls flying around? is the universe made of some kind of stuff I can't see? How many dimensions are there?!'
Some will dedicate their life to the question and what they found out is it looks like math which you can use to build stuff.
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u/stoichiophile 1d ago
Trying to create pictures in your mind of what things look like besides math is pointless because at the deepest level the stuff is literally made of math.
Maybe for some, not for me. Seeing the physical manifestation of these phenomena truly helps clarify the concept in my mind.
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u/Miss_Page_Turner Extra 1d ago
When it comes down to understanding what are actually rather complex issues (RF traveling in a cable, balun and antenna) we can learn what's going on by observing and visualizing what the electrons are doing. I think if a student's introduction to electricity starts with structure of the atom, the electron and its field, and how the movement of electrons is electricity, everything they learn from then on will be easier, because that's what electricity is.
You know what helped me? Pipe organs and flutes. Like a wire, a tube has a resonant frequency. Waves of air pressure act very much the same way a wave of electrons moves in a wire. Impedances in the pipe, for example, caused by what holes in a flute are covered or open, change the resonant frequency. It helped me visualize what Alpha-Phoenix shows in the video.
Thanks for this video! excellent stuff.
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u/stoichiophile 1d ago
Oh dang I hadn't even thought how this would apply to wind instruments!!! That's incredible. The video that /u/erlendse shared touches on how these concepts map across physical media and I had kind of registered it with things like loudspeaker horns...but not instruments.
That's cool, thank you!
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u/Miss_Page_Turner Extra 1d ago
Yes, when designing subwoofers, they will often speak of 'impedance matching' the driver cone, the cabinet volume, the shape and length of the port or horn - Just like SWR in radio, mismatched impedances cause standing waves in the system, and less energy is sent into the listening space. :o)
Physics is fun!
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u/Professional_Wing381 1d ago
If it motivates and makes you curious then it has a purpose for sure.
For what it actually looks like though, experimenters found out it looks like maths.
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u/stoichiophile 1d ago
I agree broadly. If you put that same signal through a simulator you would get an incredibly similar and much more fine-grained result at arbitrary timescales and resolutions because, as you point out, it all looks just like the math.
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u/Professional_Wing381 1d ago
There are fun ones.
Antenna is person cracking a whip which can be heard around the world.
Whksshh.
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u/Dry_Statistician_688 22h ago
Impedance is frequency dependent. Unless you have a perfect resistive load at the other end, you need a network analyzer.
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u/Chickentempting 17h ago
In the video the guy builds a space-time transmission line analyzer. Although not very practical to carry around SOTA sites, I think it helps understand at least the two non resistive frequency independent loads. I may have to watch it again.
On the other hand, there is no such thing as perfectly resistive characteristic impedance so I guess we do need a network analyser anyways.
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u/stoichiophile 1d ago
I linked this one because it directly addresses impedance matching, but if you have time I'd suggest watching this one first:
https://www.youtube.com/watch?v=2AXv49dDQJw
He builds an apparatus where he can take scope measurements from various points along a long wire. The visualizations he makes from it are incredible.
(He also being /u/Alpha-Phoenix/)
Incredible visualizations that would have helped me immensely when first trying to understand impedance and impedance matching.
(Tons of cool videos on both channels:
https://www.youtube.com/@AlphaPhoenixChannel
https://www.youtube.com/@AlphaPhoenix2 )