Impedance matching is one of the perpetual confusions for new electronics students, and for good reason: the idea that increasing the impedance of a circuit can lead to more power transmission is frighteningly unintuitive at first glance. Even once you understand this, designing a circuit with impedance matching is a tricky task, and it’s here that [Ralph Gable]’s introduction to impedance matching is helpful.
The goal of impedance matching is to maximize the amount of power transmitted from a source to a load. In some simple situations, resistance is the only significant component in impedance, and it’s possible to match impedance just by matching resistance. In most situations, though, capacitance and inductance will add a reactive component to the impedance, in which case it becomes necessary to use the complex conjugate for impedance matching.
The video goes over this theory briefly, but it’s real focus is on explaining how to read a Smith chart, an intimidating-looking tool which can be used to calculate impedances. The video covers the basic impedance-only Smith chart, as well as a full-color Smith chart which indicates both impedance and admittance.
This video is the introduction to a planned series on impedance matching, and beyond reading Smith charts, it doesn’t really get into many specifics. However, based on the clear explanations so far, it could be worth waiting for the rest of the series.
If you’re interested in more practical details, we’ve also covered another example before.
I will never feel confident at this, and I seem to have no choice but watch the video. I need some Liquid Courage, first, or something from around the house. I should throw some money at the problem, and get a NanoVNA, and keep messing with it. I could test some copper foil butter files—err distributed elements.
This, and the videos he says will follow, is important RF information that a lot of radio amateurs lack, as shown by comments under other hackaday articles on things like antennas, transmission lines, and matching networks.
…and after reading my comments, too. Oddly, I have a General Licience, and probably will go back for my extra.
The thing to remember is: RF design isn’t black magic–oh no, that’s not quite true:
https://youtu.be/eyA2lWQrxwg?si=Q_wTBtW9Gl4-I1eW&t=1011
Once you have a basic grasp of (antenna) impedance matching, the next topic should be: RF amplifiers.
I have an old Motorola data book on microwave transistors, but a modern video would start with a PDF.
2 metre ham gear can usually get away with lumped elements to match input and output. For 70cm or higher, this leads into stripline / microstrip design, with pcb tracks acting as impedance matching stubs.
That Swiss guy with the funny accent (his description not mine) has a great few videos on this where he compares real vs counterfeit antennas and goes through smith plots and stuff. I believe he uses a tinyVNA to do so but I could be wrong about that.
I still have to revisit this topic from time to time but biggest take away for me is that even a 2-3dB loss is about HALF as much of your power not getting out. Yikes. All the low loss expensive cable means nothing.
I’ve loved Smith charts ever since I was forced to learn how to use them for an electromagnetic compatibility class in EE college. As long as you can understand the math behind it, they’re a very useful tool.
Simsmith is a graphical Smith Chart simulation program that can assist with impedance matching without delving into deep math… You can import your antenna impedance from a simulator like EZNEC and apply matching components. You can also import measurements from your NANOVNA into Simsmith and subtract out the feedline, or experiment with various matching. The new improved Simsmith is called SimNEC…