I find few hams at Zoom meetings can answer that concept in a sentence or two. Why is 40 + j30 ohms a different impedance from 30 + j40 ohms?Īnd finally, why does changing the LENGTH of the feed line (again, say 50 ohm coax) alter the impedance (at your radio) but does NOT change the SWR (at least not by much). There are zillions of combinations of R,X that (with 50 ohm coax feed line) can have the identical SWR. Why do different values of R and X have the same impedance? That was kind of a piece of magic for me as I thought about this. So on my PPT presentation, I added a few slides about Smith Charts and Antenna Impedance: I've been a licensed ham for over 60 years, but rarely if ever did I have to look at or discuss a Smith Chart of an Antenna.īut having a Nano VNA forced me to relearn about plotting R and X values on a Smith Chart. In my Zoom presentations on the Nano VNA as an antenna analyzer, I often get to the topic of looking at "Antenna Impedance" (Resistance and Reactance plots) on a Smith Chart.
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