Compass for a smith chart
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Importance, but I think the Smith Chart is good for visualising what I don't think the equations deriving the Smith Chart are of any real David Kirkby, Kirkby Microwave Ltd wrote:
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These are all pretty easy to do in python, pretty much impossible with a over aģ) analyzing the cross coupling between two or more antennas and the Is a fairly complex combination of L, R, C, transformers, etc. (represented as a noise voltage and noise current) - the input impedance The input impedance of the preamplifier and its noise properties My latest RF/Antenna challenges have been:ġ) analyzing the variation in received signal power as a function ofĬhanges in the antenna impedance (over frequency) with changes inĭimensions due to manufacturing variations.Ģ) Analyzing received signal power and internal noise as a function of If I want fancierĬalculations (multiport networks) they're available as libraries, andĪll the tools easily produce plots in a variety of forms.
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(i.e.sNp files) and for simple hand calculations, python or matlabĭeal with all the complex numbers just fine. These days, I'd rather get data in a computer readable tabular form (lots of loops and covering the entire chart = hard to match all in a you could look at the input or output impedance of anĪmplifier and get a feel for "is it going to be easy or hard to match" It's a handy tool for hand calculation in certain limitedĪpplications, or for representing impedance data as "printable on paper"įorm, i.e. I've been doing EE, mostly with RF, for over 30 years and I rarely use Graphical hand calculations (for which the Smith chart was designed)Īren't as needed today - in the same way that slide rules aren't needed. I recently heard from an Engineering Professor that (in his university)Smith Charts are not taught any longer. Now I am surprised how many hams (I include myself) who are not sure howto interpret a Smith Chart once you acquire a Nano VNA. I then tried "calibrating" the Nano VNA with the SOL standardsĪt the far end of a 100 ft of coax and learned a lot about how moving theĬalibration plane rotates the Smith Chart values. That was fun for me to try and see with my Nano VNA and VNA Plotting the actual R and X values on my feed line on a Smith Charthowever makes it easy to "see" how far you are from the bull's eye (50 ohm The important point I leanred was that you cannot tell the SWR if youonly know the magnitude of the impedance. I doubt there are many errors in his REFLECTIONS I and II books. Wonder if Walt W2DU (SK) is smiling at that catch. A 50 ohm R and a 50 ohm X yields a Z = 71 ohms.