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Smith Chart
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19-11-2012, 06:36 PM
If anyone needs a refresher or starting from scratch here is a link to a series of lectures, start at 12B-1.
http://www.youtube.com/playlist?list=PL27FFD0E691A68E11 Lawrence.
19-11-2012, 08:18 PM
C'mon Alan, here is a full size print out...
I did get the basic grasp of the said chart a long time ago, not sure what prompted me to revisit the subject, tried looking on Utube for a descent presentaion and that one was the best of the worst I could find, I am stuggling a bit with it as so far as the charts full applications go. http://www.printfreegraphpaper.com/gp/smith.pdf Lawrence.
19-11-2012, 11:08 PM
Smith charts: that takes me back a fair bit! I can just about remember getting well stuck into those during my last year at college, circa. 1974. Although there have been the odd occasion since then when I have had to use them, I have always felt more re-assured by using the analytical / algebraic method on which those charts are based. But with that method you do need to be proficient in dealing with some advanced trig. functions and complex numbers - those expressions that contain the operator j: I seem to recall that I've been down that path here before . . .
 Al. Al.
20-11-2012, 07:03 AM
Good lectures, but bought back repressed memories of my struggles when first introduced to them 35 years ago... for some reason, they don't seem so bad now...
Having learnt all that stuff, I never did RF professionally so never used Smith Charts after uni, or for that matter, probably 80% of what we studied... Ho, hum...
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ʞɔıu
20-11-2012, 09:11 AM
Thanks for the replies. In respect of transmission line etc: I remember in the 60's when I was an apprentice in the R & TV trade that some of the old time TV Techs. showed me how to make a 1/4 wave stub, these were used to overcome certain reception problems with TV, but I can't remember exactly which, possibly as a notch to tune out adj. channel interference or to overcome down lead matching problems, maybe to notch out TVI breakthrough from local amature radio transmissions, do any Techs. remember this trick?, We definately used them.
Lawrence.
28-04-2013, 04:24 PM
As a newbie here can I recommend an old but powerful little program 'RFsim99'
http://www.sandiego.edu/~ekim/e194rfs01/RFSim99.exe Works with windows 98 to XP (and Wine under Linux). Plots impedance of networks on the Smith charts, calculates matching networks, filters and much more.. For the quarter wave stub see the attachments below. (Ignore the 1Gohm resistor, like most simulators, something must be connected to every node to avoid an error message.) 50cm of coax with a velocity factor of 0.67 (200/300 m/sec) is a quarter wavelength at 100MHz. At this frequency, if one end is open circuit, it will look like a short circuit at the other creating a notch as you remembered. Jim ps This is my first post on the forum so please forgive any problems with the attachments.
29-04-2013, 03:48 PM
The link is dead on my PC.
Lawrence.
29-04-2013, 03:52 PM
Keep on Fiddling!
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