-z ZLZL ZcZc z = 0

-z ZLZL ZcZc z = 0 -z ZLZL ZcZc z = 0 -z ZLZL ZcZc z = 0 Eureka! Use a stub, somewhere. How long should it be?

An article appeared in the January, 1939 issue of Electronics that changed forever the way radio engineers think about transmission lines. Phil Smith [ ] devised an extraordinarily clever circular chart that revealed graphically the complex impedance anywhere along a line. No math and minimum fuss. There's a marvelous symmetry in it's design - everything fits together neatly. So ingenious was his invention that it has been the standard of the industry - for over sixty years.

-z ZLZL ZcZc z = 0

-z ZLZL ZcZc z = 0

-z ZLZL ZcZc z = 0

-z ZLZL ZcZc z = 0

-z ZLZL ZcZc z = 0

-z ZLZL ZcZc z = 0

a x b y r Equation of circle (x - a) 2 + (y - b) 2 = r 2

clf; clear; plot([-1 1], [0 0], ’y’) axis equal axis off hold on

for r = [ ] rr = 1 / (r + 1); cr = 1 - rr; tr = 2 * pi * (0 :.01: 1); plot(cr + rr * cos (tr), rr * sin (tr), ‘y’); end

for x = [ ] rx = 1 / x; cx = rx; tx = 2 * pi * (0 :.01: 1); plot(1 - rx * sin (tx), cx - rx * cos (tx), ‘y’); plot(1 - rx * sin (tx),- cx + rx * cos (tx), ‘y’); end

for x = [ ] rx = 1 / x; cx = rx; tx = 2 * atan(x) * (0 :.01: 1); plot(1 - rx * sin (tx), cx - rx * cos (tx), ‘y’); plot(1 - rx * sin (tx),- cx + rx * cos (tx), ‘y’); end

To load To generator

22

1 0

y = 0 z = 0

Z c = 50  Z in = ? 

z = j1 z = 0

Z c = 50  Z in = ? 

0.434 Z c = 100  Z in = ?

z L = j1.8 z = j1.2

0.434 Z c = 100  Z in = ?

That Mr. Smith sure was smart.