"Cecil Moore" wrote in message
...

The Smith Chart is relatively easy to learn in steps. First step
is to learn how to normalize impedances and plot them on the
Smith Chart. The 1.0 in the center of the chart is the normalized
Z0 of the feedline.
--
73, Cecil http://www.qsl.net/w5dxp

The mention of the Smith Chart and slide rules in the same breath brings back a
lot of memories. They put meat and potatoes on the table for me and my family
for many years. I was fortunate to be in the right place at the right time at
the beginning of space exploration, during which time I had the rare priviledge
of developing antenna systems for several different spacecraft while working at
the antenna lab of the RCA Laboratories, and at RCA's Space Center, the RCA
Astro-Electronic Division until I retired in 1980.

The most challenging assignment was developing the antennas that flew on the
World's first weather satellite, TIROS 1, and several of its successors. The
challenge involved developing a transmitting antenna array that would radiate
right-hand circular polarization from two transmitters and left hand circular
from two other transmitters. The four VHF transmitters operated simultaneously
on four separate frequencies in two non-harmonically related bands.

The real challenge was in developing a matching circuit to couple the four
transmitters to the single antenna comprised of two crossed dipoles. The circuit
was constructed entirely of printed circuit stripline transmission line.

The reason for telling you this is that all the calculations during the
development of both the radiators and the matching circuit were performed with
only a slide rule and the Smith Chart. There were no calculators or computers
available at that time. Without the Smith Chart the impedance calculations would
have been so tedious that the project would have failed due to the lack of time
to complete them.

My Dad gave me a simple wooden slide rule when I was thirteen and taking
advanced algebra. Then in my senior class, beginning at fifteen, he gave me an
ivory Kueffel and Esser trig rule. While teaching electronic students in the
Navy during WW2, I acquired another K and E rule, this time a log log decitrig.
Then while developing antennas at RCA in the 50s and 60s I acquired another log
log decitrig, this time an aluminum Picket and Eckel. I still have all of these
rules in my 'antique calculator' museum.

My first calculator was an HP-35, which replaced the slide rules--couldn't
believe I was going from three significant figure precision to nine and greater!
I later acquired an HP-45, then a 55, followed by a 34-C, 15-C, and a 42-S. I
still have batteries fully charged in the last four calculators ready for use.
And even though I have several Smith Chart programs, some of which appear in
Chapter 15 of Reflections, I still use the slide-rule version of the Smith Chart
in solving certain impedance matching problems.

That's the story of my love affair with slide rules and the Smith Chart.

Walt, W2DU

PS--Chapters 10 and 11 in Reflections present a primer in learning how to
understand and use the Smith Chart.