[K3PZN-List] Interview with Philip Smith inventor of the Smith Chart

[James Owen]

I came upon this over the weekend and thought that
some of you might be interested.
73 Jim K4CGY



Interviewee:  
	Philip Smith
Interviewer:  
	Frank Polkinghorn
Date:  
	January 19, 1973

    Copyright Statement

    This manuscript is being made available for
research purposes only. All literary rights in the
manuscript, including the right to publish, are
reserved to the IEEE History Center. No part of the
manuscript may be quoted for publication without the
written permission of the Director of IEEE History
Center.

    Request for permission to quote for publication
should be addressed to the IEEE History Center Oral
History Program, Rutgers - the State University, 39
Union Street, New Brunswick, NJ 08901-8538 USA. It
should include identification of the specific passages
to be quoted, anticipated use of the passages, and
identification of the user.

    It is recommended that this oral history be cited
as follows:

    Philip Smith, Electrical Engineer, an oral history
conducted in 1973 by Frank A. Polkinghorn, IEEE
History Center, Rutgers University, New Brunswick, NJ,
USA.

Polkinghorn: This is an interview with Philip H.
Smith, former member of the technical staff of the
Bell Telephone Laboratories, authority on antenna
design, and originator of the Smith Chart for finding
complex impedance. This interview was made on January
19, 1973, by Frank A. Polkinghorn, assisted by Ralph
Lamar as recorder operator. Phil, I'd like to talk to
you about your background and your career as a radio
engineer. I think you were brought up in Lexington,
Massachusetts? Will you tell us something about your
family and education?

Smith: Yes, I was born and raised in Lexington,
Massachusetts. When I was growing up, my family owned
some twenty acres of farm land surrounding an old
twenty-two room brick-ended farmhouse and barn. The
house, which is now occupied by my sister, Mrs. Oliver
Hooper, was built in 1799 and has been in the Smith
family for six generations. I attended the Lexington
public schools, and in the fifth grade I had the same
teacher that my father had had a generation earlier,
Miss Nellie Wright. My dad worked for twenty years for
the brokerage firm of Paine, Webber and Company in
Boston before he retired to go into the butterfly
jewelry business and later a homemade candy business,
both of which my mother had started to supplement
family income.

In the early 1920s, while in Lexington High School, I
put together an amateur radio station, 1ANB, with many
homemade parts. The prefix W was not used in those
days. During this period I contributed a number of
short articles to the radio section of the Boston
Traveler. Vacuum tubes were very expensive, and the
so-called reflex circuits, in which a single vacuum
tube performed several functions simultaneously, were
of particular interest at the time. Also, Major
Armstrong had just come out with a super-regenerated
receiver. In this he periodically quenched an
oscillating amplifier tube, which gave tremendous
amplification, though difficult to control. I recall
successfully building one of these curiosities and
writing up my achievement in the Boston Traveler. My
interest in radio left no doubt in my mind that I
wanted an electrical engineering career.
Unfortunately, it also detracted from my school
grades, particularly in French and history. So I had
to take an extra year studying those subjects to pass
college entrance examination requirements.

After the equivalent of six years of French, I managed
to pass the three-year intermediate French examination
and an ancient history examination. I entered Tufts
College in 1924 and majored in communications. I
worked as a Model T Ford garage mechanic one summer,
as a draftsman for another summer, and as a radio
technician one summer for the Wireless Specialty
Apparatus Company in Jamaica Plains, Massachusetts. My
job was testing and troubleshooting Radiola receivers
at the end of a long production line. The Radiola was
the Cadillac of radio receivers at that time. They
were in a console with a built-in power supply and
loop antenna. The price tag was about $900. I
graduated from Tufts College--now Tufts University--in
1928 with a degree of B.S. in E.E.

Polkinghorn: So you went to work for Bell Labs after
that?

Smith: Yes. I was first interviewed by a General
Electric Company representative, and I was made an
offer of a job in their radio department in
Schenectady, New York, at $24 a week. Before accepting
this, and upon the advice of my Uncle Edward Dee, who
was then assistant personnel director of the Western
Electric Company, I applied for and was offered a job
at Bell Telephone Laboratories, which I accepted. My
first assignment was to the radio research department
with the Deal Beach Radio Station in Deal, New Jersey.
I started work on August 5, 1928. My salary was $30 a
week. I was told I would receive a raise of $5 per
week in six months if my work was satisfactory. We
worked an eight-hour day, five and a half days a week.
Deal was where the shortwave, transatlantic,
ship-to-shore radio telephone research was being
carried on. I had often listened in on my homemade
receiver in Lexington to the radio telephone
transmissions between Deal and the S.S. America at
sea. Now I was working there. I was fortunate to have
been assigned to work for two famous radio pioneers:
Ernest J. Stillwell and John C. Shalley. Mr. Shalley
had overall supervision of the Deal laboratory; and
Stillwell, as we called him, was the antenna expert.

My first job was constructing and testing, with Art
Cohen, another Bell Labs engineer, one or two years my
senior, a fourteen-meter directional antenna array of
eight vertical dipoles. This antenna was being the
receiving site in the town of Rotten, England, which
we jokingly called the "Rotten receiver." Shortwave
radio was--and still is--vulnerable to magnetic storms
caused by sunspots, and there was some hope that we
could get across the Atlantic on a wavelength of
fourteen meters during intervals when twenty- and
thirty-meter wavelengths were knocked out by these
storms.

Polkinghorn: What were the problems as you saw them at
that time?

Smith: Well, prior to about 1927, telephone calls to
Europe were via long-wave, very-low-frequency radio
transmission, involving extensive and costly plant
equipment which had very limited traffic capability.
The demand for this service was far more than the
system could supply. In 1927 Bell Laboratories had
completed a huge experimental model, over a hundred
feet long, that would improve the VLF transmitter
which was housed in a barn at Whippany, New Jersey.
This was a single sideband transmitter that was
capable of transmitting two telephone channels
simultaneously with inverted speech, and was intended
to supplement the existing long-wave facility at
Houlton, Maine. However, this project was never
completed because at about the same time, the far less
expensive shortwave experimental installations, such
as were being developed at Deal, were meeting with
spectacular success in overseas voice communication.
There were at least three major problems facing the
early shortwave developments: One, a lack of
understanding of the physics of shortwave radio
propagation; two, the need for development of
efficient, high-gain directional antennas; and, three,
the need for development of large high-powered vacuum
tubes. To illustrate the vacuum tube situation, the
final stage of the shortwave transmitter, which I saw
at Deal, initially consisted of a large bag of perhaps
a hundred telephone repeater tubes, which in operation
was a truly wondrous thing to behold. The Deal labs
were actively pursuing work in all three of these
areas. Personally, the work on antenna development
held a particular fascination for me. I was able to
contribute a number of basic inventions, including the
transmission line matching stub and the conductor
diameter ratio for the coaxial line, which is optimum
for power transmission.

Polkinghorn: I suppose that this is when you got
interested in finding complex impedances?

Smith: Yes. From the time I could operate a slide
rule, I've been interested in graphical
representations of mathematical relationships. In 1929
and 1930 I ran into an important need for a short
method for computing input impedances of transmission
lines. The shortwave development at Deal had reached
the point where the Long Lines Department of AT&T had
decided to go ahead with an ambitious project at
Lawrenceville, New Jersey. This involved a mile-long
array of curtain-type antennas supported on twenty-six
steel towers, each 175 feet high, all beamed on
England. And another half-mile-long similar array of
antennas beamed on Argentina, South America. Having
played a part in their design, I was given a major
share of the responsibility for their proper
electrical adjustment. This required countless
measurements of standing waves to obtain the proper
phasing and feed-line impedances. By taking advantage
of the repetitive nature of the impedance variation
along a transmission line and its relation to the
standing-wave amplitude ratio and wave position, I
devised a rectangular impedance chart in which
standing-wave ratios were represented by circles. In
January 1939 I had an article published in Electronics
Magazine on a general-purpose circular slide rule with
an impedance chart. Since then many articles by other
authors have appeared in the literature dealing with
specific uses.

Polkinghorn: I believe you wrote a book on the chart
and how to use it.

Smith: Yes. I tried to write down the complete story
of the development and uses of the so-called Smith
Chart. This chart displays the behavior of all types
of transmission lines and waveguides; consequently, it
has found universal appeal. My book, published in1969,
is entitled Electronic Applications of the Smith Chart
in Waveguide, Circuit and Component Analysis.

Polkinghorn: Well, you finally left the Deal
laboratory, didn't you?

Smith: Yes. In 1935 I left Deal on a six-month
leave-of-absence, but I never returned. Bell Labs had
decided not to go ahead with the long-wave
transatlantic radio project called T-A-R, or "tar,"
and had established a laboratory for AM broadcast
development under Bob Poole in the barn at Whippany,
New Jersey. AM broadcasting was at the beginning of a
period of renaissance due to the FCC's decision to
permit power increases up to 50,000 watts of radiated
power, provided it could be proven that this would not
result in daytime interference with other AM broadcast
stations. The key to obtaining FCC approval was the
multi-tower directional antenna which could control
radiated power levels in chosen directions. Since
increased power meant increased advertising revenue
for the station, the Western Electric Company was
flooded with requests for consultant services and new
equipment. My new job involved both. I was kept busy
for about three years calculating antenna array
patterns, designing antenna branching and phasing
circuits, and then getting involved with a mechanical
design of a complete new line of Western Electric AM
broadcast equipment. I subsequently served in the
field engineering department of the laboratories under
Stu Price, one of the charter members of the IRE,
during which time I consulted on broadcast antenna
installation problems and tuned and adjusted about
twenty directional antenna installations throughout
the eastern part of the country.

Polkinghorn: But then the war came along.

Smith: Yes. For some two years prior to U.S.
involvement, the Signal Corps had started to work on a
new secret weapon called radar, an acronym for Radio
Detecting and Ranging. Radar, as we all know, proved
to be one of the most important electrical
developments of World War II. This first radar was
known as the SCR-268, and operated on a frequency of
about 215 MHz. In 1939 the Western Electric Company
was asked to prepare manufacturing information based
on the Signal Corps model, which would enable Western
to eventually produce some 3,000 of these radars.
Their function was primarily searchlight control, but
there was some hope that they might prove to be
sufficiently accurate for fire control--and they
certainly served admirably in the Italian campaign.

As one of a team of specialists, I went to Fort
Hancock in 1939 to work on the bedspring antennas used
in this radar. These were small curtain arrays of
dipole elements. There was a separate transmitting
antenna and two separate receiving antennas, one of
which load switched; that is, it tilted the beam back
and forth rapidly in elevation and the other in
azimuth. The antennas were manually steered in azimuth
and in elevation by two separate operators who sat out
in the open on hay-rake type seats, balancing pips on
their respective A-scopes to keep the antennas on
target. The field operator kept the target pip in the
range gate on a third A-scope. The angles and range
data were mechanically linked to an analog corner
convertor and an M-4 gun director. The entire
equipment was transportable on trailers. And the
antennas, which could be rotated through 360o in
azimuth and 90o in elevation, were some forty feet in
overall length and ten feet high.

Polkinghorn: Then radars were developed operating on
higher frequencies.

Smith: By the time the U.S. joined World War II,
radars were being developed and operated on higher
frequencies and consequently with smaller antennas. In
1940 a radar was developed at Whippany, under the
direction of Bill Tynes, which operated on
approximately 700 MHz, which gave splendid service,
particularly in the Pacific. This was followed, with
the British development of the magnetron, by a number
of equipments operating around 3,000, and later
10,000, MHz. The antennas for these latter radars were
based on optical principles using parabolic reflectors
of various shapes and sizes and metal-plate lenses.
Some scanned electronically and involved considerable
ingenuity and design effort. Much help was provided by
the Bell Laboratory's radio research group at the
Holmdel, New Jersey, laboratory under Harold Friis. My
contribution was the electrical design of submarine
radar antennas for the BPS-1 and BPS-3 equipments. I
was project engineer for the SE radar. Details of
these antennas are too numerous and involved to go
into very much at this point.

Polkinghorn: After the war, I believe you went back
into broadcasting work.

Smith: After the war, FM broadcasting came into full
blossom, and Western Electric started to design and
provide a complete line of FM transmitters and
antennas. At that time I designed a novel high-gain,
stacked-array antenna whose elements resembled a
cloverleaf--a four-leaf clover. Consequently, this was
dubbed the "cloverleaf antenna." This was widely
advertised by Western Electric, and several dozen
installations around the country were made. But before
the entire program got rolling, the competition from
firms that had sprung up during the war and were now
looking for new business, was so devastating that
Western Electric decided to get out of the specialty
products business. We abruptly terminated the FM
development and sold various portions of our
non-telephone business to several different companies.
That ended my broadcast career.

Polkinghorn: You were at Murray Hill then for a while.

Smith: Yes. At Bill Dougherty's request, I went to
work in the transmission research department at Murray
Hill, New Jersey. Bill's problem was a surplus of fine
scientists and a lack of sufficient engineering
personnel. The project was to develop a new type of
coaxial cable, which consisted of a large number of
inner conductors embedded in a low-loss laminate. The
theory predicted that this type of cable would have up
to forty percent less attenuation than the simple tube
conductor cable for the same amount of conductor
dimension. This cable, known as Cloggston cable, was
invented by A.M. Cloggston at Bell Laboratories. It
was company confidential at the time. If it could have
been successfully developed and produced at a
reasonable cost, it would obviously have been of
immense value to the Bell System. After nine months'
effort, it became clear to me that tolerance
requirements and the thickness and spacing of the
conducting layers were beyond any practical
possibility to achieve. I felt that I was knocking my
head against a stone wall. The project was
subsequently put on a back burner.

Polkinghorn: So you went back to Whippany in military
projects.

Smith: Yes. I returned to supervise a group working on
the radar design for the Distant Early Warning DAR
line, which was to be extended across the Arctic
reaches of North America. We also worked on the Sage
System antennas for tracking all airplanes of known or
unknown origin flying above the continental United
States. The radar provided coverage in areas shadowed
by mountainous terrain. And there was the Nike Zeus,
the Nike X projects, Nike II projects, as well as the
low-altitude missile radar known as HAWK, later
developed by Raytheon.

Polkinghorn: The Nike Zeus had a huge antenna, as I
recall.

Smith: Yes. This antenna, built on an army project at
White Sands Missile Range, certainly was a novel and
unique design in many respects. It used a solid sphere
that was lightweight, artificial dielectric, eighty
feet in diameter. I originally proposed this design as
an alternative to the larger rotatable arrangement of
parabolic reflector-type antennas. The huge sphere
served as a common focusing element for a large number
of feed horns mounted on its surface, which produced a
multitude of individual pencil beams. The entire
assembly rotated at ten revolutions per minute on what
was then the world's largest ball-bearing, some
thirteen feet in diameter. It provided hemispheric
coverage at a data rate of three-second intervals. A
subsequent design which I had proposed, and which was
installed at Kwajalein in the Nike II installation,
used a half sphere dielectric over an extended, flat,
conducting ground plane. The ground plane provided a
mirror image of the half sphere, thereby creating the
effect of a full sphere. In this antenna the large
lens was stationary, and only the feed horn assemblies
rotated.

The dielectric lens in the Kwajalein antenna was
composed of expanded-beam polystyrene, molded into
two-foot cubes. The foam was loaded with millions of
3/8-inch-long aluminum slivers randomly oriented. The
dielectric constant of the box was varied from mere
unity at the surface of the lens to 1.4 at its center,
by varying the concentration of the slivers. The basic
principles of the variable dielectric spherical lens
are credited to Professor Lunenberg of Brown
University, which he derived from ray optics.

Polkinghorn: How did that Lunenberg antenna work out?

Smith: Well, these antennas performed fully as
predicted. However, as in any rapidly developing
field, specific models at various stages of
development cannot keep pace with newer concepts, such
as, in this case, the electronically steered phased
arrays used in later defense systems. The Nike Zeus
antenna at White Sands and the Nike II at Kwajalein
provided much insight into the target-acquisition and
tracking problem. The Nike Zeus antenna was finally
junked, but not without some criticism that it might
have been of considerable value to radio astronomers.
The Nike II at Kwajalein was also junked, and some of
the polyform can still be seen in the construction of
native huts and paddleboats. The most important
commercial spinoff from this antenna development was
the extensive use shortly thereafter of molded
expanded-beam polystyrene. And also in domestic
articles such as hot cups, cold cups, insulation,
packing forms, even surfboards, and so forth.

Polkinghorn: You also worked on the antennas for the
Safeguard System, did you not?

Smith: Yes. My group was given responsibility for the
electrical design of the phased-array antennas in the
Safeguard System. I coordinated this design effort in
the Bell Laboratories with Wheeler Labs on Long
Island, who worked with us on the subcontract. Wheeler
Labs assigned between fifteen and twenty engineers to
this project, extending over a period of about four
years. It was my job to keep them busy and productive.

Polkinghorn: What do you consider the most important
work that you did?

Smith: Well, I guess it would have to be the
development of my transmission-line impedance chart,
of which over eight and one-half million copies have
been sold. The most enjoyable work was in AM
broadcasting.

Polkinghorn: You've been quite active in professional
societies, particularly in the IRE and its succession
to the IEEE, have you not?

Smith: Yes, I have. I'm presently a member of
Commission Six of Union Radio Scientific
Internationale, or URSI, and a member of six
committees in the IEEE. Over the years I've served on
many more. I was chairman of the GAP Committee for the
IEEE's fiftieth anniversary issue of Proceedings.
Although much of my work has been associated with
standards, I've also served on section and group
awards committees and membership and on some of the
committees.

Polkinghorn: I believe you're a Fellow of the
Institute.

Smith: Yes, I was elected a Fellow in 1952, "for
contributions to the development of antennas and
graphical analysis of transmission line
characteristics."

Polkinghorn: You've written quite a few articles also,
have you not?

Smith: Yes. I have written something over thirty
articles for publication in my own name, as well as
contributed to many proposals and documents that went
out over the company's name.

Polkinghorn: I believe it would also be interesting to
know that you hold a pilot's license for airplanes.

Smith: Well, I first learned to fly and obtained my
pilot's license in 1950. I've since owned two
airplanes, which I've flown over most of the United
States, Mexico, Cuba, and the Bahamas. In all, I've
accumulated 1500 hours of flying time. Flying has
given me one of my greatest pleasures.

HOME

(m.hoffman at ieee.org)
URL:
www.ieee.org/organizations/history_center/oral_histories/transcript/smtih3.html
(Modified:21-Jul-00 02:58 PM) 

James C. Owen, III K4CGY

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