Harold A. Zahl
Encyclopedia
Harold A. Zahl was an American physicist
who had a 35-year career with the U.S. Army Signal Corps Laboratories
, making major contributions to radar
development.
, the son of a Methodist minister. While still in high school, he became an amateur radio
operator (call letters 6BHI). He graduated in physics and mathematics from North Central College
in Naperville, Illinois
, in 1927, and then attended the University of Iowa
where he earned the M.A. degree in 1929 and the Ph.D. degree in 1931, both in solid-state physics
.
Upon completing his doctorate, Zahl joined the staff of the Signal Corps Laboratories
(SCL) at Fort Monmouth, New Jersey. At the same time, he was commissioned a First Lieutenant in the U.S. Army Signal Corps.
Zahl’s initial work at the SCL was in research on detecting aircraft using thermal radiation
from their engines. In 1934, he filed a patent application on “The Art of Locating Objects by Heat Radiation.” Initially held up because of its classified nature, this was eventually granted in 1946. In 1936, the SCL started research in Radio Position Finding (RPF – later called radar). Zahl participated in the development of the Army’s first fielded RPF system, the SCR-268.
While the SCR-268 was being completed, development of an improved RPF system started and Zahl, now a Major, was assigned to lead the effort. To use a common antenna
for both transmitting and receiving, Zahl invented a gas-discharge device, called a duplexer. Two configurations of the RPF emerged: the SCR-270 (mobile) and the SCR-271 (fixed-site). These systems started to be fielded in 1940, and were used throughout the war.
The early systems had large antennas. To reduce their size, a transmitter tube that could produce high-power signals at a much higher frequency was needed (antenna size is inversely proportional to frequency). Zahl developed such a tube in 1939. Called the VT-158, it was capable of 240-kW pulsed power at up to 600 MHz. After the start of World War II, this tube formed the base of the AN/TPS-3, a light-weight, portable. early-wearning radar, and a companion the AN/TQS-3, a mortar-detection radar. A total of about 900 of these sets were built and used extensively by the Army, particularly in the Pacific Theater
. (The name 'radar' took the place of 'RPF' in 1940.)
The SCL reorganized in 1942, and the radar activities became the Camp Evans Signal Laboratory. For the next several years, Zahl worked closely with the Radiation Laboratory
at MIT in their development of microwave
radars. He was promoted to Lieutenant Colonel. At the close of the war, he resigned his commission and became a civilian employee at Camp Evans.
In 1948, Zahl was named Director of Research, and remained in this position until retiring in 1966. During these years, he made many personal contributions to advancing electronic technologies.
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
who had a 35-year career with the U.S. Army Signal Corps Laboratories
Signal Corps Laboratories
Signal Corps Laboratories was formed on June 30, 1930, as part of the U.S. Army Signal Corps at Fort Monmouth, New Jersey. Through the years, the SCL had a number of changes in name, but remained the operation providing research and development services for the Signal Corps.-Background:At the...
, making major contributions to radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
development.
Career and accomplishments
Harold Zahl was born in Chatsworth, IllinoisChatsworth, Illinois
Chatsworth is an incorporated town in Livingston County, Illinois, United States. The population was 1,265 at the 2000 census.-Geography:Chatsworth is located at ....
, the son of a Methodist minister. While still in high school, he became an amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operator (call letters 6BHI). He graduated in physics and mathematics from North Central College
North Central College
North Central College is a leading liberal arts college providing students at different stages of life and from different ethnic, economic and religious backgrounds with comprehensive educational programs.-Academics:...
in Naperville, Illinois
Naperville, Illinois
Naperville is a city in DuPage and Will Counties in Illinois in the United States, voted the second best place to live in the United States by Money Magazine in 2006. As of the 2010 census, the city had a total population of 141,853. It is the fifth largest city in the state, behind Chicago,...
, in 1927, and then attended the University of Iowa
University of Iowa
The University of Iowa is a public state-supported research university located in Iowa City, Iowa, United States. It is the oldest public university in the state. The university is organized into eleven colleges granting undergraduate, graduate, and professional degrees...
where he earned the M.A. degree in 1929 and the Ph.D. degree in 1931, both in solid-state physics
Solid-state physics
Solid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state physics studies how the large-scale properties of solid materials result from...
.
Upon completing his doctorate, Zahl joined the staff of the Signal Corps Laboratories
Signal Corps Laboratories
Signal Corps Laboratories was formed on June 30, 1930, as part of the U.S. Army Signal Corps at Fort Monmouth, New Jersey. Through the years, the SCL had a number of changes in name, but remained the operation providing research and development services for the Signal Corps.-Background:At the...
(SCL) at Fort Monmouth, New Jersey. At the same time, he was commissioned a First Lieutenant in the U.S. Army Signal Corps.
Zahl’s initial work at the SCL was in research on detecting aircraft using thermal radiation
Thermal radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation....
from their engines. In 1934, he filed a patent application on “The Art of Locating Objects by Heat Radiation.” Initially held up because of its classified nature, this was eventually granted in 1946. In 1936, the SCL started research in Radio Position Finding (RPF – later called radar). Zahl participated in the development of the Army’s first fielded RPF system, the SCR-268.
While the SCR-268 was being completed, development of an improved RPF system started and Zahl, now a Major, was assigned to lead the effort. To use a common antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
for both transmitting and receiving, Zahl invented a gas-discharge device, called a duplexer. Two configurations of the RPF emerged: the SCR-270 (mobile) and the SCR-271 (fixed-site). These systems started to be fielded in 1940, and were used throughout the war.
The early systems had large antennas. To reduce their size, a transmitter tube that could produce high-power signals at a much higher frequency was needed (antenna size is inversely proportional to frequency). Zahl developed such a tube in 1939. Called the VT-158, it was capable of 240-kW pulsed power at up to 600 MHz. After the start of World War II, this tube formed the base of the AN/TPS-3, a light-weight, portable. early-wearning radar, and a companion the AN/TQS-3, a mortar-detection radar. A total of about 900 of these sets were built and used extensively by the Army, particularly in the Pacific Theater
Pacific War
The Pacific War, also sometimes called the Asia-Pacific War refers broadly to the parts of World War II that took place in the Pacific Ocean, its islands, and in East Asia, then called the Far East...
. (The name 'radar' took the place of 'RPF' in 1940.)
The SCL reorganized in 1942, and the radar activities became the Camp Evans Signal Laboratory. For the next several years, Zahl worked closely with the Radiation Laboratory
Radiation Laboratory
The Radiation Laboratory, commonly called the Rad Lab, was located at the Massachusetts Institute of Technology in Cambridge, Massachusetts and functioned from October 1940 until December 31, 1945...
at MIT in their development of microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
radars. He was promoted to Lieutenant Colonel. At the close of the war, he resigned his commission and became a civilian employee at Camp Evans.
In 1948, Zahl was named Director of Research, and remained in this position until retiring in 1966. During these years, he made many personal contributions to advancing electronic technologies.
Recognition
- IEEE Harry Diamond Award,1954 “For his technical contributions, his long service, and his leadership in the U.S. Army Signal Corps research program.”
External links
- Staff of the CECOM LCMC Historical Office; "A Concise History of Fort Monmouth, New Jersey, and the U. S. Army CECOM Life Cycle Management Command," 2009; http://cecom.army.mil/historian/pubupdates/FM%20History%20Book%2009_4Web.pdf
- "Radar: A Report on Science at War," Office of Scientific Research and Development, distributed by Office of War Information, 15 August 1945; http://www.ibiblio.org/hyperwar/USN/ref/Radar-OSRD/index.html
- "Zahl Tube - VT-156"; http://www.tubecollector.org/vt158.htm
- Zahl, Harold A.; "A Tale of Two Crises"; Signal Magazine, Dec. 1970; http://www.infoage.org/html/zahl-tale-of-two-crises.html