Harold A. Zahl

Harold A. Zahl
Born	(1904-08-24)August 24, 1904 Chatsworth, Illinois
Died	March 11, 1973(1973-03-11) (aged 68) Red Bank, New Jersey
Citizenship	American
Alma mater	North Central College University of Iowa
Awards	Harry Diamond Award (1954) Army Decoration for Exceptional Civilian Service
Scientific career
Fields	Radar
Institutions	Signal Corps Laboratories
Thesis	Reflection of Cadmium and Zinc Atoms from Sodium Chloride Crystals (1930)
Military career
Allegiance	United States of America
Service / branch	United States Army
Years of service	1942–1946
Rank	Lieutenant colonel
Awards	Legion of Merit

Harold Adelbert Zahl (August 24, 1904 – March 11, 1973) was an American physicist who had a 35-year career with the U.S. Army Signal Corps Laboratories, making major contributions to radar development.

Career and accomplishments

Harold Zahl was born in Chatsworth, Illinois, the son of an Evangelical 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-warning 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.

Zahl was a resident of Holmdel Township, New Jersey, where he owned the Hazienda Evergreen Plantation, and died at Riverview Hospital in Red Bank on October 12, 1973.

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.”
• Department of the Army Decoration for Exceptional Civilian Service
• Legion of Merit

Bibliography

• Zahl, Harold A. (September 1930). "Reflection of Cadmium and Zinc Atoms from Sodium Chloride Crystals". Physical Review Letters. 36 (5). APS: 893–903. doi:10.1103/PhysRev.36.893. Retrieved 12 June 2015.

• Zahl, Harold A.; Golay, Marcel J. E. (1946). "Pneumatic Heat Detector". Review of Scientific Instruments. 17 (12). AIP Publishing. doi:10.1063/1.1770416. Retrieved 12 June 2015.

• Zahl, Harold A.; Marchetti, John W. (January 1946). "Radar on 50 Centimeters – The TPS-3 Radar". Electronics. McGraw–Hill: 98–104. ISSN 0013-5070. Retrieved 12 June 2015.

• Zahl, Harold A. (February 1952). "Physics in the Signal Corps". Physics Today. 5 (2). AIP: 16. doi:10.1063/1.3067477. Retrieved 13 June 2015.

• Zahl, Harold A.; Reilley, Edward M. (August 1958). "Exploratory research". Physics Today. 11 (8). AIP: 20. doi:10.1063/1.3062684. Retrieved 13 June 2015.

• Zahl, Harold A.; Ziegler, Hans K. (January 1960). "Power sources for satellites and space vehicles". Solar Energy. 4 (1). Elsevier: 32–38. doi:10.1016/0038-092X(60)90047-5. Retrieved 12 June 2015.

• Zahl, Harold A. (April–July 1960). "From an Early Sputnik Diary". Military Electronics, IRE Transactions on. MIL-4 (2–3). IEEE: 320–322. doi:10.1109/IRET-MIL.1960.5008242. Retrieved 12 June 2015.

• Zahl, Harold A. (October 1960). "One Hundred Years of Research". Military Electronics, IRE Transactions on. MIL-4 (4). IEEE: 397–401. doi:10.1109/IRET-MIL.1960.5008264. Retrieved 12 June 2015.

• Zahl, Harold A. (November 1960). "Signal Corps centennial". Physics Today. 13 (11). AIP: 34. doi:10.1063/1.3056707. Retrieved 13 June 2015.

• Zahl, Harold A. (March 1961). "Looking Backward toward Tomorrow". Aerospace and Navigational Electronics, IRE Transactions on. ANE-8 (1). IEEE: 3–6. doi:10.1109/TANE3.1961.4201770. Retrieved 12 June 2015.

• Zahl, Harold A. (May 1962). "Fifty Years of Teaching Machines". Proceedings of the IRE. 50 (5). IEEE: 575–578. doi:10.1109/JRPROC.1962.288366. Retrieved 12 June 2015.

• Zahl, Harold A. (1968). Electrons away;: Or, Tales of a government scientist. Vantage Press. ASIN B0006BTL9O. {{cite book}}: |access-date= requires |url= (help)

• Miller, Ronald I.; Snouse, Tom; Zahl, Harold A.; Clancy, Edward P. (April 1970). "More on employment". Physics Today. 23 (4). AIP: 10. doi:10.1063/1.3022056. Retrieved 13 June 2015.

• Zahl, Harold A. (December 1970). "A Tale of Two Crises". Signal Magazine. Retrieved June 12, 2015.

• Zahl, Harold A. (1972). Radar Spelled Backwards. Vantage Press. ASIN B00221YBZ0. {{cite book}}: |access-date= requires |url= (help)

References

• Colton, Roger B. (November 1945). "Radar in the United States Army History and Early Development at the Signal Corps Laboratories, Fort Monmouth, N.J." 33 (11). IEEE: 740–753. doi:10.1109/JRPROC.1945.231560. Retrieved 12 June 2015. {{cite journal}}: Cite journal requires |journal= (help)

• Davis, Harry M. (1945). "History of the Signal Corps Development of US Army Radar Equipment, Part II". Office of the Chief Signal Officer. {{cite journal}}: Cite journal requires |journal= (help)

• Orr, William I. (March 1964). "The secret tube that changed the war" (PDF). Popular Electronics. 20 (3). Ziff Davis: 57–59, 103. Retrieved 12 June 2015.

External links

• A Concise History of Fort Monmouth, New Jersey, and the U. S. Army CECOM Life Cycle Management Command (PDF). 2009. Archived from the original (PDF) on March 22, 2015. Retrieved June 12, 2015. {{cite book}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

• Radar: A Report on Science at War. August 15, 1945. Retrieved June 12, 2015.

• "Zahl Tube - VT-158". http://www.tubecollector.org/. September 2, 2014. Retrieved June 12, 2015. {{cite web}}: External link in |website= (help)

• LTC Harold A Zahl at Find a Grave