James L. Lawson
Physicist, radar pioneer, and champion amateur radio contester.
James Llewellyn "Jim" Lawson (1915–May 25, 1982) was an American physicist and amateur radio operator whose work at the MIT Radiation Laboratory during World War II proved essential to the development of microwave radar. He held a PhD from the University of Michigan and was among the few early Lab members with deep amateur radio experience, a background that directly helped solve practical engineering challenges in the field.
Lawson’s early contributions included a klystron buffer that allowed a single antenna to both transmit and receive, demonstrated on January 10, 1941. He also designed a beaded coaxial transmission line—the Lawson line—with non-uniform polystyrene bead spacing that improved frequency sensitivity over earlier designs. In March 1941, he created a spark-gap TR box, a gas-filled resonant cavity with a small metal gap that shorted during transmission and recovered for reception. Installed in the Lab’s B-18 flying laboratory around April 1, this device eliminated the need for the klystron buffer and improved signal-to-noise ratio enough to detect ships at 15 miles by mid-April. The B-18A system with Lawson’s TR box was demonstrated to RAF Commander Sir Hugh Dowding on April 29, 1941. His 10-cm TR box later served as the basis for 3-cm TR development.
In July 1941, Lawson traveled to England with four other Lab members to compare American and British 10-cm radar systems. Side-by-side tests at the Telecommunications Research Establishment in Swanage revealed that the American transmitter had higher power, while the British receiver was more sensitive. Lawson, Norman Ramsey, Taffy Bowen, and Dale Corson identified the cause: British silicon crystal detectors outperformed the grounded-grid triode mixer the Americans had adopted after their own crystals burned out. Combining the British receiver with the American transmitter tripled detection range. This led the Radiation Laboratory to adopt crystal mixers and the British Sutton Tube TR box, significantly improving later radar systems.
In fall 1941, Lawson organized and led the Experimental Systems Group (Group 44), also called the Advanced Development Group, for the rest of the Lab’s existence. The group maintained calibrated reference radar systems, tested components, studied anti-jamming techniques, and tried to anticipate radar advances.
Quick Facts
- Known For
- Lawson line, Lawson TR box, Yagi antenna design
- Employer
- MIT Radiation Laboratory, General Electric
- Education
- University of Kansas (BA, MA) / University of Michigan (PhD)
- Birth Date
- 1915
- Birth Place
- Madura, India
- Death Date
- 1982-05-25
- Death Place
- Schenectady, New York
Facts from the source article.
Lore & Background
Lawson joined the MIT Radiation Laboratory in late 1940, during the assembly of the first 10-cm airborne-intercept system. In January 1941 he discovered that a klystron used as a preamplifier could buffer the receiver crystal, allowing single-antenna operation. He then designed the Lawson line, a beaded coaxial transmission line with non-uniform bead spacing that improved frequency sensitivity. In March 1941 he created a successful spark-gap TR box, a gas-filled cavity that eliminated the klystron buffer and improved signal-to-noise ratio; the B-18 flying laboratory using this TR box could detect ships at 15 miles by mid-April 1941. In July 1941 Lawson traveled to England to compare American and British 10-cm radar systems, where tests revealed the superiority of British silicon crystal detectors, prompting the Radiation Laboratory to adopt crystal mixers.
In fall 1941 Lawson organized and led the Experimental Systems Group (Group 44), which maintained calibrated reference radar systems, contributed to component testing, undertook anti-jamming studies, and attempted to anticipate radar advances. In June 1942, while photographing pulse reflections from moving targets, he and L. B. Linford observed traces attributed to propeller modulation, leading to Project Sambo, a system for identifying friendly aircraft using propeller treatment.
After the war Lawson joined General Electric, heading the nuclear-investigation division and helping design a non-ferromagnetic synchrotron announced in April 1950. He later directed work in advanced military communications, solid-state physics, integrated circuitry, and computer science. After retiring in 1981, he conducted phase-noise research using precision test equipment from Hewlett-Packard, contributing to several HP application notes before his death.
Reader's Guide
Lawson's significance lies in his dual legacy as a wartime radar engineer and a champion amateur radio contester. At the MIT Radiation Laboratory, his TR box design made single-antenna microwave radar practical, a critical step for airborne intercept systems. Luis Alvarez later remarked that if the team had been paid in proportion to contributions, Lawson would have earned more than half the monthly payroll. His work on transmission lines and TR switching directly enabled the first operational 10-cm radar systems demonstrated to RAF leadership in April 1941.
In amateur radio, Lawson's station W2PV in Niskayuna, New York, featured towers up to 180 feet with stacked Yagi arrays. He won first place in the United States in the CQ WW Phone contest as a single operator in 1965, 1966, 1968, and 1971. Switching to multi-operator multi-transmitter operations, W2PV won first place multi-multi in ARRL DX Phone in 1976–1979 and 1981, and first place multi-multi in both modes of CQ WW in 1977. His final contest in November 1981, while gravely ill, earned first place worldwide in the multi-multi category of the CQ WW CW contest, believed to be the first time a U.S. station worked 100 countries and 30 zones on four bands. Competing stations conceded early so CQ magazine could produce the winner's plaque before his death. His posthumous book Yagi Antenna Design (1986) remains a standard reference on computer-optimized Yagi design. He was inducted into the CQ Contest Hall of Fame in April 1993.
Did You Know?
- Lawson was born in Madura, India, and moved to the United States at age thirteen.
- He helped design the OH2AM contest station in Finland in the 1960s.
More in Amateur Radio People, Part 2 1-24
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