NOMAC

no comment.

(a) MIT Lincoln Laboratory’s high frequency NOMAC (NOise Modulation and Correlation) system, known under the Army Signal Corps production name F9C. NOMAC was a communications system using noise-like signals and cross-correlation detection. Papers describing this method and system date back to 1952; or

via http://etoan.com/

[27] In 1958, MIT’s Lincoln Laboratory announced that it had bounced radar waves off Venus. That apparent success was followed by another, but in England, during Venus’ next inferior conjunction. In September 1959, investigators at Jodrell Bank announced that they had validated the 1958 results, yet Lincoln Laboratory failed to duplicate them. All uncertainty was swept aside, when the Jet Propulsion Laboratory (JPL) obtained the first unambiguous detection of echoes from Venus in 1961.

via http://history.nasa.gov/SP-4218/ch2.htm

The RLE, a joint laboratory of the Physics and Electrical Engineering Departments, continued much of the fundamental electronic research of the Radiation Laboratory. The Signal Corps, Air Force, and the Office of Naval Research jointly funded the new laboratory, with the Signal Corps overseeing the arrangement. Former Radiation Laboratory employees filled research positions at the RLE, which occupied a temporary structure on the MIT campus erected earlier for the Radiation Laboratory. The two leaders of the Lincoln Laboratory Venus radar experiment, Robert Price and Paul E. Green, Jr., were both student employees of the RLE. Price also had an Industrial Fellowship in Electronics from Sperry. Among the other early RLE fellowship sponsors were the General Radio Company, RCA, IT&T, and the Socony-Vacuum Oil Company.

Lincoln Laboratory was to design and develop what became known as SAGE (Semi-Automatic Ground Environment), a digital, integrated computerized North-American network of air defense. SAGE involved a diversity of applied research in digital computing and data processing, long-range radar, and digital communications. The Army, Navy and Air Force jointly underwrote Lincoln Laboratory through an Air Force prime contract. The Air Force provided nearly 90 percent of the funding. In 1954, Lincoln Laboratory moved out of its Radiation Laboratory buildings on the MIT campus and into a newly constructed facility at Hanscom Field, in Lexington, Massachusetts, next to the Air Force Cambridge Research Center.

 

The idea of using the Millstone Hill radar to bounce signals off Venus arose during one of the customary lunchtime discussions between Bob Price and Paul Green. As MIT doctoral students and later as Lincoln Laboratory engineers, Price and Green worked closely together under Wilbur B. Davenport, Jr., their laboratory supervisor and dissertation director. They worked on different aspects of NOMAC (NOise Modulation And Correlation), a high-frequency communication system (known by the Army Signal Corps production name F9C) that used pseudonoise sequences, and on Rake, a receiver that [31] solved NOMAC multipath propagation problems. Later, what Lincoln Laboratory called NOMAC came to be called spread spectrum.

Their work was vital to maintaining military communications in the face of enemy jamming.

Despite the maser’s low noise level, Price and Green knew that they would have to raise the level of the Venus echoes above that of the noise. Their NOMAC anti-jamming work had prepared them for this problem. They chose to integrate the return pulses over time, as Zoltán Bay had done in 1946. In theory, the signals buried in the noise reinforced each other through addition, while the noise averaged out by reason of its random nature.⁹

^{(recall how sigsally DIDN’T do that in 1943…)}

A digital computer, as well as additional digital data processing equipment, linked to the Millstone radar system performed the integration and analysis of the Venusian echoes. An analog-to-digital convertor, initially developed for ionospheric research by William B. Smith, digitized information on each radar echo. That information simultaneously was recorded on magnetic tape and fed to a solid-state digital computer. The experiment was innovative in digital-signal processing and marked one of the earliest uses of digital tape recorders.¹⁰

..

The University of Manchester Physics Department had developed a 400-MHz (75 cm), 100-kilowatt klystron. “It was a real kludge,” Evans later recalled, “because it was basically a Physics Department experiment. It was continuously pumped; it sat on top of vacuum pumps, which required liquid nitrogen for cooling.”¹⁶

in general

5. William W. Ward, “The NOMAC and Rake Systems,” The Lincoln Laboratory Journal vol. 5, no. 3 (1992): 351-365; Green 20/9/93; Price 27/9/93. Green and Price acknowledged each other in their dissertations. Green, “Correlation Detection using Stored Signals” D.Sc. diss., MIT, 1953, and Price, “Statistical Theory Applied to Communication through Multipath Disturbances,” D.Sc. diss., MIT, 1953.

A history of the subject, R. A. Scholtz, “The Origins of Spread-Spectrum Communications,” IEEE Transactions on Communications COM-30 (1982): 822-854, is reproduced in Marvin K. Simon, Jim K. Omura, Scholtz, and Barry K. Levitt, eds., Spread Spectrum Communications (Rockville, Md.: Computer Science Press, Inc., 1985), Volume 1, Chapter 2, “The Historical Origins of Spread-Spectrum Communications,” pp. 39-134. Price, “Further Notes and Anecdotes on Spread-Spectrum Origins,” IEEE Transactions on Communications COM-31 (January 1983): 85-97, provides an absorbing anecdotal sequel to Scholtz.