Armstrong at Columbia: Student to Great Radio Engineer Mischa Schwartz Charles Batchelor Professor Emeritus of Electrical Engineering Columbia University
Outline of Talk Armstrong as student EE program, early days-background Armstrong, student inventor Armstrong and FM
Armstrong as student Armstrong, b.dec.10,1890-d.jan.31, 1954 Student, EE dept., Oct.1909-Sp. 1913 Among courses taken- EE: dc, ac machinery, incl. lab s theory of electro-magnetism telegraphy, telephony non-ee: phys, math, chem, CE, ME
EE at Columbia (1) Intro. 1889, 2-yr grad. program; UG, 1892 (49 th street site) Two teachers initially: Francis Crocker, Inst. ($2000/yr) (later, Prof., Chair of Dept.) Michael Pupin, Asst. ($1500/yr) (later, Prof. of Electro-Mechanics)
EE at Columbia (2) Estab. of EE followed Edison letter, 11/82 Why a 7-yr delay?: (1) finances/space needs (2) Where to house?- within Physics? as part of Mechanical Engineering? separate program?
EE at Columbia (3) Mechanical Engineering argument- F.R. Hutton, School of Mines Quarterly, 1887 Electric energy is but one of the forces the ME should be competent to direct. The EE should therefore be first an ME. Electrician, 1883: The future EE will be essentially an ME, with one or two added qualifications.
EE at Columbia (4) By 1897, EE program the most successful among the established Eastern schools due largely to Crocker s engineering ability and Columbia s predisposition for applied science. (Rosenberg, 1990 Ph.D. dissertation) Crocker now Chair and Prof., Pupin, Prof. of Electro-Mechanics
EE, Armstrong student years EE faculty: Walter Irvine Slichter, Prof. Morton Ahrendt, Asst.Prof. John H. Morecroft, Asst Prof. Frederick Hehre, Inst. Frank Mason, Inst. Pupin, Prof. of Electro-Mechanics
Armstrong as student Most interested in telegraphy (taught by Ahrendt), lab work ( always puttering around secretive in his work ) 1911, Jr. year, came to attention of Pupin 1911, began study, grid-based tube; obtained amplification Sept. 1912, Sr., recognized tube oscillations
Armstrong, student inventor Jan. 31, 1913, regenerative receiver patent witnessed, notarized Sp. 1913, work supported by Mason and Ahrendt 1913-1914, EE Asst.,Navy wireless class Oct. 29, 1913, files receiver patent; granted, Oct. 6, 1914: No. 1,113,149 1914: works in Pupin lab; Morecroft helps
Armstrong and regenerative receiver patent, 1914-1915 Demos, extensive press coverage Dec. 1914, paper, Electrical World Talks, IRE meetings, March/Apr 1915 Paper, Proc. IRE, May 1915; Eminent engr: work of great significance Awarded first IRE Medal of Honor, 1917 De Forest- hostile, patent litigation ensues
Armstrong and Noise Reduction 1916-1919, time out for WWI: US Signal Corps, Capt./Major, Superheterodyne receiver Returns to Pupin lab as Pupin s Asst (much later, Prof of EE) begins work, reduction of atmospheric disturbances: perennial problem, radio
Noise-reducing work (cont) From Report to Pupin, April 3, 1933, first such rpt during the 19 years of the laboratory : [In the Spring of 1924] I resumed work on the old problem of the elimination of atmospheric disturbances making some progress toward its solution, despite the widespread belief it was insoluble. Some of this work was [presented] in Oct 1927 before the IRE Since that time I have been practically continuously engaged on the same problem.
Result- Armstrong in error! Oct. 1927 work and paper, Jan. 1928, Proc. IRE- cancel radio static (atmospheric disturbance); based on many expts John Carson, July 1928, Proc. IRE: showed impossible to cancel. But concluded with Static, like the poor, will always be with us. (Unfortunate comment, demolished by Armstrong few years later!)
Frequency Modulation Use explored, early days of radio: (1) reduce bandwidth (scarce commodity)? (2) improved radio transmission (RCA)? John Carson, AT&T, 1922: Bandwidth increases in FM! Little improvement in transmission, FM Result, much less interest
Armstrong and FM For years worked to improve FM systems; Consultant to RCA Four patent applications, May 18, 1927- Jan. 24, 1933. All granted Dec. 26, 1933 Last of the four, Radiosignaling, No. 1,941, 069, on wideband noise-reducing FM!
Wideband FM patent I have discovered that by imparting greater swing to the frequency of the transmitted wave than can exist in the disturbances due to tube [noise] that a very great improvement in transmission can be produced.
Wideband FM patent (2) Invention well-received by engineering community - Demo for RCA engineers, impressive! - Nov. 5, 1935 IRE meeting, same! - Paper published, Proc. IRE - Many papers by others incl. John Carson explaining noise reduction, Armstrong s paper most clear and succinct.
Summary of low-noise activity Armstrong, 1920s, much activity to reduce radio static 1928, noise cancellation work- wrong! Into 1931, worked with RCA to improve FM designs. Aug 1931: noise balancing, lower audio frequencies Sept 1931, wideband invention? Patent application Jan. 1933
Acknowledgements Much of material from University Archives and Armstrong papers, both in Rare Book Library- Thanks to help from staff of Rare Book Library, esp. Jen Comins! Some material from Lawrence Lessing, Man of High Fidelity: Edwin Howard Armstrong, 1956