BOARD OF DIRECTORS Frederick E. Terman, President Adolfo T. Cosentino, Vice President Proceedings Alfred N. Goldsmith, Editor Haraden Pratt, Treasurer Harold P. Westman, Secretary Austin Bailey of the Adolph B. Chamberlain PR E Ivan S. Coggeshall Melville Eastham Harold T. Friis Published Monthly by Virgil M. Graham 0. B. Hanson The Institute of Radio Engineers, Inc. Raymond A. Heising Lawrence C. F. Hone C. M. Jansky, Jr. Frederick B. Llewellyn VOLUME 29 December, 1941 N U M BE R 12 Browder J. Thompson Hubert M. Turner Arthur F. Van Dyck Diplex P J Noizeux, H. Krahenbillil, and B. Noviks 609 Harold A. Wheeler Lynde P. Wheeler Distortion Tests by the Intermodulation Method John K. Hilliard 614 • Optimum Conditions for Maximum Power in Class A Amplifiers Wayne B. Nottingham 620 Harold R. Zeamans, General Counsel The Calculation of Ground-Wave Field Intensity Over a • Finitely Conducting Spherical Earth K. A. Norton 623 General Amplitude Relations for Transmission Lines BOARD OF EDITORS with Unrestricted Line Parameters, Terminal Im- Alfred N. Goldsmith, Editor pedances, and Driving Point Ronold King 640 Ralph R. Batcher Civilian Receiver Design in 1942 Dorman D. Israel 649 Lloyd V. Berkner Philip S. Carter High-Frequency Radio Transmission Conditions, Oc- Lewis M. Clement tober, 1941, with Predictions for January and Feb- Elmer W. Engstrom ruary, 1942 653 William L Everitt Peter C. Goldmark Books: Frederick W. Grover "Fourier Series and Boundary Value Problems," C. M. Jansky, Jr. by Ruel V. Churchill W. L. Everitt 655 John D. Kraus "Vacuum Tube Voltmeters," by John F: Rider W. G. Dow 655 Frederick B. Llewellyn "Radio Facsimile," published by RCA Institutes Samuel S. Mackeown Technical Press R. K. Potter 655 Edward L Nelson Harry F. Olson institute News and Radio Notes 656 Greenleaf W. Pickard The Institute Moves Ahead in 1941 656 Haraden Pratt Board of Directors 657 Conan A. Priest Peder Oluf Pedersen 658 Leon J. Sivian Executive Committee. 658 Lynne C. Smeby Committee and Section Reports. 659 Browder J. Thompson Section Meetings 659 Harold A. Wheeler Committee Meetings. 659 Lynde P. Wheeler Membership 660 Laurens E. Whittemore Incorrect Addresses. 661 Gerald W. Willard William Wilson Winter Convention 662 Charles J. Young Contributors. 667 • Helen M. Stote, Assistant Editor Entered as second-class matter October 26. 1927. at the post office at Menasha. Wisconsin. under the Act of Feb- ruary 28. 1925, embodied in Paragraph 4, Section 538 of the Postal Laws and Regulations. Publication office, 450 Ahnalp Street. Menasha. Wisconsin. Editorial and advertising offices. 330 West 42nd St., New York. N. Y. Subscrip- William C. Copp, tion. $10.00 per year; foreign, $11.00. Advertising Manager John D. Crawford, Copyright. 1941, by The Militate of Radio Engineers. use. Assistant Secretary .