Sixty years ago this month, the PROCEEDINGS OF THE INSTITUTE OF RADIO ENGINEERS (IRE) included a classic paper on the theory of vacuum-tube amplifiers by Hendrik van der Bijl. At the time, he was in the laboratory of the Western Electric Company, the manufacturing unit of the American Telephone and Telegraph Company. His paper disclosed some of the important work dealing with the design of vacuum-tube triodes which he had accomplished since joining Western Electric in 1913. Van der Bijl pointed out that the vacuum tube deserved much of the credit for the “recent rather remarkable developments in the art of radio communication.” He outlined a theory based on a fundamental equation which gave the plate current as a function of plate and grid voltages and the structural parameters of the tube. He observed that it would be quite difficult to achieve satisfactory operation of electronic devices “without an explicit mathematical formulation of the operation.” He included a derivation of a tube constant which he called the “amplification constant” and showed how it could be used in the calculation of the predicted gain of a small-signal amplifier in an actual circuit. He stated that the two most important tube constants were the amplification constant and the internal impedance, both of which depended on tube structure.Van der Bijl was born in 1887 in Pretoria, South Africa, and graduated with a degree in physics from Victoria College in 1908. He then went to Germany where he earned the Ph.D. degree at the University of Leipzig in 1912. He taught physics for a year at a technological school in Dresden before coming to the United States in 1913 to accept a research position at Western Electric. He was assigned to work with Harold Arnold and others on development of reliable electronic repeaters for use in long-distance telephony. He developed a methodology for the design of vacuum tubes and used it to design the amplifiers used for the first transcontinental telephone line between New York and San Francisco, which began operation in 1915. He also designed a grid modulator circuit for an experimental vacuum-tube radio transmitter used in long-distance radio communication tests by Western Electric engineers during 1915. Van der Bijl received at least 17 United States patents, for which he filed applications between 1914 and 1918. He authored the first comprehensive book on vacuum tubes, entitled The Thermionic Vacuum Tube and its Applications, published in 1920.

Van der Bijl returned to his native South Africa in 1920 where he became an advisor to the government on industrial development. In 1923 he helped organize the Electricity Supply Commission which was responsible for creating a national electrical power system. In 1939 he established the Industrial Development Corporation of South Africa to finance industrial development and headed it for several years. During World War II he served as Director-General of War Supplies.

Van der Bijl served as President of the South African Institute of Electrical Engineers in 1927 and was elected Vice-President of the IRE in 1945. He died in Johannesburg, South Africa, in 1948 at age 61.

James E. Brittain
School of History, Technology, and Society
Georgia Institute of Technology

Submitted by Dick Reiman, Historian

Copyright 1994 IEEE. Reprinted with permission from the IEEE publication, “Scanning the Past” which covers a reprint of an article appearing in the Proceedings of the IEEE Vol. 82, No.4, April 1994.