The following articles were contributed by R. J. Reiman

and are from the Summer 1994 issue of

"The History of Electrical Engineering Newsletter"

On the afternoon of Saturday 28 May 1994, at the Lyngby Radio Station just north of Copenhagen, the Danish IEEE Section held a dedication ceremony for an IEEE Electrical Engineering Milestone in honor of a path-breaking radio transmitter. IEEE President-Elect James T. Cain represented the IEEE Executive Committee at the ceremony, which was held in conjunction with the IEEE Region 8 meeting in Copenhagen.

In the early days of wireless, messages were encoded in dots and dashes and sent by spark transmitters. Conveying voice or music by radio required a continuous-wave (CW) transmitter, and the first successful CW transmitter was the invention of the Danish engineer Valdemar Poulsen. Poulsen was already known for another invention, the Telegraphone, the world's first functional magnetic recorder, patented in 1899.

Poulsen's invention of the arc transmitter built upon the work of the English engineer William Duddell, who had discovered how to make a resonant circuit using a carbon-arc lamp. Duddell's "musical arc" operated at audio frequencies, and Duddell himself concluded that it was impossible to make the arc oscillate at radio frequencies. In 1902, however, Poulsen succeeded in doing just that -- by modifying the electrodes, placing the arc in an atmosphere of hydrocarbon vapor or pure hydrogen, and adding a transverse magnetic field.

Poulsen's transmitter was used worldwide in the second and third decades of the century until it was displaced by transmitters that employed the vacuum tube as a generator of continuous waves.

When Frank Conrad, a Westinghouse engineer, returned to his amateur-radio hobby that he had set aside during World War I, he used a vacuum-tube continuous-wave transmitter. This meant he could send speech and music, rather than the Morse Code to which he had previously been limited. He played records over the air and built up a large following among amateurs. In 1920 Harry P. Davis, a Westinghouse vice president, decided that Conrad's transmissions were an excellent way to stimulate the sale of radio equipment, and on 16 October Westinghouse asked the Department of Commerce for a special license to begin regular broadcasting. Thus was born Station KDKA, whose first transmission, broadcast on a wavelength of 360 meters at 100 watts on the evening of 2 November, reported returns of the Presidential election between Warren G. Harding and James M. Cox. Within a year seven other licensed stations followed KDKA's lead, and within two years there were almost 500 stations in the U.S.; by the end of the decade most U.S. homes contained a radio receiver.

On Friday 17 June an IEEE Electrical Engineering Milestone plaque was dedicated to honor the pioneering broadcasting station KDKA. The IEEE Pittsburgh Section nominated the achievement and conducted the dedication ceremony. The IEEE Executive Committee was represented by Past-President Martha Sloan. Milestones Coordinator, Charles R. Wright, also spoke at the ceremony. The plaque citation called attention to the role played by Davis and Conrad as well as the significance of amateur radio in the establishment of regular radio broadcasting.