History

By the early 1920s, transatlantic cable capacity was insufficient for the volume of diplomatic, commercial, and press traffic between Europe and North America. Sweden needed a direct, reliable wireless link to the United States. The solution came from Ernst Alexanderson — a Swedish-born engineer at General Electric in Schenectady, New York — who had developed a machine capable of generating continuous-wave radio signals at very low frequency by spinning a precisely machined iron rotor inside a coil at extremely high speed.

The technology was already becoming obsolete as construction began. Lee De Forest’s vacuum tube triode, invented in 1907, promised smaller, cheaper, more efficient transmitters. But Alexanderson’s machines were proven, powerful, and capable of punching signals through to any point on Earth at 17.2 kHz. Six Alexanderson alternators were built worldwide; only the Grimeton machine survives.

The station opened for commercial service in December 1924 and operated continuously until 1960, when satellite communication made VLF telegraphy economically unviable. Unlike every other station of its type, Grimeton was not dismantled. The Alexanderson Association took custody, the Swedish state listed the site, and in 2004 UNESCO recognised it as an irreplaceable document of telecommunications history.