STOCKHOLM, Sweden - A broadcasting relic and new entry on the UNESCO World Heritage list transmitted its annual message from southwestern Sweden to amateur radio enthusiasts worldwide Sunday.
The transmitter is part of the Grimeton radio station, which was built between 1922-1924 by the Radio Corp. of America - more famously known as RCA - to boost communication between this Scandinavian country and the United States some 3,730 miles across the Atlantic Ocean.
The station includes an aerial system of six 419 foot-high steel towers.
Dubbed "the great radio station" by Swedes, it was part of a then-global network of wireless telegraph communication links.
It was overtaken first by long-distance telephone and trans-Atlantic phone cables, then satellites and wireless communications and the Internet. The "great radio" is just a relic, albeit a working one.
The transmitter, the heart of which is an alternating-current generator, was developed by the Swedish-born engineer Fredrik Werner Alexandersson, a pioneer in radio engineering.
Educated in Europe, and employed by General Electric in Schenectady, N.Y., he emigrated to the United States in 1901 and lived there until he died in 1975. While working in the United States, he became the chief engineer at RCA.
Of the 20 or so 200-kilowatt Alexandersson transmitters that were built in the United States by General Electric and installed worldwide, only Grimeton remains.
The transmitter has been kept intact and in working condition since it started operating on Dec. 1, 1924.
It was originally used to relay messages from Halland in southwestern Sweden to the United States, a purpose that continued until after World War II, when it was converted for use by the Swedish navy and used to communicate with its submarines.
It was finally closed in 1955.
But interest in preserving the station increased and in 1996, Grimeton Radio, known among radio amateurs as SAQ, was listed as a national industrial monument in Sweden, ensuring its conservation.
The annual broadcast had nothing to do with July 4 being the U.S. Independence Day, said Bo Johansson, president in the Alexander Association, which oversees the station.
"It's the Sunday closest to the dedication date, July 2," he said.
He refused to say what the short message contained.
"The message is for our listeners, who will report to us if they've heard it," he explained.
UNESCO said that the radio station at Grimeton "is an outstanding monument representing the process of development of communication technology in the period following the First World War" and "an exceptionally well preserved monument to early wireless trans-Atlantic communication."