A World History of Electrically Small Antennas
In the beginning, all antennas were electrically small, as Marconi in 1908 recognized that long wavelengths were needed for long-distance transmission. The first commercial transatlantic service was initiated in 1910 at 82 kHz! An extensive network of VLF stations was built around the world before World War I. There were stations at Kootwijk, Malabar, and Java (Dutch); at Paris, Lyon, and Saigon (French); at Carnarvon (UK); at Naven (Germany); and at Sayville and Tuckerton (USA). Between World War I and World War II, VLF stations were added at Balboa, Cavite, Criggion, Leafield, Rigby, and Kalbe. Watt (1967) lists just short of 100 VLF stations. Finally, the most advanced and most powerful stations were built at Jim Creek (Washington) and Cutler (Maine). The U.S. Navy VLF communications system was started after World War I and continues till date. Frequencies ranged from roughly 10 to 100 kHz, with wavelength from 30 to 3 km. Tall towers were used, many hundreds of meters high. Antenna engineering consisted primarily of tower design, structural engineering, properties of cables, and properties of high-voltage insulators. Umbrella loading, as sketched in Figure A.1, was used starting in 1913. An analysis was given by Smith and Johnson (1947). It was recognized almost immediately that top loading would significantly improve radiation resistance, and thereby the critical parameter efficiency (Carter and Beverage, 1962).