Radio Direction Finder
In 1910, in Boulogne, France, Bellini and Tosi develop one of the earliest successful radio direction finding antennas.
Radio direction finders capture two or more measurements of the same signal, and use the marginal differences between those points to locate the signal’s source. In 1910, in Boulogne, France, the Italian engineers Ettore Bellini and Alessandro Tosi created one of the earliest successful radio direction finding antennas. Their invention (U.S. Patent # 943,960) made radio finding practical on a wider scale, and was commonly used for aerial navigation from the 1920s until the 1950s.
Heinrich Hertz launched the field of radio direction finding in 1888 with his discovery of the directional properties of radio waves. A series of inventors attempted to determine the location of radio signals through mechanical swung loop and dipole antennas, but these systems were limited in their portability and functionality because of their large size.
Hired by the French government, Bellini and Tosi set up a large wireless station at Boulogne that allowed a resultant aerial to be rotated while the actual aerial system remained fixed. They arranged two triangular antennas at right angles to receive signals. Unlike earlier models, these antennas were connected to a separate loop antenna that was not fixed. Signals from these antennas were channeled into coils wrapped around a small wooden frame. This technique allowed the signals to be recreated in the space between the coils. Bellini-Tosi antennas were used in maritime and aerial navigation. Ground stations were linked to radio sets in aircraft and ships.
“A New System of Wireless Telegraphy: The Bellini-Tosi Apparatus,” Scientific American Supplement, No. 1802, July 16, 1910.