Alexander Stepanovich Popov (sometimes spelled Popoff; Russian: Алекса́ндр Степа́нович Попо́в; March 16 [O.S. March 4] 1859 – January 13 [O.S. December 31, 1905] 1906) was a Russian physicist, who was one of the first persons to invent a radio receiving device.Popov's work as a teacher at a Russian naval school led him to explore high frequency electrical phenomena. On 7 May 1895, he presented a paper on a wireless lightning detector he had built that worked via using a coherer to detect radio noise from lightning strikes. This day is celebrated in the Russian Federation as Radio Day. In a 24 March 1896 demonstration, he transmitted radio signals 250 meters between different campus buildings in St. Petersburg. His work was based on that of another physicist – Oliver Lodge, and contemporaneous with the work of Guglielmo Marconi.