Image: Spark gap transmitter-Marconi patent 763772 fig 1

Description: Spark-gap transmitter circuit from Guglielmo Marconi's controversial patent no. 763772 for a "four circuit" wireless telegraphy radio communication system. The significant innovation of this circuit was the use of two tuned circuits, coupled by a resonant transformer (d,d'), which Marconi called a "jigger". This reduced the bandwidth of the transmitted signal, which enabled it to transmit much further, and reduced interference with transmitters on other frequencies. The receiver also employed a similar resonant transformer design with two tuned circuits, so the combined system was described as a "four circuit" design. This patent was the foundation of the Marconi Company's dominance of the wireless business during the first decades of the 20th century. It was contested by Oliver Lodge, Nikola Tesla, and John Stone Stone as violating their prior patent rights, and became the focus of a long running litigation. It was overturned in 1943 by the US Supreme Court.
Title: Spark gap transmitter-Marconi patent 763772 fig 1
Credit: Retrieved August 14, 2015 from US patent no. 763772 Guglielmo Marconi, Apparatus for wireless telegraphy, filed November 10, 1900; granted June 28, 1904
Author: Guglielmo Marconi
Usage Terms: Public domain
License: Public domain
Attribution Required?: No