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| Keywords: Emmetteur.jpeg Vue intérieure de la salle des arcs Early Poulsen arc radio transmitter at a US Navy station at Croix d'Hins Bordeaux France The two 1 megawatt transmitters shown here built by the Federal Telegraph Co in 1919 which could broadcast continuously at a power of 500 kW and for a short time at a power of 1 MW were one of the largest arc transmitters ever built <br /> The Poulsen arc converter invented in 1903 by Valdamar Poulsen was one of the earliest continuous wave radio transmitters and one of the first that could transmit AM voice It was a short-lived technology which was used from 1903 until the mid-1920s when it was replaced by much cheaper and less bulky vacuum tube transmitters The device consisted of two horizontal arc electrodes a water-cooled copper anode and a carbon cathode in a chamber of hydrogen gas between the poles of a powerful electromagnet A tuned circuit consisting of a coil and capacitor was connected to the electrodes When a DC voltage was applied to create an arc radio frequency oscillations were generated which were applied to the antenna The transmitter operated in the very low frequency VLF range and had a range of thousands of miles It was around 46 efficient and could supply an antenna current of 750 A Carte postale circa 1925 Labeyrie PD-old Marine radiotelegraphy 1925 photographs 1925 in radio Marcheprime Postcards of Gironde Poulsen arc transmitters People with machines Men at work in France 1925 in France | ||||
