a major discovery about radio signal propagation. While investigating transmitter "harmonics" – unwanted additional radio signals produced at higher frequencies than a station's normal transmission frequency – Westinghouse's Frank Conrad unexpectedly found that in some cases the harmonics could be heard farther than the primary signal, something previously thought impossible, as high-frequency shortwave signals, which had poor groundwave coverage, were thought to have a very limited transmission range. In 1924, Conrad demonstrated to Sarnoff that a low-powered shortwave station in East Pittsburgh, Pennsylvania could be readily received in London by a simple receiver using a curtain rod as an antenna, matching, at a small fraction of the cost, the performance of the massive alternator transmitters. In 1926, Dr. Harold H. Beverage further reported that a shortwave signal, transmitted on a 15-meter wavelength (approximately 20 MHz), was received in South America more readily during the daytime than the 200-kilowatt alternator transmissions. The Alexanderson alternators, control of which had led to RCA's formation, were now considered obsolete, and international communication would be primarily conducted using vacuum tube transmitters operating on shortwave bands. RCA would continue to operate international telecommunications services for the remainder of its existence, through its subsidiary RCA Communications, Inc., and later the RCA Global Communications Company. International shortwave was in turn largely supplanted by communications satellites, especially for distributing network radio and television programming. In 1975, the company formed RCA American Communications, which operated its Satcom series of geostationary communications satellites. Broadcasting The introduction of organized radio broadcasting in the early 1920s resulted in a dramatic reorientation and expansion of RCA's business activities. The development of vacuum tube radio transmitters made audio transmissions practical, in contrast with the earlier transmitters which were limited to sending the dits-and-dahs of Morse code. Since at least 1916, when he was still at American Marconi, David Sarnoff had proposed establishing broadcasting stations, but his memos to management promoting the idea for sales of a "Radio Music Box" had not been followed up at the time. Starting around 1920 a small number of broadcasting stations began operating, and soon interest in the innovation was spreading nationwide. In the summer of 1921, a Madison Square Garden employee, Julius Hopp, devised a plan to raise charitable funds by broadcasting, from ringside, the July 2, 1921 Dempsey-Carpentier heavyweight championship fight to be held in Jersey City, New Jersey. Hopp recruited theaters and halls as listening locations that