Radio broadcast .. (1922-30)

The March of Radio 359 dently a device as good as this one seems to be, may prove of great importance in the development of the talking movie. Interference from Arc Stations THE highest-powered transmitting stations in the world to-day use the Poulsen arc as the source of;high-f requency power for the antenna. A high-voltage, continuouscurrent generator supplies power to a very intense arc, burning in a closed, water-cooled chamber filled with illuminating gas or alcohol vapor. When suitable connections are made between this arc and the antenna, part of the continuous-current power supply, perhaps 40%, is changed into high-frequency power and fed to the antenna. The scheme is good only for long-wave stations. This method for generating high-frequency power is used at practically all the government's high-power stations as well as some smaller commercial stations on the west coast. Unfortunately, these arcs generate other frequencies than those desired for operating the station, some of them high enough to be heard by stations listening on wavelengths perhaps one tenth that used by the arc station. This extra power, at the higher frequencies, is undesirable both from the standpoint of efficiency and interference, and attempts have frequently been made to eliminate it. That the schemes are not quite as successful as the arc advocates would have us believe is shown by the following extract from a letter sent by one of our correspondents. —Permit me to relate that any one living in this city or within a radius of more than fifteen miles, possibly farther, has very discouraging difficulties to overcome in the line of interference from two very powerful government stations located at the Mare Island Navy yard —interference from the 100, 30, and 12-kilowatt arc stations at that place commonly referred to as "mush." One or more of these powerful arc stations is in almost constant operation during broadcast hours." The Amateurs and Professionals FOR a considerable period this winter the amateurs of America and Europe carried out tests to see how consistently communication on the 2oo-meter wavelength, with low-powered transmitting sets, could be estab ©Underwood & Underwood EDWARD J. NALLY Who was President of the Radio Corporation from the time it was founded until January of this year. He has now taken up the duties of his new post as Managing Director of International Relations for the Radio Corporation, with offices in Paris. Mr. Nally, who has been in communication business all his life, has been a prominent figure in the development of radio in this country, and because of his familiarity with conditions abroad is especially qualified to represent the growing interests in the foreign field lished. It seems remarkable how many of the American amateurs have been heard in Europe, stations from as far west even as the Pacific coast having been copied on the other side of the Atlantic. Altogether, between one hundred and two hundred stations were successful in spanning the ocean. From the latest reports available, European transmitters have not been so successful in crossing the ocean from east to west — just why is not yet apparent. We have always considered short waves as entirely unsuited for long distance communication. In fact it seems, from some of the accepted formulas of radio, as though a twohundred-meter wave would be so attenuated in its two thousand miles of travel that even an excellent receiving set would be unable to detect it. The accepted equations for wave propagation have been based on experimental data and of course the data may have been unreliable in the short-wave range. Marconi,