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Show EUmiiAUueutrMCtKaMcaRKnwjsmiRBnMk ' i s b e: : ! g New Explanation of Fading Bogies Relation Between Earth Currents Cur-rents and Reception Seen by Expert. A new explanation with reference to fading is advanced by C. Wartield Reefer, noted radio experimenter of Baltimore. lie believes "man-made static" is a big factor. "It certainly looks as though there Is a relation between the earth currents cur-rents and reception," he states. "One phase of radio transmission and reception that is being intensively investigated by radio engineers is facing," fac-ing," Mr. Keefer continues. "As a rule the longer the wavelength wave-length the less the fading effect, although al-though there are cases where the fading fad-ing on the shorter waves is very small. Most fading is relatively slow; that is! j the time interval between maximum and minimum sigual strength may be two minutes or more. Generally speaking, speak-ing, fading is more prevalent at uight. Observations made at the same location loca-tion on frequencies very close together show that they do not fade simultaneously. simultane-ously. The type may be identical, but there is no relation between the maximum max-imum and minimum values, Mr. Keefer says. "In Baltimore everyone is familiar with the behavior of W.IZ, WG V and KDKA. The first of these three stations sta-tions presents a very Interesting study As a general rule WJZ Is affected with the most troublesome type of fading. "Two well-defined types of fading are recognized synchronous and asynchronous. asyn-chronous. The first, which is uniform, may be compensated somewhat by control con-trol adjustments at the receiving set. Asynchronous fading is the type where the side bands and the carrier wave do not fade together. When the carrier wave is reduced to the value of the side bands or lower, the distortion that results is marked frequently to such a degree that speech may be unintelligible. un-intelligible. This condition has been frequently observed with WG Y and KDKA, which seem to fade uniformly in this section. "One theory recently advanced is based upon the fluctuations in the di- rectional flow and intensity of earth ( currents. Vj "It is true that natural earth currents cur-rents are Highly related to the magnetic mag-netic storms and also rather definitely correspond to soiar activity as indicated indi-cated by sun spots. Continuous records have been made of natural earth currents cur-rents at several magnetic observatories, observa-tories, including one ai Ebro, Spain, and Wathcroo, western Australia, he reports. "In or near civilization most of the earth currents notes are not natural, but are caused by leakage from various vari-ous electric services, particularly from trolley liues. For these currents the rapid changes in intensity and often direction are generally related to the changing amount and position of the currents drawn by the trolley cars. "Electricity, through electrolytic action, ac-tion, will decompose iron at the rale of twenty-one pounds of iron per ampere am-pere per year. It is possible, therefore, that such currents could, through electrolytic elec-trolytic action, change the earth's resistance re-sistance in certain areas, and so more or less permanently change reception conditions. Undoubtedly, the transmission transmis-sion of radio waves is very greatly affected af-fected by human activities, such as is evidenced by transmission over a city of steel skyscrapers. "Investigation of this theory is now j being made in Baltimore." |