War Against Fading Radios

Manawatu Times, Volume 61, Issue 8, 10 January 1936, Page 10

War Against Fading Radios

SOLVING OLD. PROBLEM ' NEW YORK, Nov. 29. Evidence of the now progress in the conquest of radio fading, one of the principal obstacles in effective shortwave communication, was presented yesterday in the current issue of "Science,” by Dr. Harry Rowe Mimno, of Cruft Laboratory, Harvard University.

Supporting the evidence presented recently by Dr. J. H. Dellinger, chief of the radio section of the Bureau or Standards in Washington—that fading periods arc predictable on the basis of the rotation periods of the sun and that sharp fading cycles of .15 minutest' duration occur at intervals of two periods of the sun’s rotation (51 days) —Dr. Mimno went a step further by presenting records tending to show that tho fading cycle noted by Dr. Dellinger occurs, regularly every sun rotation of 27 days.

Fading, because of its many contributory causes, has long presented a problem to radio men. Only in the last few years have various phases of the phenomenon become more and more predictable through exhaustive study of the sun, the earth’s magnetic conditions and tho effect on radio channels. Magnetic observations are notv made ail over the earth to forecast the stato of the earth’s magnetism, so that transoceanic radio channels can be efficiently operated. But apparently many phases of the cosmic puzzle remain to bo solved. At present, fading is avoided when possible, by shifting to channels less affected by the disturbance. Dr. Dellinger recently gathered data with which he accurately predicted the recurrence of a 15-minute period of strong fading that came on October 24. He deduced this from the fact that other disturbances appeared on March 20, May 12, July 6, and August dO. The peak of the fading occurs in daylight on the illuminated side of the globe. Dr. Mimno, in "Science,” asserts that continuous automatic records of shortwavo reception are indispensable to the exhaustive study of the phenomenon. Dr. Dellinger’s theories, ue said, are in general supported by records made in 1933, of radio echoes reflected from the ionosphere. Ho says it is unfortunate that no continuous automatic records could be obtained during the 1935 period, covered by Dr. Dclinger’s report.

Government Criticised. "During tho last 1G months the Federal Communications Commission has repeatedly postponed the rephrasing of certain obsolete regulations limiting tho use of automatic apparatus, which effectively block the continuation of fundamental research,” Dr. Mimno writes. “The commission freely admits that the ancient clause in the regulations has no engineering justification whatever when extended to our new experiments, and has therefore repeatedly promised remedial action. Already an important part of the sun-spot cycle has been completely lost by governmental decree.

“At the peak of the disturbance, transmission conditions are 'changing so rapidly that it is difficult to imagine that any long-distance short-wave communication could bo successful, though the interruptions might be so brie' that they would escape observation. “Until the apparent double period of 54 days, indicated by Dr. Dellinger’s 1935 communication records, is further substantiated, we prefer to consider that is is somewhat fortuitous and that brief intervening disturbances at the 27-day points may have escaped observation. In any case, it is probable that the 1935 ‘storm’ has lasted about as long as it is likely to endure, and that further extensions of the sequence of. dates need not be expected.”