Weighing Theories With Fact

Radio Record, Volume III, Issue 48, 13 June 1930, Page 7

Weighing Theories With Fact

Z2YA’s ‘Transmission N view of the correspondence lately appearing in our columns relative to distortion fading from 2YA and the theories advanced on the subject: by various correspondents, the following extract from an article by G M. Jansky, associate professor, University of Minnesota, U.S.A., may prove of interest :- "Of the factors which limit radio reception, there is one, dependent on. the characteristics of the transmission medium, concerning which as yet far too little is known. Statistical data have repeatedly indicated that at night there is a zone which lies approximately between 50 and 200 miles of a broadcasting station in which reception is not as good as at points farther distant. Sometimes the zone of poor reception extends closer than 50 miles, and sometimes it extends further than 200 miles, depending on wea=ther conditions, frequency and _ other factors. Under some conditions such programmes as are received, are so distorted as to be rendered useless. Increasing the power at the transmitter does not seem to overcome the difficulty." ... Such evidence as has been collected seems to connect the condition described above with fading. "Numerous observations which the author (C. M. Jansky) has made upon stations operating throughout the broadcast spectrum lead to the conclu--sion that while the rapidity of fluctuation of intensity in the broadcast band at a’particular time varies to some extent with the frequency in use at the broadcasting station, it varies to a greater extent as the distance beween the transmitter and receiving location is varied. The shorter the distance the shorter the average period. This together with the effect of the rapidity of variations of intensity upon the sensitivity of the human ear to such variations, the author believes to be the main reason for the existence of the zone of poor reception." The foregoing extract by an authority on broadcast transmissions should effectively answer those listeners who maintain that the distortion from 2YA. is directly controllable by the station. It is a strange thing that most complainants comment on the fact that good reception is invariably obtained during the day and distortion always occurs at night, yet these persons never seem to stop for a minute to consider that the night time is the real cause of the-trouble. The broadcaster gets the blame for conditions which are beyond his control. It will be seen from CG. M. Jansky’s remarks that we in New Zealand are not the only ones who suffer from "night-time distortion." They get it in U.S.A. and badly, too, at times. Obviously nothing is done at a station to cause transmission at nighttimé to be different from day-time transmission. Different results may be attributed rightly to an outside factor.