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BELL SYSTEM TECHNICAL JOURNAL 



element was used for the other four receivers, their signals being 

 recorded successively by a commutating device. Incidentally the 

 interaction betw^een these receivers was checked by observing the 

 output of any one, while changes were made in the tuning of the 

 others. The antenna was, however, so nearly aperiodic that no 

 recognizable distortion or reradiation phenomena could be detected. 

 Fig. 35 illustrates compactly variations recorded by the oscillo- 

 graph records (of which Fig. 34 is a sample), for a representative 

 period of about five minutes. Even within the dimensions of 1/16 



Time 



Fig. 35 — Curves showing single-frequency fading on spaced receivers, condensed from 



long record 



wave length there appears to exist transient field strength gradients 

 in the direction of transmission. This is shown by a change in rela- 

 tive values, in the upper set of curves which represents field strength 

 at points 1/16-wave length apart in the direction of transmission. 

 The deviation is particularly noticeable in the relation between 

 values for the local receiver and the "West receiver" which is in the 

 direction of the transmitting station. 



The lower set of curves, representing similar values across the line 

 of transmission are much more nearly parallel. From the data so far 

 obtained for the Riverhead testing site, it seems that transient night- 

 time field strength gradients are more generally evident in the direc- 



