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BEJ.L SYSTEM TECHNICAL JOURNAL 



width correspondin.i; to twice the ami^htude of the signal, as both the 

 positive and negative half-cycles are recorded. It will be observed 

 that the outer limits of the band corresponding to the peaks of the 

 sine wave are darker than the center portion of the record. This is 

 due to the fact that the rate of change of the movement of the light 



Time 



6 



Fig. 



-Single-frequency fading record. Made at Stamford, Conn., May 16, 1924, 

 1:54 a.m. Timing marks, on strip 6, 2.5 seconds apart 



Fig. 9 — Wave form of beat note signal for single-frequency test. Center trace signal 

 from vertical antenna, upper and lower traces signals from loop antenna receivers 



spot on the record is a minimum at the peak of the signal; hence, a 

 greater quantity of light affects these portions of the record. This 

 shading effect was very useful in the w'ay it brought out changes in 

 the distortion of the received signal. This is discussed fully in another 

 section of the paper. The fuzzy irregular outline on portions of the 

 records is caused by static and radio noise. The timing marks on the 

 record allow a measurement of the time interval between points of 

 minimum signal. Fig. 9 is a sample oscillogram of the wave shape 

 of a beat note signal recorded by the method described above. 



Marked changes in the fading cycle or time interval between points 

 of minimum signal may occur within a period of a few minutes, and 



