90 THE IJELL SYSTEM TECHNIf'AL JOURNAL, JANITARY 1952 



the full time assistance of R. A. Desmond and the part time assistance 

 of L. K. Lowry and S. E. Reed. All the work was done under the guidance 

 of Dr. H. T. Friis. 



APPENDIX 



This appencUx is included to illustrate some of the characteristics of 

 the propagation as shown by the recordings of 4195-mc signal levels. 

 Fig. 11 is a reproduction of some typical records obtained during severe 

 fading periods. Fig. 11(a) is an example of transmission during the sub- 

 standard conditions illustrated by the ray diagram of Fig. 3(d). Fig. 

 11(b) is typical of multiple-path type fading in which the signal com- 

 ponents arrive from elevated angles as shown in Fig. 3(a), while Fig. 1 1(c) 

 was recorded on a night when, for a time, there were abnormal reflections 

 from the water of Raritan Bay on the Murray Hill path, see Figs. 3(c), 

 G(f) and 7(e). The records of Fig. 11(d) show how the outputs of two 

 similar antennas, spaced vertically about 30 feet, differ in regard to the 

 deep fades of short duration. 



The chart of Fig. 12 shows how the fading varies with the time of year. 

 On this chart, the vertical lines represent the extremes in signal level 

 observed during the twenty four hour period from noon to noon. The 

 large signal variations are concentrated mainly in the summer months. 



The time distribution of the signal levels recorded on the Miu'ray 

 Hill-Crawford Hill path are shown in Fig. 13. Each of the cur\'es is for 

 a four-month period: the period of least fading, December, January, 

 February and March; the period of most fading, June, July, August 

 and September; and the in-between period consisting of April, May, 

 October and November. Data obtained in the years 1947, 1948, 1949 and 

 1950 are included. Fig. 14 shows similar data for the Southard Hill- 

 Crawford Hill path. The hump in the time distribution cur\'e for the 

 months of April, May, October and November is due to substandard 

 conditions, illustrated by the ray diagram of Fig. 3(d) and the typical 

 record of Fig. 11(a), which affected transmission on this path during 

 several nights in October, particularly in the years 1947 and 1950. When 

 it occurred, this type of ti'ansmission usually persisted for a period of 

 several hours. 



