PROPAGATION STUDIES AT MKUOW AVI-; FUlXjlTKNCIKS 



101 



Fig. 10 — Simulated two-path transmission. 



would be rec[iiired. The discrepancy lies in the large ratio between the 

 phase \'elocity and group velocity in the wave guide used whereas in 

 free space this ratio is, of course, ec^ual to unity. In free space the amount 

 of delay rec^uired to go from a maximum to a minimum signal corresponds 

 to a change of path difference of only about one and one-half inches. 

 With only this slight shift rec^uired to change conditions from those shown 

 In' the first picture of Fig. 10 to those shown by the last, it is not at all 

 siu'prising that the received signal is very unstable during time of multi- 

 path transmission. 



Fig. 11 shows the effect of changing relative phases in 90° steps while 

 keeping the amplitudes equal to each other. It is seen that even with the 

 carriers in direct opposition cancellation is far from complete due to the 



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mummmmi"' " *' ■ " n ' ' j '— '^ 



rv 



~ =^HASE Q' API 

 Fig. 11 — Simulated two-path transmission. 



