GAIN OF DIRECTIVE ANTENNAS 



75 



reflector was "floating." Although this arrangement most nearly 

 corresponds to the conditions assumed in the calculated curve, it is not 

 necessarily the most desirable adjustment to minimize noise arriving 

 from the rear. This diagram corresponds to the antennas designated 

 as 1-A, 2-A, and 3-A in Table I. These antennas consist effectively of 

 24 vertical couplets spaced horizontally at intervals of 14 wave-length. 

 In this table are given further data on the strength of signals 

 received on arrays, as compared with those received simultaneously on 

 a single element of similar structure and height above earth. The 

 different antennas represented involve varying conditions of wave- 



Fig. 11 — Calculated directional diagram. Twenty-four couplets spaced one-fourth 

 wave-length. Circles indicate experimental points. 



length, height above earth, adjacent terrain, and types of support. 

 These details are not believed to be of sufficient importance for dis- 

 cussion here. Two different array lengths are represented. The rela- 

 tive gains were substantially the same when observed on a local source 

 of waves and when the signal came from a distant station. The last 

 array represented in Table I was one used for transmitting. To effect 

 the test, equal power was transmitted alternately from the array and 

 from a single element while comparative measurements of electric 

 field strength were made at a distance of approximately 3500 miles. 

 The datum given is the mean of perhaps 100 observations extending 

 over a total of eight hours on three different days. Two errors are 



