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situated on the line from (OX, \r) to {\\, \T) have a similar property: 

 each has a relati\-e maximum in a single direction, with zero in the 

 opposite direction. The diagrams on the line from (OX, 07') to (|X, 

 \T) have a maximum along the horizontal axis to the left, with an 

 amplitude to the right decreasing from unity at i)T to zero at \T, 

 and then increasing to unity at \T. 



The number of lobes tends to increase as the separation is in- 

 creased, as shown by (a) of Fig. 2. A zigzag starting at (OX, \T) 



Z\ Z^\ 



Fig. 2 — (a) Number of null directions (which is also the number of lobes) for two 

 antennae, (b) Number of unit directions (directions of absolute maximum ampli- 

 tude) for any number of antennae, in terms of separation and phase difference 

 between adjacent antennae 



and made up of lines sloping up and down at an angle of 45° divides 

 the rectangular arrangement of diagrams into sections with 0, 2, 4, 

 6, . . . null directions in each diagram, respectively. On these lines 

 the number of null directions is 1, 3, 5, 7, ... , respectively, with the 

 intermediate numbers at the junction points. The number of lobes 

 is, of course, equal to the number of null directions. 



Part (b) of Fig. 2 is a diagram specifying the number of unit direc- 

 tions (directions of absolute maximum amplitude) in terms of the 

 separation and the phase difference between adjacent antennae, and 

 it holds regardless of the number of antennae, that is, the number 

 and position of the main lobes are not changed by increasing the 

 number of antennae, provided the same separation and phase differ- 

 ence are preserved between adjacent antennae. 



It is interesting to obser\e the variation in the diagrams along any 

 line in this rectangular arrangement of Fig. 1, whether horizontal. 



