210 



BELL SYSTEM TECHNICAL JOURNAL 



ANGLE ABOVE HORIZONTAL OF RHOMBIC MAXIMUM 

 FOR 21 METERS IN DEGREES 

 7 8 9 10 II 12 13 14 



-18 



-20 



-22 



68 69 70 71 72 73 74 75 76 77 78 79 80 



HALF OF SIDE INTERIOR-ANGLE OF RHOMBUS IN DEGREES ($) 



Fig. 17 — Horizontal rhombic antenna output changes with steering as shown by 

 automatic field strength recorders. Corrections for changes in signal level with 

 time, as obtained from a half-wave vertical antenna, have been applied. 



of about 68 degrees would place a null at this angle. While the range of 

 steering of the rhombic antenna in use did not permit an adjustment to 

 less than about sixty-nine degrees, the trend of the curve leaves little 

 doubt as to the correctness of our null point calculation. 



As might have been expected, the previously described fading 

 counters for studying general carrier fading showed that reductions 

 were usually obtained at the directivity positions which also gave the 

 least selective fading. This type of apparatus is incapable of determin- 

 ing whether general fading or selective fading conditions are affecting 

 the amplitude of the fixed carrier frequency. 



Conclusion 

 It is believed that the results, discussed in this paper, demonstrate 

 that sharp angular discrimination is a basically sound method of com- 

 bating selective fading. 



