Developments in Short-Wave Directive Antennas * 



By E. BRUCE 



Part 1 of this paper discusses the relative importance of the factors which 

 limit the intelligibility of short-wave radio telephone communication. The 

 more important of these factors are inherent set noise, external noise (static, 

 etc.), and signal fading. The possibility of counteracting these limitations 

 through antenna directivity is indicated. 



Part 2 describes an antenna system which maintains a desirable degree of 

 directivity throughout a broad continuous range of frequencies. The cost of 

 this antenna is more favorable than that of many types of fixed frequency 

 antennas of equal effectiveness. 



BEFORE discussing specific antenna systems, it appears desirable 

 to review the general problems of short-wave communication and 

 to observe wherein antenna design can assist in overcoming existing 

 circuit limitations. Accordingly, this paper is divided into two parts; 

 the first will outline the requirements in the problem, and the second 

 will be a description of an antenna system which has proved effective, 

 despite its low cost of construction. 



The writer's experience with antenna systems has been largely con- 

 fined to the standpoint of reception, therefore, the following discussion 

 will be largely on this basis. It will be apparent to the reader, how- 

 ever, that many of the features are likewise applicable to transmitting 

 antenna installations. 



PART 1. THE SHORT-WAVE PROBLEM 

 Radiotelephone Circuit Limitations 



An analysis of the factors limiting the excellence of the output 

 quality of a receiver governs the design of the entire radio circuit and 

 associated equipment. Assuming well-designed apparatus through- 

 out, we still encounter difficulties, especially at times of low signal 

 strength, the more important of which are enumerated as follows: 



(a) Inherent receiver noise. 



(b) External noise (static, man-made noises, etc.). 



(c) Signal fading. 



The design of the receiving antenna system has an important bearing 

 upon all three of these factors, brief explanations of which are given 

 below. 



* Presented before Sixth Annual Convention of the Inst, of Radio Engineers, 

 June 6, 1931, Chicago, Illinois. Published in Proc. I. R. E., August, 1931. 



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