664 BELL SYSTEM TECHNICAL JOURNAL 



Under certain conditions, selective fading can be combatted through 

 antenna directivity, but it is not without its difficulties in attainment. 

 This is a direct attack on the multiple path source of the evil, eliminat- 

 ing a cause which makes fading selective with frequency. At times, 

 very marked fading reduction has been obtained by this means. 



Economics of Receiving Antennas 

 We have indicated briefly that the receiving antenna system has an 

 important bearing upon all the major factors which are limitations in 

 the present short-wave art. As long as these improvements can be ef- 

 fected in the receiving antenna system at a cost less than, for instance, 

 a corresponding increase in transmitter power, concentration on the 

 development of antenna design is well warranted. 



One often hears the question whether one type of directive antenna 

 is better than some other type. The answer usually depends on an 

 economic comparison rather than an electrical one. The sharpness of 

 directivity, the gain, etc., are determined by existing conditions. Nu- 

 merous types of antennas can be designed to meet these specifications, 

 therefore it is evident that the final selection is often based on over-all 

 costs. 



In Part 2 of this paper an antenna system will be discussed which 

 is the result of an attempt to produce an effective antenna at a cost 

 more favorable than the types we have been accustomed to use up to 

 the present time. 



PART 2. LONG WIRE ANTENNAS 



Types of Directive Antennas 



Directive methods, employing a finite number of spaced elements of 

 specific phase and amplitude relations, have been known for a long 

 time. Most of the more recent innovations, in this form of antenna, 

 have pertained to the methods whereby, in their practical applications, 

 these phases and amplitudes have been achieved. Considerable use 

 has been made to date of such antennas, but they are quite expensive in 

 their larger sizes and often their frequency range is very limited. As a 

 result of these frequency restrictions, the radiotelephone receiving sta- 

 tion at Netcong, N. J., employs ten ^ antennas, all differing in their 

 design frequency but having the same favored direction toward Eng- 

 land. 



For some time, it has been appreciated that if it were possible to 

 substitute a single directive antenna, having frequency characteristics 

 sufficiently broad as to cover the above mentioned ten channels, a very 



*A. A. Oswald, "Transoceanic telephone service — short wave equipment," Bell 

 Sys. Tech. Jour., April, 1930. 



