322 BELL SYSTEM TECHNICAL JOURNAL 



combining in arrays because several of either type of antenna can be 

 made identical with one another. Wave-antennas combined in an 

 array, however, give satisfactory results. 



Although each of these factors governing the choice of the receiving 

 antenna system is important, their relative importance is indicated 

 by the order in which they have been presented. In view of the low 

 noise reception factor of the wave-antenna, its lack of frequency 

 discrimination, and its inherent stability, the wave-antenna was 

 selected for the fundamental type of antenna to be used at the receiving 

 station at Houlton. 



The Wave- Antenna 



Among the types of antennas which may be considered for use in 

 long-wave radio communication, the wave-antenna " possesses several 

 characteristics which single it out as being unique. The most impor- 

 tant of these are : 



1. The length of a wave-antenna is directly comparable to and of the same order 

 of magnitude as the wave-length of the signals for which it is designed. 



2. Considering the straight horizontal wire comprising the wave-antenna as a 

 grounded transmission line, a termination, equal to the characteristic impedance, 

 is applied to each end of that line. The wave-antenna then becomes an essentially 

 aperiodic antenna. 



3. The major response of a properly designed wave-antenna is to the horizontal 

 component of the impressed electric field. The propagated electric wave must 

 therefore have an electric component parallel to the surface over which the wave- 

 antenna is constructed. 



4. On the basis of the preceding consideration, the design of a wave-antenna 

 definitely excludes elevation of the antenna above ground to any extent greater (a) 

 than is physically necessary to provide safe clearance and (b) than that height where 

 the loss in the antenna considered as a transmission line reaches a nominal value. 

 Practically, the wave-antenna is constructed as a high-grade telephone line, on 30- 

 foot poles. 



It is evident that the major electrical characteristics which dis- 

 tinguish the wave-antenna are intimately connected with the character 

 of the surface over which the antenna is built, and with the details of 

 construction of the wave-antenna. The performance of a wave- 

 antenna at any specified location then can only be determined by 

 constructing such an antenna and measuring its constants. The 

 measurements made in determining the characteristics of any par- 

 ticular wave-antenna are outlined in the following paragraphs. 



1. Ground-Connection Impedance. It is shown in Appendix 1 that 

 the wave-antenna is considered to be a smooth line with uniformly 

 distributed constants. This assumption is met to a sufficient degree 

 in practice, but, unfortunately, it is impossible to connect to the four 

 terminals of the practical line, since the connections to the ground 

 side of the line must be made by burying wires in the earth rather than 



