TRANSOCEANIC TELEPHONE SERVICE 



287 



a signal wave arriving from the horizontal directions parallel to the 

 plane of the array, the voltages in the vertical members are in succes- 

 sive quarter-phase relationships, no standing waves are produced, and 

 no current flows through the receiver. Because current nodes occur 

 at the center of each horizontal member, the loss by reradiation from 

 these members is negligible. This is an important feature which 

 contributed to the selection of this type of antenna for Netcong. 



The size of the antenna is determined largely by the manner in which 

 the signal waves arrive although costs cannot be wholly neglected. 

 The useful length is limited by the fact that random fading occurs at 

 distances as short as ten wave-lengths and it is doubtful if an antenna 

 this long would realize the computed improvement. The cost per 

 decibel gained is small for the initial steps, but it mounts very rapidly 

 as the length of antenna increases. The height also is limited by cost 



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CURRENT 

 NODE 



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VOLTAGE 

 ANTI-NODE 



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Fig. 10 — Diagram of simple directive receiving antenna. 



and by the necessity of allowing for considerable variation in the verti- 

 cal angle of arrival as discussed in a previous paragraph. 



The antennas at Netcong are six wave-lengths long and the lowest 

 conductors are about 10 ft. off of the ground. The gains over that of a 

 half wave vertical antenna are in the order of 16 db (power ratio of 40). 

 The average improvement in signal-to-noise ratio is of the same order. 

 There are certain null points toward the sides and rear for which the 

 ratio of directional discrimination is very large. 



The transmission lines are constructed of inner and outer copper 

 tubes respectively 3/16 in. outside diameter and 5/8 in. inside diameter 

 The tubes are held concentric by torroidal shaped insulators made of 

 Isolantite, a ceramic product similar to porcelain and well adapted for 

 high-frequency voltages. This same material is used for insulating 

 purposes throughout the transmitting and receiving antennas. Trans- 

 mission lines are supported a few inches above the ground and are 

 connected to earth at short intervals. The lines vary in length from 



