TRANSOCEANIC TELEPHONE SERVICE 285 



stage require tuning when the frequency is changed. Hence to tune 

 the receiver on any one of the assigned frequencies the attendant 

 merely moves the dials of the second stage to predetermined settings, 

 switches the grid circuit to a first stage which is already tuned and 

 connected with the proper antenna and he adjusts the beating oscillator 

 to obtain an intermediate frequency of 400 kilocycles. Screened grid 

 tubes are used for the first two stages of amplification. A key shelf is 

 provided with telephone and telegraph facilities. The power plant 

 consists of standard 24-volt and 130 batteries, rectifier charging units 

 and automatic regulators. 



Receiving Antennas 



In discussing antennas for directional sending it was mentioned 

 that an identical antenna could be used for receiving purposes, but 

 since the requirements in the two cases are not the same, quite dif- 

 ferent structures have been developed, although the methods of ob- 

 taining directivity are alike. In the sending case the reduction of 

 random radiation ceases to be profitable when the increment thus added 

 to the energy, which is radiated in the direction of the distant receiving 

 station, is a relatively small part of the total. In the receiving case, 

 although the response to the wanted signal may not be increased 

 appreciably by further improvement in the directive pattern, the 

 reduction in noise and interference from random directions justifies 

 additional improvement. Expressed another way, the objective in 

 the transmitting case is a high gain compared to a nondirectional 

 antenna, whereas in the receiving case the objectives are, first, a 

 high average signal-to-noise ratio and, second, a gain sufficient to 

 override the noise inherent to the receiving set. Satisfying the first 

 accomplishes the second. 



Improvement of the average directional discrimination means a 

 nearer approach to ideal conditions. Whereas steel towers, section- 

 alized cables, guys and the like, when properly located relative to the 

 conductors of a sending antenna, do not cause any appreciable power 

 loss, their presence near the receiving antenna may prevent the 

 realization of the extreme directive properties which are wanted. 

 Moreover, there is need for much greater rigidity in the positions of the 

 conductors. For this reason the antennas at Netcong are supported 

 on wooden frames constructed like large crates. 



Due to the variable conditions surrounding the propagation of short 

 waves in space, the vertical angle of arrival of the signal wave at the 

 receiving station frequently changes considerably throughout a twenty- 

 four hour period and is not always the same from day to day. In 

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