OVERSEAS RADIO EXTENSION 247 



circuit capacity across the Atlantic. In this connection, it should be 

 noted also that a new type of submarine telephone cable is under 

 development and is planned to be laid across the North Atlantic when 

 completed. While this cable will provide only one two-way circuit, 

 it is expected to be free from atmospheric disturbances and to fortify 

 greatly the telephone service between North America and Europe. 



The ship-shore telephone service which is being given on the North 

 Atlantic includes a land station connection with the land line network 

 in both the United States and in England and through these land 

 stations service is given to most of North America and Western 

 Europe. Four of the larger transatlantic vessels are equipped. The 

 service may be expected to include in time additional shore stations 

 and many other vessels. It is an example of a class of service for 

 which radio alone is available, that of extending telephone service to 

 moving craft at sea or in the air. 



Short-Wave Technique 



With the exception of the long-wave circuit across the North At- 

 lantic, all of the links indicated in Fig. 2 are of the short-wave type. 

 As to these different short-wave stations throughout the world, there 

 is, of course, considerable difference between them in the requirements 

 which are being met and the performance obtained. However, the 

 same fundamental principles are being followed in all of the countries 

 and the short-wave telephone technique may be said to be rather 

 remarkably alike throughout the world. Transmission is on the or- 

 dinary double side-band basis since the necessity for narrowing the 

 band is not of great importance in the present state of the art and the 

 difficulty of single side-band operated at high frequencies is very much 

 greater. In general, the transmitters are of the vacuum tube type 

 employing master oscillators which are stepped up in frequency and in 

 power for the final transmission ; directive antennas are employed for 

 both transmitting and receiving, and in the receiving apparatus use 

 is made of the double detection principle with its advantages in giving 

 stable operation with high amplification and high selectivity. 



In the case of the radiotelephone stations which connect with the 

 United States, the short-wave technique is further characterized by 

 the use of transmitting sets which are provided with a piezo-crystal 

 oscillator with temperature control for stabilizing the transmitting 

 frequency, and the use of interchangeable coils which permit the fre- 

 quency of the transmitter to be changed in keeping with the require- 

 ments for the different times of the day and year. The carrier output 

 of 15 kw. corresponds to a peak output of about 60 kw. The hnal 



