Transoceanic Radio Telephone Development * 



By RALPH BOWN 



TEN years have elapsed since the opening to public use on January 

 7, 1927, of the first long distance radio telephone circuit. This 

 form of intercontinental communication has now come into practical 

 business and social use. A network of radio circuits interconnects 

 nearly all the land wire telephone systems of the world. The art has 

 passed through the pioneering stage and is well into a period of growth. 

 The technical side of this development, which the present paper 

 reviews, divides naturally into four categories. The first covers those 

 factors which made possible the beginning of commercial radio tele- 

 phony.^ In the second are the things without which its rapid growth 

 and wide expansion could not have occurred. In the third, are a few 

 incidental but interesting or valuable technical features. The fourth 

 considers future improvements now in view. 



Essential Initial Developments 



Radio telephony presents difficulties in addition to those existing in 

 radio telegraphy because: (1) The communication is two-way, and the 

 radio system must be linked in with the wire telephone systems and 

 available to any telephone instrument; (2) The subscriber cannot 

 deliver himself of his message until the connection is actually estab- 

 lished, and on this account delay due to unfavorable transmission con- 

 ditions is less tolerable; (3) The grade of transmission required to 

 satisfy the average telephone user is higher than that tolerable in aural 

 tone telegraph reception by an experienced operator. 



These requirements emphasized the need for accurate and quantita- 

 tive knowledge of radio transmission performance as a basis for en- 

 gineering radio telephone systems. There was at the same time a 

 similar need for transmission data in the engineering of early radio 

 broadcast installations. The effort brought to bear on these twin prob- 

 lems resulted in the development of practical field methods of measuring 



* Digest of a paper presented at the Spring Convention of the Institute of Radio 

 Engineers, New York, May 10, 1937, and published in full in Proc. I. R. E., September, 

 1937. 



1 A description of the early years of radio telephone development preceding exten- 

 sive commercial application, together with a discussion of the origins of the whole 

 art, will be found in companion paper "The Origin and Development of Radio 

 Telephony," by Lloyd Espenschied, published in Proc. I. R. E., September, 1937. 



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