Systems for Wide-Band Transmission Over 

 Coaxial Lines 



By L. ESPENSCHIED and M. E. STRIEBY 



In this paper systems are described whereby frequency band widths of 

 the order of 1000 kc. or more may be transmitted for long distances over 

 coaxial lines and utilized for purposes of multiplex telephony or television. 

 A coaxial line is a metal tube surrounding a central conductor and separated 

 from it by insulating supports. 



TT appears from recent development work that under some condi- 

 -*- tions it will be economically advantageous to make use of consider- 

 ably wider frequency ranges for telephone and telegraph transmission 

 than are now in use ^' ^ or than are covered in the recent paper on carrier 

 in cable. ^ Furthermore, the possibilities of television have come into 

 active consideration and it is realized that a band of the order of one 

 million cycles or more in width would be essential for television of 

 reasonably high definition if that art were to come into practical 

 use.^'^ 



This paper describes certain apparatus and structures which have 

 been developed to employ such wide frequency ranges. The future 

 commercial application of these systems will depend upon a great 

 many factors, including the demand for additional large groups of 

 communication facilities or of facilities for television. Their prac- 

 tical introduction is, therefore, not immediately contemplated and, in 

 any event, will necessarily be a very gradual process. 



Types of High-Frequency Circuits 



The existing types of wire circuits can be worked to frequencies of 

 tens of thousands of cycles, as is evidenced by the widespread applica- 

 tion of carrier systems to the open-wire telephone plant and by the 

 development of carrier systems for telephone cable circuits.^- ^ Fur- 

 ther development may lead to the operation of still higher frequencies 

 over the existing types of plant. However, for protection against 

 external interference these circuits rely upon balance, and as the 

 frequency band is widened, it becomes more and more difficult to 

 maintain a sufficiently high degree of balance. The balance require- 

 ments may be made less severe by using an individual shield around 



* For references, see end of paper. 



654 



* Published in Electrical Engineering, October, 1934. Scheduled for presentation 

 at Winter Convention of A. I. E. E., New York, N. Y., January, 1935. 



