Coaxial Cable System for Television Transmission* 



By M. E. STRIEBY 



'TpHE reports which have been made on the progress in television 

 -*■ development increase the expectation that the broadcasting of 

 visual programs will soon be realized. In anticipation of that result, 

 the Bell Laboratories has been engaged for some time in the develop- 

 ment of wire line circuits for transmitting television signals between 

 studios and broadcasting transmitters, or between cities, as may some 

 day be required if television follows in the footsteps of sound program 

 broadcasting. 



The wide frequency bands required for television and the dearth 

 of available frequencies appear to force the broadcasting of television 

 signals into the ultra-high frequency range. At these high frequencies, 

 the coverage which can be obtained from a broadcasting station is 

 very limited as compared to that obtainable in the sound broadcasting 

 frequency range. Hence, if television programs are to reach large 

 sections of the country simultaneously, the provision of interconnec- 

 tions between large numbers of television broadcasting transmitters will 

 become even more important than it is today for sound broadcasting. 



Coaxial cables have received much publicity as transmission lines 

 for television. The original conception and use of the coaxial form 

 of cable was first as a low frequency submarine conductor and later 

 as a lead-in for radio antennas. The idea of a coaxial cable or other 

 medium for the transmission of very broad frequency bands orig- 

 inated in the course of telephone development in America.^ The first 

 lengths of such cable for broad-band transmission were made here and 

 its first use for the transmission of a large number of simultaneous 

 telephone conversations was between New York and Philadelphia.^ 

 In this country the important reason for developing coaxial cable 

 systems was, and still is, that they appear to oflfer material economies 

 in the provision of large groups of long distance telephone facilities. 

 Television has been secondary. 



Recently experiments have been made on the transmission of 

 television signals over the coaxial cable between New York and 

 Philadelphia. This cable contains two coaxial conductor units within 



* Presented at A. I. E. E. Winter Convention, New York City, Jan. 27, 1938. 

 Published in June 1938 issue of Elec. Engg. 



438 



