The Bell System Technical Journal 



July, 1930 



Radio Telephone Service to Ships at Sea * 



By WILLIAM WILSON and LLOYD ESPENSCHIED 



The ])aper discusses the American end of the ship-to-shore radio telephone 

 system and the connecting equipment on board the Leviathan. The most 

 suitable wavelengths for this service are in the short-wave range, but the use 

 of these wavelengths complicates the problem, since different wavelengths 

 are required according to the distance of the ship from shore, the time of day, 

 season of year, etc. The problem on shipboard is further complicated by the 

 fact that the transmitting and receiving systems are necessarily near together 

 and special precautions are necessary to take care of interference from the 

 radio telephone transmitter and the radio telegraphic services. In addition 

 to interference from these sources, there is a background of interference in the 

 ships' electrical equipment, all of which necessitates a much more powerful 

 land station than is necessary on shipboard. 



In the present system, the shore transmitter has a power rating of 15 kw. 

 and the ship transmitter of 500 watts. The shore transmitting station is lo- 

 cated at Ocean Gate, N. J., and the receiving station at Forked River, N. J. 

 At both of these locations, directive antennas are employed which cover the 

 ships' lanes. The stations are connected by wire to the Long Lines toll office 

 in New York, and the o\'er-all control of the circuit is carried out from this 

 ])oint. Both the ship and shore transmitters are crystal controlled. The 

 ship's receiver is highly selective and is of the double-detection type. Com- 

 munication between the ship and the shore is carried out by use of a pair of 

 frequencies, one for transmission in each of the two directions, separated 

 from each other by about three per cent. Ships of a number of nations 

 are being equipped with wireless telephone apparatus and as the service 

 expands, it will undoubtedly be necessary to formulate a plan in which inter- 

 national agreement is reached on the allocations of frequencies for ship-to- 

 shore telephony and telegraphy, in order that undue interference within the 

 ser\'ices themselves or between the two services shall not ensue. 



IN view of the developments which have recently taken place in the 

 field of ship-to-shore radio telephony, it would appear appropriate 

 to review the state of the science and to discuss the problems which 

 have arisen, the facilities which have been installed, and the general 

 results obtained. 



The ship-to-shore radio telephone system, which is here described, 

 was opened for public service between the Leviathan and the United 

 States on December 8, 1929. This was the first extension of the public 

 telephone service to a ship at sea and enabled calls to be made between 

 the vessel and any Bell System subscriber. The system as set up is 

 intended primarily for giving telephone service to the larger passenger- 

 carrying vessels as an extension to the wire network, and should be 

 distinguished from the more simple uses which have been made of radio 



* Presented at the North Eastern District Meeting of the A. I. E. E., Springfield, 

 Mass., May 1930. 



407 

 27 



