Radio broadcast .. (1922-30)

Phoning Home from Mid-Ocean How the Problem of Simultaneous Radiophone Transmission and Reception Was Solved Aboard the S. S. America, and Reliable Communication Routed Direct from a Land Radio Station to Telephone Subscribers. An Indication of a Home-to-Stateroom Telephone Service that May Soon Be Generally Applied By G. HAROLD PORTER General Superintendent, Marine Dept., Radio Corporation of America WHEN the steamship America sailed from New York on April i5th, 1922, destined for her usual brief visit to European ports, little did the public realize the significance attached to this particular trip. To a group of eminent engineers this was more important than the maiden trip of the big vessel, for her radio cabin held certain secrets that were close to their hearts. The combined efforts of these men, representing the Radio Corporation of America, the General Electric Company, the American Telephone and Telegraph Company, and the Western Electric Company, have been focused for some time on the problem of establishing a shipboard radio telephone exchange. This, they intended, should provide the interchange of intelligence at sea, on a limited scale, with the same facility with which present land telephones handle the communications of our nation. The realization of this plan in the form of a practical working radio service between ships on the high seas and land stations would provide a communication system differing radically from that which is now in universal use. Manifold problems would find their solution in the successful conclusion of this venture which, since the very birth of radio, has been the subject of untiring study. In the wake of progress, it is natural that we should find methods of the past superseded by the ever increasing products of advanced research. Radio is no exception. The principal undesirable feature of present-day radio systems, which the engineers working on the America s installation sought to supplant, was the switch employed for changing from the sending to the receiving conditions and vice I'crsa. It is almost universal practice in radio tele phone communication to-day to use a " sendreceive" switch to connect the antenna to either the transmitting outfit or the receiving set, depending on which one is to be used. At the end of each transmitted message, the operator always makes a conventional signal indicating to the receiving operator that each must throw the send-receive switch to its opposite position. Of course, the interchange of thought would be far more rapid with a system permitting either participant of the conversation to interrupt the other instantaneously. This would avoid the loss of continuity in a conversation and the calls for "repeats" now frequently encountered. Undoubtedly the greatest need for this duplex or two-way radio telephony is the installation of it in such a way that the public may avail themselves of it. Inexperienced persons could not be expected to operate a send-receive switch at the proper moment, and, accordingly, some substitute had to be found. To the novice, the development of the wireless telephone so that it could be used as, and in connection with, the ordinary wire telephone, presents no particular difficulties; but to the trained engineer, the details and obstacles encountered are endless. Supported by the resources of some of the country's foremost research laboratories, months of painstaking efforts and measurements of the greatest precision were required before such a system was ready for trial. THE engineers who worked on this system were concerned with carrying on two operations at the same time: the first, detecting the incoming antenna current and transforming it into speech, and the second, permitting the voice currents aboard the America to advance from the antenna into space, as waves, reaching