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"SPACE RADIO" AND "LINE RADIO"
By dr. LOUIS COHEN
IN SPEAKING of radio we generally think "space radio," the usual method of intelligence transmission by means of electromagnetic waves radiating in all directions from a central source, an antenna. In contradistinction to this form of radio, another form, "line radio," electromagnetic waves guided by wires, the invention of General Squier, is rapidly coming into wide use. These two forms of radio have many things in common yet fill different public needs in the matter of communication. In both methods the engineering practices and methods are identical; high frequency currents are employed, and the same instrumentalities for generating electromagnetic waves, tuning, modulation, detection and amplification are utilized. The methods, however, for transmitting the energy from the transmitter to the receiver are different. 1 n one case the energy is radiated in all directions, broadcasted, and everybody who so desires is at liberty to receive the signals, while in the other case the
DR. LOUIS COHEN Consulting engineer, Signal Corps, U. Si A,
energy is confined to a limited region and can be received only at one or more definite points.
At this time of a growing popular interest in "space radio" and increasing demands for the broadcasting of news and information, requiring a greater and greater number of wave channels to carry the broadcasting traffic, it may be well to consider the great possibilities of "line radio" to take care of all individual communications, leaving all the available wave channels in "space radio" for communication between mobile stations, such as ships and airplanes, places inaccessible to wire lines, and broadcasting. By the use of "line radio" the existing telephone and telegraph lines may be loaded up by multiplying the number of messages carried on any single line so as to take care of all possible public requirements for personal communication, and in a very economical manner at that.
It must be remembered that the number of wave channels available for "space radio" are limited. Every communication monopolizes, for the time being, a definite width of wave band and should, therefore, be employed only for such services as will be for the greatest possible public usefulness, or 'for such other services as cannot be accomplished by the old methods of line telegraphy and telephony or "line radio." Broadcasting is a service that can be accomplished only by "space radio" and the use of "space radio" should be limited as much as possible to that service. On the other hand, in "line radio" the number of circuit channels can be increased almost indefinitely and always kept up to capacity to meet all public needs for individual communication, personal or business. "Space radio" and "line radio" are two aspects of the same art, both utilizing the same methods and instrumentalities; the developments and improvements in one are generally applicable to the other, but they supplement each other in the matter of use. In considering any new regulations in the matter of wave distribution service, etc., it would be well to keep in mind the possibilities of "line radio" for individual communication, reserving "space radio," to a very large extent at least, for broadcasting.