Man's physical universe

xanabras

536 MAGNETISM AND ELECTRICITY

frequency-modulation system, the broadcasting station and the receiver

are tuned to waves of a certain amplitude so that other waves

of the same frequency will not produce any interference unless they

are of the same amplitude.

Frequency modulation employs ultrashort radio waves, and therefore

broadcasting beyond the horizon is not possible because the

ultrashort radio waves are not reflected back to the earth by the ionized

layer of gases known as the Heaviside layer in the upper atmosphere

as are the longer radio waves. This limitation of frequency-modulation

broadcasting would really be an advantage because there would not

be any interference from distant stations. The range of frequencymodulation

broadcasting stations is constant both day and night.

If two stations using frequency modulation were broadcasting on

the same frequency, only the more powerful station would be heard.

Frequency modulation makes possible many more broadcasting

stations and makes operation costs of a station much lower because

less power is required.

Facsimile Broadcasting Has Many Possibilities for Important Applications

in Modem Life.

Tabloid newspapers are already being broadcast by a number of

radio stations. These newspapers are received and printed by instruments

similar to those that transmit photographs by wireless. They

are capable of printing five 83^^ X 11 pages an hour. Plans were under

way in 1940 to print newspapers on ocean liners by facsimile from

shore transmitters. Facsimile broadcasting is four times as fast as

teletype. It is now being installed in police cars to transmit photographs

of wanted criminals, fingerprints, and messages which are thus

available in a permanent form.

One might well imagine a vast system of facsimile broadcasting

that would take the place of our mail system for many short communications

where time is important, thus filling the gap between telegraph

and mail facilities.

The Radio Has Revolutionized Communication.

The dramatic evolution of the radio within one decade from a mysterious

plaything to the almost universally accepted instrument of

entertainment and mass communication has few counterparts in

social history. Commercial broadcasting was begun only in 1920, and

yet twelve years later it was estimated that over sixteen million

receiving sets were in use. The radio and the other agencies of com-

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