Radio age research, manufacturing, communications, broadcasting, television (1941)

instruments guided planes safuly through bad weather. The electron tube and its circuits made radio telephony practicable. They simplified and made more effi- cient both the radiotelephone trans- mitter and the receiver. Out of this came radio broadcasting, which is the greatest system of mass com- munication ever developed by man. Continuous and intensive research and development have greatly im- proved receivers and have so low- ered their costs that they are within the reach of every pocketbook. Home receivers are operated from electric light circuits. Battery oper- ated receivers are now used only where electric light service is not available, or where portability is required as in pocket and "per- sonal" receivers. Modern receivers embody such advances as tubes operating on alternating current, circuits adapted for either alternat- ing or direct current operation, screen-grid tubes which reduce ra- diation, multi-function tubes such as pentodes, hum reduction devices, push-button tuning, magic-eye tun- ing indicators, and many others. All of these improvements in re- ceivers have contributed much to the phenomenal growth of the radio industry in the past quarter cen- tury. In 1941, 12,000,000 receivers were sold in this country and nearly 60,000,000 were then in use. There are appro.ximately 1,000 broadcasting stations in the United States. They have been connected into networks to provide both na- tional and world-wide broadcasting. International broadcasting has also been provided by means of trans- oceanic radio circuits which deliver foreign programs to our domestic networks and our domestic pro- grams to foreign networks. Direct international broadcasting is also conducted by means of short waves beamed to the recipient countries. Radio and electronic research have revolutionized and modernized sound recording and reproducing SCIENTIFIC DEVELOPMENT OF MANY DIF- FERENT TTiTES OF ELECTRON TUBES IS ONE OF THE MAJOR ACTIVITIES AT RCA LABORATORIES. HERE, AN EXPERIMENTAL TUBE IS BEING AIR-EXHAUSTED UNDER CAREFULLY CONTROLLED CONDITIONS. for both the home and the theatre. Modern phonograph records are re- corded electronically and are incom- parably superior to those previously recorded mechanically. The repro- ductions from these records by modern radio-jjhonographs are also effected electronically with greatly improved realism and beauty. p]Iectronically recorded and re- produced sound added to motion pictures has made the silent film completely obsolete and has remade and revitalized the motion picture industry. All motion picture stu- dios and theatres are equipped with sound recorders and reproducers which have been highly perfected by research and development. New Services Coming Continuous research has revealed the utility of the very short radio waves — those in the very-high, ultra-high and super-high frequen- cy ranges of the radio spectrum. It is making available for practical application vast unused portions of the radio frequency spectrum which have potentialities far greater than all radio services of the past. In general these high freciuencies have the characteristic of "short distance" or "line of sight" trans- mission. The range depends largely on the height of the transmitting and receiving antennas. They are also almost entirely free of atmos- pheric static, and they have greater inherent stability in the space cir- cuit than other frequencies. Being especially useful for relatively short range and local uses, they make many new services possible. The u.se of a given band of these fre- iiuencies can be repeated many times in this country without inter- ference between stations. They are eminently favorable for use in new services which require the trans- mission of very large amounts of information in very short intervals. In short, they open a new epoch in domestic and other short-range communication services. Among them are high frequency broadcasting, or "FM", which pro- vides substantially improved tonal (juality in broadcast reception and makes many more broadcasting sta- tions possible. FM broadcasting is destined to expand rapidly. Post- war broadcast receivers will gener- ally be provided with wave bands for receiving programs from the many FM stations which will dot the country. Research has produced many other important applications of frequency modulation in commu- nication and signaling services. Undoubtedly the most advanced contribution that research has made to the progress of radio during the past 25 years is electronic televi- sion. Its potential value and impor- tance to the public and to the radio industry are incalculable. It, too. makes use of the newly opened por- [14 RADIO AGE]