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

Record Details:

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contact with RCA service eiiKin- eers, as well as engineers in the field, led us to design the "ground- plane" antenna used in police radio. In high-frequency broadcasting, it is usually desirable to radiate signals to all points of the compass. This prevents robbing one section in order to concentrate the signal in other areas. A simple antenna radiates a good bit of energy at angles above the horizontal plane. Therefore, a logical step toward in- creasing signal strength in the hor- izontal plane seemed to be to take the wasted energy from the higher angles and redirect it to the hori- zon. The RCA Laboratories devel- opment group produced an antenna for this specific purpose. This antenna resembles a turn- stile and, indeed, that is the name by which it now is known. The first models of it used open wire feeders and exposed insulators. It was necessary to adjust or "match" the transmission lines leading from the transmitter to the antenna after installation. The RCA antenna group contin- ued work on "Turnstile" antenna development over a period of sev- eral years, so that a few years ago, when FM broadcasting became pop- ular, a design was ready which could be installed completely, ready to operate without field adjust- ments. Advantages of the turnstile an- tenna are apparent as we consider the problem of transmitting tele- vision. For in telecasting, the an- tenna must match the transmission line from the transmitter over a wide band of frequencies. In one version of the turnstile, the means of obtaining the circular radiation pattern automatically provides the broad-band feature. And when pro- vided with a rather simple network, it may be operated as an ordinary antenna for both sound and picture transmitter without the use of com- plicated filters. Increasing use of very high fre- quencies in radio brings the prob- lems of antennas to the foreground and adds to their number. The tough job for engineers who are doing research on antenna systems and associated circuits is that of deciding which one of the problems to attack first. EMERGENCY WALKIE-TALKIES Police. Firemen and Doctors Maij be Equipped u)it(i This Neui Radio Communications Mantel After the War —Other Possihilities Outlined MILITARY needs have brought such advanced developments in radio communication that fire- men and policemen in the postwar Iieriod may be equipped with walkie-talkies to fight fire and crime with radio. And through the same medium doctors may keep in touch with offices and hospitals, and operators of trains, busses, taxis and trucks would receive their instructions from headquarters while on the move. No Sudden Transition H. F. Mickel. manager of the Police and Emergency Communica- tions Section of RCA Victor, Cam- den, outlined the foregoing possi- bilities at a recent conference of the International Municipal Signal Association in Philadelphia, attend- ed by signal .system experts and officials of cities throughout the country. .Although he declared the possi- l)ilities almost limitless in commu- nications and industrial electronics. Mr. Mickel emphasized there would be no sudden transition from the present status. Rather, he said, existing equipments and methods would be improved and expanded instead of being rendered obsolete overnight. As an early possibility in the public safety field, the RCA engi- neer suggested that firemen carry- ing walkie-talkie sets small enough not to hamper their movements could be directed inside a blazing building by a superior officer on the outside who would be supplied the necessai'y information by the men throughout the structure. The same technique, he said, could be em- ployed in combatting forest fires. Another probable development, Mr. Mickel forecast, would be the equipping of all foot and traffic po- licemen with tiny two-way radio sets through which they could keep in constant touch with headquar- ters. These applications, he said, will be made possible through the development of new circuits, tiny tubes and components. "It is probable that future emer- gency comnuinications systems will tend toward the use of higher fre- quencies in the radio spectrum," Mr. Mickel said. "Again let me point out that this is the result of gradual evolution rather than the aiiplication of a radically new prin- [16 RADIO AGE]