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The Value of the Newest Tube WHAT THE SCREEN-GRID SET DOES MANY ARGUMENTS pro and con on screen- grid receivers are taking place behind and in front of counters where sets are sold, and it is no secret that such arguments have occurred in the offices of large set manufacturers, or that these manufacturers are di- vided into two general groups, those who do and .those who don't believe that screen- grid radio is 1929's panacea. What are the facts about screen-grid radios? In the following paragraphs some of the advances that are pos- sible in receiver design be- cause of the advent of this new tube are pointed out. It must not be assumed merely because such advances are possible, that they already exist. Nor must it be as- sumed that the screen-grid radio will displace other types of sets. In the words of several large set engineers, the screen-grid tube is another tool; a useful one, but one which must not be taken as the cure-all for every radio ill. Some of 1929's receivers using screen-grid tubes will be su- perior to sets made a year ago without the advantage of the new tube; it is equally true that a general advancement has taken place in the year and that sets using three-element tubes throughout have progressed toward the goal of better selectivity, better sensitivity, and improved fidelity. Screen-grid tubes make possible a more sensitive, and more selective receiver than was possible a year ago, and one in What Screen-Grid Radio Means which the fidelity of repro- duction may be improved over that obtainable in 1928. Let us look at the sensi- tivity angle. Last year (1928) receivers were about ten times as sensitive as those of a year or two previous. And many sets of 1929 are ten times as sensitive as those of 1928! What does this mean? It means that one can receive more distant stations, or a given station louder, or a given station from a greater distance, or lower-powered transmitters, or he can attain all of last year's results on a smaller antenna. On page 213 will be found a drawing showing the effect of increasing the sensitivity of a receiver by ten times. If an antenna 12 feet high was required in 1928 to deliver a given loud speaker signal from a given station, an an- tenna only 1.2 feet high will be necessary in 1929. Well- designed screen-grid receivers can get along with only a very small wire or a metal screen as an antenna. For apartment dwellers, this means the complete elimination of the unsightly and dangerous antenna erected on the roof far from the re- ceiver. In another illustration an attempt s made to show how the receiving range of a receiver may be increased by the use of screen-grid tubes. If the sensitivity of a receiver is increased ten times, the receiver can be placed ten times the distance from a given station and still deliver the same loud speaker 25 TYPICAL RECEIVER 227-TYPE TUBES Q9 : 10 ' 10 ; 10 : 5 20 2 '3 - 575.000 - » TOTAL AMPLIFICATION /I screen-grid receiver using five tubes compared in overall amplification with a six-tube receiver using three-element tubes 212 • AUGUST 1929 •