Radio broadcast .. (1922-30)

.RADIO BROADCAST. reception conditions at the test point is obvious, but even this is not sufficient to produce positive judgments unless switch- ing arrangements are available which make instantaneous comparison of the attained volume with a given signal possi- ble. With such facilities, tuning in a distant station on two receivers and switching quickly from one receiver to another makes a simple and satisfactory test of radio-frequency amplification. These performance tests are easily made and give a direct comparison of the factors which determine the service viv^ vnjc cApciiac. Aiieitiuic, a receiver will give to the ([ TRADE MAGAZINE PREJUDICES J mechanical inspection consumer. A chart of the type shown on page 82 L permits the systematic rat- ing and reporting of this series of tests. Having completed the performance tests, examina- tion should then be made of the voltages delivered by the receiver's power supply under various conditions. Usually some means is sup- plied for adjusting voltage input to the power supply for two or more effective line voltages. By means of a good set-checker, the grid and plate voltages supplied each tube should be meas- ured with the input voltage supply properly adjusted. The examination should de- termine that none of the tubes are operated above their rated voltage. High potentials particularly should not be tolerated because this causes rapid deterioration of tubes in the hands of the consumer and gives exceptionally good per- formance with respect to selectivity and sensitivity only when the tubes are new. Superiority in these respects, so at- tained, is certain to cause trouble later because purchasers will soon complain of short tube life. Mechanical Examination THE RECEIVER should next be subjected to mechanical inspection, preferably aided by the service instruction manual supplied by the manufacturer. The dial-control mech- anism should be inspected carefully by applying friction at a convenient point on the condenser drum and observing if there is any play or slip when the knob is turned. Rheostats should work smoothly. Gang condensers should be of rigid construc- tion and the contacts between the rotors should be inspected carefully to assure a permanent electrical connection. For convenience in servicing, the ease with which the chassis and the power supply is removed is of importance. The service manual and the chassis itself should be examined to see if simple wire codes are used so that routine tests may be easily made. Condensers in the power pack and audio transformers should be readily removable and convenient test points should be available. The hum balancing means should be accessible, while the means used to balance the gang condensers should /T IS a common idea—all loo common — that trade magazines must never talk of technical matters. Such conservatism can be justified up to a certain point, but beyond that, it is harmful. Since their beginning, trade magazines have stressed certain aspects of selling, such as window displays, summer campaigns, over-the-counter selling, etc., to the exclusion of all other matters. Indeed trade magazines, are commonly regarded as properly containing nothing else. Other aspects, such as the semi-technical angle (less important but still deserving some attention), have been neglected completely. Look at the set advertising in the various trade magazines. Do you not find such statements as, "245-type tubes in push- pull;" "automatic voltage, regulation;" "screen-grid tubes;" "dynamic loud speaker;" and "band-pass tuning?" These are technical facts — and salesmen use them. And there are other technical things about radio receivers equally effective in sales, that have never been explained in merchandizing language. Take a specific case — for example, a Spartan receiver. As a salesman, do you know in what way Sparlon sets are essentially different from any other receivers? On page 99 of this issue will be found an article in which the unusual character- istics of the Spartan are clearly indicated. Read it. Read the article on the Radiola 60 series on page 15 of the May issue, another example of the same type of article. And, after reading them, let us know what you think of them. be such that they are accessible to the serviceman but not to the set-owner. The chart also contains a table to aid in making a systematic mechanical inspection. The experienced dealer knows that convenience in servicing conserves profit and maintains customer satisfaction. Con- sidering the receiver solely from the performance standpoint, without giving thought to future service which may be necessary, has often led to the adoption of a line which may sell readily but which absorbs much of the profit earned by sales because of later ser- vice expense. Therefore, the is most essential as service accessibility and means of detecting and shooting trouble is of considerable importance. While the me- chanical inspection should be made with this point in view, general mechanical design should not be over- looked. Rigidity in the chassis, sturdy variable condensers, well anchored wiring, firm shielding com- partments, and absence of exposed delicate parts should be observed. I am certain that dealers inspecting a new line will be greatly aided by follow- ing a systematic and com- prehensive procedure in making their tests. Further- more, they will find them- selves much better equipped to make a compelling and accurate presentation to prospects of the capabilities which their favorite lines possess. NOTES ON BROADCASTING ^N INDICATION of the interest in fight broadcasts is given by a statement of the New York Edison Comp- any. During the Sharkey-Stribling bout, broadcast from Miami, Florida, current consumption began to rise above the normal load at nine o'clock, had risen to 25,000 kw. over that in use on ordinary nights by ten o'clock, soared to 40,000 kw. about the time the fight ended at 10:30, and reached a maximum of around 54,000 kw. at 11 P.M. A lot of late staying up must have been caused because the load did not return to normal until one A.M. SENATOR NYE, of North Dakota, will offer a bill for the erection of a Government radio broadcasting station to radiate debates of Congress on important issues. In view of the N.B.C. offer to broadcast important debates over net- works and the impossibility that Nye's one station can reach an appreciable part of the listening public, the project is as wasteful as it is useless. L CENSE HAS been applied for by the Freshman Company to erect two experimental television transmitters at their plant in Clifton, N. J., according to J. D. R. Freed, vice- president of the company. — THE EDITORS. J IN ii A • JUNE • 1929 • 83