Radio Broadcast (Nov 1923-Apr 1924)

More About the Super-Heterodyne ARTICLES have appeared in this magazine on the super-heterodyne receiver in the L February, August, November, December, 1923, issues, as well as in January and March, 1924. There will be another important article in our April number. Since all of these articles, except that of Mr. Paul Godley in February, 1923, and that of Mr. Walter van B. Roberts in August, 1923, specify intermediate frequency transformers — type UV-1716 — which have become difficult to purchase, many eager experimenters have not been able to build one of these sets. Transformers are now appearing on the market for this purpose. In our April issue, we will publish the details of transformers which may easily be built, which will effectively replace the UV-1716 and others necessary for the superheterodynes we have described. On page 347 of our August, 1923, issue, Walter Roberts describes the windings and characteristics of a suitable intermediate frequency amplifier which will work quite satisfactorily. Mr. Godley's article in February, 1923, was introductory, showed fundamental circuits of an excellent receiver he built. In August, 1923, Mr. Roberts described a six-tube outfit with UV-199 tubes, of which he writes: "this receiver has all the advantages of the super-heterodyne control, the neutrodyne type amplifier, and the "reflex" system rolled into one." In Mr. George Eltz's two articles, he describes in December, how to make a "super" out of extras around the laboratory. In his November, 1923, contribution, he describes a seven-tube outfit which has been very neatly installed and arranged. Mr. Haynes in January, 1924, and in this present issue, has described his seven-tube super, avoiding the use of the unobtainable UV-1716 transformer. In our Lab section for the April, 1924, issue, we will have an article describing how to make a satisfactory intermediate frequency transformer, which may be used in the Haynes super-heterodyne circuit, as well as information on the super-heterodyne for 100 meter reception. How Spark Interference Was Reduced By JACK BINNS Radio Editor, New York Tribune M UCH of the interference encountered by broadcast listeners comes from commercial spark stations which use the wavelength of 450 meters. The recent conference at New York, presided over by Arthur Batcheller, Supervisor of Radio, Second District, which abolished this wavelength, was called as a result of the interest of the Radio Club of America and its President, George Burghard. The agreement by which the 450-meter wave was abandoned and most ship to shore communication moved up above 600 meters came as a direct result of the personal interest which President Coolidge has taken in the entire radio art. This interest commenced when his address to Congress was broadcast. Shortly after that a committee headed by George E. Burghard, president of the Radio Club of America, called upon the President to bring to his attention the serious interference caused by ship to shore communication on the 450-meter wave. The committee pointed out to the President that the 450meter wave was only used by the United States and was not authorized under the International Radio Convention. This agreement, however, is entirely voluntary and has no binding force. The radio inspector cannot legally enforce it, so that at any time, any of the operating companies may violate, it should occasion arise. In view of the tremendous improvement which has been effected as a direct result of the agreement, steps should be taken immediately to see that it is embodied in an act of Congress that will give the full force of the law behind it. In this connection, every radio fan should write to his particular representative, urging the enactment of such a rule. Since the new order went into effect, officers of the Radio Club of America have been carrying on a very careful study of the resulting situation, particularly to determine just how much interference has been cut down. The survey included constant listening-in to distant as well as local programs with highly sensitive receivers such as the super-heterodyne. This work has been carried on by the officers of the club, including Major E. H. Armstrong. IMMEDIATE IMPROVEMENT TN OUTLINING results, George E. Burghard, *■ president of the club, said: "The effect of the agreement became apparent immediately, especially on the higher wavelengths used by the broadcasting stations in different parts of the country. For instance, in the City of New York, with a superheterodyne receiver, we have been able to reproduce, with a great deal of regularity, the programs from station KSD, in St. Louis, which operates on the wavelength of 546 meters. This reception has been done with practically absolute freedom from spark interference.