Radio broadcast .. (1922-30)

DECEMBER, 1927 A CRYSTAL-CONTROLLED STATION a skilled electrician and radio mechanic, chauffeur and myself, tuned at the curb in front of the elec- 'tric company and could hear the working of the oscilloclast—we then drove five squares and tuned in and could hear the instrument and at intermediate points fora little more than a mile, showing that the treatment waves were being broadcast a mile or more. We then secured specimens for electronic examination from a distance of half a block up to three miles and from many intermediate points. The number of specimens secured from begin- ning of broadcasting, from November i, 1926, to present date, January 20, 1927, were thirty- three. We have found that out of that number twenty-three have been made negative—the balance, ten, have been greatly reduced, showing that it will only require a week or ten days further broadcasting of the treatment waves to render them negative. The amplified treatment machines are run by batteries that are fed from the electric light socket and will last from four to six months; otherwise batteries only last a few days. The five-stage radio-transmitter is also fitted up with a large battery supplied by electric socket and it in turn supplies the dry batteries, making the apparatus very efficient and durable. ... In the last six weeks or more, with broad- casting outfit we have treated electronically a population of fifty thousand (50,000) on an average of two hours per day, making a total of one hundred thousand (100,000) hours per day. If the broadcasting electronic treatment waves have rendered negative two-thirds of the fifty-thousand (50,000) population and reducing the other one-third, as was proven in the thirty- three test cases (two-thirds made negative, one- third reducing) taken out of the same population we can readily see the great benefit and per day value to the people. Giving the value of one dollar per hour for treatment of each individual (which is a low tariff fee) we have a total of $100,000.00 per day. If a transmitter fed from batteries can benefit the surrounding population to the extent of $100,000. per day, conceive of the value of a 100- kw. outfit devoted to the same philanthropic pur- pose! Why not make it 10,000 kw., while we are at it? Assuming that the professor's present equip- ment has a capacity of 20 watts, the io,ooo-kw. set would be worth §50,000,000,000. a day to the citizens of the United States, on the valuation basis assumed in the first place. This is of the general order of the amount of business trans- acted in the country in a year. It is clear, there- fore, that a stupendous wealth producing agency is in the hands of the electronic practitioner, which, I suppose, makes him feel very bad. For my own part, I have some qualms. By broadcasting these electronic treatments, the learned Doc cures all the people within reach of their ailments. But why only the people? Any such general specific must also be good for animals. Horses will be cured of the blind stag- gers, tubercular monkeys will rise from their beds, sick cockroaches will report at the office fit for work. The rats, pediculi, and bed-bugs (Cimex leciularins) may benefit even more than human beings, who may thereby be crowded off the earth. I hope that the electronic broadcaster will consider this aspect of the matter and quiet my fears if he can. Some Catalogues ULLETIN No. i of H. F. Wareing and Associates, on Modulator Reactors, will prove of interest to some broadcasting stations. This company, whose address is 401 Pereles Building, Milwaukee, Wis., is in the business of supplying apparatus and service to broadcasting stations. The first bulletin includes a discussion of modulator reactor design, and a price list of types stated to be suitable for trans- mitters from 5o-watt to lo-kilowatt size. The corresponding currents for which the chokes are built vary from 0.25 to 5.00 amperes, at d.c. voltages of 1000-5000. Ten- thirty-, and fifty- henry reactors are available. Bulletins on other broadcast station equipment are to be issued by H. F. Wareing and Associates at intervals, ac- cording to the announcement reaching us. The Samson Electric Company of Canton, Massachusetts, distributes a "Radio Division Price List" including, besides the usual radio parts sold to receiver constructors, such items as microphone input transformers, tube-to-line and line-to-tube transformers, mixer equipment, and other specialized broadcast transmitter and public address material. They have made up a blueprint showing a small public address system assembled with their parts. Provision is made for microphone, radio set, and phonograph pick-up. There are three 0.25 ampere (filament) tubes, and apparently the output stage is push-pull, using 5- or 7.5-watt tubes. On this basis the volume capacity should approximately equal that of the Western Electric 3-A size P. A. system. Design and Operation of Broad- casting Stations 18. Pie^o-Electric Control THE field of piezo-electric phenomena includes the generation of electrical po- tentials in various substances by the application of physical pressure, and, conversely, changes in physical dimensions directly corre- lated with electrical conditions. It is not a new division of physics; the piezo-electric properties of quartz, for example, were investigated by P. and J. Curie in 1889. The effect itself was dis- covered by the brothers some years earlier. Prof. W. G. Cady, about eight years ago, began the work which resulted in the application in the radio art of crystal frequency control. He re- ported his investigation of "The Piezo-Electric Resonator" in the Proceedings of the Institute of Radio Engineers, Vol. 10, No. 2, April, 1922. Oscillating crystals are used as frequency stan- dards in wave meters and monitoring units, some practical forms much used by broadcasting stations being those produced commercially by the General Radio Company. RADIO BROADCAST has printed two comprehensive articles by M. T. Dow on crystal circuits and measurement ap- plications (January and September, 1927). A direct form of frequency control of particular in- terest to broadcasters is that in which the trans- mitter functions as a radio-frequency amplifier, the master oscillator being a crystal-controlled tube. Some recent engineering publications on this aspect include three in the I. R. E. Proceed- ings: A. Crossley: "Piezo-Electric Crystal- Controlled Transmitters" (Vol. 15, No. i, Jan., 1927); A. Meissner: "Piezo-Electric Crystals at Radio Frequencies" (Vol. 15, No. 4, April, 1927); and H. E. Hallborg: "Some Practical Aspects"of Short-Wave Operation at High Power" (Vol. 15, No. 6, June, 1927). In the present article an attempt will be made to introduce the subject to broadcast operators who have not worked with crystal-controlled transmitters so that when they are called on to operate such equipment they will be in possession of some of the elemen- tary facts. In itself the use of a crystal is no guarantee of frequency stabilization to any required degree of accuracy. Some broadcasters seem to believe that the use of a crystal in almost any kind of holder, with some sort of radio-frequency am- plifier following, will insure constant frequency radiation. Actually a crystal is of little use unless Choke Main Plate Supply THE CIRCUIT DIAGRAM OF A CRYSTAL-CONTROLLED TRANSMITTER In actual practice, tubes A and B in the third stage generally consist of two banks of power tubes. The filaments of only one set of tubes are lighted and they deliver power to the antenna circuit while the other bank, with the filaments not lighted, acts as a neutralizing circuit to prevent the active bank from breaking into self oscillation. In operation, if an accident happened to the active bank, the fila ments could immediately be turned off and the filaments of what was the inactive bank turned on. The latter bank of power tubes would then deliver power to the antenna while the other bank func- tioned as a neutralizing condenser