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USE OF CHOKE COIL
AND TRANSFORMERS I Lattsr Provide the Most Prac tical Method of Coupling for the Amateur. I Figure XXVIII shows the actual circuit of a three-stage resistance coupled amplifier. The output of such a circuit is K times K times K the input or assuming the amplification factor of each tube to be 10, the output would be 1,000 times the input. The resist ance R Is the coupling resistance whose function it is to transform the plate current variation to potential next tube. The capacity C is slmpty a means of allowing the potential variations across the coupling resistance R to be applied to the grid of the next tube, yet not allowing the "B" battery ap plied to the plate circuit of a tube to be applied to the grid of the next. Because of using the condenser to, what one might say, insulate the grid from the "B" battery potential, It is necessary to use a grid leak, to keep the charge which collects on the grid from becoming excessive and reducing the plate current to zero. One of the chief disadvantages of the resistance coupled amplifier Is that very high plate battery poten 4 r>**s&n**r 1 r ■p\ >5 S Ztr/M/Z" i z. Y i J 7 T&ns/or/nar ChujeZZrra Mi ■/< C 7~ !7? * . 7c ■r r 5 * s T - 4 ZT /3 « TtZes/sZarfce CoujoZe cZ /Z/rr^oZZ/Zer 77j xrvm The ampllflca tials are necessary, tion per tube of a resistance-coupled amplifier Is not as high as it Is for some other methods but it is stable 4 and does not distort the input as much as do some other methods used which give greater amplification per tube. Resistance-coupled amplifying may he used to amplify either radio or audio frequency. A method of transforming the change In plate current of a vacuum tube to differences in potential is by means of a choke coil. A choke coil consists of a number of turns of wire wound up In a multilayer coil and may or may not have an Iron core. A coil of this kind offers a high im pedance to the flow of alternating cur rent,, hut has a relatively low direct current resistance The choke coil on account of hav ing a low ohmic resistance, will have a smaller method of coupling, so that lower "B" battery potential can be used on choke coil coupled amplifiers and the batteries can be of smaller capacity. The choke coll not only has Induct ance but a certain amount of distrib uted capacity. The distributed ca pacity of the coil plus the capacity of the plate with respect to the filament together with the inductance of the coil, give to the plate circuit a cer tain definite period. That is, the plate circuit Is an oscillating circuit whose resonant frequency is determined by the total capacity and inductance In the circuit. If the choke coll be made variable, It will not only serve to transform the plate current variation with maximum plate potential variations, but ft will also serve to tune out unwanted fre quencles. When the plate circuit of the amplifier is tuned, the resonant frequency is amplified K times, but all other frequencies are amplified to a less degree Another and by far the most widely used method of coupling suc cessive tubes in a cascade amplifier is by means of transformers. The trans former method of coupling amplifier tubes may be considered a develop ment and a refinement of the simpler choke coil method. Coupling tubes hy means of properly designed trans formers will give a greater amplifl cation per tube than bny of the other methods. Figure XXXI shows the diagram of a three-stage transformer coupled amplifier, where P and S are respec tlvely the primaries and secondaries of the coupling transformers. The transformer as a whole Is so designed as to convert the plate current varia fions into maximum potential varia lions. The plate circuit of each tube which includes the primary winding ef a coupling transformer must be assigned for maximum power arnpll flcation, while at the same time the ratio of the transformer must be such as to deliver maximum potential to the grid circuit of the next tube. The greatest advantages of the transformer method of coupling audio frequency amplifiers are the high de gree of amplification, the relative simplicity of operation, and the low plate voltage required. Chief among the disadvantages of the transformer coupled frequency amplifier Is noise. Also the trans formers amplify different frequencies to different degrees, which means that when this type of coupling is used for radiophone reception, the voice is distorted by the amplifying transformers. However, from a prac tical standpoint, the average amateur will have better results using trans former coupled audio frequency ampli fiers tiian from any other method that can be used with the tubes and equip ment now available. GREAT BRITAIN VS. AMERICA Radio Amateurs of Those Countries Pursuing Distinct Courses in Development of Receivers. Two separate and distinct courses are being followed by the radio ama teurs of this country and Great Brit ain in the development of receiving apparatus for continuous-wave teleg raphy and wireless telephony. Both courses are of the utmost Importance to the art, and each will exert a great influence on the future of radio com munication and entertainment. The American amateurs have gone along the lines of regeneration and amplification of audible signals, as well as development of long-distance reception on short waves by the super heterodyne principle. On the other side of the Atlantic the British amateurs, restricted In their hobby by ultra-conservative government regulations, have turned their atten tion solely to radio-frequency ampli fication. This has given excellent re sults on all long and medium wave lengths, but its success on shorter wave lengths has depended solely upon die expert handling of the operator, who has been compelled to use tuned coupling circuits between each of the radio-frequency vacuum tubes. It Is too early yet to tell which of the two systems will ultimately tri umph, but there is no doubt that the laurels at the present moment rest upon the American amateurs through the latest achievement of their leader, Armstrong, in the production of the super-regenerative system. I SHORT FLASHES ; f The enormous popularity of | | milking time: "Come bos!" | lu making a regenerative set | employing two variometers and | a variocoupler be careful not to | £ e t the instruments too close | together. If they are, the set I howl. A set of this type I should be mounted in a box I not Iess t,lan sixteen inches \ lon £ | J 0 * 111 J- Carty, often re | t erre d t0 as the wizard of the | telephone, has had added to his I many complimentary college de | & rees t ^ lat of doctor of science, Yale unlversKv. Doctor Carty, w ^° ran ks as a brigadier gen era ^ * n signal corps reserve, A " was Si ven this last honor for being a radio expert, Sir Artllur Conan Doyle pre diets communication with the dead by radi i within four years, Ar thur is firm In the belief ^at that time 'we will have the direct communication ^ at Edison hoped and that those who have passed beyond have transmitters In the ^ ne et * ler and all that we neec * will be the receiver, # radio has started out a new croj) of solicitors offering the stock of fake companies, with alleged glittering prospects. A general warning is being broadcast for fans to be on the lookout for these smooth gentlemen. A young radio sharp at Og densburg, N. Y., recently heard through his set : "Come home with tlie car, Howard ; I have to go to the store." Who can say that a set in the pasture will not soon call the cows at I HOME TOWN HELP 5 l> Oö EFFECTIVE PLEA FOR ZONING Practically Impossible to Construct Proper Sewerage System Without Up-to-Date Arrangement. The value of completely zoning a city or village is demonstrated in many ways. One of these Is In tlie op portunity it gives the engineers to de sign and build sewer systems on pre cise information as to the character, number and use of buildings that will occupy the district which the sewer system is to serve. The Information derived from the zoning ordinance and the official maps will tell him In advance that the area to be drained is zoned, say, for a single-family district. This means to the engineer a smaller density of pop ulation, a smaller volume of sewage, shallower and smaller sewers. Without zoning, the engineer Is obliged to estimate the type and in tensity of the development of any given district and design his sewers on the basis of his estimate. If In his estimate he did not pro vide for large numbers of apartment buildings or hotels, requiring provision for a much greater .volume of sew age and deeper basements to be drained, his sewers will be found to bo inadequate to take care of the dis trict as it finally develops. The inadequate sewer Is distressing and costly, as It means the backing up of the sewage Into basements. In volving the loss of property by flood ing, the expense of cleaning out the filth and silt which are deposited after the water has seeped away and the menacing the health of occupants of the buildings.—From a Report of the Zoning Committee of the Western Society of Engineers. NOT YET NATION OF RENTERS Home Owning Is by No Means a Lost Among People United States. Is home owning a lost ambition? Are we becoming a nation of cliff dwellers and renters? Not If we put faith in the figures compiled by the lately established bureau of housing of the Department of Commerce, ob serves the Nation's Business. Of 08 cities of more than 100,000 population but 20 show a loss in percentage of homes owned be tween 1910 and 19S0 (the figures are from the census bureau), and the losses are more than offset by the g-fiins of the other 48. Of the 20 where losses were recorded, four, De troit, Cleveland, St. Louis and Los Angeles, are In the first ten cities In point of population. Altlmugh In New York more homes are owned than In any other city, the percentage Is the lowest, but 12.7, yet even here the percentage has grown from 11.7 in 1910 and 12.1 in 1900. Manhattan presents the most striking situation. With more than half a mil lion homes, less than 11,000 were owned, little more than 2 per cent. If home owning he a form of civic virtue, then Des Moines may gather her chaste skirts about her as painted Manhattan passes, for the Iowa para gon among cities shows a percentage of home ownership of 51.2, a growth from 45.0 per cent In 1910 and 38.5 in 1900. In only one other community of more than 100,000 Inhabitants are half the homes owned and that Is Grand Rapids, Mich. Old Houses Being Made Over. An era of remaking old houses runs across tlie entire country, according to Northwest lumbermen. | | | | I | f f ' | Following the building shortage of late years has come an appreciation that any house, old or new, has untold possibilities of alteration. Architects have been called upon to produce in stances of "before and after" of ram shackle, barnlike structures made over into charming homes. Old barns have been rebuilt into studios, sheds and warehouses into residences of taste. There is an enormous demand on the Northwest planing mills for mold ings, trimmings, shingles, sidings, in side finishings, lumber and fancy grained fir, hemlock or cedar for cab inet work. Lumbermen declare this demand has come from the alteration wave over the nation, repairing and adding built in features. | I | | f | I | | | | ! How Zoning Saves Money. It Is estimated by the city engineer of the city of St. Louis that zoning would have saved the property owners about 15 per cent of the cost of sewer construction. If this saving Is true In the case ol sewers, Is It not equally true of the other services which combined make a mighty sum? Avenged. "Good heavens, man ; pretty badly smashed up, ain't you? Anybody with you ?" "Yes, the chap who was trying to sell me this used car."—Harper's Mag azine. Use and Appearance. "Do you think your bathing suit Is proper?" "Proper enough as a bathing suit," replied Miss Cayenne, "though per haps deserving of criticism as scenery." FOR REAL ECONOMY In the Kitchen USE CALUMET | The Economy BAKING POWDER A Big Time and Money Saver When you bake with Calumet you know there will be no loss or failures. That's why it is far less expensive than some other brands selling for lesa MAOC IYA Wirft » ? ♦. • 3 %(? BEST BT TEST Don't be led into taking Quantity £or Quality Calumet proved best by test in millions of Bake-Day contests. Largest selling brand in the world. Contains only such ingredi ents as have been approved by U. S. Pure Food Authorities. The World's Greatest Baking Powder THAT WAS ASKING TOO MUCH Bishop Probably Had Read That "Much Shall Be Forgiven," but Really, Professor Jones! An English clergyman now visiting this country tells a story of an emi nent Church of England ecclesiastic now dead, who on the occasion of the gathering of the British association, invited the members to an entertain ment at his place. But he sent no card to one member of the association, who, thinking that he was the vic tim of an oversight, mentioned the matter to a mutual friend. "I will speak to the bishop and make that rigid," said the friend. "It was a mere accident." He did speak to the bishop, to this effect ; "By some mischance, Professor Jones has not been invited to the en tertainment. Of course you mean him to come?" "No, indeed. I do not," said the bishop. "Nothing can Induce me to ask under my roof a man who lias defended the execution of Socrates!"— Philadelphia Ledger. Art C-rushed to Earth. Stanislaw Szukalski, a New York sculptor, marries a Chicago girl and makes her live on a pig farm. "Sculpturing isn't very profitable," he says, "hut those whd raise pigs make a lot of money." Thus, once more, is art crushed to earth.—Washington Times. Compensation Is the law of exist ence tlie world over. -, Let's disarm the thermometer M EATS and starches for the body fuel for the furnace. are like Why not adopt for breakfast or lunch, Grape Nuts with cream or milk and a little fresh fruit —and turn off the internal heat? Here's plete nourishment, with cool comfort. Grape-Nuts contains all the nourishment of whole wheat flour and malted barley, including the vital mineral elements and bran "roughage, and it is partially pre-digested in the long baking process by which it is made. There's a wonderful charm for the appetite in the crisp, sweet goodness of this ready-to-eat food, and fitness and lightness afterward, which meet summer's heat with a smile. Your grocer will supply you with Grape-Nutsl com "There's a "Reason fl for Grape-Nuts - 3*5 -"t |L_ 5«*»jsase» HI Made by Posfmn Cereal Co., Ir Bailie Creek, Mica. \ DO. vEMgri !Y Ht \ EVIDENTLY HER UNLUCKY DAY Woman Probably Convinced That at That Moment Her "Jinx" Was Strictly on the Job. I was very busy upstairs with some necessary writing, and, glancing out the window, beheld Mrs. "Stay-For ever," a neighbor, coming up the walk. Calling my small daughter, I told her to tell the visitor I was not at home. She descended the stairs to do my bid ding and I tipped softly to the top of the stairs to hear the conversation. "Mother home?" inquired Mrs. Nelgh bor. "No, ma'am," said my faithful child. At tiiis unfortunate moment the heavy blue beads I wore around my neck broke and rattled down In the hall like a heavy hailstorm. My small daughter glanced at the dancing glass particles and, looking up In consterna tion, cried, "O, mother you broke your pretty blue beads!"—Chicago Tribune. A Much Tried Man. A Chicago man, whose hobby Is the clipping and collecting of humorous advertisements, especially those ap pearing in tlie "want" columns, has recently added the following to his collection, an advertisement that ap peared in a paper In that city; "WANTED—A loud, second-hand phonograph for reprisals." No Pleasure Without a Partner. A man would have no pleasure in discovering all tlie beauties of tlie uni verse, even in heaven Itself, unless he had a partner with whom he might share his joys.—Cicero. MADE NO SORT OF APPEAL Colored Messenger Couldn't See Whero the "Sport" Came In In That Kind of Fishing. In a government office In Washing ton one day a Californian was dis coursing on the sport of fishing off the Pacific coast. "We all get out In small motor boats," said he, "and fish with a lung line baited with (lying fish. Anything less than a hundred-pound tuna isn't considered good sport." A colored messenger had been lis tening with great Interest to this con versation. "Excuse me, boss," he said, wide eyed, as ho stepped up to the group, "but did I understand you to say that you wore fishin' for hundred-pound fish in a little motorboat?" "Yes," said the Californian, "we go out frequently." "But," urged the messenger, "ain't you all afeared you might ketch one?'' —Pittsburgh Dispatch. j Why and Where. Relieving Officer (to applicant whs is slightly deaf)—And where did you marry your wife? Applicant—I'll be hanged if I know. sir. Relieving Officer — What! Don't know where you were married? Applicant — Beg pardon, sir. I thought you said why.—London Tlt Blts. Some towns spend more time in sounding their slogans than in clean ing their streets.