The Electrical experimenter

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so THE ELECTRICAL EXPERIMENTER May, 1917 >^^ CLUESTION BOX This department is for the sole benefit of all electrical experimenters. will be publisht. Rules under which questions will be answered: Questions will be answered here for the benefit of all, but only matter of aufBicient interest 1. Only three questions can be submitted to be answered. .... ... -j 1 2 Only one side of sheet to be written on; matter must be typewritten or else written in ink, no penciled matter considered 3' Sketches diagrams, etc . must be on separate sheets. Questions addrest to this department cannot be answered by mail free of charge. 4' If a quick answer is desired by mail, a nominal charge of 25 cents is made for each question " " —' '-'" — ^ calculations a special rate will be charged •-*" -" '" "' -' " *" "-' '"" *-'''"~ ""•'' ' Correspondents will be informed as to the fee before such questions are answered. RADIO QUERIES, (760.) Harold Jaiieway, Edmonds, Wash., asks Q. 1. Could I hear amateur stations with a loose coupler, galena detector, fixt condenser, and an Electro "Government" 'phone in connection witli an aerial lifty feet high and thirty feet long? If not what other instruments would I need? A. 1. There is no reason why you should not receive amateur stations with the instruments you mention. A variable condenser shunted across the secondary of your loose coupler will increase the selectivity very much. Q. 2. How can I drill holes in a marble slab so that I can mount a ground switch upon it? A. 2. An ordinary steel twist drill should be employed which should be constantly kept wet by applying water to its boring surface. Q. 3. Would I be violating the rules of the Fire Underwriters if I put a box over my outside ground switch and covered the ground wire with lath? A. 3. Yes. The ground wire should be kept free from any surrounding objects. POWER FROM PRIVATE PLANT. (760-A.) W. C. Guibb, Grabill, Ind., wishes to know Q. 1. What is the best way to use the output of a private lighting system in a radio sending set? The generator has an output of 30 to 45 volts and 13.3 amperes, and charges a storage battery of 16 cells. A. 1. The best way to utilize the electric power generated by your private plant is to employ a spark coil outfit; the size 01 the coil will depend upon the distance which you desire to cover. Q. 2. Can I use it in connection with an open or closed core transformer, or is the spark coil the only way? A. 2. Yes, providing that a mechanical vibrator is used in conjunction with it when using an open core transformer. This can either be directly operated by the transformer core or else you may employ an independent vibrator. We would advise that you employ a spark coil, say about a 4inch coil, and you will find that it will give better service than if an open core transformer is used. Q. 3. Could I not use the combined voltage of the generator and battery and have sufficient voltage? A. 3. Yes ; but the voltage will not be sufficient or of the correct character to operate a transformer without a mechanical interrupter. UNDAMPED WAVE RECEPTION. (761.) Walter H. Clifltord, Worcester, Mass., writes; Q. 1. Is it possible to employ a mineral detector in place of an .Audion detector for receiving undamped signals? If so, what connection of instruments should be used? A. 1. It is possible to receive undamped waves by employing a crystal detector providin.g a tikkcr of some kind is employed in the detector circuit. The diagram of ^ „„..„„„. ^ „. . - If the questions entail considerable research work or intricate connections is given herewith and shows a circuit breaker or tikker being used. Q. 2. Will you please publish a diagram of the connection of the instruments used in a simple inductive wireless telephone circuit ? A. 2. Our diagram gives the connection of a simple radio telephone employing the induction principle. The transmitting coil should be five feet in diameter while the receiving coil is four feet. Each coil is wound with one hundred turns of annunciator wire. Q. 3. Is it advisable to employ a helix with a one inch spark coil? A. 3. If you desire to bring your transmitting wave length to some definite value, you should employ a helix. Proper Connection for "Tikker" Type of Radio Receiving Circuit for Undamped Wave Signals. Hook-up for Inductive Wireless 'Phone. SELENIUM. (762.) E. W. Donaldson, Fairmont, W. Va., wishes to know Q. 1. In what quantities is the element selenium available ? A. 1. This element can be supplied to j^ou in any quantities desired, and it may be procured fi/om The Electro Importing Co., New York. X.Y., or Electro-Set Co., of Cleveland, Ohio. Q. 2. Does it remain constant in its conductivity linder ppriods of use, say three or four seconds: several times a day or longer? .•\. 2. The conductivity of selenium crystals under the influence of light is not constant but variable. The variation of conductivity of lenium depends upon many factors, such as the applied voltage, source and intensity of illumination and chemical purity of "the selenium crystal. MOTOR STARTING QUERY. (763.) Q. L started? J. .A.dler, New York, X.Y., asks: How should a shunt motor be A. 1. First, the field current is applied at full line voltage; then the armature current is thrown on at much less than line voltage, the voltage being held down or controlled by resistance in a starting box; as the motor comes up to normal speed, resistance is cut out step by step until full line voltage is imprest on the armature. This is all accomplished by one motion of the handle of a well-designed rheostat or starting box. Most starting boxes are so arranged with a magnetic release or otherwise, that the motor is automatically cut out of the circuit in case the line voltage should, thru any accident, be shut oflf. Q. 2. What is an accumulatively wound compound motor? A. 2. It is a motor whose series and shunt field windings are in the same direction and therefore as the load comes on the series field assists the shunt field and a stronger magnetization and increased torque, with slightly reduced speed, results. STORAGE BATTERIES. (764.) Harry Blumenthal, Harrison, X.j., Q. wants 1. To to know wliit use is the storage battery sometimes' put in electric lighting or power station*? A. 1. To carry the peak of the load, i.e., that excessiv^ portion of the load which, for instance! in electric lighting stations has to be carried only for two or three hours a da^f. They cafry the entire load at minimum hours; to ^ct as equalizers or reservoir. Q. 2. How do Faure plates compare with those of the Plante type? A. 2. They are usually lighter and have a higher shed tlie capacity, but have a tendency to material from the grid, thus making the battery useless. Q. 3. At what of dilute sulfuric density acid at is the resistance a minimum? A. 3. |At 1.260 Baume. MOTOR ACTION. (765.) L. Askel, Detroit, Mich., asks: Q. 1. Why does the speed of a shunt motor increase when the position of the bruslies A. 1. is off neutral ? When the brushes are shifted from the neutral plane, the reverse voltage between the brushes is decreased, the speed remaining unchanged. Accordingly, the pressure in the supply mains forces an increased current thru the armature, thus producing an increased armature pull, which causes the speed to increase until the reverse voltage reaches a value sufficiently large to reduce the current to the value re(|uired to supply the necessary driving torque. Q. 2. Can you tell me the existing mutual relations of motor torque and speed? A. 2. The character of the work to be done not only determines the condition of the motor torque '.and speed required, but also the suitability of a particular type of (Conti)ixicd on paijc 5-')
May, 1917 THE ELECTRICAL EXPERIMENTER SI 8c in Stamps Brings You nilPI^'C 300 -PAGE ELECTRICAL UUl/IV O and WIRELESS CATALOG You then have everything in wireless and electrical supplies worthwhile at prices that mean a substantial saving to you. Our catalog is recognized by all experienced and advanced amateurs as the Beacon Light on what to buy. Ask your wireless friends. Great cost of catalog and low prices prohibit distribution unless upon receipt of 8 cents, which you may deduct on first dollar purchase. SHORT WAVE REGENERATIVE SET Every worth while feature is incorporated in this Regenerative Set. Initial tests in our laboratory and at the local Scott High School brought in with remarkable clearness amateur stations in Texas, Louisiana. Wisconsin, and all eastern states. Amplification and selectivity surpassed several other sets tested in conjunction with it. We have no hesitancy in claiming for this instrument no superior, and in fact we thus far know of none that equals it. It is designed for wave lengths from 180 to 475 meters. Casc6'.t"x I I '^ " x 6'^", nand rubbed mahogany finish. Panel, polished Formica. Set has variable coupling. This is essential for selectivity and 1 the elimination of static, thereby insuring greatest I possible range. Primary circuit a d j u s table by lingle turns. Grid inductance I I 1 po adjustable by 12 int switch. Special variable I I condenser included I in circuit for I close tuning. $24.75 Prepaid. SOME STARTLING REDUCTIONS FOUND IN CATALOG NO. 11 Reduced Price T-O Thordarson Flexible Transformer $12.25 T- 1 •• " " 16.23 T-2 " ' " Protective Device free with each transformer 19.75 Type ** C '* Sayville Gap, Copper Electrodes, Rotary Wheel /' Bakelite 5»y" dia. All electrodes are of Va" round copper, Revolvingelectrodea ^z^" 'o"8- S*^*'°"^''y ^l^*^ trodes '^s" inch long. The use of copper for the electrodes and their unusual size makes thisgapmuch more efficient than any other gap of its type on the market. The copper conducts the heat away from the sparking surfaces. AH advanced radioengineersconcede that copper is unsurpassed for electrodes. Gap equipped with Universal motor. For use on stations up to 3 K. W, Undamped Loading Inductance Hearthe Arc stations in Germany and elsewhere. No. 528 for secondary loading coil and lor tuning the wing circuit. $7.75 No. 1526 for primary loading coil. $7.75 Two No. 528 and one No. 1526. $22.00 None on the market equals these undamped loaders at $10.00 each. No. 22 & 28Silk Covered Wire is used on primary and secondary, respec- tively. Variation of inductance is by means of 20 point instrument type switch mounted on y^" Bakelite. With an ordinarily loose coupler wave length 15.000 meters. Reduced Price No. A 395. Oscilliation Transformer $13.50 Model 5AA Navy Type Transformer 17.25 No. 1091 Arlington Transformer 7.50 *• * No. 1092 6.50 Send 8c for this Catalog today. You need it THE WILLIAM B. DUCK CO., 230-232 Superior St., Toledo, OHIO TYPE OJ3—$400.00 COMPLETE Oacillion Tok'graph, cnpiible of transmittiiiK the voice 15 niiloti, or telegraphic mess:ii?e3 40 miles. Linger transmitters fur greater ranges. r^% TYPE EJ2—PRICE $32.00. NEW AUDION AMPLIFIER FOR INCREASING STRENGTH OF RE- CEIVED SIGNALS 25 TIMES. It is not a Detector in any form. At Last! Electromagnetic waves of any length from an incandescent lamp. TYPE "S"— $60.00 DeForest "Oscillion" (Oscillating-Audion) Generator of absolutely undamped oscillations of any frequency. Permits Radio Telephone speech surpassins in clearness that over any wire. For Laboratory and Research Work has a field utterly unfilled. Patents issued and pending. =MANUFACTURED BY= DEFOREST RADIO TELEPHONE AND TELEGRAPH COMPANY NEW YORK CITY Office nnd Factory 1391 SEDGWICK AVE. Cable Address; RADIOTEL, N. Y. You benefit by mentioning "The Electrical Ex^'crimenter" when uriting to advertisers. TYPE RJII—2500— 12000 METERS. $35.00 THE DEFOREST LOADING INDUCTANCE TYPE VC4—PRICE $20.00 VARIABLE CONDENSER This Condenser is similar to our coinniLTcialtype but is enclosed in an oak cabinet. It has ^S semi-circular aluminum plates. The maximum capacity is approximately .0025 M. F.
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