The Birmingham age-herald., 1922-06-04
How to Make Spark Coil

AiCaSC 1NSik itiC iOH NeNAA
 make 1ts inch spark coil if pur-
 chase a vibrator will an aerial. 30
 feet long, composed of three strands,
 and a lead-in 2s feet long be o. K.
 for sending?-H H.
 A. It will be necessary, first of
 all, to get bundle of soft iron wire for use as a core. It should be made Of No. 20 or No. 22 B. S. guage. specially designed for core wire. For 1is inch spark coil this shoudl be I inches long and ss inch in diameter.
 This core should be packed tightly in
 tube of those dimensions Over the tube you will have to wind two lay
 CTS of No 16 D. C. C. wire. These layers should be 6is inches long, leaving the core projecting at each end Care must be taken to see that
 the wire of the primary Is wound
 very tightly and compactly. The sec
 ondary will have to be wound with
 extreme care. If you can purchase
 one already wound so much the bet ter, but if you cannot 1t will be nec-
 essary in order to obtain the l F inch spark to wind 15,0o0 turns of No. 37 ena mel-covered wire for the second ary. This winding must be made in two sections over two paper tubes wrapped around the primary. The paper tubes can be formed of five or six layers of heavy paper, so that the | finished tube, is of the diameter de- sired for the inside of the secondary Y inding and of the proper width. The
 diameter of this should be 1 h inches
 and the width 2ss inches, so you have two sections of that diameter and
 width. Start each layer of wire about 2ss inches from the edges of the paper, and wind the wire in smooth. even layers. leaving about the same distance at the end. Wrap on two layers of waxed paper between each layer of wire and the next layer of wire. The paper must be put on smoothly and evenly. so as to afford firm foundation for the next layer of wire. If at any time while the wire Is being wound it should break, solder the two ends together very carefully and then cover up the joints with insulating material. Both sections should be wound in the same direction. and the inside wire of one should be connected to the outside wire of the other and soldered. The aerial that you describe will be per feotly all right for sending. provided. of course, that you have the license to do SO.
 When Trans-AtIantics Work e. At what time of the day or night are the big, transatlantic sta tions working as a rule?-P. B. A. These stations are practically in continuous operation day ana night Of course. a great deal, de- bends upon the volume of traffic. It is a pretty sure thing. however. that you will hear at least one of them all the time. Their wave lengths
 range between 10000 and 10000 meters.
 Wire to Use on Loop
 Q. I should like to know if could use No. Is enameled wire for a loop aerial? Would 1t work if it is only 3efeet high and 8 feet wide, with 10 turns?-F. H.
 A. There Is no reason that I know
 of why this loop should not work. provided the proper apparatus is used | In conjunction with 1t. No. IS bare wire would be better. The turn
 should be spaced # inch apart. Of course. with a loop three feet square, | 1t will be necessary to use at least two stages of ampiification and you
 might have to add radio frequency
 republication.
 Using Dry Cells
 ! O. Would the large size call bell
 batteries serve as we'll as the proper 1 "B" batteries. providing a sufficient | number Is used to bring the voltage up to the required amount? What l difference, excepting cost. would there be in using call bell batteries as an
 "A" battery ?--L c. R.
 i A. It will be perfectly all right to use dry cell batteries of the call bell | tpye for . .B'' battery, provided, of quantity of them In series to bring 1 the voitage up to the necessary amount Using this type of dry cell | batteries for the purpose of lighting | the fiiament of your vacuum tube is a very unsatisfactory and costly pro- csdure, beeause of the fact that each 1 of the vacuum tubes uses slightly more than one ampsre of current. Under the ecircumstances the dry bat tery would not last you more than few minutes before 1t became sx- hausted. As matter of fact there Is no real satisfactory substitute for the storage battery for this purpose.
 wave LenEth of Tuner o. IhAve . twc- slider turning coil. | with 7o4 turns of 12 copper wire. fixed condenser, crystal detector, pair of 1.oo0 ohm receivers and an aerial of l two wires 50 feet each with 20-foot 1 lead-in. Kindly tell me the wave length of this set. If I add another coil to this, of 300 turns and connect | 1t in series. will get a very clear wave length with the two coils?- 1 L. B.. W.
 A. The natural wave length of l your aerial Is approximately s6 me-
 ters- The, maximum wave length which your set will respond to is Ap- 1 proximAtely 4000 meters. The addi- l ton of another coil of 300 turns In ssTicA with tho aerial and your | present turning coll will enable you | to lfeten te etations of longer wave 1 lnn gths with maximum range of ! somewhat hstv cen s,Soo and 5000
 mstess xAess statlSas will. of