-iT\CK 
 ANKEX 
 
 CT
 
 RADIO t RAFT 
 
 Booklet No. 1
 
 Miidel Illustrating Arrangement o1 Radio Kfffi\ inu Set.
 
 Handcraft Projects for School antl Home Shops 
 
 RADIO CRAFT 
 
 (Radio Booklet No. 1) 
 
 FRANK I. SOLAR 
 
 Nortliorn lliuh Stiiool, Detroit, Michigan. 
 
 Editor of "Tool Craft, roys and Useful Articles a Buy Can Make.' 
 
 "Practical Construction Work for Home and School Shops," 
 "Bird Housts uf Simplt- Constiuction" 
 
 
 The liriice I'lihlishing Company, 
 Milwaukee, Wisconsin.
 
 Cupyiight 1S)22 
 The Bi-uce Publishing Company 
 Printed in V. S. A.
 
 TABLE OF CONTENTS 
 
 Radio Sets as Manual Trainin.u- Prujects 7 
 
 Eadio Craft 9 
 
 The Aerial 13 
 
 Tuning Coil No. 1 Ki 
 
 Plate of Tuning Coil No. 1 IT 
 
 Tuning Coil No. 2 18 
 
 Plato of Tuning Coil No. 2 19 
 
 Making the Condenser 20 
 
 Plate of the Condenser 21 
 
 Making a Detector 22 
 
 Plate of a Detector 23 
 
 Receiving Transformer or Loose Coupler 24 
 
 Plate of Receiving Transformer 2.t 
 
 Hook Ups for Coils and Coupler 2S 
 
 Plate of Hook Ups and Coupler 29 
 
 2065680
 
 RADIO SETS AS MANUAL TRAINING PROJECTS 
 
 The making: of toys, boats, bird houses, kites and 
 aeroplanes have all been accepted in turn with great 
 enthusiasm by boys in manual training classes. Noth- 
 ing however, like the Radio Craze has ever caused the 
 boys to beg to come in and work, the girls to inquire if 
 it would be possible for them to do work, and fathers 
 and mothers, to come to our shops for parts and infor- 
 mation, for setting up Radio receiving sets. 
 
 Most of the projects made in our shops such as book 
 racks, etc., will serve the purpose if H-inch longer or 
 shorter than the drawing. This is not true with the 
 wireless receiving set, which requires less material than 
 the usual models, but each part must be a certain size 
 to make the next part work, and the boy appreciates 
 the meaning of real accuracy. It also instills in him a 
 desire to search the shelves of the public library and to 
 study books on this subject. It makes him rack his 
 brain to figure out how to make use of available sci'ap 
 material to take the place of parts that he has not the 
 money to purchase. 
 
 The crowning feature, however, of this project is 
 that when finished it looks so different from the usual 
 
 article the boy brings home, almost like an infernal ma- 
 chine, that the whole family is interested to the extent 
 of offering their help to get the thing rigged up for a 
 tryout. This is so different from the usual interest 
 shown when the boy's work is brought home, which con- 
 sists of an expression — isn't it nice. Then the article 
 is forgotten. 
 
 The boy has a chance to tinker with the elements and 
 with many different kinds of materials. This is the best 
 kind of education, and the desire for learning comes 
 from within. It is a chance for father and son to get 
 together and work on a problem that is of interest to 
 both. 
 
 Let the boys experiment, for it will drive them off 
 the streets into the school and home work shops where 
 ever.v boy and man should spend some of his spare time. 
 While there he will make articles that will not only 
 afford pleasure and pastime but will be a benefit edu- 
 cationall.v to the household. Let the good work go on. 
 
 F. I. S.
 
 RADIO CRAFT 
 
 lllustratiun 1. Tunini.'' Coil. See page Ifi.
 
 RADIO CRAFT 
 
 Radio and wireless experinientins' by amateurs in 
 this country had gotten nicely underway about the time 
 the World war started. Due to the fact that war de- 
 partment reg'ulations required aerials to be disman- 
 tled, amateurs had to lay aside their equipment for 
 a while. However, after peace was declared experi- 
 menting' soon became popular again. After the special 
 training received in service many more young people 
 were interested and had considerable more practical and 
 theoretical knowledge of the work than those interested 
 before the war. 
 
 The average person was not any more interested in 
 Radio, than in any other new feature brought to his 
 attention. The reason for this was that most broad- 
 casting was done in code, and it is a considerable task 
 to master the code so one can receive. And even for 
 those who could receive, the information gained, was 
 of little interest. 
 
 When different agencies began broadcasting music, 
 entertainments, lectures, news, etc., to be heard by the 
 aid of the radio-phone, everyone became interested. 
 And today we have thousands of people all over the 
 world enjoying entertainments daily. 
 
 There are no laws governing the use of receiving sets 
 and the handy person can make one that will receive 
 the broadcasting in his vicinity. The sending, how- 
 
 ever, requires an expensive apparatus and also a license, 
 the obtaining of which involves certain qualifications 
 and requirements. This is of little concern to most 
 people as they are content to listen to others of interest 
 rather than spend their time jamming the air. 
 
 Almost any of the apparatus used for broadcasting 
 and receiving can be made or assembled by the handy 
 man, boy and mechanic. Although material required is 
 quite expensive for the larger outfits, the average ex- 
 pert worker, even if competent to make a set, could 
 not afford to invest a great amount in material. Per- 
 sons who can afford to will no doubt buy a complete set, 
 and even if they were capable would not have the time 
 to make their own sets. There are thousands of people 
 who would like to listen in on the programs offered. 
 They would like to make their own outfits and can do so 
 by following the directions given in the following pages. 
 
 The following drawings and instructions are given to 
 be used by the handv man and boy in the home and 
 school shops. It is not intended to give any technical 
 discussion in this description but to show by drawings 
 and a brief explanation how to set up a receiving outfit 
 at a minimum cost. This set is similar to many that 
 my boys have already made. By the aid of such sets 
 they are receiving gi-eat enjoyment listening to the code 
 and the wondei-ful programs they are able to get.
 
 10 
 
 RADIO CRAFT 
 
 One of these little receiving sets will be worth a 
 great deal to the busy mother unable to leave home 
 evenings, to crippled people confined to their beds or 
 chairs, to convalescents, and people living far out in 
 the country and at resorts in the summer time. 
 
 Do not be misled by statements that for a dollar or 
 two you can make a set that can be connected to your 
 victrola and heard all over the house, or that will re- 
 ceive concerts broadcast at a great distance. This is 
 not true. To do this requires a set composed of at least 
 the following equipment, in addition to the receivers 
 and aerial : a rheostat, amplifier panel, bulb, grid con- 
 denser, grid leak, six volt (A) battery and a (B) bat- 
 tery. An outfit of this kind costs $65 and up. 
 
 The wireless and radio-phone are still in an experi- 
 mental stage and it is advisable to investigate and pick 
 a reliable standard set rather than to invest consider- 
 able money in inferior wireless apparatus. In a short 
 time marvelous new equipment will be on the market 
 and an outfit may be hooked to the electric circuit and 
 even the ordinary telephone may be used to receive 
 broadcasting. It would be well woith while for those 
 interested in this new venture to make a home made 
 receiving- set first and do a little experimenting until 
 they decide on the larger set they want. Most of this 
 beginning apparatus can later be hooked in with the 
 more expensive set. 
 
 lllustratiun 
 
 .\ I'lirlabk- Hume .\lLide Outfit.
 
 RADIO CRAFT 
 
 11 
 
 Illustration 3. A Pocket Outfit. 
 
 Illustration 4. A Tuning Coil and the Boy \\'ho Made It.
 
 12 
 
 RADIO CRAFT 
 
 Illustration 5. Home Mr.de Loose Couplers, Condenser. Detector .thH Coil Wound on Nails.
 
 THE AERIAL 
 
 The first thiiiK to be cun.sidered when installing a 
 receiving set is the aerial. Of course it is possible to 
 get results from your bed spring's, the eaves trough, a 
 metal railing and many other things, but natuially a 
 specially erected aer'al is the most satisfactory. 
 
 A loop aerial may be erected indoors. It may be 
 stretched in the attic or any room. Some have .strung' 
 the aerial across the room from the picture molding on 
 one side to the molding on the other. A row of picture 
 hooks or sci-ew eyes will do to support it. While it is up 
 out of the way it is not very convenient on house clean- 
 ing day. Two coat hangers hunLi' at either end of the 
 room will make good stretchers. 
 
 Sound waves travel through the ether and are caught 
 by the antenna of the aerial, which is the part sus- 
 pended between the stretchers. 
 
 Almost any length of aerial at any height from the 
 ground will give results for receiving from a short 
 distance. The higher from the .uround and the longer 
 the antenna the better. 
 
 Excellent results will be obtained by a 7.5 to 1.50 f<iot 
 aerial placed from 30 to .50 feet from the ground. The 
 antenna should be allowed to sag a little so it can blow 
 in the breeze and thus shake off the snow and ice which 
 might collect and break it if strung tight. 
 
 For small sets to receive from a short distance any 
 kind of wire will do, either bare or insulated. The best 
 wire to use is No. 14 copper or aluminum (bare). For 
 guy wii-es use No. 10 or 12 telephone wire. 
 
 The laws require that amateurs send on not over a 
 200 meter wave length. The four wire aerial, illus- 
 trated in Fig. 1 is 7.5 or 80 feet long, and is about right 
 for sending this length wave. The masts which are 
 fastened and braced to the peaks of the roof may be 
 any length. The stretchers should be about nme feet 
 long and the wires equally spaced. At the free end M 
 the wires may or may not be connected with each other. 
 The other end N, from which the lead in is taken, should 
 have each wire of the antenna connected to one that 
 leads in to the instrument. 
 
 Fig. 2 shows a short one wire aerial having the 
 masts fastened to the front and back of the house. Fig. 
 3 shows bicycle rims or barrel hoops used, where it is 
 not convenient to get long stretchers. 
 
 Fig. 4 is an aerial stretched from a house to a garage 
 and Fig. 5 shows one wired to chimneys on an apart- 
 ment building. 
 
 Fig. 6 illustrates, at A and B, how ordinary porce- 
 lain cleats or glass pony insulators are used where the 
 antenna is connected to the spreaders. The one wire 
 aerial insulated, as shown in Fig. 7, is made as long as 
 
 13
 
 14 
 
 RADIO CRAFT 
 
 possibk' and is the easiest to erect and will j;ivo good 
 results. The loose ends can be attached to screw eyes 
 screwed at any convenient place from the house to the 
 barn, a tree, post or the garage. 
 
 A lightning switch, if large enough to be of any 
 account, is rather expensive. A drawing for one that 
 can be made from Vg-inch or thicker sheet copper, and 
 a cement base is given in lUus. 1. A box of wood can 
 be made into which to pour the cement. Pegs should 
 
 be insei'ted in the cement while soft and jiulled out 
 after it has hardened to make holes for fastening to 
 the window sill. The posts can be held in place by a 
 piece of stick suspended over the top of the box while 
 the cement is hardening. To conform to wiring regu- 
 lations it will be necessary to place a plate of composi- 
 tion material beneath the cement. 
 
 A porcelain, glass or rubber tube may be used to 
 insulate the lead in wire where it passes through the 
 sash.
 
 RADIO CRAFT 
 
 15 
 
 RADIO AERIAL 
 
 LiaHTNiNG Switch 
 
 Fia 3 
 
 , Bicycle Rims 
 
 OR 
 
 Barrel Hoops 
 
 ferf 
 
 O^ 
 
 Details of Aerial and Suggestive Methods »»f Mounting.
 
 TUNINC; (OIL No. 1 
 
 The radio waves are sent out in different lengths by 
 different broadcastinj;: stations. The ones you wish to 
 receive must be tuned in so you can receive them. This 
 is accomplished by moving the sliders on the sliding 
 rods. 
 
 This outfit is made up complete so that by connecting 
 your aerial at A your ground at B and your phones at 
 G and H you are ready to tune in and receive. 
 
 The coil can be wound on either a cardboard tube or 
 a solid piece of wood. If w-ood is used be sure it is 
 well seasoned or it will shrink and your wire will hang 
 loose on it. 
 
 The first thing to make is the coil. For this get a 
 rolling pin and saw off the handles. To hold one-half 
 pound of wire it should be 2% inches in diameter and 
 10^4 inches long. Make a groove with the marking gauge 
 iV.-inch from one end. Drive a brad alongside the 
 groove and then give that end of the pin a coat of 
 shellac. We are going to make the coil by winding No. 
 22 enameled copper wire around the pin. Twist the wire 
 around the nail twice, about 6 inches from the end of 
 the wire. This end is left for making a connection. 
 Now wind around the pin, the first time around running 
 the wire in the groove. This is done while the shellac 
 is wet and it will help hold the wire in place when it 
 
 dries. 11' you shellac as you wind, it will not be neces- 
 sary to get the shellac on your hands. When you have 
 reached the other end of the pin drive another brad and 
 fasten the wire as before but the six inches at this 
 end should be wound around a pencil making a pig 
 tail. This end has no connection. 
 
 
 lUustration 6. Winding a Coil. 
 
 16
 
 RADIO CRAFT 
 
 17 
 
 M- Ca T \NhI5KER 
 
 N- Crystal cup 
 O- TiGiiTNiNc Screw 
 
 P' CRYSTAL 
 
 u 
 
 -/2- 
 
 TUNINGCOIL No. I. 
 
 ■^PouND No SB Enamel £0 
 Copper Wire- Bare 
 
 Rolling Pin 
 
 Slider 
 
 L J L J 
 
 -iir 
 
 :ir.., 
 
 ^^rFI 
 
 Base 
 
 Plan For v^/ring 
 
 RIAL iCoNDEHSER 4 Sliders 
 
 Z Detector SPisTail 
 
 i Slider Roos 
 ^ 3 4 c 
 
 Details of Tuning Coil No. 1.
 
 18 
 
 RADIO CRAFT 
 
 Lay the coil aside and niakp the ends. Fasten them to 
 the coil with screws about IV2 inches from the top of the 
 end pieces. Next make the base and fasten to the end 
 pieces and then the legs and fasten them to the base. 
 
 Now if you wish to purchase your parts, buy two 
 A-inch square brass slider rods and sliders to fit. Also 
 a condenser and a detector. If you wish to make all 
 parts, information for makinp them can be had from 
 following drawings. 
 
 Your connections can be made at the end of the 
 slider rods by fastening the wires under the brass round 
 head screws that hold the slider rods in place. 
 
 Now we shall wire the tuning coil. Bore holes for the 
 binding posts at A and B and also for the wires that 
 are connected to them. Connect straight wire left at 
 the end of the coil to A, after running it through the 
 
 hole in the end piece and scraping off the insulation to 
 make a good connection. Connect wire to the end of 
 the slider rod at C, run through the hole in the base, 
 across underneath the base, up through the hole at the 
 opposite end and through the one in the end and con- 
 nect to B. Connect a wire to post G on the condenser 
 and run through holes to post B. Connect H on the 
 condenser to F on the detector. Connect E the crystal 
 cup screw with slider rod D. 
 
 The cat whisker of the detector is lettered M, the 
 crystal P, the crystal cup N and the set screw O. 
 
 The wood work on this instrument should be stained 
 and shellaced or varnished to add to its appearance. 
 
 Scrape the enamel from the wire where the points of 
 the sliders touch. Be sure all connections are well made 
 and no insulation is left between them. 
 
 This instrument is ready for use. 
 
 TUNING COIL NO. 2 
 
 This coil has the same capacity as coil No. 1 but can 
 be made much cheaper as the wire is the only thing that 
 need be purchased . 
 
 An ordinary oat meal or cereal box is used in place 
 of the rolling pin on which to wind the coil. Be sure 
 that the cereal box is dry and give it a coat of shellac 
 to stiffen it. If the coil is wound on a damp box, the 
 wire will come loose when the box dries out. 
 
 Begin work on this instrument by making and wind- 
 ing the coil. The top and bottom of the box are re- 
 moved and wooden discs are tacked in the ends of the 
 tube. The discs can be sawed to shape with a coping 
 saw. 
 
 Make the wood frame for holding the coil. This needs 
 no further explanation, as the construction and sizes 
 of different parts can be learned from the drawing.
 
 RADIO CRAFT 
 
 19 
 
 Tuning coil No.i. 
 
 This coil isCapable Of receiving a 5 
 WELL A3 No.i But As No rods. Sliders Or 
 Posts Are used only viire need Be Purchased 
 
 No 14 COPPER WIRE 
 
 r-TA K£ Two 
 
 Details for Making Tuning Coil No.
 
 20 
 
 RADIO CRAFT 
 
 The sliders are made of wire and slide lui tlie wooden 
 frames connected to the uprights at the ends. This 
 saves the expense of slider rods, etc. 
 
 The windin,?: of the coil and the wirin."- of this instru- 
 ment are the same as explained for Coil No. 1. 
 
 Screw eyes and rubber bands should be adjusted, as 
 shown on the drawing, at both ends of the instrument. 
 The rubber bands hold the points of the sliders in 
 close contact to the coil. Scrape the insulation where 
 the sliders touch the coil, as instructed for Coil No. 1. 
 
 The instrument should be stained and shellaced or 
 varnished to add to its appearance. 
 
 Instead of hooking to the end of the slider rod, as 
 instructed for Coil No. 1, on this coil hook to the eye in 
 the slider itself. 
 
 MAKIN(; THE CONDENSER 
 
 It is the practice in connecting up receiving sets to 
 use a small fixed condenser across the telephone ter- 
 minals. The condenser acts as a stopping condenser. 
 In small set hook ups some are able to get results with- 
 out the condenser. 
 
 Materials needed for the condenser are as follows: 
 
 1 Piece of wood, % x^Vi x 6 inches. 
 
 2 Pieces of Cardboard, 3V4 x5% inches. 
 
 10 Sheets of tin foil, 3x4y2 inches. 
 
 11 Pieces of waxed paper, .3'4 x4 inches. 
 2 Binding posts. 
 
 4 Pieces of thin sheet brass. 
 Some vaseline. 
 
 Begin making the condenser by cutting 11 pieces ol 
 waxed paper according to pattern C. 
 
 Next cut ten pieces of tin foil according to pattern B 
 and two pieces of cardboard like pattern A. 
 
 Place a piece of cardboard A on the table and with 
 the fingers spread on the upper face a thin covering 
 of vaseline, .just enough to hold the first sheet of waxed 
 paper in place. Lay the first sheet of waxed paper C. 
 on the cardboard and grease the upper side as you did 
 the cardboard. Now place the first sheet of tin foil on 
 the waxed paper, with the %" x %" projection, ex- 
 tending at one end. Continue piling up the pieces as 
 indicated on the drawing. The next piece of tin foil 
 should have %" x %" projection, extending at the oppo- 
 site end. Continue greasing and piling the parts, being 
 sure to alternate the projection on the tin foil sheets. 
 
 Cut the thin sheet brass washers and put in place. 
 
 iVIake the wooden base and bore holes for the binding 
 posts. 
 
 Place the condenser on the wood, after it has been 
 pressed together tightly. Locate and bore holes. As- 
 semble according to the drawing ready for connecting 
 to the set. 
 
 If desired the condenser may be connected directly 
 to the base of the tuning coil instead of attaching to the 
 wooden base. 
 
 In the corner of the drawing will be found pictures 
 of commercial condensers, that can be purchased for 
 from 30c to $1, depending on the workmanship.
 
 RAniO CRAFT 
 
 21 
 
 4 A__ 
 
 B -■ :-, 
 B - 
 B — = 
 
 fl — — 
 
 c 
 
 VJaxed Paper 
 Bread Wrapper 
 
 '^ 
 
 Condenser 
 
 Nut ^^, 
 
 t 3" 
 
 Dt-tails uf a Hume Made L'undenser.
 
 MAKING A DETECTOR 
 
 The sound waves as they are eauR-ht by the antenna 
 are not of a desirable type of current. They must be 
 changed to the suitable type and this is done by the 
 detector. 
 
 The materials used for the commercial product con- 
 sist of a wooden base, two binding posts, a crystal cup 
 and a part called a cat whisker, which is nothing more 
 than a pig tail made of bronze spring \vire. The pig 
 tail is made by winding the wire around a finishing 
 nail. 
 
 The crystal is nothing more than lead sulphite and 
 may be called galena, carborundum, silicon, etc. This 
 mineral must be chipped off to make a bright surface 
 and a good contact with the cat whisker. Dust soon 
 gathers on the surface of the crystal. This can be pre- 
 vented by covering the whole detector with a large 
 drinking goblet or wooden box. 
 
 Practically every home made detector is made in a 
 different way and of different materials. The reason 
 for this is that there are only two essential points; 
 first some means of holding the cat whisker so it can be 
 moved about and adjusted on the crystal; and second 
 some means of holding the crystal tightly. 
 
 The detector can be set up on a special base or on 
 the base of the tuning coil. 
 
 For Type 1 get a piece of wood %" x 214" x 4I/2", 
 an old cuff or suspender clip, a piece of sheet brass, five 
 round head bi'ass screws and a piece of fine brass or 
 bronze spring wire. Bend the clip and brass strip to 
 form, as indicated on the drawing, and drill holes for 
 the screws. If the hole for the cat whisker screw is 
 made smaller than the size of the screw the screw when 
 forced through the hole will tap out the hole. Assemble 
 the parts, solder the cat whisker to the screw and a wing- 
 in the slot in the head of the screw. Insert the crystal 
 in clip, and tlii' detector is ready fur business. 
 
 Type 2 is made similar to Type 1, except that all 
 parts may be purchased and only the assembling is to 
 be done. The conni'ctions in this case are made betvvi'en 
 the nuts at J. 
 
 The adjustment and sensitiveness of the detector 
 are responsible for the success of your set. So it is 
 quite important that you buy a good piece of tested 
 mineral or crystal. 
 
 Be sure when making connections antl before sol- 
 dering any joints that all parts are well scraped. 
 Not scraping off the insulation is often the cause of 
 poor results. 
 
 22
 
 RADIO CRAFT 
 
 23 
 
 DETECTOR 
 
 Type / 
 
 Type 2 
 
 CUFF CL IP 
 
 
 V 
 
 B 
 
 ^ 
 
 ^ 
 
 J 
 
 
 
 i 
 
 
 ^-^ 
 
 
 4 - 
 
 F 
 
 tniflO 
 
 Commercial Type 
 
 F 
 
 £ 
 
 .J^ 
 
 
 /^ 
 
 Boy OF GALENA 
 
 /^- Wood 
 
 B- No 36 Bra 35 Spring Wipe 
 
 C- Galena 
 
 D- Sheet Brass 
 
 E- Heavy Copper vjire 
 
 f- Bin DING Post 
 
 G-Galena Cup 
 
 h-Set Screw 
 
 J- Brass Stove Bol t ^Nuts 
 
 Details for the Conbtrucliun of a Detector.
 
 RECEIVING TRANSFORMER OR LOOSE COUPLER 
 
 A loose coupler is more difficult to make than a tuning 
 coil but it will give better results. 
 
 It is for the same purpose as the coil, i. e., to tunc 
 in the sound waves. 
 
 With this coupler, a good detector, a sensitive piece 
 of galena, a pair of 2,000 ohm receivers, 100 feet of 
 copper antenna well insulated suspended on an aerial 
 50 feet from the ground an operator should be able to 
 receive from 200 to 300 miles. 
 
 The coupler is composed of two tubes both wounil 
 with wire, one sliding inside of the other. The larger 
 tube is called the primary and the smaller the secon- 
 dary. The primary is set to the wave length by adjust- 
 ing the top slider. Then the switch on the secondary and 
 the coupler (drawing the secondary in and out on the 
 rods) are manipulated until the loudest sound is heard. 
 
 If you do not possess many tools and it would be 
 difficult for you to make the box it need not all be made. 
 The only parts needed are the bottom and the two ends. 
 
 For the tubes get an oatmeal or other cereal box for 
 the primai-y and a salt box for the secondary. Be sure 
 they are dry before winding the wire on them, so they 
 will not dry out and shrink after being wound. It will 
 stiffen the cardboard to shellac it well before using. 
 
 With a coping saw, cut the opening in the front piece 
 and then make %" discs according to the drawing to fit 
 the back of the primary and both ends of the secondary, 
 also a Vi" disc to fasten to the front of the secondary. 
 
 Get a w." sliding curtain rod, that is one that has a 
 tin tube in which the solid rod slides. Cut off two pieces 
 of each tube and rod the length of the box. The tubes 
 are to be inserted in the ends of the secondary and the 
 solid rods are to be filed square and to a point and 
 driven in holes throu.;h the disc in the back of the 
 primary and into the back of the box. 
 
 Wind the prnnary with No. 24 cotton covered copper 
 wire and when finished give it a good coat of shellac. 
 It will take about one quarter of a pound. Start Vu" 
 from the end of the box. Fasten the ends by punching 
 small holes in the cereal box and threading the end of 
 the wire into the box. The wire at the back end should 
 be twisted so it will not come loose; but the one at the 
 front end should be left quite long, as it is to be 
 threaded back through the box and out at the back end 
 where it is fastened to the binding post (X). 
 
 When the primary is wound it should be tacked with 
 •■■" brads to the disc at the back and to the circumfer- 
 ence of the hole cut in the front piece. 
 
 24
 
 RADIO CRAFT 
 
 25 
 
 
 Receiving Transformer 
 
 OR 
 
 LOOSE COUPLER 
 
 SLIDING CURTA<.\ 
 ROD AND TUBE 
 
 Details, for Makinu a Loo!>f Coupler and Picture of Commercial Type.
 
 26 
 
 RADIO CRAFT 
 
 Purchase or make a slider, and also get a i',-. " slider 
 rod 6^4" long. Fasten the rod to the top of the box as 
 indicated and connect it to a binding: post at Z with a 
 piece of insulated wire having one end turned under 
 the screw at Y. 
 
 Now we shall wind the secondary. For the secondary 
 we need about one quarter pound of No. 30 silk covered 
 copper wire, a rotary lever switch, twelve V*" taps or 
 brass headed tacks and two pieces of flexible copper 
 wire, each 18" lonir. Silk covered electric light cord 
 will do for the flexible wire. 
 
 Along the top of the secondary, divide off' the space 
 into twelve parts and at each division punch a hole 
 with a darning needle. Start about '^ inch from 
 the end to make the divisions and end about th's 
 distance from the other end. Start winding by thread- 
 ing the end of the wire through the first hole No. 1 at 
 the back end of the secondary. Scrape the end of this 
 wire and solder it to one end of one of the pieces of 
 flexible wire. This flexible wire is to be threaded out of 
 the tube through hole A when this front disc is finally 
 fastened in place. Start now and wind until the wire 
 comes to the center of the next hole. {Do not cut the 
 wire but make a long loop tliut irill reach two inches 
 out of the front of the tube) thread through hole No. 2. 
 
 Contimic to wind and loop through holes until hole 12 
 is reached. 
 
 Now scratch the insulation off" of the wire at the end 
 of each loop and fasten under the nut of the taps or 
 solder to the ends of brass-headed tacks, if they are used 
 for taps. Of course the location of the taps must be 
 spaced off on the front disk of the secondary and holes 
 bored for them, and also for the switch. Fasten one 
 end of the other flexible wire to the switch post inside 
 the tube and thread out with the other flexible wii-e 
 through hole A. Now place the front head in the tube 
 and fasten with '4" round head screws so it can be 
 easily removed if repairs have to be made to the wires 
 inside of the tube. 
 
 Scratch the insulation off the wire coil on tlic pri- 
 mary, directly under the slider rod so that the slider 
 will make a good contact. The tongue of the slider will 
 have to be bent no doubt to the proper shape. 
 
 For the hook up look at the diagram on the sheet of 
 hook ups. 
 
 Z is connected to the aerial, X is connected to the 
 ground, the switch of the secondary to the condenser 
 and the other flexible wire from hole 1 to the detector. 
 
 To improve the looks of your instrument stain ma- 
 hogany, varnish and rub down or enamel it black.
 
 RADIO CRAFT 
 
 27 
 
 Illustration 7. Kadio Apparatus Made by Boys Under the Author's Direction and Successfully Used.
 
 HOOK UPS FOR COILS AND COUPLER 
 
 The term hook up is one used commonly by radio 
 operators and means the method of wiring the pieces 
 of apparatus together to mal<e up a set. 
 
 There are many different ways of wiring or connect- 
 ing the instruments together to get results and little 
 difference can be noticed by the different methods. So 
 if by chance you connect your set differently from the 
 diagrams given on the drawini;- you may get just as 
 good results. 
 
 We shall trace the hook up in Fig. 1. The aerial A is 
 connected to the lightning switch at the center post B 
 by the lead in wire, X. If you cannot afford a lightning 
 switch, arrange your lead-in wire so it can be discon- 
 nected from the post B, fastened to an iron weight and 
 swung at least 6 feet away from the house to the 
 ground when not in use. If you have a switch connect 
 the ground post C by a piece of No. (! wire to a piece 
 of gas pipe, driven into the ground. When not in use 
 throw your switch to this post C. 
 
 Connect post D with the end of your coil wire E. 
 The other end of your coil wire is pig tailed and has 
 no connection, as F. Connect H to your water faucet, 
 a radiator, or a wire run to a pipe driven in the ground 
 at G. Also connect one post of your condenser .1 to 
 your ground wire G. Connect the other post E of your 
 condenser to post L of your detector N. Now connect 
 
 post N of your detector to post O the end of the other 
 slider rod and your circuit is made. 
 
 The terminal of your receivers should be hooked to 
 the binding posts at K and J on the condenser. 
 
 Receivers are made in different types. A commonly 
 used kind is the ordinary telephone receiver which is 
 about 75 or 80 ohms. This type is not very satisfactory 
 because it must be held by the hand while receiving. 
 The amateur one-part head piece, which is also about 
 7.') ohms, just brings the message to one ear and allows 
 surrounding sounds to go to the other. The two part 
 head set of from 2,000 to 3,000 ohms is very satisfac- 
 tory. A 2,000 ohm head piece means that each part is 
 a 1,000 ohm unit. 
 
 Fig. 2 shows another hook up for the tuning coil 
 and can be easily traced after reading the description 
 for Fig. 1. 
 
 Fig. o is a book u|) foi- the loose coupicf. The 
 aerial in this case is connected with the slidi r II. The 
 front end of the pi'imarv wire P is connected to ground 
 G. The switch Q is connected with flexible wire to the 
 post R of the condenser I. The post S of condenser is 
 connected to post T of detector. The post U of the de- 
 tector is connected with flexible wire fastened to the 
 end of the wire at the back end of the secondary \V. 
 Y is the primary. 
 
 28
 
 IIADIO CRAFT 
 
 29 
 
 Aic«, 
 
 HOOK UPS FOR COILS AND COUPLER 
 
 Fig. I 
 
 Slid£R 
 
 I g = ffoo 
 
 na. 3. 
 
 Coil 
 
 1^ 
 
 I ? ^ 
 
 Fiat- 
 
 A -AERIAL 
 
 X- Lead In 
 G-Grouno 
 M' Detector 
 I - Condenser 
 Y' Primary 
 \N- Secondary 
 Q^ Switch 
 
 Head Set Receivers 
 
 Diagrams lur Hook Ups
 
 30 
 
 RADIO CliAFT 
 
 Illustration 8. 
 Even the Doll May Share the Evening's Broadcastinjf. 
 
 Illustration 9. 
 Making: Work a Plt-asuri' with the Radiophone.
 
 UNIVERSITY OF CALIFORNIA LIBRARY 
 
 Los Angeles 
 This book is DUE on the last date stamped below. 
 
 HEPDID-UW: 
 
 NOV 2 4 1986
 
 B 000 003 233 4
 
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 I 
 
 II 
 
 fll!