Experilnental Crystal Set Receivers An anthology of articles extracted from 1911 and 1912 issues of MODERN ELECTRIC~ MAGAZINE repnnted by Lindsay Publications Inc Experilnental Crystal Set Receivers Hints, Tips 8 Secrets submitted to the publisher of Reprinted by Originally published by Lindsay Publications Inc Hugo Gernsback Bradley IL 60915 New York Design© 2005 original articles appeared in 1911 & 1912 issues of ISBN 1-55918-327-6 Modern Electrics Magazine 2 3 4 5 A GALENA DETECTOR COMBINATION GALENA DE liking; but I would suggest, for the up Herewith is a photo of my detector. It TECTOR. rights, Yi inch square brass rod, each I works well, and needs no descriptive matter This detector is used in case a quick inch high. The distance between Ar and to work by. The whole surface oi the Crystal "Galena" change is necessary. If one of the points A2 I~ inches, and 1 inch between A1 can be easily searched, by gently lifting t11e of this detector happens to be knocked and BL The springs between X and A I spring with a match and letting it down again. out of adjustment by static or other will hold the mineral in tight adjustment, means the other detector can be easily while the check nut in A2 holds the other thrown in the circuit by making use of rod from slipping. the two point switch. The arm of this Contributed by switch b connected to one side of the cir JESSE SAUTER. cuit while the points are connected to Bx and B2. The base of this detector, or Ax, A2, A3. are all connected together CONTACT FOR LOOSE COUPLER and led to the other side of the circuit. While building a loose coupler of the style You will find that this detector can be described in "How to Make Wireless Instru ments," the idea of placing two springs on my secondary to make contact with the rods did not seem very good to me, so I bought two brass curtain rods, J/16 inches diameter, of the kind that has a small lube ,JicJing into a slightly larger one. l used the small tubes for the rods on which the secondary slides, and after cutting two piece; of the larger tube the lengt11 of my secondary, I soldered one end of the wire wound on the secondary to one large tube and the wire from chc switch to the other tube. I then placed the tubes in holes bored one inch above and 1,elow the center of the end pieces of the secondary. I find that it is possible to obtain a better con· tact by this means than by the springs, be· cause the whole weight of the secondary lies upon the brass tubes, and I also find that the secondary slides much easier this way. adjusted to the highest degree of sensi Contributed by T. E. JONES. M odeni Electrics has a good circulation in tiveness, and is easy to construct, its di this colony, and is very popular. mensions being m(\de according to your Contributed by 2 W. F. HALL, Australia. A TUNING COIL SLIDER. AN ADJUSTABLE CONDENSER. that this condenser cannot be used for secondary purposes. The rod is made of two No. 14 brass The condenser consists of 10,000 Contributed by J i\lVIES G. FITCHETT. wires, D. square inches of tin foil and wax paper, The slider is made of a brass block, made up in seven sections as per B, three-eighths inch square and. one sketch; l'.I: pieces of brass, 1 inch by 1 HOW TO MAKE AN EXHAUS -0 eighth l n ch inch by 3-16 inch, and 2 pieces ~ inch TED COHERER. thick. Tw o by 3-16 inch by 7~ inches; 14 binding Procure tJ.IJ: inches of glass tubing h o I e s arc posts; and 12 plugs to ~t holes as p~r such as is used in a chemical labora drilled o n e - sketch. The condenser 1s made up m tory, about one-quarter of an inch i_n sixteenth inch the regular way, first a sheet of wax pa diameter. Take a dime and cut from 1t from the edge, per, then a sheet of tin foil, until sev~n two disks, B, about one-quarter of an F, so that the condensers have been made. It will inch in diameter. Next get two inches E wfiti rtehse whiolll esju. st pblea isne, etnh abty t htehree siks eptcrahc, tiwcahlilcyh nios lvimeriyt of copper or brass rod one-quarter of The spring, to the different capacities that can be ..·1,-.- . Q.- ·~ C, is to 1~1ake obtained. This condenser can be used contact w t t h for primary circuits or tuning, and is B the tuning coil a very useful instrument around the wire, and is laboratory for experimenting purpos_es. o~ fastened to the The tinfoil sheets can be cut any size A•01"1C block, B, by to suit the maker. It is understood 0 BC·-SCOILP¥P£1i'1R PI.~ f means of the E· " " ~"8fltA.5~e.AP battery bind 2·~1EClS~0JC~i< 7f H.• TtiS! 'l"l'tfr/P..\/(iW. i n g post, G, M. t.. and the hard J.4-B1NOIN<i an -iud1 in oiamcter and cut it into two rubber knob, E. POSTS pieces each one inch long. Solder the silver disks to one end of each of these The brass wires are fastened to the rods, E, neatly. Next get t"wo pieces of tuning coil ends by means of brass No. 22 platinum wire, each one and a screws. Contributed by half inches in length; drill a small hole in the other end of the rods and solder BERTHEL CARLSON. the wire in these as in E. The next is a delicate job. Both of these plugs are filed to lit t·he tllhe 3 off the short piece and leave the tip. test tubes, with corks to fit; enough Place the filings in the tube, made of tinfoil to cover both outer and inner !14 per cenl. nickel and G per cent. sil sides of the tubes; two binding posts, ,·er. These can be obt?ined from coins, and four or five feet of green flexible using a clean new file. Slip the other wire. plug into position and pull the plati To begi11 construction, smaller spool num wire through the tip, as shown at a is glued to bottom of larger spool b, N. Space the plugs 011e-sixtcenth of an to form a stand. Then six %-i11ch inch apart, and seal olT this tip as was holes FI arc bored straight through the first. The tube is now filled with both butts. Cnre must be taken to get mercury, using a funnel, tap the tube these holes spaced evenly apart. so as to expel all the air bubbles. Fill The test lube~. after being covered snugly and also must be airtight. Ex this tube completely and place your with the tinfoil by gluing, are slipped treme care should be taken not to thumb on the end. Invert, and place into the holes in the stand forming the break the tube, as it must be over forty the open end under the surface of the Leyden jars. The corks have a hole c inches long. Next seal the plugs in the mercury, then release your thumb. bored through their middle, in which tube. You will need a small bowl, Then with the aid oi a helper seal off some mercury, and burner, also a help the tube above the mercun· level. as er. Hold one end of the tube over the the mercury will drop to the thi~ty­ flame until it is red-hot as in L. Then inch leYe! as in P. Place. brass caps seize with the fingers and draw it out over the sealed ends, making contact to a point; break this off about one with the platinum wire. The instru quarter of an inch from the long end ment is now ready for use. and the end will look like J. Slip one Contributed by plug through the open end and draw FANNON BEAUCHAMP. the platinum wire through the small end; hold this over the flame, and LEYDEN JAR CONDENSER. the glass will adhere to the platinum. Measure about foar inches from the The materials needed for the con sealed end and hold it in the flame: struction of this condenser are: two is inserted a wll'e S, connecting the also hold another piece of tubing in the wire spools, one about six inches in inner covering of tinfoil to binding flame at the same time; when both are diameter, the other tliree inches, the post d. Then wires are wrapped hot touch the small pier:e to the long larger being four inches high, the tightly around the outside covering o[ piece at the four-inch mark and draw smaller Lhree inches in height; six the tubes w, connecting to binding out a small tip, as shown at M. Brc~Ll< post e. 4 After varnishing, the device is ready found convenient to screw into the for work. brass rod, if the outer coil is not suf Contributed by ficiently flexible to allow the rod to go JOHN B. BRADY. through both holes. The condenser is built up of a num ber of sheets of tinfoil and paraffined A PORTABLE RECEIVING OUT paper or some !iimilar dielecti-ic, as FIT. shown. The le;ids are made to a switch "' Below is described a portable wire less outfit smaller than a small camera, than 4Y.lxiJ:~x3X inches. Black stain SET C\..OSEO in which sensitiveness is not sacrificed and a coat of varnish will give a fin to saving of space. ished appearance. It consists of a variometer, a conden Contributed by ser contained within the inner coil, and LEWIS C. MUMFORD. a detector of any type preferred by the maker. The ,·ariometer consists of a card ROTARY LOOSE COUPLER. board cylinder, 1Ux30 inches in diam eter, with the inner cylinder 3 inches fNER T\lat The [ollowing gives data for con- outside diameter. Both cylinders are wound with an equal amount o[ No. 24 B. & S. gauge enameled wire. In as shown in Fig. 2, after which the placing the inner coil in position, a whole conderiser is embedded in para brass piece as shown in D'ig. 1 may be ffin. Two condensers would be an im provement. The mineral detector, either perikon r.t:,, ~;;,;~:~"" or silicon, is used. The type sho>vn in •"v"'•o•a< _.~- . the drawing is very satisfactory. F1Q 1. - The details of the construction of the box containing the instruments are left to the maker. The over-all dimensions should be at the most a trifle more struction of a loose coupler. The prim ary is made of wood, and the secon 5 darv of hose. C..o"'or/'13rr> ·~JG 2- cut a groove on the circumference about half an inch wide, and a quar """""""c; ter inch deep, as per illustration. Then I think the diagram explains all de with No. 24 enameled wire. The novel wind about a hundred turns of No. 36 tails. part is that each slider works in insulated copper wire on this disk, Contributed by dependently, and that they are in leaving the ends for attaching to bind WM. T. REBENHAULT. sulated from one another. It is con ing posts. Over this wind twenty nected into the circuit the same as any turns of No. 22 copper wire in the other double slide tuner. Drawing is same direction, having insulated it well A ROTARY TUNING COIL. self-explanatory. from Lhe No. 3f5 wire, also leaving The following is a description of Contributed by leads for two binding posts. Then on my double slide, rotary, and very ac- C. J. SEDLAK. positions indicated in diagram, screw RuaaE'R TUNING TRANSFORMER l'fN08 111'!81'£ WA(,Wfl't S As anybody knows who has tried it, TUNtN<; COil. the making of a transformer for tun " 0 ing is a difficult job, and also a very cl.umsy one. Another objection is the expense oi material. A very efficient substitute can be made as follows: Cut ., out a disk of wood one inch thick arid about four inches in diameter. Then curate tuner. The circle and base are of 1 inch stock, the circle being wound 6 in bindit~g posts, connecting the ends After the pan is fastened to the base, HOW TO MAKE A SENSITIVE of the wires, one to each binding post, two uprights arc provided, which are GALVANOMETER. and mark them. Here we now have fastened to ~he base. about four inches f'in<ling the need of a good galvan a condcn~cd form of tuning trans irom the pan. Between the uprights, ometer, and one that would be very forme~, with_a _very short wave length. a metal rod is suspended, from which ;;ensiti,-c, witl1out paying a high price A tuning coil 1s now connected in se wires are dropped down into each ries with this instrument, and we have glass; and which is connected to the tor one, I succeeded in working out Lile follo\\'ing-: an arrangement which tunes sharper other binding posl. (See Fig. 2.) and with much less trouble than the The glasses are now filled with a Make a base 4x4x% inches thick, nf mahogany or walnut and bevel the ordinary .tuning transformer, and cost solution of salt and water. edges as shown in Fig. J. Make two ing a great deal less, as almost every The capacity of this condenser is standards or sides, 2;4x3.J4x.0 inches. amateur possesses a tuning coil. The ,-aried according to the amount of so- No. 22 wire is connected in the aerial circuit, and the No. 36 in the receiver circuit. I have found this to work as good as a regular tuning transformer. Contributed by WALLACE ELLS. ADJUSTABLE CONDENSER FOR SENDING ONLY. 1"!1,.,-jA,,L.[ d:.•$~ First, select six or eight thin table glasses, free from bubbles and cracks. lution i!1 the pan; or if a large capacity Fasten these to the base, with some Lt is best to wax the tops of each glass JS required, the pan is filled with this good glue, 2,l!,I inches apart (inside to prevent leakage. (See Fig. 1.) solution up to the top. If a low ca measurements). Second, get a metal pan which will pacity is required, the solution in the Nol\' make a top of the same ma hold all of ~he glasses, and which is pan may be but a few inches. Thus terial as the base, size 2;Y.lx2y.lx% of the same !height as the glasses. the capacity of the condenser is va inches, and bevel the top edges of this. The pan should be mounted on a ried according to the amount ol solu Drill a hole in the center, large enough base, provided with two binding posts. tion in the pan. to admit a battery nut, see Fig. 2. To one of the binding posts a wire is Contributed by Shape a piece of copper or brass as fastened, which, in turn, is soldered to JAY JAKOWSKY. shown in Fig. 3. Make a cross piece to the pa11. fit this, Fig. 3a. "Fasten the support 7 to the under side of the top, Fig. 4. mirror, ~x;h inches, and fasten in the other ends are brought on the outside. This part of the apparatus works the slots (on the top of the cylinder), with to binding posts; sec Fig. 7. same as t!he adjustinent of the E. I. glue. Fasten a small silk thread to the Now make a back and front from a Co.'s electrolytic detector. Examine center of tq1e mirror with a drop of piece of plain glass and fasten the front Fig. 4 carefully and all will be clear. glue, and the other end of the thread so that it will be removable. Fasten \fake a thumb screw as described in must be fastened to the small hook on <1 dial on two pieces of wire so that it November, 19ro, issue of Modern Elec the plunger, Fig. 7. The spring on the ll'ill be adjustable and finish instru trics, page 452. The top may now be put bottom of Fig. 7 is made cf No. 10 ment with several coats of shellac. in place with glue, and is shown copper wire which has been annealed, Fig. 7 shows a side view of the in complete in Fig. 4. one end being fastened to the copper strument, and Fig. S shows a view Next we must make a copper cylin q'linder and the other end to the base from the top. der one inch long by one-half inch '~it:h a small tack. Contributed by diameter. Prick or punch two small Now make two coils, each two inclhes FRANK L. BUNKER holes one-quarter of an inch from the long by one inch wide by three-quarters of an inch thick. \iVind them in the top, and diametrically opposite; also two one-sixteenth of an inch from the form of an arc as described by Fig. 6. HOW TO MAKE A GALVAN They should be wound on pasteboard bottom. These are for the magnetic OSCOPE. forms, and wound with fifty feet each needles. Cut two slats in the top one of No. 36 wire. The resistance will A galvanoscopc for detecting $mall eight'h of an inch deep and (wide then be approximately 100 ohms. They currents of electricity can be made enough to receive a small mirror, size should be fastened to the sides of the from a coil of wi.re, A ; a glass tube, Y<(x0 inch), diametrically opposite. box, witlh two pieces of wood as shown B, full of water; a core, C; and a Magnetize two needles or small bits in Ga, and connected in series. The base, D; with binding posts as shown. of steel about one to three-quarters of The core, C, which is made of iron and an inch long. Place one of these in cork is a trifle lighter than the water it displaces, and will therefore remain the top holes of the copper cylinder in the tube normally; but as soon as with its north pole to the left. Now a current of electricity passes through place the other needle in the bottom the coil, the core is drawn down out holes, with the norfth pole to the right. ui sig1ht. The current required is very This is to prevent the earth's magnetic small as the core is so nearly balanced field from affecting the readings, and that the lea!'t nttrnction will cause it is called the astatic system. The to sink. The glnss tube may be a test needles may now be fastened with a tube :is shown in Fig. 2. or any empty drop of glue or shellac. Now cut a 8