Radio mirror (Jan-Oct 1923)

■nan. 12 RADIO DIGEST ILLUSTRATED Bank Winding Gives Selective Tuning Coupler Design Allows Choice of Plant Desired The accompanying circuit is very sensitive and selective providing the variocoupler is used as outlined. I use a variable B battery and have a variable con WORKSHOP KINKS? EARN A DOLLAR— THERE are many little kinks worked out at home that would aid your fellow Radio worker if he only knew about them. There are new hook-ups, new ways of making parts and various unique ways1 of operating sets that are discovered every day. Radio Digest is very much interested in securing such material. Send them in with full details, including stamped envelope so rejected copy may be returned. The work must be entirely original, not copied. RADIO KINKS DEPARTMENT, Radio Digest Illustrated, 123 West Madison St., Chicago, 111. denser with a vernier and two fixed condensers. Best results will be obtained with condensers using mica as a dielectric. The volume of tone will be surprising the first time it is used and with one step of amplification, 10 to 1 ratio, it is all that can be desired. I am using this pet hookup in preference to one with a variometer and variocoupler. I use an indoor aerial, two wires 32 feet long, and a soldered ground. Just a detector tube is used in the set. I have heard out of town stations clear and distinct while local stations are in the air. There is practically no body capacity in this set. — C. "W. Miller, Chicago, 111. Special Coil Winding I have been getting good results with my crystal set which, outside of the coil, is extremely simple. -The hook-up contains one coil only. On this coil are wound alternately the primary (60 turns of number 22 bare wire) and the secondary has 60 turns of number 30 cotton or silk covered wire. The coil is about 6 inches SENSITIVE AND SELECTIVE HOOK-UP Bank wino first anolas.totui TAPATZ0.2S.35, 4-5ANDS&TS TORN ; .ooos vERNiea VAR. CONO. REVOLVING PLATES * TOQROOND Hf^+m^ long and 3 inches in diameter — oval shaped. As the bare wire is larger the slider touches it and not the small insulated wire. The slider is controlled by the dial and it turns in a semicircle. — Bill Keating, Minneapolis, Minn. Multiple Catwhisker If you have trouble in finding a sensitive place on the crystal try the method which I have used with much success. 5TEELVIVR.E CRY$TAU Secure a small piece of steel wool and then wind a piece of wire around it, allowing some of the steel to stick out at the end. Cut the end off with a pair of tinner's snips to make a "broom" end and spread the ends out evenly. Attach this steel wool whisker to the set. Apply the broom end lightly to the crystal. Tou will have many steel points out of which one or more will find a sensitive spot. — Eli Nemensky, New York, N. T. Don't Throw Set Together It is only necessary to glance at many homemade Radio receiving sets to find out they have been literally "thrown" together. Carelessness is a fault, and explains why so many sets will not function efficiently. For instance, wiring is allowed to loop and stray around in every direction, connections are left unsoldered, wires are merely twisted around one another, poor connections are made to the binding posts, and coils and other apparatus are loosely mounted. The reason for all of this is A. B. C. LESSONS (Continued from page 11) ary by the osillations received from the antenna. The operation of a vacuum tube will vary somewhat with different relative adjustment of filament current and plate voltage. It is these changes in operating characteristics with different adjustments that makes it possible to use the vacuum tube for the various purposes in Radio practice. The A Battery The A battery is the one used for supplying current to the filaments of the vacuum tubes, and ordinarily must have a terminal voltage of 6 volts. The battery may be either of the lead-sulphuric acid type or the Edison-alkaline type. A greater pressure than 6 volts must never be used, or otherwise the filament is likely to be burned out. After the battery has been in service for some time, it will be exhausted, and consequently must be recharged. The B Battery The B battery is the one used for supplying the required potential to the plate, and for the average detector tube has a terminal voltage of 22% volts. Ordinary door bell dry cells could be used for this purpose, providing enough of them were connected in series to produce the necessary 22% volts. This amount of pressure is needed because most detector tubes are made to work best under these conditions. In other words, at this pressure maximum electron flow occurs and hence maximum current flows in the plate circuit. Tubes used as amplifiers, however, require a higher plate voltage. The B battery need not be of the storage battery type because the current they are required to furnish is only a few thousandths of an ampere, and this does not warrant the higher cost. life of B Battery A question that is often asked is how long will the B battery last? This Is quite difficult to answer, for there are a number of different factors that enter in and determine the life of a battery. Among these are the care exercised in the making of the battery, and the use and abuse the battery receives in the hands of the owner. A good grade of B battery will give reliable service for a long period; from 500 to 1,500 hours of use. In the course of time, however, every battery will gradually wear out and become weak. The usual indication of a B battery becoming weak is given by the telephone receivers, for at the start the signals come in strong and firm and then gradually decrease in intensity or "fade." It is true that at times this condition may also be due to some other cause, d Testing' Cells A battery can be tested fairly satisfactorily with the aid of a battery voltmeter connected across the terminals of the battery. This test, however, should be made only after the battery has been in use for an hour or so. and not after the battery has been resting for a time. Try the test on the various battery terminals, and if the readings are much below the markings for these terminals, the battery is practically run down and should be replaced by a new one. Of course, any of the common wet cells can be used with good results, but their bulky size makes their use a little awkward and inconvenient. Since the voltage required for a B battery is 22% volts, and since a single wet cell has a voltage of only 1.1 volts, about twenty such cells would have to be used connected in series. Chapter Ten Having completed our study of the principles of construction and operation of the three-electrode vacuum tube, we are now ready to see how it is employed in Radio receiving circuits. Chapter Ten which will appear next week, will consequently be devoted to a number of efficient vacuum tube circuits. It will be a most interesting chapter and contain many practical operating hints for the owner of a vacuum tube set. "it is only temporary." As a matter of fact, all this poor work interferes seriously with efficient operation and tuning of the set. It is evident that many leads and bad connections on low tension circuits lead to a waste of current and are still more disastrous on high tension circuits. Loose by means of solder. Small soldering lugs provide a ready and neat means of doing this. Extra Phone Connectors An excellent and inexpensive multiple phone connector is shown in the illustration. This device can be used where it is desired to use an extra head set. Two ordinary set screw binding posts such as 8. ABINDING POSTS 6 STUD HAOE BY CUTTING OFF SCREW C CORD TIPS are often used for phone cord tips, are fastened end to end with a stud made by cutting off one of the screws of the post. The phone tips are then connected in series as shown. — H. L. Peterson, Charles City, Iowa. Small pieces of rubber hose or tubing make fair insulators for the lead-in wire where it passes around the cornice of a building. The wire is run through. RADIO-APPLAUSE POST CARDS A neatly printed post card for acknowledgement to broadcasting stations your reception of their entertainments. 2 dozen 25 cents postpaid. D. J. SPANGLER, Elkhart, Ind. GOVT. RADIO STORAGE BATTERIES New Signal Corps Batteries. Edison 3 cell type BB-4, $4.50; Edison single cells for W.D.-ll tubes, $1.50: Edison 60 A.H. for W.D.-ll tubes, $5.25; 6 Volts Edison. $7.75; "B" battery Edison single elements, 4o ea. ; double, 10c ea. PEANUT TUBES Wonderful det. and amplifier, smallest tube made; aeroplane style. 1 V., Yi Amp., %" dia. i 2%" long. Just a few at $9.50. Ack Quick If you want a real pocket set tube. FTJIiLY GUARANTEED. FLEWELLING .006 CONDENSERS & PARTS .006 Bakelite mounted Buby Mica-Copper, N. P. binding posts, set (3), $2.90. Var. Grid Leaks (clearer music, louder signals on any cir. ), 75c. Var. Grid Cond., .00025 or .0005 max., 45c. Special Audio Trans., $3.45. Spider coils. Easier tuned, clearer signals; green Bilk on Bakelite, $1.75 ea. REINARTZ LATEST COILS Double green silk wire on polished Bakelite spider, $1.95. Eeinartz plate circuit choices (triple adjustable), $1.70. RADIO FREQUENCY IRON & PARTS .003 Iron for cores; special wire and forms to construct R. F. Transf. of highest efficiency. Detailed plans, 50c. REFLEX CIRCUIT TRANSFORMERS Special Reflex Trans. & Dlag. that really works, $3.65. VERNIER FOR VARIABLE CONDENSER Works with any condenser. Keauires no extra soaee, 95c. HI-POWER AMPLIFYING TRANSFORMER Best I Loudest! No burn-outs. $2.95 with BPeo. diagram. 20 OHM RHEO. FOR 201-A OR WJ>.-11 tubes, $1.60. 8 ohm for new DeForest tubes. $1.55. Include Postage with order. Write for complete list QUALITY RADIO SHOP, RICHMOND, IND. Ground Line Kept Damp with Water Pipe Well Most fans in hooking up a Radio outfit either have a poor aerial and a good ground or a good aerial and a^poor ground. Almost always it's a poor ground. Here is a very simple way to make a good ground, one that will keep itself wet for a long time without having to watch it. UEAO-TN WIRE Secure a piece of galvanized pipe % inch in diameter and 5% feet long, also a piece of 2 inch pipe 3 feet long. Drive the % inch pipe into the ground about 1 . foot. Fill the pipe with water and let it settle, then fill it up again. The water in the 2-inch pipe serves to keep the smaller pipe full all the time and also keeps the ground wet around the smaller pipe. — Dick H. Roberts. Don't Boil in Paraffin Spider-web coils should not be boiled in paraffin, as this causes a considerable increase in the distributed capacity of the coils. In order to protect the insulation of the coils, from absorbing moisture, they may be painted with or immersed in collodion. Like everything else you buy, do not expect too much from a cheap ready made set. PHANTOM-CIRCUIT Build Your Own. This marvel of mystery, using no loop, no aerial and no ground, brings in music instead of interference. We have heard stations 950 miles distant on one tube. By using WD-11 tube set can be entirely self contained. Very easy to build from our instructions, use your own spare parts, nothing complicated like radio frequency or super regenerative. Only one tuning control. Complete instructions, with hookup and photo of circuit mailed to you for 60 cents. Stamps accepted. VESCO RADIO SHOP, Box D-704, Vacaville. Calif. ORIGINAL NATHANIEL Baldwin Type C HEAD SET Complete SPECIAL PRICE $11.75 Free with each pair of these world's best phones we give absolutely free a $5.00 Sheltone Loud Speaker This is a wonderful Loud Speaker. Both for less than the regular price of the phones. Head set can be used in the regular way as well as on Loud Speaker. Cash with Order or C. O. D. WALTER SCOTT 10 St. Lukes PI., MONTCLAIR, N. J. Delicate Soldering Both the manufacturers' and amateurs' problems on all fine work are readily solved by the instrument constructed for this particular purpose. THE POST SOLDERING IRON Platinum Heating Unit— Interchangeable Tips— Universal Current Large & Small 6 V ONE-HALF ACTUAL SIZE Awarded Certificate of Excellency, N. Y. Evening Mail Radio Institute From your Dealer, or write POST ELECTRIC COMPANY (Dept. 509), 30 E. 42nd St., New York