Radio mirror (Jan-Oct 1923)

14 RADIO DIGEST ILLUSTRATED R.F. AND A.F. ON CRYSTAL SET \j7 SiNSLC SLIDE TUNING COIL. JL. | g.p. n I AMPLIFIER TUBE AMPLIFIER TUBE Jl <» i: AUDIO FREQ. TRANSFORMER 6V. -.1.1.1 THIS hook-up was developed to meet the request of a fan who wanted to add Radio and audio frequency to his crystal set. The additional parts required outside of batteries and tubes, are inexpensive and simple. If necessary (in case of a long antenna) a .001 mfd. variable condenser is added in the antenna lead as shown. A singleslide tuning coil is used for tuning this circuit. A 50-turn honeycomb coil with a .0005 variable condenser shunted across it permits adjustment of wave length in the coupling between the Radio frequency amplifier tube and the crystal detector. Any standard audio frequency transformer is used in the coupling between the crystal detector and the audio frequency amplifier tube. The .001 mfd. fixed condenser across the primary of the audio frequency transformer acts as a by-pass of Radio frequency strays that may leak through. In the same manner a .025 mfd. fixed condenses is shunted across the plate battery, which should have a voltage of from 60 to 80. The controls for tuning have been reduced to a minimum so that the tuning of this circuit will be exceptionally simple. The Reader's View Ignorant Badio Dealers It is unfortunate that so few dealers in Radio apparatus know anything about Radio. In buying my outfit, I visited 18 dealers in a city of 150,000 people. Seventeen of the number had absolutely no idea of the distance range of the apparatus they sell nor could they answer intelligent questions concerning cost of upkeep or relative value of different types of aerials. One of the number was an amateur and "knew his stuff" and told us truthfully what he knew about Radio sets. He demonstrated fourteen makes for us. We bought a set, with loud speaker, and it works fine. I became very much of a fan and bought a smaller set for my own home. I had the same experience in selecting a small set — dealers knew little or nothing about them, and would not let me try them. A dealer was also ignorant of his stuff but let me take a set on 15 days' trial. I found it to be entirely satisfactory. Have heard plainly, clearly and with little interference a total of 62 stations scattered from Cuba to Portland, Ore., and from New York to San Francisco. I know my set. On December 18 to 23 I was in , . There is a broadcasting station there and five dealers in Radio apparatus. I spent not less than two hours with each, and they were all unable to get a single out-of-town station satisfactorily on their demonstrating sets. Not only that, but I distinctly heard them advise prospective customers to do things that any "boob" that has owned a set thirty days knows not to do. I called the dealer to one side and remonstrated and with his permission made a few changes in bis lead-in wire, adjusted plate voltage on his demonstrating set and brought in five distant, out-of-town stations loud and clear through a loud speaker. I am not interested in any way in the sale of Radio apparatus^ but at the request of this dealer I looked over four sets that were not giving satisfaction, made necessary changes and adjustments and each of the four sets worked fine on local and distant stations. Some dealers are preaching the doctrine, "Most any sort of aerial from bed spring, loop, or 50 feet of wire strung around a ceiling will do!" These types of aerials do for local stations, but for distant reception, outside single-wire aerials are so much better with most sets. — S.P.D., Somerville, Tenn., via A. T. & T. Co., New York, N. Y. Classroom lectures on history are to be broadcast by Radio from the University of Washington. Radio Tubes Repaired UV 200 — C 300 $3.00 UV 201— C 301 3.50 WD 1 1— or VT 2 4.00 The right filament and proper vacuum. All tubes guaranteed as good as new. Mark plainly. Pack carefully. Radio Supply and Repair Co. 125 WEST LAKE STREET R«t our prices on Radio Equipment. Interference Eliminator The illustration shows a hook-up in which A represents a single slide tuner which is tuned to the undesfred wave length and the tuner on the set is tuned for the desired wave length. The unde sired wave length passes down the single slide tuner and you have no interference. A variable condenser is shown at B, which when inserted will give better tuning than the one slide coil. — Lester V. Hergman, New York, N. Y. REFLEX CIRCUITS (Continued from page 13) the by-pass condenser is automatically connected across the phones. The plate battery voltage will run from 60 to 100, depending on the types of tubes that are to be used. These all should be hard amplifying tubes. The 50,000-ohm resistance and the 20-milhenry Radio frequency choke coil are obtainable at the Radio stores. The second and third tubes can be controlled through one rheostat instead of two, if desired, but the first tube should have an individual rheostat. In using detector crystals for reflex hook-ups, the same conditions apply as in the normal circuits. For this reason no special characteristics are required other than what is normally expected. Many developments have taken place in the last few months so that a number of the bothersome adjustments have been eliminated. ' How to ^btdldihe Reinhortzlieeeiver is told, complete with illustrations and diagrams, in the latest addition to our FREE looseleaf, handbookcatalog now on the press. Amateurs find the Reinhartz hookup by far the simplest yet designed. In efficiency it rivals the Armstrong and other wellknown circuits. All the parts necessary for building your Reinhartz Receiver are listed in the "ChiRad" handbook catalog — save yourself the trouble of shopping around. Write for your copy today — ask for "Chi-Rad" Handbook, Edition RR. Chicago Radio Apparatus Co. 415 So. Dearborn Street CHICAGO Cardboard Tubes Are Easily Made at Home It often happens that the Radiophan wants a cardboard tube of a size not available. I find that it is a simple matter to make them. A bottle, dry cell or any other round object, which is 1/16 or 1/8 inch smaller than the outside diameter of the size desired, is used for the pattern. If these are not at hand a section cut from a limb of a maple tree may be used. The tube is made of layers of paper like kraft paper. The paper is cut to 6 or 7 inches wide and about 5 feet long. Apply parafin to the object on which you intend to wind the paper and prepare a paste by mixing yellow dextrine with water until you have a smooth paste, roll your paper once around the pattern to keep the paste out, then apply the dextrine on the paper and spread it very thin all over it, then roll the pattern along on the paper. If there is not enough paper in the strip add more and spread on the dextrine. The paper will not always roll straight, but this will not be detrimental as there will be 2 inches for trimming when the roll is complete. When the desired thickness has been reached leave it on the pattern if possible and place it in an oven to dry. When thoroughly dry trim it with tinner's snips, a razor blade, rasp, sandpaper or anything that you may have available for this purpose. When finished you will have a tube equal to anything you can buy. — Edward Gille, Quincy, 111. Simple Honeycomb Coil Mounting The mounting shown in the illustration is original with me, although it is so simple it may have been used many times. In making of the Flewelling circuit I was confronted with the problem of mounting the coils in the simplest manner possible, as I have no workshop. I wound two sections of a mailing tube as directed, then cut out a small piece of wood about 1 inch square and about % inch thick. The piece was covered with tire tape. The block was strapped to the coil. A small wood box, such as is used for packing fountain pens, made themounting. One coil was permanently fastened RADIO MAILING LISTS 12,400 Radio Dealera. eoverme V. S. by states Per M $ 7. 50 1,614 Radio Mfrs., coverini U. S. by ntatea. Per list 15.00 1,757 Radio Supply Jobbers, coverios U. S. by states, Per list 15. 00 2G0 'ItsdioIStations Pec lirt 4.00' 257 Mira. who make and assemble complete Radio Seta , — . _ , Per list 4.00 25,000 Radio Amatenre & Mfra. of Radio Stations. Per M 7. 50 Ask for price list covering Canada and England. Send remittance with orda . Trade Circular Addressing Co., 166 W. Adams Su Chicago, 1U. SPECIAL Stock Reducing Sale -limited Supply All New Merchandise Terms C. 0. D. — First Come, First Served Immediate Shipment Myers Vacuum Tubes. »f»Q og Each, net .pO.OO Myers Adapters. 4»1 OZ\ Each, net «pl.AV Myers Audio Frequency Choke ^O OG Coils. Each, net «BA.OO Myers Radio Frequency Choke *0 ">C Coils. Each, net «p«J.OO ■Myers Receptacles. <£/"» r7f\ Each, net ^M.i\J Mica Fixed Condensers, .25 Mfd. <M fbC Each, net $«*.UO Mica Fixed Condensers, 2.0 Mfd. itl '7f\ Each, net ^i./U HARTMAN RADIO COMPANY MANSFIELD, OHIO References — Any bank or banker in Mansfield, Ohio. to the box end and the other to the sliding cover, as shown. The box was then attached to the back of the panel. The tip of the sliding cover was left protruding over the panel at the end. Sliding the cover back and forth provided a means of tuning in the coils. This gives parallel variance rather than angular, and it produces the cheapest mounting that can be procured. — G. E. Lippincott, Philadelphia, Pa. One Tube Set The illustration shows a circuit using a detector tube that has given good results. The antenna for this circuit is 10 feet high and 25 feet long — one wire. The type of a variocoupler used in this circuit is the one fitted with a rotor set on the upper end of the coil. — Le Roy Dolen, Sapulpa, Okla. Electrical Terms Universal electrical terms are easily understood by using a simple water analogy. Volts, or potential, the equivalent to pounds pressure. Amperes^are equivalent to gallons, measuring volume. Watts are the power units, or ^volts times amperes. Ohms are the resistance unit. HU0S0N-R0 Quality Radio Products Dealers: Write for Your Discounts 123 W. Madison, CHICAGO Marked Savings! W. D. 11 Tube, $5.25; W. D. 11 Socket.. .56 $3.50 Baldwin R. F. Transformer.. 2.98 $8 .00 Baldwin Variocoupler 6.50 $6.50 Fisher Variocoupler (large size).. 4.95 $45.00 Magnavox (new type) 34.75 $20.00 Baldwin Claraphone 16.25 Baldwin Phones (type C) 9.50 $12.00 Western Electric Phones 9.50 $1.00 Freshman Var. Grid. Leak & Cond. .80 $7.00 Federal Audio Transformer 5.50 23 P. Var. Condenser $1.25; 43 P. Var.. 1.75 Prices quoted on other items. Mail, money order only. Include stamps for postage. RADIO MAIL SERVICE J^/cM? KELLOGG SWITCHBOARD & SUPPLY COMPANY Chicago DELICATE SOLDERING Both the manufacturer's and amateur's problem on all fine work is readily solved by the instrument constructed for this particular purpose. The Post Soldering Iron Platinum Heating Unit Interchangeable Tips (Large and Small) Universal Current LISTS AT ONE-HAW ACTUAL SIZE Awarded Certificate of Excellency. N. T. Evening Mail Radio Institute From your dealer or write LISTS AT $6.00 POST ELECTRIC COMPANY, $6.00 Dept. 509, 30 E. 42nd St. NEW YORK