Radio mirror (Jan-Oct 1923)

MilV tZ, 10.' 1 RADIO DIGEST How to Make One Condenser Flivver Super Set Part II — Construction of Variocoupler By E. T. Fletvelling IN OUR last article we began a description of how to build the new one condenser Flewelling super set, and started the details of the tuning inductance and tickler coil. Before going on with the constructional details I believe that it would be a very good idea to show some of the advantages that might be expected from the construction of this receiver. Securing the Best Keception We are going to describe how to secure the most from the set, and because of the construction we will find ourselves in possession of really two sets instead of one and can then take our choice of the one that we like best, or of the one that best suits our local conditions. Really, what we will describe will be this — a single circuit straight regenerative receiver and the Flewelling super receiver, and we will be able to change from one to the other as we wish, simply by moving one switch, and possibly a slight adjustment of the grid leak. Such a receiver is wonderfully adapted to local conditions of any kind and will enable one to receive broadcasting of some kind, no matter where one may be located, whether in the woods, an apartment, or an automobile, and too, the builder may be confident of securing very much greater volume than is obtained with a one-tube set, reports of loud speaker operation on local stations are very common. To builders of this set, the writer promises that he will use every possible effort to describe it, that the most may be obtained from it and it may not be amiss to say here that he uses such a set himself in preference to any other, and that aside from any personal feeling in the matter. Panel Mounted Apparatus In this series we are going to use panel mounted apparatus with coils, etc., in the rear, so that if it is desired the completed set may be put into a suitable cabinet. A great many persons do not The tuning inductance described in our last article, if wound on the 4-inch tubing that was specified, would have a wave Perhaps the easiest way to take off the tap is to wind to the point where a tap is desired, clean off the insulation at this SWITCH KNOB Figure 2 length range of about 300 to 600 meters on the average antenna. Last week some of the broadcasting stations were re-assigned wave lengths that went as low as 225 meters and in order to reach this point it will be best if taps are taken off of the coil at the 30 and 40 turn points. That will give us the following for the completed coil: 130 turns of No. 22 or No. 24 doublecovered wire wound on a cardboard or bakelite tube 4 inches in diameter, with taps taken off at the following points: 30, 40, 50, 75, 100, 115, 130 turns, or a total of 7 taps. As stated before, no attempt should be W1I > , 1 N ; ■CARDBOARD '£f;l STRIP r .: J 1 ' • •»" • i i z - 7 POINTS TO BE TAPPED Figure 1 like outside mounted coils and for this reason we began our description of the set by describing how one might build his own self-contained tuning inductance and tickler coil for mounting in the rear of the panel. This inductance is of the tapped type eo that one may choose the required number of turns and therefore differs from the honeycomb coils that were called for in previous articles. Honeycomb coils are very suitable for the circuit, but because of the difficulty of mounting them on the rear of the panel and because of so many who wish to build their own coil and set together with the difficulty that some have in choosing the right size coil to match up with the antenna used, we will use the good old reliable tapped inductance for this particular set. LOUD SPEAKER FREE The wonderful SHELTONE LOUD SPEAKER with every original NATH. 8%" Hich— BeautiIulBubberi«PJPini»h BALDWIN Type C Headset Complete I PERSONALLY test every pair of phones to GIVE YOU a headset that has no *n>a]. YOU CAN USE HEADSET IN REGULAR WAY ALSO. My price on these special selected <M O (\f\ Phones is. postpaid «J>l^i.UU Cash with Order or C. O. D. WALTER SCOTT, 10 St. Lake. Place, MonteUir, N.J U made to bring out taps from separate turns. A typographical error gave the tap as 85 turns when it should have been 75 turns, which is the preferable point. Winding on the Coil The winding may be put on the tube without leaving any opening for the tickler shaft as sufficiently close coupling will be obtained by mounting the tickler ball at one end of the tube, as will be shown. ilow lo build the Reinartz Receiver is told, complete with illustrations and diagrams, in the latest addition to the "ChiRad" Handbook-Catalog. Our Handbook also includes: 1. Technical discussions of standard radio apparatus and equipment. 2. Radio definitions, wireless codes, wire tables, definitions, etc. Pin this ad to your letter and mail it together with a dime for your copy of the Handbook. Send for it, today! CHICAGO RADIO APPARATUS CO. 415 South Dearborn Street, Chicago. B. D. point for %-inch, then lay under the bared section a piece of cardboard one inch by 6 inches long. Continue around the tube until the cardboard strip is met again, bend the strip back out of the way and continue winding until the next tap, when the strip is bent back to go under the bared section again. This gives a tight winding throughout and leaves the bare sections free from the rest of the winding so that we may solder our taps to them without interfering with the rest of the coil. The completed coil would look like the sketch, Figure 1. Winding the Rotor Suitable holes must be drilled into the tube for the mounting of the tickler ball and this detail will be left to the builder of the set. The holes may either be drilled through the sides of the tube or, you can if you wish, mount the ball and its shaft at the end of the tube — it is simply a matter of preference. The ball should be large enough that it will fit the tube fairly snug and yet not interfere with it. One hundred to 125 turns of wire on the rotor ball will be (Continued on page 18) t FLEWELLING ALL PARTS NECESSARY DEALERS: ATTRACTIVE DISCOUNTS % !|l|.JW:flrI.H 123 W.MadixonJt, Chicago ¥ "N0 ^EEBf* Variable high resistance unit, i/io to 5 megohms. Does the 'work of a thousand grid leaks. Contains standard mica condenser of proper capacity. Bakelite. Price $2. A DRY CELL TUBE F0R$2 Something new in radio. Diode ! A two element vacuum tube that is more sensitive than a crystal. Diode does the work of a high priced instrument and eliminates the use of storage and "B" batteries. Its reception of word and note is absolutely without a howl. The low cost of Diode and its economical operation turns radio into an inexpensive luxury. Tube with socket $2.50. Ask your dealer or write direct, sending dealer's name. BRANCH OFFICES: 802 Forsyth Bldg., Atlanta, Ga. 703 Granite Bldg., Pittsburgh, Pa. 709 Mission St., San Francisco, Cal. 1028 Fourth Ave., Huntington, W. Va. 636 Victory Bldg., Philadelphia, Pa. Munsey Bldg., Washington, D. C. 1121 Pine St., Seattle, Wash. 337 S. Western Ave., Los Angeles, Cal. 53 W. Jackson Blvd., Chicago, 111. 1403 Monadnock Block, Chicago, 111. 1011 Chestnut St., Philadelphia, Pa. C. H. Wallis & Co., 1409 Syndicate Trust Bldg., St. Louis, Mo, ELECTRAD CORPORATION OF AMERICA, DEPT. B, 6V* ■428 Broadway , New York J§