Radio mirror (Jan-Oct 1923)

April 28, 19-' s K A D 10 dk; est 15 How to Make One Condenser Flivver Super Set Part I — Amplifier Details; Making the Inductance By E. T. Flewelling IT WAS promised in the April 14 number of the' Digest that further details regarding the construction of the Flewelling Amplifier would be discussed in a future installment of this .series. So many thousands of Radiophans have poured in letters requesting further information on this subject that it is planned to devote this, the first installment of a new series describing the greatest development yet of the Flewelling Flivver, which is none other than the One-Condenser Super. Another consideration, which must be allowed before proceeding. In the April 14 issue the One-Condenser Flewelling was shown with no B battery potential on the amplifier tube. This error of omission was made by the draughtsman in preparing the circuit for illustration, and was not noticed until too late. The corrected circuit is shown herewith. Explanation of Circuit In the diagram illustrated the condenser 4 takes the place of the former bank of three fixed condensers of .006 mfd. capacity and the variable grid leak shunted across them. Condenser 4 has a capacity of .006 mfd. It will be noticed that a single pole double throw switch is connected in the circuit at this point. By throwing this switch to point 1, the hook-up becomes purely regenerative, shunting the .006 mfd. condenser and breaking the plate connection to the grid circuit. By means of this switch it is possible to make comparisons between signals on an ordinary regenerative apparatus, and the wonderful stimulation in the same signals effected by converting the apparatus to a Flewelling Super. Guarding Against Back Coupling The necessity of guarding against the possibility of back coupling from amplifier to detector, or vice versa, has often been pointed out in the previous series of articles in the Digest. In this seemingly trivial point of apparatus design and construction lies one of the secrets that is of paramount importance in the successful accomplishment of amplification. The second point to consider is the necessity of guarding against the free action of the whistle, or blocking action, characteristic of the Flewelling Super detector, upon the grid of the amplifier tube. Due consideration must be given both Just Out! PANEL MOUNTING FRESHMAN Variable Resistance Leaks The latest and most essential part of an efficient tube set. Price complete with either .00025 or .0005 mfd. Micon Condenser $1.00 Price without Condenser 75c Mounted on any panel in a few seconds. Enables you to get stations that you never heard before. The only Variable Leak that is entirely sealed. THE NEW CONSTRUCTION of all FRESHMAN Leaks guarantees permanent resistance, unbroken range of 180 degrees. No pencil markings. Eliminates hissing. Clarifies signals. At your dealers— otherwise send purchase price and you will be supplied postpaid. CHAS. FRESHMAN GO. Inc. 106 SEVENTH AVE., NEW YORK CITY these stumbling blocks, else no success may be righteously expected in the use of the completed amplifier. Otherwise the experimenter will .simply amplify all of the tube noises, static or atmospherics, and other extraneous sounds, and will re Patent situation Prevents Diagram Due to the patent situation the writer will be unable to publish a diagram showing what has been found to be the best method of handling amplification with the Flewelling Circuit, but this will be taken ceive but very little relative amplification of the signal coming in. Elimination of Troubles Considering the elimination of these troubles, first remember what has been previously said regarding coupling back. Shielding of the amplifier will help considerably and a separate B battery for the amplifier becomes a necessity. Were it not for the expense, a separate A battery might also be of help, but the extra cost makes this impractical. In regard to keeping the whistle action from the grid of the amplifier, this is really the most important point. This may be done in two ways, the first of which is by far the most satisfactory. This is the placing of a filter between the detector and the amplifier tubes. In the second method instead of keeping the action from the grid we "sidetrack" it by the placing of a high resistance across the primary of the audiofrequency transformer. This high resistance would be of the order of from 100,000 to 5,000,000 ohms. A good variable leak will serve very nicely for this purpose. RADIO At Cat Prices Standard parts only in original packing. Sold on a "money-back" basis. PHONES S S.00 Brandes Superior $ 5.95 12.00 Nathaniel Baldwin Type C. Double.. 8.95 7.50 llodell's special 3.95 TUBES 1% Yolt Peanut Tube 2.00 U. V. 201 5.50 1% Volt Mercury 4.95 CABINETS Made in our factory 7" x 10" (.45 7" X IS" 2.15 7" x 24" 2.95 MISCELLANEOUS Solderall, Tube 25 $12.00 Amplitone, Nickel Horn 4.95 25.00 Aerex Crystal Set 9.95 DUBaTEK Permanent Crystal Detector 2.00 W.D.-ll Adapter 65 $1.50 Lightning Arrester, Indoor and Outdoor Type .95 5.50 — ISO Degree Variocoupler on Bakelite, Silk Wound Wire 2.45 2-inch Bakelite Dials 25 4-inch Electros Dials 75 3-inch Bakelite Dials 35 $ 1.00 Freshman Variable Grid Leak and Condenser Combined 75 1.00 Bakelite Socket 50 5.00 W. D. 12 Audio Frequency transformer 3.75 3.00 Owl Radio Frequency transformer.. 1.50 5.50 Coto coil Radio frequency transformer 3.45 5.00 Sleeper Radio frequency transformer 1.95 5.00 Acme Audio and Radio transformer 3.45 8.00 Dayton Variometer 5.45 8.00 Dayton Variocoupler 5.45 5.50 Murdock variable condenser. 23-plats 2.95 6.50 Murdock variable condenser, 43-plate 3.25 132.00 Radiola R. C. set 79.50 The new Morrison Siren loud speaker 18.50 5.00 Multi-Radioscope 1.50 Little Gem set 6.50 50.00 Turney single tube set 18.50 1.25 Western Electric Ammeter for testing B batteries 49 2.00 22% volt B. battery 1.00 New radio map 35 When Ordering by Mail Add Postage by the Following Scale PURCHASES Tp to $1.00 add 10c $1.01 to $2.00 " 15c 2.01 to 3.00 " 20c 3.01 to 5.00 '• 25c 5.01 to 7.00 " 30c 7.01 to 1.0.00 " 40c Money Order or Personal Check Accepted RADIO STORES Dept. F. 9, 191 Fulton Street, N.Y.C. care of for the Radiophans within a very short time. The above method of handling amplification is very good. Because we find it necessary to postpone for a few issues complete details on the amplifier for the circuit let us consider the building of the new type of Flewelling Super. The first circuit that was published contained three large fixed condensers plus an extra grid leak. After pounding out the theory and closely analyzing the action of the circuit we found that the extra grid leak and two of the large condensers were unnecessary. Exactly the same action and results are obtained by the use of a standard tickler coil circuit plus an added connection and one large .006 mfd. condenser. The diagram for this circuit is shown herewith and constituted what is undoubtedly the simplest known form of the circuit. Complete Instructions to be Given Success with the Flewelling circuit has been absolutely phenomenal but, judging by the number of inquiries and reports of success received within the last few weeks since this circuit was originally published, we know that there is a very large demand on the part of the fans for complete instructions concerning how they themselves may construct the circuit. Therefore, we shall begin a series of articles describing completely in every detail how the simplified Flewelling circuit may be constructed, using only the simplest, most easily obtainable and chea jest but best materials. There have been so many attempts to merchandise and commercialize the name Flewelling that hereafter it will be impossible to mention any specific make of apparatus. Inductance Winding We will start in with a common cardboard 4 inches in diameter and 6 inches long. Also secure a rotor ball 3% inches in diameter and mount it suitably so that it will rotate freely within the cardboard tube. Now if your tube and ball are not of the exact dimensions, don't go to the expense of buying others. These are given as general dimensions and anything will serve if it is reasonably near the size given. (Continued on page 18) FLEWELLING ALL PARTS NECESSARY DEALERS: ATTRACTIVE DISCOUNTS !|IJ.TM:flrI.H 123 W.Madixon JtChicago f One radio fan writes: "The finish is so far superior, and the working qualities so satisfactory there is no question but that future sets built by me and my friends will have Radion Panels." SADION IMWJ The self-evident superiority of RADION Panels has created for them a tremendous popularity among those who build their own sets. It is so easy to drill, cut and engrave RADION, and there is not the slightest danger of chipping. The beautiful surface polish exceeds the finish on the finest of hard woods. Every panel is protected by its individual envelope on which complete instructions are printed. These are the 18 stock sizes carried by most dealers: RADION PANELS, Stock Sizes, 3/16 in thickness. Size — Black Mahoganite 7x21 $2.65 $3.25 7x24 3.00 3.70 7x48 6.00 7.40 9x14 2.25 2.75 10x12 2.15 2.60 12x14 2.85 3.45 12x21 4.25 5.20 14x18 4.25 5.20 20x24 8.50 10.35 Size— 6x7 Black $0.75 Mahoganite $0.90 6x14 6x21 7x 9 1.50 1.15 1.40 1.85 2.75 1.40 7x10 7x12 1.25 1.50 1.55 1.85 1.75 2.20 2.75 Your dealer can usually supply any of the above sizes from stock. If you cannot get it send us your order with the price (give the dealers' name), and we will ship promptly. RADION excels in the four most important insulation characteristics, namely: Low phase angle difference; low dielectric constant; high resistivity; low absorption of moisture. Remember all hard rubber panels are not RADION, nor do they possess the electrical and mechanical characteristics of RADION. Be sure you get the genuine. See that every panel is stamped and in its original envelope. DEALERS * W y°u d° HOt handle RADION Panels, Dials, Knobs, Sockets, etc., we have a proposition which will interest you. Write for catalogue and price-list or consult any leading electrical or radio jobber in your territory. American Hard Rubber Company Department R. D. 15 Mercer Street, New York, N. Y. Chicago Office: Conway Bldg. Oldest and largest manufacturers of Hard Rubber and its products. i^tf