Radio mirror (Jan-Oct 1923)

May s> l0~3 RADIO DIGEST 11 Simple Arrangement Adds Step of R.F. Radio Frequency Permits Loop Aerial to Be Used It Is a very simple matter to add a step of Radio Frequency amplification using the system shown by the accompanying diagram. The simplicity of the arrange 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 ways 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 123 West Madison SU Chicago, 111. ment is exceeded only by its efficiency and very few parts are needed to construct the amplifier. The antenna connection is arranged so that either a loop or outdoor antenna may be used. For a loop, shunt the antenna binding post marked No. 2 to the ground post and connect any standard loop without condenser. For an outdoor antenna, use the antenna binding post marked No. 1 so that the condenser in the set will not be connected. The other details of the set are standard parts, variometer, tube and socket with proper batteries according to the tube, a 3-plate and a 23-plate variable condenser, a 200 to 400-ohm potentiometer and a filament rheostat. With this outfit it is unnecessary to have direct connection between the Radio frequency amplifier and the primary circuit of the tuning unit. Instead, if found to be too harsh for local stations, attach the ends of a coil of about 25 turns of an oatmeal box with a No. 25 wire to the output of the Radio frequency amplifier unit and place the coil near the tuning unit, about 3 or 4 inches from the primary coil. — Jj. W, Martin, Houston, Texas. Moving Coil Speaker The best-known loud speaker is composed of a metallic horn connected to what is actually a telephone receiver of large size. The permanent magnet is energized by an external source of current, and the diaphragm is actuated by a coil of wire suspended between the pole pieces of the electromagnet. The actuating current passes through the suspended coil. \z RADIO AMPLIFICATION HOOK-UP 0 A ©-T-O B <& Shape for Resistance Spring When laying out the phosphor bronze contact piece for the Flewelling variable leak care should be taken to have this piece of the proper shape. This is to make the change of resistance gradual. It is quite evident to students of mechanics that a beam supported at one end STRENGTH PREFERABLE CONSTROCTIOf) and of uniform thickness should have the shape of a triangle, if the stress is to be uniform. Furthermore, it is best to go one step further and make the contact piece so that the end nearest the adjusting screw will be raised from contact with the resistance unit before the supporting end is raised. — Carl Schindler, West Allis, Wis. MULTIPOINT (Patent Pending) A Synthetfo CRYSTAL "DETECTOR sensitive over its entire surface Eliminates all detector troubles. Extraordinary clearness and volume. Endorsed by Badio experts and press. Sold in Sealed Packages only. Join the ever increasing Rusonite fans. Price mounted, Sensi Cft^. Hveness guaranteed O W. RUSONITE CATWHISKER 14 Karat Gold Multiple Contact Super OC. Sensitive «3C Order from your dealer or direct from us. RUSONITE PRODUCTS CORP. 19 Park Row. N. Y. NEW CONSTRUCTION of an FRESHMAN Variable Resistance Leaks guarantees long life and permanent resistance— no pencil markingsassures an unbroken range of 180 degrees. Eliminates hissing. Clarifies signals. A New Leak for PANEL MOUNTING Mounted on any panel in a few seconds— 2 mounting screws serving as connections behind the panel. Complete with either .00025 or .0005 mfd. Micon Condenser $1.00 Without 7C/» Condenser I «JC A necessary essential for every tube receiving set At your dealer's— otherwise send purchase price and you will be supplied postpaid Also ask your dealer for a free diagram of the Kaufman and Flewelling circuits. (Ras. Freshman \$xadio\ Condenser 106 Seventh Avenue New York City Variable Grid Leak Many Radiophans have old rheostats lying around whose resistance wire is either loose or broken. It is possible to make a variable grid leak out of one of these. Pry out the fiber ring on which the wire is wound and remove the wire. Then replace the fiber ring and glue it back into place. Next take a very fine file and make the surface of the fiber, where the contact lever touches, very smooth. Mark this surface all the way around with a pencil. Connect one end of this marking to a binding post. It will then be seen that resistance can be varied by just turning the knob located on the other side of the panel. Line Switch on Battery Saves Charge and Tubes Practically all filament rheostats are constructed with a zero point or "off" position which serves the purpose of a switch between the vacuum tube and the storage or A battery. However, it oftentimes happens that in the hurry of cutting off for the night, the rheostats are not turned completely off. Under these circumstances, the filament battery is left connected in the circuit discharging all night long through the resistance. To prevent this, it is advisable to connect a separate battery line switch, which through practice and force of habit, should be opened first before the filament rheostats are turned back to zero. Then, if the latter operation is not performed, the battery circuit will be opened anyway by means of the line switch. — P. J. M. Clute, Schenectady, N. Y. <r HILCO VARIOCOUPLER Especially Adaptable for REFLEX DEALERS: SEND FOR LITERATURE =\ \\\\MA\ 123 W.MadiTon StXhicagc 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 and Small) 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 $6 Most for the Money in Radio z >> "SENIOR" SET When you buy a Michigan "Senior" Regenerative Receiver for $125.00 or a "Junior" Receiver for $57.50, you get the clearest, most satisfactory long distance service that an equal investment ever brought. These sets are licensed under Armstrong U.S. Pat 1,113.149 and pending Letters Pat No. 807,388. This means that they represent the highest achievement in Radio Engineering.