Radio mirror (Jan-Oct 1923)

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RADIO DIGEST March 17, 1923 1 apped Coil and Variocoupler Circuit Feed Back Produced by Two Coils on One Tube The materials necessary to make the hook-up shown in the accompanying illustration consist of one variocoupler, one 43-plate condenser, one tapped coil on a 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 Illustrated, 123 West Madison St., Chicago, 111. tube three inches in diameter and 12 inches long, one detector unit and other accessories such as B battery, headset, etc. In a way the circuit is critical. The secondary of the coupler must be turned until regeneration is obtained. When once at this point, the set can be left alone, but still it will tune out the little fellow. The tapped coil consists of two separate coils, wound in the same direction but not connected. They are each tapped. About 40 turns of No. 16 or 18 ware is used for the aerial inductance. The upper portion should be the aerial inductance, and the lower the plate feed back. — Willard Tolhis, Bethesda, O. A. B. C. LESSONS (Continued from page 11) plifier tube. Into the output circuit of this tube the telephone receivers are connected in series with the battery B-2. As was stated before, a higher plate pressure is needed for amplifier tubes than is required for detector tubes. The B batteries used in amplifier circuits generally have a pressure of 45 volts, although pressures even as high as 67 and 90 volts are sometimes used. Often a single 45-volt B battery is used with a 22%-volt tap, the plate circuit of the detector tube being connected to this tap while the plate circuit of the amplifier tubes is connected to the 45-volt terminal. Audio Frequency Transformers The transformers used for linking the output circuit with the input circuit of the next amplifier tube are known as audio frequency transformers, for they are used to step-up the voltage of the audio frequency electrical oscillations impressed across the primary winding. The number of times that a transformer steps up the voltage depends upon the relative number of turns in the secondary and primary windings. Transformers are consequently rated according to the number of times they step up the voltage, this factor being termed the transformation Radio. A 10 to 1 transformer steps up the voltage ten times. It also has ten times as many turns on the secondary winding as on the primary winding. Whenever two stages of audio frequency amplification are employed, it is better to use two transformers having a different votage ratio, especially if the ratio of the first is high. If the first transi former has a 10 to 1 ratio, it is better to use for the second transformer one having a ratio of 5 or 3 to 1. However, equally good results can be obtained, and some claim even better, if two transformers of the same ratio are used, providing the transformation ratio is not too high. Thus, very good results can be obtained by using two transformers each having a 5 to 1 ratio. Radio Frequency Amplification Often when the receiving apparatus is not very sensitive, or when the transmitting station is so far away that the incoming waves are too weak to properly affect the detector, it is possible to strengthen or amplify these signals before they reach the detector tube. Such amplification is known as Radio-frequency amplification, for the oscillations that are being strengthened or amplified are still at a Radio frequency. The same amplifier tubes as were used for audio-frequency amplification can also be ueed for Radio frequency amplification. However, any number of steps of Radiofrequency amplification can be used without in any way affecting the quality of the signals. The successive steps of Radiofrequency amplifiers can be linked to each other in several ways, although Radio HOOK-UP FOR SELECTIVE TUNING Yh GRID LEAK £COND. G P S FIRST STEP. 45 V. ■WPL .ooi mjd •= 6ROUND. frequency transformers are most commonly used. These transformers differ from the audio-frequency transformers mentioned above in that they do not contain an iron core. Regenerative Amplification Another form of amplification used very extensively is that known as regeneration or regenerative amplification. In regenerative amplification the plate circuit of the detector tube is tuned by means of some form of inductance, such as a variometer, until it has exactly the same oscillation frequency as that of the incoming waves. Under these conditions some of the energy of the plate circuit is actually fed-back upon the grid circuit, with the result that it is again sent through the detector tube and amplified to a large extent. Each of these methods of amplification will be taken up in detail in later chapters, where practical instructions will also be given for constructing the various types of amplifiers. TWO SUPERSENSITIVE CIRCUITS (Both Copyrighted) My Highly Improved Reinartz brings in all Important stations on both coasts and Mexican border, loud, clear and without distortion. We dance to music from Atlanta received on one loud Baldwin unit. Build one of these wonderful sets from my blueprints and specifications, price 50c. or with a perfect and complete double wound spiderweb coil, $3.00 by mail. No other windings used. Photo of my set on a glass panel with every order. My W. D. II Circuit is especially designed for use with the "Pickle" tube and brings out the full value of that little tube as nn other circuit can. Stations 1000 miles away come In clearly on one tube. This set is small, complete, portable. For the man who wishes the highest efficiency this Is the set to build. Price of blueprint and specifications $1.00, or with complete and perfect windings $5.00. Photo of set with every order. Either set is cheap and easy to build, easy to operate. Everything clearly shown. Please don't send stamps. S. A. Twitchell. 1925 Western Ave., Minneapolis, Minn. WD-11 OUTFIT {PEANUT TUBE) This wonderful dry battery (| n OP outfit with a range of 600 «f> I < • OD miles comes to you ready I J Less to assemble, panel drilled Tube and marked, mahogany ^^""i™^^"i finished box, condenser ready to screw in place. Variocoupler wound complete, rheostat, dials, binding posts, socket, wire, screws and picture diagram for wiring, all at above price. Two-stage Amplifier Box to match the above. $14.15 Variocou piers, $4.00 value 2.85 Variometers, $4.50 value 3.10 Transformers, $4.50 value 3 75 Reinartz tuning coil, $3.00 value 185 Rheostat, $1.00 value so Sockets, EOc value 38 I V2" switch lever, 50c value 30 Baldwin type "C" phones, $12.00 value 9.00 Frost or Murdock phones, $5.00 value 4,25 Postage extra. No personal checks received. Let us quote on your wants. RADIO PARTS CO. 8 So. Austin Boulevard, CHICAGO, ILL. Chapter Twelve The practical construction of a twostage audio frequency amplifier, as well as a detector employing regenerative amplification will be taken up in Chapter Twelve. Everyone interested in the constructure of either of these circuits should not miss this most important chapter. HEAR ATLANTA ON CRYSTAL We receive programs from Atlanta, Minneapolis, Davenport, Fort Worth, Dallas, Kansas City, St. Louis, Denver, San Antonio on crystal without batteries. Your crystal set requires only easy, inexpensive changes. Send stamp for further information, or $1 for copyrighted drawing and instructions. Everything clearly explained. Satisfaction guaranteed. LEON LAMBERT, 505 South Volutsia, Wichita, Kan. ATWATER KENT D^alAPC LITERATURE UCdierS ON REQUEST and DISCOUNTS TWTW 123 W. Mad iron .It. Chicago GOV'T 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, 4c each; double, 10c each. PEANUT TUBES Wonderful det. and amplifier, smallest tube made; aeroplane style. 1 Volt Vi Amp. W dia. x 2%" long. Just a few at $9.50. Act quick if you want a real pocket set tube. FULLY GUARANTEED. FLEWELLING .006 CONDENSERS & PARTS .006 Bakelite mounted Ruby Mica-Copper N. P. binding posts, set (3) $2.90. Var. Grid Leaks (clearer music, louder signals on any car.), 75c. Var. Grid Cond., .00025 or .0005 max., 45c. Spec. Flew. Audio Trans., $3.45. Spider coils, easier tuned, clearer signals; green silk on Bakelite, $1.75 each. REINARTZ LATEST COILS AND PARTS Double .green silk wire on polished Bakelite spider, $1.95; Reinartz plate circuit chokes (triple adjustable), $1.70. Special Reinartz Audio Transformer with diagram, $3.35. Complete set Reinartz tuner and detector parte, $10.65. Tuner Det and 2 stage parts, $17.95. 2 stage outfit, $8.35. Hi-Power Loud Speaker with pair latest Baldwin Phones, $10.90. HI-POWER AMPLIFYING TRANSFORMERS Best! Loudest! No burn-outs. $2.65 with spec, diagram. RADIO FREQUENCY IRON AND PARTS .003 Iron for cores; special wire and forms to construct R. F. Transf. of highest efficiency. Detail plans, 50o. REFLEX CIRCUIT TRANSFORMERS Special Reflex Trans, and Diag. that really works, $3.65. VERNIER FOR VARIABLE CONDENSERS Works with any condenser. Requires no extra space. 95c. Armstrong Super, new 3 tube outfit, beautifully built, at jaorlfice. 20 OHM RHEO. FOR 201-A or W. D.-ll tubes, $1.60. 8 ohm for new DeForest tubes, $1.55. Include postage with order. Write for complete list, QUALITY RADIO SHOP, RICHMOND, IND. One Knob Control for Tuning a Crystal Set The set described is tuned completely by means of a variable condenser, the inductance being fixed. The detector may be of any make, but I would suggest the use of a. Grewol. The variable condenser is of the Crosley make, which is in the form of a book. The antenna is 300 feet long and 50 feet high, ard the inductance consists of a 2% -inch cardboard tube wound with 75 turns of magnet wire. Of course, if the antenna is shortened. the. number of turns on the inductance must be increased. With this set the writer has heard all of the local stations as well as WBAP, Fort Worth, Texas, which is 250 miles distant. Two other stations were easily heard, WDAF, a powerful station in Kansas City, Mo., 650 miles away, and WFAA of Dallas, Texas. — Milton Hobbs, Houston, Texas. IMPROVED RADIO <t*% ^tS. DETECTOR TUBES V4faa £9 IMPROVED RADIO *0 9C AMPLIFIERS V^'Od W.T.50I PEANUT TUBES *0 ^C WITH ADAPTER f£( #9 Sent on receipt of price, prepaid LUX MANUFACTURING CO. 1045 No. Wells St. CHICAGO, ILL. ADJUSTABLE COIL MOUNTINGS FOR FLEWELLING CIRCUIT Triple Coil Mounting $5.00 List Double Coil Mountings 3.50 List Licensed under TJ. S. De Forest Pat. 1365170 A patented feature locks the coil in place and prevents the coil from being thrown out of a d j u s tment once station is tuned in. Dealers write for special discounts AST0RL0ID MFG. CO., lnc.^&Avv. Radio Distances Easily Read Use Cram's Detailed Radio Map covering the United States and Canada. Just one hundred miles to the inch. Map plate 30x20 inehes, on sheet 34x28 inches. Latest call numbers at sides and bottom. Used by Radio Digest and other Radio Experts. Radio Districts and headquarters and time divisions. New edition now ready. Ideal for the purpose. POSTPAID Pocket Form $0.35 Heavy Paper in Tube 50 Wall Style Wooden Rollers.... 1.50 On Heavy Board for Tacks 6.75 Special quantity prices to trade and advertisers The George F. Cram Co. Ill N. MARKET STREET DEPT. RD CHICAGO, ILL. 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 6W 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