Radio Digest (Oct 1923-July 1924)

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March 29, 192J, RADIO DIGEST — Illustrated 21 The Latest in Super-Heterodyne Hook-Ups Part III — Two Forms of Super-Heterodynes By H. J. Marx (Figure 5) 90vdh 45 V. -j-g fy_^4$V j i IN the last article two foreign forms of super-heterodyne circuits were presented. In this article two more circuits are offered for examination and analysis. One was designed by Paul Fonteneau, president of the Radio Club of Nantes, France, while the other is a typical American circuit that is being developed in Chicago. Both of these circuits are much simpler to understand and are more within the possibility of construction of our average fan. More definite information and values are given for experimentation. Fonteneau Circuit The circuit shown in Figure 6 is a sixtube hook-up with the usual oscillator, two detectors and three stages of amplification. It will be noticed that there are three sets of resistance couplings and a stage of tuned air core transformer which has a very loose coupling between the primary and the secondary. Another unusual feature is the variable coupling tickler running from the plate circuit of the second detector back to this loose coupled transformer. This makes the circuit distinctly regenerative in addition, to the heterodyne action. Tuning Unit The tuning unit consists of 100 turns of number 22 sec. wire wound on a 3-inch tube and tapped every ten turns. These taps are connected to two inductance switches, one for the primary circuit and the other for the secondary circuit. Two .0005 mfd. variable condensers are used to tune the primary and secondary circuits. The details of the oscillator coupler coils are as follows: The pick-up coil consists of 35 turns of number 22 sec. wire wound on a 1%-inch rotor, and the. grid and plate coils are made up of two honeycomb coils in fixed relation to each other, with the pick-up rotor between them. These two coils are from 25 to 50 turns each, depending on the range and strength of the oscillation desired. The loos% coupled transformer can be made up of a three-honeycomb coil unit with the following coil values: Primary, 300 turns; secondary, 300 turns; and tickler, 150 turns. As these values will vary at times, some experimental work is necessary before maximum results can be obtained. The condenser in the grid circuit of the last tube (2nd detector) is indicated as .001 mfd. — this should be .0001 mfd. The 9iy2% of All Radio Tubes Are Needlessly Destroyed Accurate estimates show that less than 9 out of every 100 tubes give their full normal service and 91 are destroyed — usually burnt out from excess current. The chances are 10-1 against you unless you use Radeco Safety Fuses These tube savers are now saving thousands of tubes. They are endorsed by the leading Radio Publications. They slip on the filament terminals of the tube and in no way interfere with the operation of the set. Price $0.50 each (The cheapest insurance) Install Radeco Safety Fuses now and whenever you buy a new tube insist on a Radeco Fuse to protect it. JOBBERS— We want a few live distributors to whom we can offer a very attractive proposition. RADIO EQUIPMENT COMPANY New England's Oldest Exclusive Radio House 20 Stuart Street BOSTON, MASS. The Twitchell Auxiliary Tuner Patents Pending. Name Registered. MORE THAN A WAVE TRAP A TWITCHELL AUXILIARY TUNER connected to any make of tube receiving set will positively cut out any local broadcasting or code stations so you may tune in all long distance stations any time regardless of local conditions. Unlike any wave trap, THE TWITCHELL AUXILIARY TUNER does not ever decrease but in many cases increases the volume from distant stations. These TUNERS are in daily use within 400 feet of large broadcasting stations and enable their owners to easily and completely cut out the local station and bring in distant stations at any time on a loud speaker. This instrument will also enable you to bring in programs sent out on longer waves than you can tune in without it, thus bringing all the broadcasting stations within the wave length range of the many sets of limited range now in use. Copyrighted diagram of this tuner, 50c, or with all parts, $9.00. Complete instrument in walnut cabinet, ready to use, $15.00. A New and Wonderfully Efficient Coil for the Reinartz circuit for those who want the best. Price $4.00, or with blueprint for either one or three tubes, $4.50. This circuit brings in both coasts loud and clear and is the most successful Reinartz modification yet produced. All goods prepaid. These instruments are easy to build, easy to operate. Everything clearly shown 192S WESTERN AVENUE S. A. TWITCHELL MINNEAPOLIS, MINN. other two grid condensers in the amplifying tubes are correct, as shown. The grid leak of the first detector should have a resistance of four megohms, and the grid condenser should have a capacity of .0005 microfarads. The oscillator tube has a separate filament battery in order to avoid the tendency of the oscillation frequency leaking to the amplifier circuit. The antenna used with this set was a two-wire aerial 100 feet long and 35 feet above the ground, running north and south. Eight-Tube Circuit The circuit shown in Figure 5 can be used with a loop, or if an outdoor antenna is used a variocoupler or other form of tuning unit can be added. The loop is tuned with a .0005 mfd. variable < ondenser, which should be of high electrical efficiency in order to get the desired selectivity. The usual fixed tuned coupling transformer is used. The grid returns of the three amplifier tubes (super-audible stages) are connected to a 400-ohm poten(Continued on page 24) And Guarantee You in Writing 2 Years of Better Battery Performance STA-RITE RADIO BATTERIES are made especially for Radio and the big saving is made possible by coming direct to you instead of thru distributors, dealers, etc. Boxes are made of oak, finished in mahogany and the plates very thick and will give a steady discharge over a long period. No premiums, just good, honest battery value. TRY TO BEAT THESE PRICES 2 Volt for W. D. 1 1 and 12 4 Volt for U. V. 199 Tubes RADIO B. STORAGE Glass Jars, Heavy Plates — Case of 12 Cells, 24 V $4.00 .7.00 4.90 6 Volt 60 Amphr. ■ $ 7.50 6 Volt 80 " 8.50 6 Volt 100 " 10.00 6 Volt 120 " 12.10 6 Volt 150 " 14.00 6 Volt 200 " 17.00 Department 5 Get Yours Today — NOW — Send No Money The batteries are fully guaranteed in writing and shipped subject to examination on the day your order is received. You pay on delivery or deduct S per cent if full cash accompanies order. You may deduct 10 per cent if two or more are ordered at one time. STA-RITE BATTERY CO. LOUISVILLE, KY. Standard Merchandise Only S. HAMMER RADIO CO. 303 Atkins Ave. Brooklyn, N. Y. Anything and Everything in Radio A New Simple Way to Build a Neutrodyne Set We give you the entire set completely wired in a Genuine Mahogany Cabinet, with the exception of the Neutroformers and Neu d» p* pil f\(\ trodons, which we supply and you mount yourself, for the *r 1^ 1^ "^ low price of ABSOLUTELY GUARANTEED 55' $80 Freed Eisemann Parts for 5 Tube Neutrodyne 47Q QQ None Shipped C. 0. D. PHONES $ 5.00 Tumey, 3000 ohms..$ 2.75 12.00 Western Electric . . 8.75 6.00 Brandes Superior... 4.75 12. 00 Baldwin Type C 7.05 7.00 Federal 4.85 8.50 N. & K. Phones 8.60 5.50 Stroniberg Carlson... 4.50 12.00 Dr. Seibt 6000 ohms. 5.75 1.00 1.50 1.00 1.25 1.30 1.50 1.50 .90 1.00 2.00 1.85 1.S5 2.00 RHEOSTATS Fada 30 ohm Federal 25 ohm Amsco 6 ohm Amsco 20 ohm Amsco 30 ohm Cutler Hammer 6 ohm Ver Cutler Hammer 30 ohni PI Klosner 6 or 30 ohm. Pacent 6. 20 or 30 ohm Kilkostat Bradley-Stat Hr;ulU>yleak Ermcostat .90 1.25 .85 1.00 1. 10 1.15 1.15 .80 .90 1.85 1.70 1.70 1.70 LOUD SPEAKERS $30.00 Music Master $24.00 35.00 Magnavox 29.00 30.00 Herald 26.00 10.00 Brandes Table Talker 9.25 17.50 Pathe 15.25 Baldwin Unit 4.65 Amer. Radiophone T'nit.... 3.95 Geraco Music Master Unit. 9.00 JACKS AND PLUGS Pacent Double .lack 70 Pacent Single Jack 60 Federal Single Jack 65 A 5 TUBE NEUTRODYNE Set wired complete Mahogany Cabinet with Genuine Fada Parts :*85 00 EXTRA SPECIAL!!! $120 Fada 4 Tube Neu COC flft trodyne Set No. 160. . . .*3«».w None Shipped C. 0. D :ircuit .*_, _, 00 Daiistrom 6 Way Plug $1.20 Cico 2 Way Plug 55 Weston Plug 90 4 CIRCUIT TUNER Complete parts for the improved Cockaday 4 Circuit, Tuner, exactly specified b y Cockaday .... VARIABLE CONDENSERS ll-PLATE $2.00 Signal $1.40 2. Mi I'. S. L. 1-45 1.80 Amsco 1-30 23-PLATE 2.50 Signal 1.60 8.75 U. S. L 1-65 2.30 17-P1. Amsco 1.65 2.50 Amsco 1.95 43PLATE 2.75 Signal 1.65 8.25 r. S. I. 1-80 3.00 Amsco 2.75 VERNIER CONDENSERS ll-PLATE 6.00 Hammarlund 4.95 4.50 I". S. Tool 3.50 4.50 D. S. 1 3.10 4.00 Amsco 2.95 23-PLATE 6.50 Hammarlund 5.65 5.00 f. S. Tool 3.60 5.00 V. S. L 3.45 4.50 Amsco 3.35 43-PLATE 5.50 Hammarlund 6.25 5.50 U. S. Tool 4.05 5.00 Amsco 3.95 4.50 Amsco 17-P1 3.35 $5.50 Amsco 26-P1 $4.10 3.00 Compensating Condenser 2.65 DIALS AND SOCKETS 3" Amsco Bakelite 45 4" Amsco Bakelite 80 Bell Socket 65 Melon Socket 80 Triple Socket 2.50 Bakelite Socket 45 CMelton Socket 65 TRANSFORMERS Federal No. 65 Acme All-American Aniertran Thor.iarson Coma Duplex Modern Push-Pull.. Erla All American P. P. Duratran It. F General Badio 7.00 5.00 5.00 7.00 4.50 12.50 12.50 5.00 12 00 5.00 5.00 POTENTIOMETERS 1.25 Pacent 1.50 Am.-io 1.50 Cutler Hammer 1.50 Klosner MISCELLANEOUS Pathe Phusif.imiers Ambassador Coils . Cockad.iv Coils, Precision.. Cockadav Coils. E AMPLEX GRID TENSER Larite Resistances. 48.000 ohms $2.00 RelnarU Coll Erla Crystals Brach Lightning Arresters 5.35 3.85 3.85 5.60 3.75 10. 00 10.50 4.25 10.00 4.50 4.35 1. 10 1.25 1.15 1.25 $7.95 5.25 4.50 3.35 1. 10 1. 10 1.40 .95 .2.65 ALL MAIL ORDERS SHIPPED PROMPTLY. Orders over $5.00 will be shipped prepaid. Money •rders #r COD Not insured unless insurance charges Included. Write for Price List.