Radio Digest (Oct 1923-July 1924)

October 27, 1923 RADIO DIGEST — Illustrated Audio Amplification for the Flewelling Set Two Stages of Audio Frequency Added for Volume WHILE it is the purpose of this article to describe how a suitable audio amplifier for the Flewelling circuit may be built, I believe that our readers will find that most of the notes will be entirely applicable to audio amplification for any Radio set. There are so many things to be taken By E. T. Flewelling tone will immediately become very blurred; if indeed one can hear it at all through the various squeaks and howls. A three step set was built under just such conditions as this and the reception was such that if we had good luck, we could understand what was said by the announcer. To this set was added jacks to far more exactness in the building, it was decided to construct these experimental amplifiers in three stages, knowing that if three stages were successful, then two stages would also be correct. We found that an amplifier could be made or ruined as an amplifier simply by the arrangement of the parts or the wiring. can take the necessary parts and build a Radio «et complete with U • audio amplification and obtain very much greater volume and much cleaner-cm ceptlon than we have often si-cn in two stage amplifiers, these matters are worthy of observance. It is surprising 1 • the leads between parts can be made if we into consideration In this subject that it is hard to decide where to commence. The writer has been so impressed during very exhaustive tests with audio amplification by the effects caused by arrangement of wiring and particular parts used, that perhaps this end of the subject should be taken up first. Let us consider first the type of transformer to use. Of course, we cannot name any specific types of apparatus, so that I will be unable to be of any assistance to our readers on this point. It was quite well demonstrated during the tests spoken of above that satisfactory operation of an amplifier was not in general obtained with transformers of a high ratio, that is, transformers in the 10 to 1 or 6 to 1 class. Better results can be obtained with transformers of a ratio of 5 to 1 or less. The' reason is that the high ratio transformer has so many turns of wire on its coils that its impedance and resistance value are such as to unfavorably affect the grid and feedback conditions. There are so many Radio sets using amplifiers that show traces of this trouble that it might be well here to show how it may be recognized. Correct Amplification. An amplifier operating with transformers of the high ratio type will' quite often sound furry or have the "tin horn" sound that is so objectionable. Almost invariably the clear-cut sharp resonant note amplifier will be one using transformers of low ratio, or at least transformers that are wound with larger size wire than is ordinarily used on a high ratio transformer. That the above is so is easily demonstrated by adding a third step to the usual two step amplifier, when the YouDon't Need TllhftCto get out of town. If you • ••**^*want now stations on your crystal set WRITE ME TODAY. Mine works 400 to 1,000 miles without tubes or batteries 1 Thousands nave bought my plans and now set results like mine. CHANGES OFTEN COST LESS THAN A DOLLAR. Send self-addressed envelope lor further information. Leon Lambert, South Volutsia, Wichita. Kansas. WD-11 and WD-12 Tubes Repaired WDII or WD-12 $3.50 C-300 or UV-200 2.75 C-301 or UV-201 3.00 C-302 or UV-202 3.50 C-301 A or UV-201A 3.50 Moorehead Detectors 2.75 Moorehead Amplifiers 3.00 DV-6 or DV-6A 3.00 Also the new UV1 99 3.50 NEW DX 1 % VOLT TUBES . 4.00 All tubes guaranteed to work like new Mail Orders Given Prompt Attention "24 Hour Service" RADIO TUBE CORP. 55 HALS EY STREET NEWARK, N. 3. Tubes Sent Parcel Post, C. O. D. control the filament, that is, we could plug in on the second step or the third step, lighting the filaments by the insertion of the jack or putting them out upon its withdrawal. The addition of these jacks demonstrated that they were not a success, because after their installation we were unable to understand anything that was said. These notes regarding the ratio of the transformers the writer believes to be extremely important to heed in constructing an amplifier; and the above might be summed up by the simple statement that in general low ratio audio frequency transformers are preferable and recommended, while the use of filament control jacks is not advisable. Wiring the Set Another extremely interesting thing, and really of vital importance in the construction of an amplifier, is the matter of wiring the set. During our tests, probably fifty amplifiers were built, and because three stages of amplification demanded Askyour Dealer «WHEGEHOG (Trade Mark) AUDIO TRANSFORMER $3.50 This little wonder is the surprise and talk of Radio Engineers everywhere. Fix in your mind's eye an AUDIO Transformer about the size of an English walnut and you have the "HEGEHOG" for size. Then recall the best Radio amplification you" ever heard, and you have the "HEGEHOG" for volume and tone quality. Our new patented design and construction (100% shielded) makes this possible. It's a real bit of engineering, and we would like to have YOU try one. Ratios 1 to 3, 1 to 4 and 1 to 5 $3.50 1 to 10 4.50 ^rtmWr fyttirU fampuny 3810 Ravenswood Avenue, CHICAGO, U. S. A. We have always been strong advocates of short leads and the elimination of all unnecessary parts and wiring in dealing with Radio sets, and we find that invariably the best operating amplifiers are those that followed along those lines. By the use of reconstructed sockets, transformers, terminals and home-made tuners, condensers, etc., the writer has been able to make amplifiers that are so free from feedback conditions that any amateur builder might follow this rule with every assurance of success. • Short Leads In Set The foregoing, as we said, is so important that great care should be taken that the points given be considered. It does seem that, if an inexperienced amateur (Patent Pending) THE PERFECT SYNTHETIC CRYSTAL DETECTOR, SENSITIVE OVER ENTIRE SURFACE. No Hunting for "Spots." Loud and Clear. Endorsed by thousands of satisfied users. Sensitiveness Guaranteed. 50c Price, Mounted. 14 K. GOLD SUPERSENSITIVE RUSONTTE CATWHISKER. Permanent. Will OC_ Not Oxidize. Price *oc RUSONITE REFLEX CRYSTAL. Manufactured Expressly for Reflex Circuits. Will Stand Up Under Heavy Plate Volt «1 Ark age. Guaranteed. Price. Mounted . . «*>*•'■"■' Order from your dealer or direct from RUSONITE PRODUCTS CORP. 15 Park Row New York. N. Y. •Super Values Flewelling Circuit Complete List Our Price Price 7x9 Radion Panel $ 1.15 $ .90 23 Plate Var Condensers 3.00 1.50 3 .006 Mica Condensers 3.00 2.00 C. R. L. Var Grid Leak 1.85 1.30 Two Coll Honeycomb mount adjustable with knobs 4.00 2.55 50 Turn Honeycomb Coil 1.54 1.00 75 Turn Honeycomb Coil 1.54 1.00 (Mounted) One tube socket 1.00 .40 Klosner vernier rheostat with dial. . . 1.50 1.00 One three inch Dial 1.00 .25 (Taper Knob) 8 Rinding Posts 80 .40 Baseboard for Mounting 75 .40 Complete Instructions for Assembly and Wiring 50 .50 Regular Price $21.63 OUR PRICE $13?5 Reinartz Circuit Complete List Our Price Price Genuine Reinartz Coil endorsed by John L Reinartz and bearing his signature. The only genuine coil for this circuit on the market. All others are imitations $ 2.50 One 7x10xj:!j Radion ranel 1.25 National Bakelite Socket 1.00 Klosner Vernier Rheostat with dial. 1.50 Two 23 Plate veriable condensers at $3.00 each 6.00 Switch Points and Nuts 80 Six Switck Stop Points and Nuts. . .40 Freshman Grid Leak and Condenser 1.00 Seven Binding Posls 70 25 ft. Tinned Bus Bar 50 3 Switch Levers with knobs 75 One Baseboard for mounting 75 One Fixed Phone Condenser 40 One Single Jack 1.00 Blue Prints with complete instructions for assembly and mounting. .50 $ 2.00 1.00 .40 1.00 3.00 .40 .20 .65 .35 .30 .35 .40 .25 .25 .50 Regular Prico OUR PRICE $1 \Q$ All the necessary screws, nuts and miscellaneous small Darts which are necessary to coiui are included in the above prices. Any part In cither of these circuits may bo purchased Independently at the advertised cut prices. LOUD SPEAKERS List Price Our Price $161.00 Western Electric 10-A $125.75 55.00 Western Electric 10-D 44.00 60.00 Magnavox Type R-3 51.00 35.00 Magnavox Type R-2 29.50 $30.00 Music Master $24.50 25.00 Atlas Amplitone 19.50 25.00 Trinity Type A-l 19.50 22.50 Belcanto 18.00 28.50 Dictogrand 23-50 List PHONFS 0ur Price rnV/mtO Price $6.00 BRANDES $5.25 8.00 N&.K GERMAN 5.75 7.00 FEDERAL 5.50 List' TIIRFS 0ur Price * WDJCO prjee $5.00 RADIOTRON U. V. 200 $3.95 5.00 CUNNINGHAM C. 300 3.95 6.50 RADIOTRON U. V. 201-A 5.75 6.50 CUNNINGHAM C. 301-A 5.75 6.50 RADIOTRON W. D. II 5.75 6.50 CUNNINGHAM C. II 5.75 6.50 RADIOTRON W. D. 12 5.75 6.50 CUNNINGHAM C. 12 5.75 6.50 RADIOTRON U. V. 199 5.75 6.50 CUNNINGHAM C. 299 5.75 eV£ CONDENSERS P°r^ $1.80 3 PLATE VERNIER $.90 5.00 23 PLATE VERNIER 2.50 5.50 43 PLATE VERNIER 2-75 3.00 23 PLATE PLAIN 150 2.80 43 PLATE PLAIN 190 AUDIO TRANSFORMERS List Our Price Price $4.50 ALL AMERICAN, 3 to I Ratio $3.95 4.75 ALL AMERICAN. 5 to I Ratio 4.10 4.75 ALL AMERICAN, 10 to I Ratio 4.10 7.00 AMERTRAN 5.55 7.00 FEDERAL No. 65 5.55 ALL Mail Orders Shipped Promptly. Send Money Order, including Postage Write for Our Catalogue HANES-ZENER CO., 3 West 29th Street, New York City The RADIO MAIL ORDER HOUSE— Known for Low Prices