Radio age (Jan-Dec 1926)

RADIO AGE for February, 1926 The Magazine of the Ho&ft Build the Set That Holds 4 World's Records The receiver that brought in stations 6,000 to 8,000 miles distant with loud speaker volume night after night. All records fully verified. Holds World's Records For (1) Longest distance ever received on a loop aerial — 8,375 miles (2) Most consistent reception of stations 6,000 to 8,000 miles distant— 117 programs in three months. (3) Brought in 6 different stations in 2J^ hours — all over 6,000 miles. PRICE: Complete Set of Parts $89.00 (Includes all parts necessary to make an exact duplicate of this wonderful receiver, together with book of instructions and complete blue prints.) Story of development and proofs of records sent on receipt of stamped and addressed envelope. Scott Radio Laboratories 35 S. Dearborn St., Chicago Dealers and Set Builders, write for discounts YOU CAN GET Greater refle: or crystal set BROWNLIE VERNIER DETECTOR $2.00 At your dealer or Direct. ROLAND BROWNLIE & CO. 21 Sanders St. Medford M Eliminate Audio Distortion ( Continued from page 26) equally well. Even when the headphones, connected as in Fig. 2, respond with drums and low notes galore, the loud speaker does not do justice to them, even though showing a tremendous improvement over the previous output. Neither would the headphones, were they pushed to great volume, for their natural period is only slightly higher than that of the ordinary horn speaker. A large cone speaker reproduces bass notes well, but rather slights the high tones. I use a combination of a large cone speaker and a horn speaker, connected in series and operated on a power tube for real reproduction. A most surprising change greets the ear when either the horn speaker or the cone speaker is used alone, but with both of them high and low tones receive their due. The richness, musical range and grandeur of orchestral and band music is delightful with such a system and even the human voice regains most of its naturalness. The very high tones are likely to cause a rustling sound in a large cone speaker, but it is very easy to eliminate these high tones from the low note speaker completely by simply shuting it with a fairly large fixed condenser. The capacity must be found by experiment, but one between .004 and .06 is suitable. A number of condensers can be put in parallel until the speaker's output is improved by the elimination of the high notes. These are then more properly reproduced on the horn type speaker. The condenser, by the way, is a helpful stunt for the mandolin type low note speaker which I recently described. Thus loud speaker range has a good deal to do with musical quality and this range depends greatly upon the size of its diaphragm. My own low note cone speaker is a simple affair made out of a cone 20 inches in* diameter cut from stiff drawing paper. The actuating unit is taken from a Baldwin phone, with the mica diaphragm taken out and a separate connecting pin run from the tip of the cone to the armature. The spring at the rear of the armature is removed and the armature maintained in a midposition between the pole pieces by the holding force of the connecting pin and the cone, which is tacked down to a wooden framework. But, whatever the loud speaker combination has do with the quality of tone, it is certain the amplifier has a whole lot bigger part to play in it. The series headphone tests outlined are the surest way to locate distortion, for it is so easy to compare the several stages and focus the attention upon the single stage in which distortion occurs. You Cannot Afford to Miss the Priceless Hookup Ideas in the "Annual" for 1926. Pin your dollar to the coupon on Page 36 and get your copy. First edition just off the press. fr Same device winds both spider web or ™ solenoid coils in different sizes. Coils easily removed in perfect shape. All metal brass and aluminum. Approved by Popular Radio. For sole only by * FRANKLIN COIL WINDER 81 Irving Place, New York City. You can wind Coils forallCircuil Shows how to get — greater distance, more volume, amazing selectivity, finer tone Science has discovered a new principle in radio amplification ... a striking new development that is bringing unheard of results. This principle is founded upon a new kind of coil — the Erla Balloon Circloid. It brings 4 distinct improvements. These are explained in a fascinating book just published and being mailed free. Edition limited — write today Get this book and read about this newest scientific radio principle. See the many different circuits in which it may be used. Find out how you can turn your present set into the latest example of radio engineering — and at a remarkably small cost. There are only a limited number of these books, so you must write immediately. Address Electrical Research Laboratories 2500 Cottase Grove Ave.. Dept. 61 Chioago. 111. To the Man with an Idea I offer a comprehensive, experienced efficient service for his prompt, legal protection and the development of his proposition. Send sketch of model and description, for advice as to cost, search through prior United States patents, etc. Preliminary advice gladly furnished without charge. My experience and familiarity with various arts frequently enable me to accurately advise clients as to probable patentability before they go to any expense. Booklet of valuable information and form for properly disclosing your idea free on request. Write today. RICHARD B. OWEN, Patent Lawyer 81 Owen Bldg., Washington, D. C. 2278-M Woolworth Bldg., N. Y. City Tell them you read it in Radio Age