Radio Digest (Apr 1925-Jan 1926)

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April 18, 1925 RADIO DIGES T— Illustrated 21 Change Regenerative Receiver to R. F. Rheostat, Socket and Tube Are Parts Needed So many kicks have been voiced of late about regenerative detector circuits, and so many ways have been tried out to add Radio frequency to the sets, and all with WORKSHOP KINKS EARN A DOLLAR— THERE are many little kinks worked out at home that would aid your fellow Radio worker if only he 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 obtaining 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, 510 North Dearborn St., Chicago an effort to simplicity, so that the sets the fans now have may be readily changed by the owners, that it is impossible to follow them out and get any desired results. I had much hopes of seeing something that I could use easily, but failing to do so, I set about building something to fill the want. The first circuit shows how I accomplished what seemingly was a difficult job. All the parts extra to change a receiver from an ordinary regenerator to a tuned Radio frequency set is a vacuum tube, a socket and a rheostat. In most cases these parts will find plenty of room in the set for them. An old regenerative circuit with the Radio frequency added is shown in the space outlined by the dashed lines. The wire that connects the rotor and audio transformer is disconnected and is connected direct to the 45 volts of the B battery, never more than 67 volts. The grid condenser and leak is removed and the grid and coil are connected direct. The grid condenser and leak are now connected between the plate connection on the rotor and the grid connection on the tube socket that is added. The plate connection of the added socket is connected to the audio transformer where the rotor was connected, or the phones, if no audio was used. A rheostat is placed in the negative side of the A battery. The dial reading in all probability will now read backward, tout if it does just reverse the connections to the rotor. The tuned Radio frequency circuit that you now have is what is known as the reverse feedback system. For those who desire to build this simple system out and out use the second diagram shown. For extra sharpness of tuning a modified Haynes tuning system is used. Take an ordinary 90-degree variocoupler and on the stator tap the antenna at 15 turns from the opposite end to the tapped one. On a standard variocoupler all stations on all wave lengths will come IF YOUR SET HAS A NONOISE VARIABLE GRID-LEAK its maker has used the best materials obtainable Here is a real variable Grid-Leak. The NONOISE is variable through a resistance range of % to 7 megohms. It can be varied smoothly and silently without loss of the signal. No two sets, are exactly alike, therefore the NONOISE that can be adjusted to the performance of your set gives the best results. No matter how good your set may be, a NONOISE will improve it. Price 85 cents If your dealer cannot supply you we will be pleased to fill your order. Don't send any money. Just drop us a postcard and the NONOISE will be sent Parcel Post, collect. Pay the postman upon delivery. RADIO FOUNDATION, INC. 150 East 53rd Street " H«w York City EXTRA TUBE PLACED IN CIRCUIT X "A" "fe'22kV 45V I 90V qj^ in on the second and third tap. The rotor will tune only about 10 degrees from vertical for all wave lengths, and is not much used in tuning. It is used chiefly to bring in and control the volume. The rotor being at all times about at right angles to the stator. — A. J. Anderson, Greenville, Ky. Vernier Dial Attachment This attachment is made up of a small rubber and wooden disc glued together and then mounted on a spring shaft which is attached to the panel front at the WOOD RUBE>5t£ m 8 8 NUT proper distance from the dial to make contact with the dial edge. The illustration is self explanatory. — Clement Pack, Menssha, Wisconsin. Wire for the antenna should be a good conductor of electricity. Some good conT ductors are copper, phosphor bronze and aluminum. Send in Your Paralyzed Tubes to be Restored to Health in Our Laboratory CkQOf of your worn-out tubes can *sO /0 be put in first class condition. Better than that, out of the last 500 tubes received by us all but five were made to operate as good as new. We can REACTIVATE UV-201A, C-301A, UV-199, C-299 and any other thoriated filament such as Atlas, Magnatron, De Forest, etc. We cannot reactivate UV-200, C-300, WD-11 or WD-12 tubes, nor can we reactivate burned out tubes. It Costs You Only $1.00 if we can restore your tube so that it operates satisfactorily. If we are not successful, our charge is only 25c. Why pay the price for new tubes when we can make yours as good as new for only $1.00. MAIL IN YOUR TUBES TO US FOR PROMPT RETURN, Parcel Post, C. 0. D. A. O'CONNOR & COMPANY 9712 Euclid Ave. Cleveland, Ohio A good pair of telephones is essential for successful operation of a crystal set. Every precaution should be taken to prolong the life of a good vacuum tube. STAR DETECTORS SATISFY Type G, Now $1.00 Type K, Now $1.25 ML Dear Sirs: Received your detector O. K. It's all you say and then some. On a simple crystal I received the following stations : WGY. WHAZ, WEAF, KDKA, WOK and WTAM. Respectfully yours, A. W. Gale, Gloversville, N. Y., 9 Spring Street. The above letter is typical of hundreds received during the past two years on our type G Fixt Crystal Detector, which has been much improved this year and sells at $1.00. Formerly $1.25. THE TYPE K STAR ADJUSTABLE DETECTOR is a very satisfactory crystal for Reflex and Crystal sets. We make a complete line of crystals which includes every standard material and are in position to quote attractive prices on quantity orders. We can match the field on quality and price. Let us quote you. State quantity. B-Metal Loud Talking Crystal STAR CRYSTAL CO. 14th Floor, 525 Woodward Ave. DETROIT. MICH. Binding Posts Used in Place of Aerial Switch Instead of using a series parallel switch to change the aerial in series parallel in the primary circuit I use the system as o I o IN PARALLEL illustrated. Three binding posts are used for the aerial and ground instead of two and the connections are made as shown. If it is desired to have the condenser in series with the circuit the aerial is connected to the center binding post and the w o o ¥ o IN SERIES ground to the bottom, but if it is wanted in parallel the aerial is connected to the top binding post and the ground to the center and bottom binding posts. — Walter Carron, Los Angeles, Calif. This Full SizeLoud Speaker at DiredFacfori) Price. 85 9 Save practically HALF on this $18 horn. Buy direct and cutout dealer's and jobber's profits. Horn ia 19H inches high; 12H -inch bell; Florentine brown stipple finish; finest diaphragm unit made; metal base, goose-neck and bell. Clear, full -toned, exact reproduction. Money-back guarantee. 5-Tube Receiver $ 48 _50 Our direct factory price saves you $25 or more. Range 1500 to 3000 miles. Simple to operate. Very selective. Highest grade, laboratory tested parts, wired to Naval standards. Beautiful handrubbedgenuinemahogany cabinet. Guaranteed unconditionally to equal any receiver soid regularly at retail for $65 to $75. 5 Days1 Free Trial special OFFER Try the Dexter Receiver FprJOdays.Dgter $ »nd Horn 5 days. Your jn combination at ^ / money refunded in full if Send no money. Pay post you decide to return them, man or expressman. DEXTER METAL MFG. GO. 10 S. 18th Street Address Established .■__ . Phila., Pa. Radio Engineering 18iS Division M up your set with good tubes make all the difference in the world. You'll agree with that statement the moment you switch to MAGNATRONS, the moment you notice how clearly and powerfully these tubes bring the concerts to you. MAGNATRONS are for sale by the better dealers everywhere. The type DC-201 A, the DC-199, and the DC-199 with large base each sell for only $3. C0NNEWEY ELECTRIC LABORATORIES 309 5th Ave., H Y. City Factories, Hobofcn, 7i }■