Radio Digest (July 1924-Apr 1925)

April 4, 1925 RADIO DIGES T— Illustrated 21 Loud Speaker Field Current Control Plug Drawn Breaks Speaker Unit Circuit When using loud speakers that require a field current it is quite bothersome to disconnect it every time, and many times it is forgotten and thus the battery is 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 run down and must be re-charged before the set can be used again. With the old types of loud speakers no means have been provided for to disconnect the current, and it has been quite difficult for the amateur to arrange a means of controlling this current. In the illustration is shown a simple switch for controlling the field current, it being turned on every time the plug which connects to the loud speaker is placed into the jack. Usually the jack, which is used for the loud speaker, is seldom used for the phones, and this means should prove convenient, especially to those who have found it difficult to arrange a switch. The jack used should be either the single or double circuit filament control type and should be quite heavy, with a stout spring for the current control, so that no arc will form when the current is broken. — Evermont Pisel, Lebanon Junction, Kentucky. CIRCUIT JACK WITH DIAGRAM TO BATTERY 0 © B+ PL. Low-Lossing the Condenser Low loss condensers put pep in the set. They make it selective, easy to tune and often eliminates body capacity. If you have any condensers that are not of the low loss type you can convert them into such by a little work on them. For a long time I was under the impression that a low loss condenser had a very minimum amount of insulation. The first condenser I bought of this type ORDINARY FIBER, END PLATE WIRE FOR. GROUNDING PLATE TO ROTARY PL ATE5 LOW LOSS TYPE AFTER PART OF INSULATION IS REMOVED — » Aerial and Ground Condenser Interference from local stations can be decreased in many cases by shunting a fixed condenser across the aerial and ground binding posts. This type of condenser may be made with two sheets of tin-foil, 3 inches square, separated by a sheet of paper. A permanent unit of the mica dielectric type condenser type, having a capacity of .000025 mfd. should be installed. UNCLE SAM (R5ES <are the easiest sets in the world to calibrate /brtiene is only one dial A CALIBRATION FREE Ac* *o*r dealer or mmd «• fomr <w»t» in ittapt for wiring «Kogrwme of circuits in which Out remarkable c+i com be naadL UNCLE SAM ELECTRIC CO., 100 E. Sixth St., PloinfitOd, N. J. asK ' are theu genuine tkadiotrom?JL WD-ll Radiotron •CO. U. \. CAT OO SHOWING HOW METAL END I Ol PLATE CAN BE Vi/ ADDED dispelled the idea completely. The low loss condenser has a return for the magnetic field in the form of metal end plates — at least most types have, and a small amount of hard rubber insulation. In converting a regular condenser to a low loss type, two things are necessary to make a complete job of it. First, cut away as much of the insulation as possible without damaging the condenser. Next, make metal end plates of aluminum, copper, or zinc, taking care that they are insulated from the stationary plates and ground them to the rotary plates. The easiest method of grounding them is to run a lead wire to the binding post at the back of the condenser. — C. L. Smith, Jackson, Miss. Coils Kept Tight on Tube with Wire Ends When winding a coil on a tube and taps are wanted the difficulty arises in keeping the wire tight after the loop is made. The illustration shows a way to do this and when the coil is complete it is not necessary to have any binding material. At the place where the tap is to be taken off three holes are drilled in line with the direction of the wire and the wire is run down through the hole DURHAM Grid Leaks Used by Eagle, Howard.Thompson, Zenith and other*. Fit If&l a" ,ets Sold on guarantee. _ Metallized Fixed Leaks CQ« 18 sizes; under Vi meg., •^ 75c; over 'A meg., 50c. Class Sealed Variable Leaks 3 sizes fit all sets; 75c each for 1/10, 5 and *7CC 10 megs #7 ait dealers or postpaid DURHAM & COMPANY, Inc. 1936 Market Street • Philadelphia, Pa. Buy Tubes fay Name WD-Il Radiotron Centering Instrument Shafts Procure a piece of medium stiff paper with one straight edge and of any convenient width with a length to reach around the circumference of the rotor or stator. Lay the paper around the part to be marked and cut the ends just so that they will touch — must not overlapthus forming a length exactly equal to the circumference. Remove the strip and fold it in the exact center. The crease at the fold is marked. Replace the strip as before. The straight side of the strip at the points where the ends meet and where the center was marked are diametrically opposite and form the exact center point where the shaft passes through the rotor or stator. — John Odill, Norway, Mich. M«. V. » .*'. orr Counterpoise Aids Tuning If you happen to have two aerials on the roof try one of them as a counterpoise. Simply disconnect your regular ground from the set and in its stead put the lead-in from the other aerial. The aerials do not necessarily have to be arranged one above the other. Listen for YOUR Name SEND NO MONEY Send postal applause cards and hear your name read over YOUR radio. Stations gladly put on numbers at your request. All the RAGE. Good grade cards. Quality prinUn^Satisfacticjiguaranteed^You'll be delighted. FREE LOG for Your stations with first order. Places tor call, cities, wave lengths, 4 dial settings, remarks, etc. List by wave lengths of principal stations. Other valuable information. Beautiful rippled cover. YOUR OWN Name and Address Printed FREE on each card. Be individual. Post Card back (requires ic stamp). 100 only $1.35; 200— $1.95; 300— $2.45; 500— $3.45 plus few cents postage. Don't send one cent. Pay postman after cards arrive. If you prefer to pay with order, we prepay postage. Money RETURNED if not DELIGHTED. £lu„j2. bJS judse 0rder today— NOW. Postal will do. RADIO PRINTERS, Dept. 7414, MENDOTA, ILL. STAR DETECTORS SATISFY Type K, Now $1.25 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. WOR 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. P* C CROSS SECTION VIEW OF WINDING TUBE AND METHOD OF TAPPING at A and brought up through the center hole. In order to do this the wire must , be cut and the start or new end run down through the hole C and up through the center hole and both ends twisted at B. — M. Daugard, Syracuse, N. T, Too Much Expected The one great evil which prevails today is the endeavor on the part of the individual tuning the set to get the loudest signals possible regardless/ of clarity. Much has been said about quality being the main consideration in a Radio set, but as we listen to some sets we feel sure this is only a secondary consideration. Much depends on the loud speaker unit itself. Some units will stand up and give good quality on strong signals, while it is important in others that they are not pushed to the limit. Don't strive to get the last drop of power from a set. Don't force the tubes nor use too much regeneration. Good quality will give you the enjoyment you should have from your Radio set. To take the tinny sound out of a metal loud speaker horn, spatter it slowly with a mixture of hot paraffin and salt to which a little vinegar has been added to make it adhesive. When the horn cools apply several coats of black paint. ^* for>m Circuits Designed and made in strict accordance with the very latest and most authentic improvements in lowloss construction. Greater Distance, sharper Selectivity, more volume. Prices for 3 Circuit Tuner ....$7.00 Roberts' Knockout 8.00 Superdyne 8.00 Superheterodyne 3.50 Sent direct to your door C 0. D., plus Parcel Post Send $1.00 for full sized blue prints of panel and base board for 3 tube low-loss receiver, and also $1.00 for Perfection Vernier. Perfection Radio Mfg. Co. Office: 317 — 1520 Chestnut Street Philadelphia, Fa. Send in Your Paralyzed Tubes to be Restored to Health in Our Laboratory QO Of of your worn-out tubes can •70 /O 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-ll 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 9708 Euclid Ave. Cleveland, Ohio