Radio mirror (Jan-Oct 1923)

May 12, iqj] RADIO DIGEST Making a Three Tube Reflex De Luxe Receiver Part II — Sub-Panel Layout By II. J. Marx NOT only the present but also the prospective popularity of reflex circuits is indicated by the considerable amount of interest that is being shown by Kadiophans in the different types of these circuits. Many are the questions that are askod relative to the efficiency of operation and results that can be anticipated. Details are being requested of the many variations that are possible. Two Classes of Circuits For review, there are two classes of reflex circuits, one of which covers that form of circuit where each stage of audio frequency is reflexed through the tubes in the same order as the Radio frequency, called the straight reflex, and the other where the audio frequency passes through the tubes in reverse order of the Radio frequency stages, known as the inverse reflex. A further sub-division can be made on the basis of the types of intertube coupling, such as transformer, resistance, tuned impedance, etc. Of these the transformer coupling has received the most attention. Other types of coupling show promising indications but have not been fully developed for maximum results. One f.an asks for an analysis of the Neutrodyne Reflex — this is not a special form of reflex, but rather an application of a method of neutralizing intertube coupling capacity effects. As this will be taken up in an article on the subject no details will be given at this time. Efficiency of the Reflex A typical question asked, is "'What can one expect from an average working reflex?" Unfortunately a satisfactory an L__J y32"p»1lxt. I J Wml S/32' OKItA. t I OR AT. TRANS (HI&H VOOTROt) -j— H!ASS ANGLES FASTENED TO STUDS ON END OF CONDENSER. BRASS ANGLES FASTENED TO STUDS ON END OF CONDENSER. leads which always furnish a fine variety of howls and squeals. Who then can figure what can be expected? What May be Expected in Reflex Circuits The writer, however, has developed an efficiency percentage of what may be expected in reflex circuits compared to the corresponding stages in a straight circuit: One tube set — Radio frequency, 75 per cent; audio frequency, 75 per cent. Two tube set — straight reflex — Radio frequency, 70 per cent; audio frequency, 65 per cent. Inverse reflex — Radio fre fin . ii , n BRASS ANGLE FASTENED TO END OF CONDENSER.. <2> BASE OF CAB1NCT -w Figure 1 swer is very difficult, not because the operation of reflex circuits is unreliable, but on account of variations found in the efficiency of all apparatus used in Radio. For example, as has been stated before, the efficiency of a reflex circuit depends to a great degree on the vacuum tubes and how the coupling methods match up with the characteristics of the tubes. As an illustration, the impedance value of the average peanut tube is such that it will not operate satisfactorily with the average transformer. Therefore in a reflex circuit this handicap is increased because of the necessary relation of the two transformers to the tube. Then again, even a poor circuit will, in some places, give good results, while in other places, big cities for example, even the best of circuits will often refuse to do anything but the ordinary class of reception. One man may have a wonderfully efficient aerial while the other fellow with a similar set gets nothing on account of a poor antenna. Some fans have the knack of wiring a set up right without inductive reactions between quency, 75 per cent; audio frequency, 75 per cent. The use of a crystal detector may decrease the volume that may be expected from the detector stage, provided a tube RADIO "BUGS" Get into Business for Yourself Why not turn your hobby into money? You can easily make $15.00 a day, or as much more as you like, by our wonderful plan of selling Radio direct to the millions of people just waiting for our better parts or sets. We furnish everything you need at lowest factory prices and tell you how to build a profitable business of your own. Knott products are up-to-the-minute. Knott plans are unique and unbeatable. Radio is just beginning to come into its own — are you? Want to make more money — want to be your own boss? Write TODAY for FREE instructions, How To Sell Real Radio. E. R. KNOTT MACHINE CO. l-D EHery St., S. BOSTON 27, MASS. CENTER. LINE OF_» BOTH PANELS S-/3Z DRIVL FOR AT. TRANS. Figure 2 were used, but it makes up for it in the simplicity of operation and clearness of the reception. The crystal volume then may be considered as 80 per cent of that of the tube. Applying these rules to the Reflex De Luxe the relative efficiency should be that of a good five tube set. Theoretically this hook-up is equivalent to two stages of Radio frequency, detector and three of audio frequency — the summation of the efficiency values gives a relative value of 80 per cent on the whole or equivalent to about five tubes. This has been substantiated by the results obtained with this set. Naturally the various factors effecting the efficiency of all circuits may alter these values considerably. The Sub-Panel Since no baseboard was used, it was found necessary to assemble all apparatus on the main panel. This was finally accomplished by means of a sub-panel that was mounted on the ends of the variable condensers by means of brass angles INSIDE OF fVMIM PANEL GUARANTEED VACUUM TUBES V/2 Volt Detectors $3.95 1% Volt Detectors and Amplifiers 4.9S 6 Volt Detectors and Amplifiers 3.25 Above Tubes shipped prepaid WE REPAIR YOUR BURNT OUT VACUUM TUBES Quick Service ...$3.50 UV-200 2.75 UV-201 .. ... 3.00 When sending Tubes for repair include with your remittance parcel postage for one pound. Tubes suaranteed equal to new. Abalene Radio 416 D Broadway New York, N. Y. as shown in Figure 1, Four of these angles were used, two each on each condenser on the right and left side of the main panel. Depending on the condenser construction, this mounting method connects the brass angles in direct electrical circuit (Continued on page 18) ."ormicS: jUamiuted Phenolic Cm denation Product .SHEETS TUBES RODS RADIO PANELS POLISHED BLACK FINISH CUT PERFECTLY SQUARE TD ANY SIZE VSZ THICK 1/2* PER SO. INCH /|6" THICK %* PER SO. INCH %2" THICK K PER SQ. INCH '/8 " THICK 1^2* PER SQ. INCH SA&" THICK 2* PER SOINCH Mj. " THICK 2/2* PER SO. INCH 3/Q" THICK 4* PER SQL INCH VZ " THICK 5 !4* PER SO INCH _SEND FOR COMPLETE PRICE UST PROMPT ATTENTION TO MAIL ORDERS DEALERS PRICES ON APPLICATION STA R R ETT M FG. CO. 519 SOUTH GREEN ST. CHICAGO U. S. Bureau of Lighthouses Has Indorsed SPIDER WEB COILS Eugene T. Turney's patent on Spider Web Winding is the only one granted by the Government. TURNEY SPIDER WEB PLEX Turney Spider Web Coils are wound on automatic machines — also patente d . Absolute uniformity is certain. Yes, Government Bureau tests tell the story — Spider Web Windings have proved to be the best form of Inductances in Radio today. And so they will be used in Government Lighthouse Sets. Turney Spider Web Coils are wound by a newly patented machine that keeps the wire completely surrounded by dielectric, 95% of which is air. Result — harmonics which are exceptionally pure and many times more resonant than ordinary handwound Coils. Are cheaper, less bulky, and more efficient than Duolateral Coils. WAVE LENGTH RANGE-^960 meters with condenser in shunt. No body capacity. Eliminates the Variocoupler as a tuning unit. The Radio News says editorially: "We make the prediction that Spider Web, or basket weave. Coils will be used by Radio Experimenters exclusively before many months have passed." See Your Dealer, or Mailed Direct on Receipt of Cash or (fc/f CA Money. Order (No Stamps or Checks) **••'" Hook-ups for Tube and Crystal Sets Included. TRISTAN SALES CORPORATION SOLE NATIONAL DISTRIBUTORS No. 1 Union Square New York City