Radio Digest (Apr 1925-Jan 1926)

22 RADIO D I G E S T— Illustrated September 12, 1925 Questions and Answers Edelman's Heteroflex (14303) DHS. Alda, Nebr. A few question regarding the Heteroflex. Have built several of your sets among them being: the Hetduogen, but about as soon as I get them going 1 dispose of same. Now I would like to make the Heteroflex. With reg-ard to coils 0 and 10, is 10 wound over 9 or simply side by side on a tube as it were? Does the tap on 10 come off at end next to 9 or at far end? What make is resistance number 5 and where do I get it? What make transformers 13, 14 and 15 and where can I secure them? What make crystal and where secured? Radio equipment is extremely hard to procure here, making it necessary to write to Kansas City or Chicago. A. — The coils 9 and 10 may very well he flat of the spiderweb or Pfanstiehl types secured on a rod so they can be varied in their proximity. The tap comes off near the outside end. Resistance number 5 may be a CRL unit of about 1.S00 ohms, or a Federal potentiometer of that resistance. Transformers 13, 14 and 15 may be the filter and two intermediates of any super kit. In the laboratory we used a Radio receptor with the filter as 14 and two intermediates as 13 and 15. Practically any good adjustable crystal detector may be employed. We happened to have a Freshman that worked well. Bridges and Supers (14299) WBW Akron, Ohio. Milo Gurney, in his articles on the balanced bridge for radio frequency, gives illustrations of two stages of radio frequency in figure 37 of his series of articles. Figure 37 shows only two variable condensers there being none shown across the third radio frequency transformer secondary. If this diagram is correct on that hook-up there would be only two controls for wave length on a two-stage radio frequency hook-up. This interests me because all other two-stage radio frequency hook-ups require three dials to control the wave length. Was that diagram correct? I built a four-filter super-het by Fournier's instructions and would like to put radio frequency ahead of it but do not want any additional controls for wave lengtn than I have at present; there being but two dials. I have read these articles with interest and thought I saw in figure 37, a chance to omit the second tube of that diagram and its units, thereby gaining a stage of radio frequency ahead of my super-het without additional variable controls for wave length. I am using Rauland-Lyric transformers, two stages on my super-het. Everything is satisfactorily reproduced on the first stage but I must reduce my potentiometer by adding in the second stage. Is it at all practical to use two transformers and two tubes in parallel to handle the tremendous volume obtained from the second detector? I do not rare for push-pull amplification and have thought that paralleling two transformers and two tubes might give the advantages claimed for push-pull. The figure 36, of Mr. Gurney's articles shows a small variable condenser leading from the plal» to the coil L2. Also a dotted fixed condenser marked, Ca. Is this dotted Ca an illustrated capacity of the co'idenser C7 or is it the additional small vernier condenser described by him in the following issue balancing the plate and grid of the tube? Or is the condenser C7 the one to be constructed and the only variable control between the plate and grid capacities? A. — There was an omission in the drawing of figure 37 which we, of course, sincerely regret. There should have been three condensers. This has been reproduced correctly on pago 19 of the September 5 issue. W. have shown two types of radio frequency amplifier which can riir! VolU RADIO Storage "B" Battery Lasts Indefinitely— Pays for Itself Economy and performance unheard of before. Recharged •t a n^ffhgn'ble eo«t. Approved and lifted oh Standard by Hadlft* tUAio Autl fry* Pop, R*/Jlo Lnbantnrien, Pop. 8rl. In*t Standard*, R-> dfo N'-*n Lab.. l>fBi. Inc.. and other ho. O-vr'ait InitffjU'-Tn. r>i')lf:-«d with fytlid I(ufS>rr Car*, an fnimraocw acainU add wn-J K-iinif. Kxtra heavy iflaas jam. Heavy, rycir^d IiU'.m. Of>r POOH today! SEND NO MONEY £&&SJ^'i8lZ$lr& «sM#r la ra*»i*.-«d. Extra Offer: A batt> n*« In. t#rlei '06 voltai, #12.76. P»» *xtir**mtii aft*r examining1 batteries. 6 per cot discount fef caabwitb order. Mall pour order now! WORLD BATTERY COMPANY 1219 So. Wabash Ave., Dept.7e Chicago, UL Mvkrrm of O* Fiitwu* World Radut "A" SOtrinc BatUrv 4-voU.lOQAmp. SI1.U; JtOAmp. $19.20: Ho Amp. tlk-W* AM equipped with Ootid £tt6cv Com. fVicea. World (STORAGE BATTERIES BrtrinrBullo Dlil. .t 210 HMton tor th. raw 1000 • KttfolM Igraci l'->e r, Button. WiJIK.. Chicago. W.ub for.nnoijne.ro':nt.. be added to a super, one in Mr. Thatcher's article in the August 15 issue and one on the Kinks page of the August 22 issue. The phenomena you notice of having to reduce the potentiometer on the second stage of a super is quite customary when all are in one cabinet. The transformers you have are among the very best made. It would help if the two audio stages were placed in a separate cabinet. The dotted line fixed capacity to which you refer in figure 36 of Gurney's articles is that between the plate and the grid in the tube, always present and that which we are trying to balance out. Four Tube Dry Cell Receiver (141S8) VFF, Berger, Mo. I am looking for a good hook-up using 199 tubes. I can not use a storage battery because I have no way to recharge it. You need not send a panel layout; all I need is the diagram (by symbols) and the constants such as number of turns, value of resistance, etc. If you have a diagram covering these requirements in a back issue let me know which one it is. Here are some important points; not more than three tuning dials, not more than four tubes, suitable for 199s, one stage of tuned radio frequency, tube detector with regeneration, two stages of audio amplification. I would like to reflex the stage of radio frequency if this can be done without impairing the efficiency. A. — We wish to advise that the complete specifications for a receiver that perfectly meets your requirements were given in an article by Mr. Goodrich contained in our issue of May 23rd. Under separate cover we are sending you a copy of that issue and you will find that the receiver mentioned uses four 199 tubes with one stage of turned R.F. regenerative and two audio. Reflexing would impair the selectivity. Charger Interference (14318) RC, Racine, "Wis. Next door to me there lives a Radio fan who has a vibrating type of charger. He has storage B batteries, as well as the storage A. Consequently, he is charging batteries a greater part of the time. Four families are prevented from listening, even for locals, because of it. Is it possible for the owner to stop this noise? Or, if he refuses, can the other fans do anything on their own sets? A. — Wd would suggest your reading the articles in Radio Digest August 1 and 8, furnished through the courtesy of the Radio branch of the Department of Marine and Fisheries of Ottawa, Can. This pair of articles contain information for remedying your trouble. If you cannot get satisfaction from your neighbor, write to E. A. Beane, Federal Radio supervisor, ninth district, Federal building, Chicago. Journal Filter Coils (14208) CCA, South Bend, Ind. Will you kindly send me at once the specifications in full detail on the N. T. Journal filter coils? I would appreciate an early reply. A. — We must advise that we are unable to furnish you with the specifications for the N. Y. Journal filter coils. We suggest that you write to the Radio editor of the New York Journal, New York city, and he will probably be very glad to forward a copy of the issue of that paper containing this information. Men to build radio sets in spare time. Leon Lambert, Wichita, Kansas. PATENT ATTORNEYS PATENTS. Booklet free. Highest referencet. Best results. WATSON E. COLEMAN. Patent Lawyer, CH G Street, Washington. D. C. A. B. C. RADIO COURSE (Continued from page 20) This antenna circuit is coupled to a tuned secondary circuit composed of the inductance La and capacity Cj. The secondary circuit is connected between the filament and grid of tube I. The incoming signals are successively amplified by the three tubes I, II and III, coupled to each other by air-core transformers, or by means of special radio frequency iron core transformers. The amplified Radio signals are then impressed, through a transformer T3, between the grid and filament of a tube IV which is made to operate as a detector by means of the grid condenser C3 shunted by a high resistance ri. The audio frequency pulsations in the plate current of tube IV are amplified in succession by tubes V, VI and VII, and are finally sent through the telephone receivers T. Tubes I, II, III, V, VI and VII should be operated at the central part of their static characteristic curve so that symmetrical variations of grid potential will produce symmetrical variations in plate current. The detector tube should be operated at the upper or lower bend of its static characteristic curve in order to get the maximum amount of detector action. (The three electrode vacuum tube is most flexible with respect to the uses to which it may be put. Professor Moreton, having' discussed its use as detector and amplifier, will, next week, take it up as a regenerative amplifier and oscillator. — Editor's Note.) EDISON PLATE BATTERY (Continued from page 21) of luck made it possible for me to build the complete outfit, including cabinet and rectifier, for somewhat less than $12.00. It will cost you closer to $18.00 if you get the elements from a dealer, but even at that it is a good bargain. If you get an old cell, completely discharge it, open it with a can opener, and pour out the electrolyte; with great caution. Potassium hydroxide is wicked stuff — quite as vicious as sulphuric acid. More on that subject later. Take the plates apart, with due admiration for the beautiful workmanship, and wash them. The little rectangles are the negative elements and the long, pencil shaped things are the positive elements. You now have to bore a small hole through each element near the top, and it is easier to do this boring before you take the little individual elements from SALESMEN WANTED With cars calling on Radio Retailers. Side line or regular. Money maker. Small sample. Advise territory you cover. Confidential. Salesmanager, 3821 Morrell, Kansas City, Mo. Any Radio Map a Month Old Is Out of Date Unless It Has a Monthly Supplimental Service THE AIR-LINE RADIO MAP and LOG With Patented Movable Mile Scale Has This Service Lists stations by call letters, also by wave lengths. UNIQUE BROADCASTING SCHEDULE. LOG shows location; difference in time; power, meters and kilocycles; spaces to list dial settings; time heard, distance, signal ftrength. Whether you use outdoor aerial or loop, direction of loop, phones or loud speaker. 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Clinton SL, Chicago nmwrr nil m—— 1 mm %jehl)oMs Standard ""THE distinctive shape of The Amplion ■*• Isthereeultof many yearsof acoustic experiments by the origrinators and oldest makers of loud speakers. Objectionable resonance Is eliminated by rubber bushlngv between horn, conduit and unit. Send for booklet, dealers' names. THEAMPU0N CORPORATION OF AMERICA Emeu five Offices: Suits A. 280 Madison Ave.. NEW YORK Burndtpt 01 Canada, Ltd., Toronto. the frames in which they are clamped. Use a sharp blow with a prick punch to start each hole, and do not be surprised if you discover that the steel shells are horribly hard to bore through. I broke three drills in the process; charged to eost of battery. The holes should not be much larger than the iron wire, or you will lose much of the nickel and iron powder. Now cut up the iron wire into pieces about 6 inches long and fasten the elements together in pairs, a negative and a positive. You can determine the exact length of the wire by figuring that neither element should touch the bottom of the glass tube, and the negative should be about half way up. The wire should go through the hole in one and be twisted tightly upon itself, should go over the edge of the tube, horizontally to the edge of the next tube and down to the other element of the pair. Thus both will be suspended in the solution and, even if the wires are not twisted absolutely tight, there will be no noise. Where a tap is to be taken off between cells, use a slightly longer wire and make a loop. Also make loops on the ends of the wires from the single elements at the beginning and end of each 50-volt block. To make connection with the copper wiring to the switchboard, solder a lug on the end of the copper wire, slip a short machine bolt through the lug, slip on a small washer, poke the bolt through the loop in the iron wire, put on the nut and tighten with a screw driver. (The finishing touches on cell, assembly, the mixing of the electrolyte and the construction of the charger, together with a complete wiring' diagram of the whole assembly ready for operation, will be given by Mr. Brigjfs in the second and concluding article next week. — Editor's Note). The British Broadcasting company is to celebrate its third anniversary Friday, November 13 (hoodoo day) with a great Radio revel all over Great Britain. The chief event will be at the Royal Albert Hall, London, which accommodates over 10,000 people. It's OUT — Complete everlasting ready to run non-arid, non-sulphating 22% -volt rechargeable "B" storage battery. $2.95. Includes chemical. Does not lose Its charge standing Idle. Special 2-22% volts (45 volts) (6.25; 90 volts $10.00: 112% volts $12.50; 135 volts $14.75: 157% volts $16.80. Nearly 3 years sold on a non-red tape. 30-day trial offer, with complete refund if not thoroughly satisfied. Further guaranteed 2 years. 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From dealers or sent direct postpaid. FREE technical circular especially prepared by W. W. Harper, designer of the Metaloid. Price $5.00 CRIBBEN RADIO CORPORATION 971 Montana St. Chicago, 111. Mlttf