Radio Digest (Oct 1923-July 1924)

March 29, 192k RADIO DIGEST — Illustrated 29 Simple Explanation of Radio for Everybody (Continued from page 23) i For some reason, reflex circuits began tions are without number — the writer has with crystal detectors; why, no one seems over forty, but there are probably over [ to know. Possibly it was the difficulty mw?6\ T Figure 111. 300. We will consider a few, beginning with those using but a single tube, from which the reader can work out many others and will understand the various systems used as he comes in contact with them. Inverse duplex will be considered as a separate article, although really an improved system of reflexing. experienced at first in preventing the whole from oscillating and a crystal detector made control easier. In Figure 108 we have a single tube used for both R.F. and A.F. amplification in conjunction with a crystal detector. Incoming signals pass through the usual variocoupler to the grid of the tube, are amplified, and pass MILOPLEX WAVE TRAP (Continued from page 19) one more trap I must build for you) this will end the series, or it will, rather, my conversation on wave traps and filters; therefore, as many of you are getting circuit hungry, week after next I'll give you an old circuit in a new dress. I say old — well, not so old, either; but one that every engineer and every ham, including the Wulf Houngs (is that the way you spell it?) know by heart, yet few have built it because it appeared so simple; yet very often such apparently easily built babies are the star performers when one gives them a chance — and in the regenerative class this little teeney-weenie fellow is pretty hard to lick aziz. Remember the frog who said "Show me the pool" when he hopped up on the pool table? "Which but prompts me to say that I will not disquise the circuit — but rather see if it cannot be refined so it may do some finer tuning and a .006, or near it, may be found hanging on a binding post if the artist doesn't slip. Perfection PERFECT RECEPTION NO ROOFACROBATICS REDUCES STATIC AND INTERFERENCE INCREASES SELECTIVITY Just stretcA it Across a Room At your Dealer's or Direct Price $2.00 Postpaid Perfection Radio Mfg. Co. 24th and Race Streets PHILADELPHIA B METAL Loud Talking Crystal Sold only by reliable dealers and at full price. The Premier Crystal of the Radio World today. Ideal for REFLEX or CRYSTAL sets. Order, if possible, from your dealer. If he does not have it, send to us for one. Price, 50 cents postpaid. New Jobbers and Distributors Plan Now Ready B-METAL REFINING COMPANY 525 Woodward Avenue, Suite 46 DETROIT. MICH. A \ "^^^Ofi^'' Mystery Man to Be Revealed. Following it— and just because some thousands of you are curious to know just who I am — will be an article which should go down in history as a positively unauthorized interview regarding who I am — how I came to be so mysterious — where I received my feeble Radio education, and a lot of side lights — and toil lights relative to what the reporter thought I said when he asked me to answer his several questions. But, getting back to the trap, the first diagram shows the coil as it should appear when wound, while the second diagram shows the method of connecting it into your circuit. (TO BE CONTINUED) YOU DON'T NEED TUBES to hear concerts from out of town. If you want to get new stations ON YOUR CRYSTAL SET write me today. I get new records every day from people using my plans who hear programs on Crystal from stations 400 TO 1O0O MILES AWAY No tubes, batteries or amplifying apparatus necessary. I hear KDKA (Pittsburgh Pa.) on Galena. You may already have everything you need and just have it connected up wrong. Send selfaddressed envelope for picture of my set, and reasons why you need my plans. LEON LAMBERT 501 South Volutsia, Wichita, Kan. ^Workte Greatest^ FREE rilien 2-Year Guarante Your Proof of Performanc Save 50% Thousands of Radio Digest Readers will profit by this amazing offer. They will buy the famous 2-year guaranteed World Battery at the lowest price ever quoted. They will get a hydrometer and a "B" Battery FREE. And they get the best battery built. Compare These Prices Five Per Cent Discount for Cash with Order Special 2 Volt Storage Battery $5.00 For WD-11 and WD-12 Tubes. Will run 2C0 ■ours on one charge. Rechargeable. Special 4-v. Storage Battery $8.00 For UV-199 Tubes. Same features as 2 Volt. 6 Volt. 60 Amps..$ 8.50 6 Volt, 80 Amps.. 10.00 6 Volt, 100 Amps. 12.50 6 Volt, 120 Amps. 14.50 6 Volt. 140 Amps. 16.00 Send No Money. Just clip this ad and mail with your name and address. The battery you specify will be shipped to you the day your order is received. When the battery arrives, inspect it — read our 2-year guarantee before you pay one penny. Get the "B" Battery and hydrometer FREE. Order today. WORLD BATTERY CO. Dept. "L," 60 E. Roosevelt Road Chicago, III. into the primary of the radio frequency transformer T-l, which is in series with the phones and B battery. Being at Radio frequency, the signals do not affect the phones and pass through the fixed condenser C-3. However, on passing through T-l, current was set up in the secondary of T-l, which is rectified and detected by the crystal detector and passed on as pulsating direct current to the primary of T-2. This creates similar impulses, now at audio frequencies, in the secondary of T-2 which is in the grid circuit of the tube. The tube handles these as an audio frequency amplifier, amplifies and passes them again to T-l and the phones. Being now audio frequency impulses they do not affect T-l but do affect the phones. Condenser C-3 oannot by-pass them. It will be noticed in Figure 108 that the secondary of our audio frequency transformer is in the grid circuit return lead of the tube; in the wire running from our variocoupler and condenser to the filament. It is not essential that it be placed there and many excellent hook-ups will be found where it is placed between the grid and tuner as in Figure 109. The action is identically as outlined above and it is merely a matter of personal opinion or convenience in connecting the set, as to which place to insert this transformer. Reflex Applied to Radio Frequency As mentioned before, reflex can be applied to practically any type of R. F. coupling and in Figure 110 we have a single tube and crystal detector hook-up in which tuned impedance is used. The route of the incoming energy is similar to that of previous circuits, but instead of passing through a primary and secondary of a Radio frequency transformer, the inductance L-l and condenser C-l are tuned to the point where infinite impedance is offered to signals and they pass on to the crystal detector and then again through FAHNESTOCK'S RADIO PRODUCTS PRCSEy Improved Ground Clamp Equipped with Fahnestock Patent Wire Connectors Easily Attached. No Soldering — For Radio Use Only Our name stamped on all our products. None genuine without it. FAHNESTOCK ELECTRIC CO. Long Island City, N. Y. Dealers can obtain Fahnestock Products from following; distributors: NEW YORK Spartan Elect. Co. BOSTON Wetmore-Savage Co. F. D. Pitts Co. DETROIT Detroit Electric Co. CHICAGO Barawik Co. MILWAUKEE Julius Andrae & Sons Co. PHILADELPHIA H. C. Roberts Elec. Supply Co. PITTSBURG Ludwick, Homme' Co. WESTERN DISTRIBUTORS Marshall & Co., Los Angeles, Cal. 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The tuned impedance circuit may consist of a 35 turn honeycomb coll and a .001 mfd condi : or a 50 turn honeycomb coil and a condenser. Figure 111 offers an interesting combination of units. The input tuning system may be the same as that used in the three foregoing circuits or that shown. The unique feature lies in the tuned secondary of the Radio frequency transformer. It will be noted that the coni la across the entire secondary the lead to the primary of the audio transformer and the crystal detector goes to a switch arm. Such an arrangement gives a sort of volume control and permits of close tuning of this secondary. L-l may consist of 50 turns of wire, about Number 26, on a 2%-fnch tube while L-2 is 50 turns of Number 26 on a 3-inch tube, tapped at the 10th, 20th, 30th and 40th turns. Condenser C-l may have a maximum capacity of .0006 or .0008 mfd. (TO BE CONTINUED) Transformers for the price of 111 NEUTR0DYNE No Distortion Greater Volume Half.Price For $6 we will send postpaid TWO of the famous Globe Audio Transformers, made especially for Neutrodync sets. MONEY BACK GUARANTEE If you are not fully satisfied with the transformers, return them within 5 days and your money will be refunded. COYNE RADIO SERVICE Suite 803 507 Fifth Avenue, New York City CONNEWEY ELECTRIC LABORATORIES 309 Fifth Avenue NEW YORK CITY ^•^ <^* <^*> «^*' <^» «^* <^s> 4> *^> ARRESTERS The new Keystone Arrester Is made of genuine Bakellte with mouUled-ln binding ro«ts and provides maximum protection against lightning and static charges. Fully approved bv Underwriters — should be In ov. rv aerial lead the year 'round. Absolutely weather, dust and damp proof and uMium to lost — it will operate for This pioneer arrester is back-. is' experience in lightning air design. 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