Radio mirror (Jan-Oct 1923)

July 28, 1923 RADIO DIGEST 11 First Steps for Beginners in Radio Chapter XI, Part I — Super Regeneration By Thomas W. Benson, A. M. I. R. E. DEGINNERS will find the accompanying ** series by Mr. Benson very helpful in learning the rudiments of the popular science of Radiotelephony. The articles yet to appear are: Chapter XI, Part II— Super Regeneration. Chapter XII— Reflex Circuit Operation. Chapter XIII — About Headsets and Loud Speakers. Chapter XIV— Batteries Used in Radiophony. THE mere mention of the word superregeneration gives rise to ideas and dreams of the Master Set that will eventually be evolved from the maze of circuits now in use and make possible the reception from every station on the face of the old world. And although it promised much, the three tube set as originally described by Armstrong seems to have fallen down when taken in hand by the amateur and even by the more experienced men in Radio. This is no reflection on the efficiency of the circuit, but simply means that much work must be done before the more complicated circuits are made simple enough for the average man to handle. Theory of Super-Regeneration. The theory of super-regeneration is so simple that it is strange it was not thought of long ago. Since the ^first days of regenerative receivers it was noticed that when the coupling between the tickler and the grid was made too close the set howled. This was due to the plate current feeding back into the grid, the added negative charge on the grid further varying the plate current, which again reacted on the grid more forcibly. In this manner the currents built up to such a strength that the tube went into self-oscillation and I0OT modified circuit that can be readily assembled by the experimenter. The contents for the various parts are given in the illustration. It will be seen that the first tube is in a regenerative circuit, the plate being coupled to the grid circuit by a tickler coil. we must make a compromise. It is logical that the longer the building-up process is allowed to go on the louder will be the signals, but since the checking point will then be further apart, they occur at an audible frequency. When we check them at a fre Figure 47 — The one tube flivver that has given good results The second tube is connected to form an oscillator, the plate being closely coupled to the grid with a condenser in the grid circuit to control the amount of energy reaching the grid and thus the intensity of the oscillations. The grid of the second tube is connected through a filter to the grid of the first tube. This filter keeps the received currents from reaching the grid of the oscillator tube. The action can be described in this manner: When the tubes are lighted a high whistling note is heard in the receivers. This is due to the oscillations in the second tube taking place at audible frequency. On adjusting the variable condenser across the primary coil of the first tube a series of harmonic notes will be heard, due to the beat action between the oscillatory currents in both tubes. 250T \Soot Figure 46 — A super circuit using honeycomb coils, showing how one tube functions to control regeneration in other tube howled or screamed. The intensity of this howling was many times that of any signal coming in on the set. And everyone would say, "Gee, if the stuff would only come in like that." And why not? Since this building up of the currents in the tube is gradual, or step by step, taking only a very small interval of time, it is conceivable that we could permit the tube to build up the currents to a high value and then check the process and let the building up begin all over again. Were this checking to take place at a rate above audibility, the resultant sounds would be unbroken. And this is just what Armstrong did to produce the super-regenerative circuit. Operation of the Circuit. The operation of the circuit will be clear by considering Figure 46, which shows a Carter "Tu-Way" Plug Takes I to 4 head sets; takes all types of tip terminals: fits alt standard Jacks Does more for a dollar and does it better than any other plug CARTER RADIO CO., 205 S. State St., CHICAGO SYNTHETIC RADIO CRYSTAL Qn Approval For 30 <t Zob elStein laboratories 322 9™ST.8ROOKLYN.N.Y.SouthE650 Now, when a signal is received and the circuits properly adjusted, the first tube will tend to regenerate and build up to a howl, but before the tube can start to howl the oscillations in the second tube make the grid too negative and the tube stops oscillating for an instant, when the current from the oscillating tube changes its polarity the first tube starts to build up again and is again checked. In this manner extremely loud signals can be obtained. But Ritter Loop Aerial $1 Including wood parts — wire and binding posts. Can be assembled In a few minutes — Portable, requires little space. 36 inches across. Interference — Static — Lightning practically eliminated. Instructions with every SET. By Mail. 10c Extra. Bitter Radio Company 230 Canal Street, NEW YORK POSITIVE RESULTS are being obtained by thousands of satisfied users of the EASTERN COIL SETS for the COCKADAY CIRCUIT The remarkable features which are making this circuit more popular each day are its simplicity of construction and control — wonderful selectivity-^rlifltanee records — clearness and loudness of reception, and the fact that all capacity squealing, interference, eta, are eliminated. Made as per specifications of Mr. Cockaday, using No. 18 wire with D coil bank-wound. COMPLETE SET OF B, C AND *0 7C D COILS— PRICE ^£..iU Hook-up, directions and material list furnished free with each set of coils. Mail Orders Filled. Dealers Communicate EASTERN RADIO MFG. CO. 22 WARREN STREET NEW YORK, N. Y. quency above audibility the first tube cannot build up as long, and a loss in signal strength results. The usual practice then is to have the checking occur at such a rate that a faint high pitched whistle is constantly heard in the receivers. By proper adjustment, this whistle is not annoying and does not interfere with the received signals. Use of Power Tubes. For the best results, it is necessary to use power tubes with high voltages on the plate, although the regular amplifying tubes can be used with some loss in signal strength. There is no doubt that this circuit does give excellent results when properly adjusted, but it takes infinite patience and many hours of testing before one gets the hang of making all the adjustments necessary to get results. The writer has worked for hours over such a circuit, pulled it apart in disgust and hooked it up again, determined to make it work before any results worthy of note were obtained. The circuit originally demonstrated by Armstrong employed one stage of audio frequency amplification, which introduced further difficulties. Realizing that the audio frequency amplifier would amplify the audible controlling current, it is necessary to filter this out before it reaches the amplifier, or it will reach an annoying volume. We can then sum up super-regeneraton as simply a regenerative circuit which is prevented from oscillating during one-half the cycle of the oscillation in a second tube and permitted to build up during the other half of the cycle. Therefore, any regenerative circuit that is subject to a checking potential on its grid at or near the highest range of audibility will functino as a super-regenerator. The One-Tube Pliwer. By combining the source of audio frequency, or, as it is often termed, the variation frequency, in the same circuit with the tuning inductance we have the one tube flivver super-regenerator that is making good. This circuit is shown in Figure 47 and consists of a tuned plate regenerative circuit using a loop aerial with honeycomb inductances connected in the plate and grid circuits. The coil in the grid ciruit is a 1,250-turn coil, that in the plate being a 1,500-turn coil. The condenser across the B battery and coils serves to bypass the higher Radio frequency currents in the cir ( Continued on page 14) Northern Electric Peanut Tubes, Type 21 5A DFAI FR<s ATTRACTIVE UCALtLKZ DISCOUNTS NOTE: We are the Largest Exclusive Radio Jobbers in the Middle West 123 W.Madixon^t.Chicago THE LARGEST RADIO STORE IN AMERICA BUILD YOUR OWN SET THE FINEST RADIO STOCK IN AMERICA ACCORDING TO OUR INSTRUCTIONS RESULTS GUARANTEED — PANELS ON ALL SETS DRILLEDREADY TO MOUNT Complete Parts for Flewelling Circuit, $12.45 Beg. 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