Radio mirror (Jan-Oct 1923)

RADIO DIGEST ILLUSTRATED 13 The "How" of the Simplified Super Circuit Part I — Setting Up the Flivver Successfully SINCE the publication of the simplified super circuit, the writer has had the opportunity to spend considerable time watching its action and building the theory of its operation. . Hundreds of letters have been received telling the trials, tribulations, and successes of those who have tried out the circuit. These things have brought together quite a few items of interest. Follow Specifications Strictly for Success An analysis of the letters received shows that those who have successfully built the Simplified Super have in every case followed strictly the specifications called for. Xo letter has yet been received relating failure that did not also contain its own answer. The experimenter did not use the apparatus especially called for, or else evidently had decided, upon a glance at the hook-up that he could by changing the circuit a little, considerably improve upon its action. It is surprising how many letters of this type have been received. To try to improve a hook-up or to change it to meet the apparatus that one happens to have on hand without at first trying the original, is to my mind the height of foolishness, because it immediately calls for an assumption that the originator merely hit upon a new circuit, gave it to the public at once without a care that it might be improved upon and then fell asleep. Now this little story is being written with no other idea than to help out those who wish to work with the Simplified Super, and also to add in the notes to follow a little information that perhaps is not known to everyone in the world. Hundreds of Circuits Fail If I said that two hundred different combinations of hook-ups, apparatus, etc., had been tried, that would be a very low estimate. All of these combinations with small exception refused to fire. Those which did go were not equal to the finally developed circuit that has been published, with the possible exception of one. This one referred to seems to accomplish about all that the flivver circuit does, but has failed so far to match quite the results given by a nicely balanced flivver circuit. I will be pleased to show this alternative circuit with its notes in the next few issues of Radio Digest because it calls for even less apparatus and adjustment than the flivver circuit and illustrates the principle used just as well. About the Use of loops Most folks seem to assume that a loop of average size will work properly, and it will doubtless be of value to them to have the following brought to their mind. First note that a receiving set depends for its audibility and distance qualities upon the effective height of the antenna. Without going into mathematics this works slightly different than at first glance might be assumed. The answer is this. If an average three-foot loop were computed, it would be found that it possessed the ability of an open antenna approximately one foot high. A loop has the directional quality as one of its most valuable advantages, but unfortunately most of this is lost when using a super set on a loop. It is understood that any antenna system must be tuned to take care of the wave desired, but one is apt to forget entirely that a loop is nothing after all but an antenna. Therefore it too must be tuned. There are at least two ways to do this, one by connecting a variable condenser in parallel with the loop and another by building a loop that is absolutely right so far as capacity, inductance, etc., are concerned. One can see how difficult that would be for the average person. To sum up, if your set "sings" when tried alone and goes dead when connected to an energy collector, you can be sure that a series condenser is needed. Points About Flivver's Operation When the set is complete it is best to adjust the leaks, etc., before being con By E. T. Flewelling nected to any energy collector. We know that the values for the set itself are correct. Therefore, if we adjust it alone, we will have no outside influence to throw us off. As has been stated in previous articles, or antennas have different values, yet most of them, especially grounds and open antennas, average up to a value that will be workable with the set as specified. If a particular energy collector kills your set when you connect it on, you will In the Digest Exclusively — WHEN E. T. Flewelling and his set "that made good in a day" were discovered byRadio Digest, the flivver circuit was practically unknown. Its appearance in the Digest is another scoop. MR. FLEWELLING has agreed to write exclusively for Radio Digest. The article on this page is the first of a series to appear every week which will help the Radiophan in the perfecting of his own flivver set. when the set is correctly adjusted one can hear a little shrill whistle, and as the coupling of the coils is changed there is added the sound like the tearing of cloth. Upon approaching the wave of a broadcaster one will hear a series of small weak squawks which increase in loudness and finally spill over to become dead as the wave is tuned in correctly. To Use Radio Digest as Forum Inasmuch as I am unable to have a private secretary, it has become impossible for me to answer all of the letters that I receive concerning this circuit. I would indeed be glad to receive comments and results secured, but it has become a physical impossibility for me to answer personally all of the questions asked, much as I would like to do it. For this reason I will write for Radio Digest all available dope on the circuit so that further questions should be unnecessary. From the above you can easily get, perhaps, the most important point about setting up the Flivver Circuit. It is this — don't use a single thing that is different from the articles called for unless you are prepared to fight it out yourself. Not a single set has failed to work as yet when properly set up and adjusted, so don't let the idea that there is a dark secret somewhere in it bother you, because there isn't any. Aerial Must Preserve Balance We will take up the matter of aerials first, because the set will be used on all kinds . and varieties. The low frequency oscillation (it really is not an oscillation) that is responsible for the action of the super depends upon the set having the just correctly balanced values of inductance, capacity and resistance in the circuit. If the set itself has these values correct it will function properly, the values and hook-ups published are correct so no trouble will be experienced from this source. Now if we put an antenna, ground, or loop, either of which may be termed an energy collector, in with the set we must be careful to preserve the correct balance. This point seems to be the one giving the most trouble and a few words concerning it will not be amiss. All grounds, loops, Crystal Receiving Set Uses Honeycomb Coil For the benefit of other crystal detector fans I am showing this hook-up with Waerial a <h HONEY ' COMB COIL CRYSTAL TUNING COIL SLIDERS PHONES *S=" GROUND. ■Which I have received speech and music over a distance of 500 miles and code 1500 miles. It is the two slide tuner set with a 35 or 50 turn honeycomb coil as a load coil. The stations I have heard with this hook-up are KDKA, WHB, WGM, WSB, WOC, WRM, WI/W and 8X1. — Raymond B. Searl, Bloomington, 111. be able to compensate for it in most cases by the use of, preferably, a variable condenser in series. That is, run your signal through a variable condenser before it reaches the set. This condenser is adjusted to the point where the set comes to life again and is further used as an aid to tuning to the wave length desired. The set is then quiet excepting that the whistle is still audible. The lower the tone, and the louder the whistle, the greater is the amount of amplification obtained, and the grid leak should be -set for the happy medium. After which, it may be left in that adjustment. Tickler Coil Adjustment This brings us to the tickler adjustment. If, when your set is finished, you get no sound from it, several factors must be considered. These will be taken up as we go along. The first is the polarity of the tickler coil (75 or 90-turn coil). If the magnetic field of this coil works with the first coil (50-turn) you are all right, but if the magnetic field works against the first coil, the set is dead. This condition is corrected easily by reversing the leads to the tickler coil. If you use improper coils for these two coils (Giblin-Remler 50 and 75 or 90-turn coils are specified), you either will get no action or poor results, depending upon how closely the values of your coils approach those of the specified coils. It seems that hundreds of Radiophans have tried variocouplers using the stator as the inductance and the rotor as the tickler. As a rule the results have been inferior. They might be improved to an acceptable point by rewinding the rotor to 75 to 125 turns instead of the number generally used. Use of Variocoupler If a variocoupler is used, be careful not to have too many unused turns on the stator, because the field set up as a result of these unused turns will have a tendency to upset the balance of the set. Most of the variocouplers for broadcasting now on the market have a suitable number of turns on the stator or tube, but not enough on the rotor or ball for operation on a super set. Of course the exact number of turns in either case cannot be given because of one factor at least, we do not know the diameter of the forms used to wind upon. Inasmuch as the space available is not sufficient to cover the subject in one article it will be necessary to continue our discussion in the next issue of Radio Digest. To secure good signals never burn vacuum tube filaments brighter than necessary. When figuring on the wave length of your aerial, remember the lead-in counts. At the New York Radio Show the JEWETT SUPER-TWELVE Achieved a Real Triumph This Super Non-Regenerative Receiver, the latest creation of Professor J. H. Morecroft of Columbia University — eliminates Distortion, Howling, Screeching; and is UNSURPASSED in TONE — SELECTIVITY — CLEARNESS and EFFICIENCY. CAN BE OPERATED WITH V/2 Volt Tubes without storage battery ; also indoor aerial or loop. Price without accessories $75.00 f. o. b. factory. Grid Condenser and Leak To insure accessibility as well as rigidity to the grid condenser a piece of A-inch fibre or bakelite may be cut and drilled to correspond with the condenser terminal holes and one side of the assembly bolted together with a small bolt. The other terminal can be fastened directly to the grid terminal of the socket. This will lessen wiring complications and will place the grid leak in a position where the pencil marks can be altered if necessary. The writer has found that the number of pencil marks does not seem to affect the tube operation to a noticeable extent. However, in a closely assembled receiver the grid leak is a rather sensitive adjustment,— H. E. Jameson, Milwaukee, Wis. All Jewett Dealers are authorized and have Protected Territory and Liberal Discounts. Write for Details of Sales Policy. Jewett Manufacturing Corporation NEWARK, N. J. B*