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Show (Editad by G. Douslas Wardrop. Editor of Radio Merchandising.) By C. H. WARD Articles to help tie beginner In radio are appearing In countless numbers num-bers in the radio publications, newspapers news-papers and elsewhere, and rightly so, for the number of newcomers in the art Is legion. There are also discussions discus-sions of the niceties, theories of operation, oper-ation, and more or less complicated and unique layouts of apparatus for the advanced amateur the fellow who has the inclination, time and apparatus to go Into the theory of radio for Its own sake and to help in the development develop-ment of the art. Personally I feel that I belong to neither class and have often heard the same comment from other amateurs. The Experienced Amateur. Let me speak for these other fellows fel-lows when I s3y that we understand the principles Involved In a practical way, that we usually want to have a hand in the construction and installation installa-tion of our apparatus and that we have the habit of changing our apparatus and circuits for better or for worse sometimes to the intense Jlspleasure of our listening family fam-ily and friends. Foremost In our minds, though, are good results we find it necessary to know the theory of radio, but we are more interested In the doing than In the knowing. If our radio experience began before the war, its history is probably about as follows, up to the introduction of phone broadcasting : Loose coupler and crystal. Loose coupler and audion, A "tickler hook-up" using the old coupler or honeycomb coils. Finally the climax Is a "short wave set." The latter seems like an indefinite in-definite term, but to the amateurs of a V Mix raft rariewer coupling, ranarelv Vano This Regenerative Hook-up Is Very Efficient and Is Particularly Useful for the Longer Wave Lengths. short time ago it could only mean one tiling a regenerative set consisting of three tuned circuits using a variocoup-ler variocoup-ler and two variometers. When Broadcasting Was Young. If we were to carry our history a little way into the future, it would probably have something to do with a radio frequency amplifying system and a loop aerial. However, most of us still look on that short wave set with awe, for we remember those dots and dashes from low-power, far distant stations that other "radio bugs" could only hear in their Imaginations. And when broadcasting started, there were nights when It seemed that the program pro-gram was In the same room and the sound details of the announcer's voice were almost uncanny. One could hear him draw his breath and make the other little noises incident to speech that remind us of the wonderful reproductions repro-ductions of Harry Lauder's voice on the phonograph. But unfortunately there were nights when programs did not measure up in ne quality to e- n the cheapest phonograph especiiuly when our friends dropped in to listen for an evening. Yes, there have been nights when even the sound of a voice of any kind would have been welcome to our ears, and others when signals started to swing and our nerves were so shattered trying to keep In tune that we swung up and copied Navy press Just to be sure of something. To make matters more embarrassing, possibly, we stopped In to hear the neighbor's set one of the new broadcasting re-. re-. celvers an immaculate little thing with two knobs to play with and possibly pos-sibly a set of dry cells to light Its filament, fila-ment, and behold, we heard the whole concert through. Of course, the tone quality Isn't In the same class as that from our three-circuit set when it decides de-cides to perform, but still we have to hand It to our neighbor for he always gets something and sometimes we get nothing. Personal Experiences. From here on I must stick to personal per-sonal experiences. Possibly they will be repetitions of other fellows' experiences, experi-ences, but they may help others to get the results I am getting now good ' results. When I saw my neighbor's set and others like It, I at first decided that the refinements introduced In large scale manufacture of receiving sets for concert reception made possible a set that could not be duplicated by the home workshop except by chance, and we should all remember that this is true, no matter how good our results may be. Later, however, when I found the boys turning out one and two circuit cir-cuit sets that performed almost as well as manufactured ones, and some of them very crude in construction, It seemed to be up to me to junk the old short wave set and build something new. While planning the new set It occurred oc-curred to me thatjall such sets differed from the conventional three-circuit tuner In having a direct inductive coupling between the plate and grid circuits. In other respects they varied widely and It was difficult to select the best arrangement. I never did decide which one to build but instead of simplifying sim-plifying my circuit, I complicated it It is hardly necessary to state that tone quality, selectivity and relief from static are attained to a greater degree de-gree with three-tuned circuits than with the simpler arrangements, and the addition of means for coupling the grid and plate circuits provides stability sta-bility and ease in tuning which are sometimes difficult to obtain In the conventional three-circuit tuner. Of course considerably more time Is consumed con-sumed in tuning the three-circuit set-when set-when first put in operation, but this has never been a serious matter if results re-sults could later be duplicated using the same adjustment for the same stations. sta-tions. This has been found possible with the set stabilized by direct feedback feed-back coupling, while in the ordinary three-circuit tuner adjustments for good phone reception vary dully. Early Methods. The first means of coupling which was devised consisted In splitting up the plate variometer stator winding Into two1 halves. One half was left in the plate circuit and the other connected con-nected In series with the secondary of the varlocoupler and grid variometer. The operation of the set connected In this way proved that the coupling provided pro-vided was a decided stabilizer or, in other words, that the Idea was good. Stations were tuned in with practically the same adjustments day after day; the set remained in operation without further adjustment for as long as desired, de-sired, and the tone quality was equal to the best results obtained with the nsual connections. Two of the broadcasting stations regularly heard, however, and many familiar amateur C.W- stations could not be heard. These stations were all brought back by changing to the arrangement ar-rangement shown in the accompanying diagram, where a separate coupler is used for grid-plate coupling and the plate variometer left Intact. The coupler used was made up on the common com-mon varlocoupler forms with 30 turns of No. 22 cotton-covered wire on both stator and rotor. The stator is In the grid circuit and the rotor in series with the plate variometer. I consider the resulting set the last word in regenerative regen-erative receivers, barring the refinements refine-ments In design and manufacture that could well be introduced, and I believe others will find It so until they are able to bid Old Man Static farewell with a loop and R. F. amplifiers. The coupler used in this set Is 3V4 Inches in diameter and the stator la four inches long, but It is obvious that slight changes in dlrmslons and wlnd" ing will not affect the results obtained, as both circuits concerned are separately sep-arately tuned. (, Radio News.) |