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Show CiO --U 1 ? of ;o V ' 1 i;i!itH!6!iiisH A." "5 v I Wiring Diagram of the Two-Tube Reflex Receiver Will Aid in Proper Arrangement Ar-rangement of the Apparatus. By JAMES E. CARTIER, In New York Herald-Tribune. Tins const nicl iun of sreminuly difll-cult difll-cult niiilrl-iiilic railio receivers seems to have been the .stumbling block of ninny iuiiatcur builders. For this rea-son rea-son tlie hume constructor has been inclined in-clined to build sets along simpler lilies. Although a two-lube receiver does not Hcem capable of receiving signals like one of lis bigger brotliers it is surprising sur-prising Just what results may be obtained ob-tained willi such u set if properly constructed. con-structed. Tlii Air Service two-tube reflex receiver re-ceiver employing the well known llarl;-ness llarl;-ness circuit seems to be one of reasonably rea-sonably simple design. The list of parts for the construction of tins receiver re-ceiver is as follows : 7 by l--lnch panel. 7 by 1 1 -Inch baseboard. Two slundard sockets. Two iindio-fre(uency transformers. One rheostat (six ohm). ltattery switch. Crystal detector. Ihiublo circuit Jack. iSiiiKU; circuit jack. Set of six binding posts. Iwo .(HKMi nitd. condensers. Two radio-freiiiiency transformers. Of the above-mentioned parts the two radio-frequency transformers may be easily constructed by the hnmly radio builder, or may be bought in kit form ready to assemble. Coil-Winding Data. For the benefit of those who desire to construct their ovn radio-frequency transformers the data will be given herein. The secondary of both of the coupling coup-ling transformers Is the first to be wound on the tube form. The secondary sec-ondary of the transformer coupled to the antenna circuit should have CO turns of No. 24 wire, wound on a 2-lneh 2-lneh form, and over tills should be wrapped a sheet of insulating cloth or waxed paper. This serves as an Insulator In-sulator between the primary and secondary sec-ondary coils. The primary should consist con-sist of ten turns of the same size wire wound over the insulation cloth and in the same direction as the secondary. It Is absolutely necessary that both colls be wound In the same direction If best results are to be had. The primary of the second coupling transformer is slightly different in size. This transformer Is wound on the same diameter tube and assumes the same physical proportions as the transformer trans-former Just described, the chief difference differ-ence being that the primary consists of 32 turns Instead of 10. In order to make It possible for the set to be mounted In as small a space as possible the coupling coils may be mounted directly on the back of the condensers with the secondary wires connected to the two terminals. The primary wires should be left disconnected discon-nected until the set Is to be wired. Then they may be connected to the respective places in the circuit. The two transformers should be mounted at right angles to each other In order to minimize coupling between the two. The drilling of the panel and the wiring of the set Is no more diiiicult than the ordinary simple regenerative receiver. The wiring diagram, as shown, will aid the constructor in the proper arrangement of the apparatus. Will Not Oscillate. A particular advantage of this re-, re-, coiver is that it will neither oscillate nor radiate an interfering wave on the i.ir. One of the tubes employed in the receiver acts as a radio-frequency am-.::tier am-.::tier and is retlexed so as it acts as a radio nnd audio-frequency amplifier i.l the same time, or in other words, t'.eos liouhie duty. The detecting is ae-iwapKshed ae-iwapKshed by means of a simple crystal crys-tal detector. Such a simple receiver, although seemingly small in size, ought to be capable of receiving many stations, both local and distant with suitieieut volume to operate a loud speaker. Either loop or outdoor antenna may be used on such a retiex receiver, al-laough al-laough the latter will give better results re-sults on distant stations. Mounting the Apparatus. The two variable condensers are mounted on the extreme ends of the panel with the rheostat and crystal detector In the middle. This arrangement arrange-ment allows the operator to control the set with ease, all controls being within easy reach. When wiring the amplifier best results re-sults will be obtained by having the audio-frequency transformers placed at right angles to each other. This does away with the possibility of howling. rarticular care should be exercised In wirvng the system. Make sure the j wires are as short and direct as possible. pos-sible. In no case should the grid wires come near a plate wire. If It is found necessary to cross grid and plate wires there should be at least an Inch between them and In no case should they run parallel. This circuit will operate equally well with any of the standard hard amplifying amplify-ing tubes now on the market. The 201 A and 301 A are particularly recommended. recom-mended. Best results should be obtained ob-tained when using a plate voltage of about 90 volts. The set has been found to have the quality of being quite selective. If a good grade of crystal detector is employed em-ployed very little adjustment will be necessary. I'articitlar stress should be made on the point that the performance of the set depends largely on the wiring. Wires In the radio-frequency circuit, especially the plate and grid wires, should not be run parallel. If these points are observed the builder ought not to have any dlfliculty in making the set operate well und.ir favorable conditions. |