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Show irr Two-Tube Set for City or Country Distance, Volume, Selectivity Selectiv-ity Assured; Dry-Cell Tubes May Be Used. By RODNEY VAMBRISK. in Radio World. A pood little receiver for distance, volume, nnd selectivity is shown in the diagram. It is also well suited for portable purposes, since the entire set can he built in a small space, and dry-cell tubes, such as the -09 type, may be used. The antenna wire, properly prop-erly insulated, can be strung up between be-tween two trees, while the ground can be made in the moist earth with the aid of a piece of iron pipe. Only Two Controls. There are only two controls, the variable condenser CI, which may be a .0005, .00035 or .00023 mfd., and the tickler. The filaments are automatically automati-cally adjusted with the aid of 4V -199 amperites, Al and A2. The coils can be made or purchased. When buying:, be careful to select a coil matched to the variable condenser to be used. If the coils are to be made, use 2ai-inch 2ai-inch diameter tubing for the primary and secondary windings and 1-inch tubing for the tickler. No. 22 dec wire can be used for the primary and secondary sec-ondary windings. No. 26 ssc being nsed for the tickler. LI consists of ten turns, regardless of which type condenser is used. L2, using the .0005 mfd. condenser, consists of 55 turns. Using the .00035 mfd., it consists of 70 turns. Using the .00025 mfd., it consists of SO. The tickler, with the .0005 mfd., consists of 35 turns. With the .00035 and .00025 mfd., it consists of 40 turns. It will be necessary to wind the wire over itself in these cases. The grid condenser CI has a capacity of .0001, while the grid leak Rl has a capacity of 6 megohms. The bypass condenser C3 has a capacity of 0.001 mfd. Any type of audio-frequency transformer can be used, the low ratio type being preferable. A cabinet which is 6 inches high, 10 Inches long and about a foot deep can be used to house the parts and the batteries. Only about 5 inches of the space will be found necessary to house the tuning elements. "C" batteries bat-teries should be used for filament supply, sup-ply, while for "E" supply, three small 22Vi batteries should be used. Place the coil and condenser as far apart as pos.ible. The sockets should be placed with the F posts to the panel. The (".lament switch should be placed In between the tickler and condenser controls. Although L2 In the circuit d:aL-ram Is drawn as if it were two separate roils, it is or.ly one continuous wind- 1 1 e Circuit Diagram of Two-Tube Receiver Receiv-er for Home or Portable Use. Only Two Controls. Ing. It was drawn that way to Indicate Indi-cate the mutual inductance relationship relation-ship between the tickler (plate) and the grid winding. Use Speaker in City. When using the set in the city It will be found quite practical to use a speaker. The antenna should be about 75 feet In length. Either hard-drawn hard-drawn bare No. 14 copper or insulated wire should be used. The lead-In should be soldered onto the antenna wire, while the ends of the wire are securely attached to the Insulators In the home; it Is only necessary to hook Hie Insulators onto screws In the trpe when In the country. Try to choose u tree which has the fewest loaves und Is In the direction of the smalrnst rr:raher of trees. It will be found that good results itixy also be had by driving n large i.iil In the tree and tying the bare hd of the antenna wire to this nail. 'J lie highest portion of the tree should l.e ij."rl. T'se he main trunk of the tree If possible. |