High Frequency Apparatus Page 85

CHAPTER IX. ONE-HALF KILOWATT TRANSFORMER OUTFIT. If the experimenter is the fortunate possessor of a supply of alternating current from electric lighting mains, he may well devote his energies to the construction and use of transformer apparatus rather than bother with either the induction coil or kicking coil outfits previously described. The transformer is easily and cheaply made, and, in results, it is, beyond any doubt, superior to any other device for the charging of condensers. The Core. The transformer core is composed of thin sheets of silicon steel which is prepared expressly for transformer cores. The core is built up to form a hollow rectangle as shown in Fig. 1 which gives the overall dimensions. The first step is to procure the silicon steel cut to size; this procedure is recommended rather than attempting to cut the large sheets in the home workshop. Unless a gate-shear is available the job is a slow and very unprofitable one as the pieces will not lie flat if cut with an ordinary pair of tinner's shears. The core irons may be purchased cut to size at a reasonable price. The core irons are procured in two sizes, Fig. 2, for the ends or legs of the core and for the sides or yokes. Of each size, 230 pieces will be required. The windings are placed on the shorter legs of the core, i. e., the legs made up of the 2 x 434 in. pieces. These pieces are to be built up in two piles, the pieces being placed with ends over85