Then place the remaining fiber head, S, on each of the "legs" and finish assembling the core by slipping in the end strips D.
Square the core up perfectly true and fasten by four fiber strips M, Fig. 49, 9 3/4 inches long, 1 3/4 inches wide and 1/2-inch thick. The strips are placed in the position shown in Fig. 46 and a hole P bored in the end of each. Four 1/4-inch bolts, two of which are 3 inches long and two 3 1/2 inches, pass through the holes in the strips, so that when the nuts are screwed on the core is clamped firmly. The two longer bolts are placed at the same end of the transformer.
Fig. 49. Transformer with One Secondary removed.
The terminals of the primary lead out to four binding posts mounted on the fiber strips. The pillars which support the secondary binding posts are fiber rods, 1 inch in diameter and 2 inches long. The lower end of each is bored and tapped to fit the upper ends of the longer bolts which clamp the fiber strips together. An insulating shield must be placed between the two secondary windings to prevent sparks from jumping across. A piece of fiber 5 x 5 x 1/8 inches will serve nicely for this purpose. If the primary windings are placed in series the transformer will consume about 300 watts. When the transformer is placed in a box and the box filled with some boiled amber petroleum, the windings may be connected in parallel and the transformer will consume about 500 watts. It will then transmit over 100 miles providing the aerial is at least 100 feet high.
The wiring connections are diagramed in Fig. 50. A variable inductance or reactance coil is connected in series with the primary circuit to steady the current, as explained in the paragraph under reactance. A reactance suitable for this transformer may be constructed by winding two layers of No. 12 B. S. gauge cotton covered wire, six inches long, around a hollow wooden tube made of cigar box wood. The core is built up of soft sheet iron to form a rectangle 8 x 1 3/4 x 1 3/4 inches which will just slide in and out of the tube. The windings should be about six inches long.
Fig. 50. Wiring Diagram.
Five half-gallon Leyden jars form about the right capacity for the secondary of the transformer when the windings are in series. Twice that number must be used when the windings are in parallel.
The secondary sections must always be kept in series, as otherwise the voltage would not be high enough to properly charge the condenser.