Fig. 127 illustrates the construction of such an oscillation transformer.
The base is wood and measures 14 x 5 1/2 x 1 inches. The primary winding is wound on a cardboard or fiber tube 4 1/4 inches long, having an internal diameter of 2 3/4 inches and an external diameter of 3 inches. The heads, L and M, are the same size as those of the double slide tuning coil. The head, L, has a circular hole 2 3/4 inches in diameter cut in the center in order to permit the secondary coil to slide in and out of the primary.
Fig. 127. Oscillation Transformer.
The secondary coil is a piece of round curtain pole 2 1/2 inches in diameter and 3 inches long. A 5/16-inch hole is bored through its axis. The head, K, of the secondary coil is 3 3/4 x 3 3/4 x 3/4 inches. A ten-point switch on K is so connected that it divides the secondary into ten equal parts and permits any number of the divisions to be used as desired.
Fig. 128. United Wireless Receiving Transformer.
A wooden post, J, 2 1/2 inches high and 1 1/4 inches wide, supports one end of a 1/4-inch brass rod upon which the secondary slides back and forth.
Fig. 129. Details of Receiving Transformer.