Nikola Tesla Books
HIGH FREQUENCY APPARATUS The data given in this chapter is for the construction of a coil built expressly for radio and high frequency work and it is totally different in windings and proportions from the ordinary spark coil that is intended primarily to give a long spark. The coil to be described is not rated in spark length but in watts capacity. Through the use of a suitable interrupter, this coil may be operated at 10 volts and 10 amperes continuously. The secondary winding is of comparatively low resistance, thus it is well adapted to the purpose of charging condensers. Core and Primary.-The core of this coil is a bundle of soft iron wires tightly compressed into a cylinder 12 in. long and 1½ in. in diameter. The core wire can be purchased ready cut and perfectly straight so that its formation into a cylinder is a simple matter. Given the necessary amount of straight iron wires, the builder grasps the bundle with both hands and with a twisting motion forms the wire into a compact cylinder. A piece of wire is then wound around the middle of the core and twisted. Another is added at each end. The twisting operation is then continued, taking up the slack in the binding wires by twisting the ends with a pair of pliers. Soon the bundle will be perfectly straight and hard. Starting at one end, the binding wires may be removed and a winding of silk ribbon started spirally over the core. Binding wires 12"- Core bundle of iron wires Tape binding started Fig. 5.-Core with tape binding started End of scre
