Nikola Tesla Books
HIGH FREQUENCY PLANT CULTURE 165 developing. The adjustment of the gap will be considered in due time, when the instructions are given for the operation of the completed apparatus. The Oscillation Transformer.-The reader has been told of the construction of the transformer which steps the commercial lighting current up to a potential of several thousand volts, the condenser which stores up this high voltage, and the spark gap or discharger across which leaps the stored-up current in the condenser. The discharge of the condenser across the gap sets up electric oscillations or, as it is termed, a high frequency current. In order that this current may be rendered suitable for the purposes of electro-culture, however, its potential must be raised to a very much higher degree and the object will be to explain the construction of the special type of transformer or coil employed in the process of stepping up the already high potential, high frequency current. The high frequency transformer differs from the type used for the conversion of low frequency or commercial currents in that it has no core of iron and the turns in its primary and secondary are numbered in tens and hundreds, respectively, instead of in hundreds and thousands, as is the case with the transformer used for lighting and power work. Furthermore, on account of the extremely high potentials induced in the oscillation transformer, the insulation problem must be treated in a somewhat radical manner. This problem is not, however, so difficult of solution as it might seem. The coil may be of generous proportions, since close coupling of the primary and secondary winding is not essential, and the permissible air space affords a most effective insulator. While the efficiency of oil insulation in cases similar to the present one is not questioned for one moment, still the air insulation, if properly carried out, offers exceptional advantages over all
