The condenser, it will be remembered is the means of storing up the energy, which suddenly rushing across the spark gap, produces the oscillations necessary to generate the electric waves. A battery of leyden jars may be used as a transmitting condenser in connection with small induction coils. Their objection in large stations is that they are very cumbersome and some energy is lost by the brush discharges around the tops of the jars. The usual form of condenser consists of alternate sheets of tinfoil and glass plates arranged in a pile. The alternate sheets of tinfoil are connected together to form the terminals of the instrument. The condenser is usually encased in a wooden box poured full of wax or oil to increase the insulation and efficiency. Condensers are arranged in units so that any desired capacity may be readily secured by adding the proper number of units. The capacity of a condenser is its relative ability to receive and retain an electrical charge.
FIG. 46.—Diagram showing construction of condenser.
The helix is an instrument consisting of copper or brass wire wound around a frame of hard rubber or seasoned wood. A certain amount of inductance is necessary in a wireless telegraph circuit in order to develop high frequency oscillations. Inductance is the property of an electric circuit by virtue of which lines of force are developed around it. The helix furnishes the inductance in the circuit or at least the greater part. Connections are established to the turns of the helix by means of clips which snap on and off the wires.
FIG. 47.—Tubular condenser.
FIG. 48.—Helix.
FIG. 49.—Close coupled helix.