FIG. 50.—Spark gap.
FIG. 51.—Circuit showing tuned transmitting system employing close coupled helix.
The spark gap is the medium for discharging the aerial and condenser and setting up the oscillations. It usually consists of a pair of electrodes supported by suitable standards and so arranged that the distance between the electrodes can be accurately adjusted. The electrodes usually take the form of hollow faced cylindrical rods having flanges to radiate the heat generated and prevent the spark from arcing. Various metals are used for spark gaps. Silver is probably the best but its expense is prohibitive. A special hard zinc alloy is most generally used.
FIG. 52.—Photo of spark gap.
FIG. 53.—Quenched spark gap.
