Safety gaps are used to protect the coil system from high voltage surges that can occur when the streamer happens to hit the primary coil or any other part that happens to be within reach of the streamer. Also, the safety gap helps protect the capacitor(s) from over voltage. There is a situation that is called "ring up", when the spark gap doesn't fire when it is supposed to, the voltages that supply the cap can "ring up" (increase tremendiously) and create an over voltage situation. This is sure death for the capacitor if it is being used right at its rating. e.g. you have a 20,000 volt cap and the supply voltage is running close to 15,000 volts, a ring up can increase the voltage to 20,000 volts +.

                The general concensius for the design of a Safety gap is normally 3 brass balls spaced about .25" apart from the center ball and the 2 outer balls are connected to either the High Voltage output leads or across the capacitor. The middle ball is connected to the RF ground system. The safety gap should be set to a distance that allows the gap to fire every once and a while... or if you prefer, set the gap so that it fires consistantly and then open the gaps a little at a time untill you get more activity off of the toriod and less activity from the spark gap. For example, if your main gaps are set for .25", set the safety gap for .35" total gap width. Measurements will vary on your coil, compared to mine.
 
 

         Safety gap with center ball hooked to RF Ground
 
 
 

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