A head-on view of the trigger coil which is mounted in front of the balun coil.  Note that the trigger coil wires are fastened close to the balun-tube feed wires by using plastic "tie-wraps".  The trigger coil wire is insulated with Teflon tubing, as are the spiral wires wrapped around the tube.  Note that the trigger coil wires are fastened closely to the spiral lead wires.  This serves to form a pair of small capacitors between the trigger coil circuit and the balun.  These invsisible capacitors transfer some of the RF energy from the balun to the trigger coil just before the tube fires.  The trigger coil then steps up the voltage by resonance action and applies the resulting high RF voltage to the tube electrodes, iniating a glow discharge in each end of the tube.  This glow discharge causes the main RF signal from the spiral wires to light the tube quickly.