This view shows both the balun (wrapped in fibreglass tape) and the trigger coil. To the left of and behind the balun, is the hole in the rear of the tube enclosure where the RF cable enters through an SO-239 coaxial connector.  The balun is wired directly to the connector.  The connector is mounted on a metal plate which covers the hole in the case.  The plate is screwed to the outside of the case.  Note the strips of aluminum tape radiating out from the connector.  These strips make an electrical connection between the metal sheet on the outside of the case and the metal sheet on the inside of the case. This is necessary for proper RF shielding and for proper RF power transfer to the balun from the coax cable.  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.