Insulated drill collar gap sub assembly for a toroidal coupled telemetry system

An insulated drill collar and gap for a toroidal coupled telemetry system comprising:

• a first annular sub member operable to be connected at one end to a drill collar and form a part of the drill collar, said first annular sub member having
• a base portion at said one end thereof, and
• an axial extension at the other end thereof, having a cross-sectional dimension less than the cross-sectional dimension of said base portion;
• a second annular sub member operable to be connected at one end to a drill collar, and form a part of the drill collar, said second annular sub member having
• a base portion at said one end thereof, and
• an axially extending recess at the other end thereof, and having a cross-sectional dimension compatible with but greater than the cross-sectional dimension of said axial extension to form a peripheral gap between said axial extension and said axially extending recess;
• dielectric material positioned within and occupying said gap between said axial extension and said axially extending recess to form an electrical isolation between said axial extension and said axially extending recess;
• axial bearing means connecting said first annular sub member to said second annular sub member;
• dielectric means positioned between said first and second annular sub members at said axial bearing means to electrically isolate said first and second annular sub members at said bearing location;
• and
• longitudinally extending means for preventing relative rotation between said first annular sub member and said second annular sub member wherein a connection between said first annular sub member and said second annular sub member is formed of structural integrity and concomitant electrical isolation.