[TowerTalk] Splicing Mast

[Shawn Donley]

My instincts tell me this is a bad idea, but perhaps others have done this successfully.   I currently have an OB9-5 HF yagi (spec 7.8 ft^2 projected area) mounted one foot above the top of my tower.   The mast is 2 inch OD steel DOM with 5 ft inside the tower to the rotator and 7 ft above the tower.   Can't find the mast wall thickness at the moment but I think its 0.12 inches.  Thrust bearing is at the top of the tower.    I'm considering adding a 40M rotary dipole (3.4 ft^2) above the yagi.  But I need to place it at least 10 ft above the yagi to minimize coupling, plus I need 3 ft above the dipole for the dipole truss bracket.  That means I need 13 ft "more" mast.   Is it possible to splice an additional 13 ft of DOM onto the existing mast using a steel structural tube inserted inside the mast pieces and bolted through the masts?  If so, how long should this joint tube be?   The tower is a crank-up so I can work up there comfortably with a man lift when it's cranked down. 


tnx for your thoughts.

N3AE