find a mast and replace teh mast only. remove the antenna assy then dismantle it , remove the rope , pull out the broken mast and then put it back together. refit and reconnect. turn radio on wait for motor to go all the way up and insert new mast. turn radio off. then guide mast into place. done.
if you are unsure post up pics of the antenna assy and I'll walk you through it.