I know questions regarding Z antenna have been asked before but I've not seen any answers for my problem yet.   My antenna motor works fine but the mast wouldn't work due to a broken mast line.  I located similar sized mono filament trimmer line and tried replacing the original plastic/nylon cable.  The issue is reconnecting the top antenna portion to the new cable.  I've tried recreating the original connection (a round metal collar) but noting I've tried clamps well enough to not come loose.  Also, the diameter has to be small enough to be pulled into the top portion of the antenna.   I'd hate to toss an otherwise good unit and buy a non original replacement but I can't pay from $400.00 to over $4K (outragious on ebay) for an original.  Any ideas?

It sounds like you need is a crimping tool that is small enough to put enough pressure on the top antenna section to hold it to the filament. I have made a simple crimping tool using a vise grip pliers and a Dremmel tool with a small cut off wheel. You need to grind a small groove into each side of the vise grip's jaws that is slightly smaller that the antenna's porting that is to be crimped. It would be helpful if you had several test pieces so the amount of crimp could be adjusted but that may not be possible. 

Thanks for the suggestion Cruzzar.  Sounds like a good idea.  I think I'll give it a try this evening  and see if it works.