Whats the deal with the antenna?

I'm trying to put on a shorter antenna, but i can't even get the old one off. All you should have to do is twist the stock one counterclockwise and it should come out, but it's tight and i don't want to do anything stupid. What am i doing wrong here besides being a total idiot?

just get a clamp wrench and turn it...
i can undo mine by hand...