Been a while since posting had a busy few weeks! 

So ive been living with a dodgy aerial in my car for a while now and it's starting to come to a head so I'm gonna have an investigate. The thread on my aerial itself is corroded and the previous owner fitted a short aerial. 

Does anyone know if I can replace the thread? Or will I have to change the whole unit?

Think it's the whole unit 

Better to change the whole unit, the standard aerial sucks hard so a shortie must be even worse.