You should be getting decent radio reception with an aerial that long. Mine mostly only extends to two or three sections (I think it has about seven sections in all) it will receive even when full retracted. The aerial probably just needs a clean. Take a cloth and a can of WD40 and apply it liberally with the cloth held around the base of the aerial to catch any overspill. Gently (G E N T L Y) pull the aerial out to its full extension and apply more WD40. Wipe it clean, apply more WD40. Repeat until completely clean. Switch the radio off to retract it, and do this several times each time manually extending the aerial and applying WD40 as necessary. If it's not totally buggered it should recover. Once it's clean you really shouldn't have too much of a problem. If it's bent or refuses to self extend I believe a replacement telescoping whip can be got from Ford for about £20.00. Once you've got it working and if it still doesn't give you good reception you will need to check the aerial cable (coax) is properly hooked up. The plug sometimes won't seat properly in the back of the radio. Check the entire length of coax for cuts or signs of abuse. If you can't find any then it's probably the radio. Get it out and take it to a repair shop for a check up.
hope this helps
