Identify your antenna type
Need to fix a bent or broken antenna? That problem goes back as far as car radios and marauding teenagers. The two most common styles are “pillar mounts,” which slide in and out of the top of door pillars, and “fixed masts,” nonretractable ones that are mounted on fenders. (We won't include power antennas here.) Both styles are easy to fix yourself. Start the repair by buying a replacement unit (less than $20) from an auto parts store or antennamastsRus.com.
Repair pillar-mount antennas
New pillar-mount antennas come with the coaxial cables already attached. So after you unscrew and pull out the old unit, cut the old cable and use it to fish the new cable through the pillar to the radio. (Splicing the old cable to the new one isn't recommended; you may get radio interference.) But be careful! If the splice comes apart inside the pillar, you'll have to remove the pillar trim to fish the new cable. Form a hook in the old cable, loop a picture-hanging wire through it and then wrap it with tape for added insurance. You'll have to remove the car radio to hook up the new cable. For about $5, you can buy removal instructions from carstereoremoval.com.
Repair fixed-mast antennas
Fixed-mast antennas are much easier to replace. Buy a universal kit (about $15) from any auto parts store. Just unscrew the bent mast with an adjustable wrench and install the new mast. You may have to install an adapter (included in the kit) to match the thread size.