If the shaft of a car antenna is broken or damaged but the antenna base is intact, you can attach a replacement shaft rather than installing a complete antenna. Buy a flexible shaft made of a rubber-covered conductor. Using pliers, break off the remains of the old shaft close to the base. File the remaining end of the old shaft to a slight taper and push on the new shaft. Tighten the retaining screws.
Installing a new antenna – If the antenna is broken off at the base, replace the entire assembly. There are many types of replacement antennas, including one that disappears into the fender and can be lifted only with a special key. This type is almost as resistant to damage as a power antenna but it costs far less.
Reach under the dashboard, locate the antenna cable in the radio, and disconnect it. Loosen the antenna nut and work the antenna assembly out of the mounting hole. Cut the cable from the old antenna and tape the plug of the new antenna to the cut cable. To draw the new cable into place, carefully pull the plug end of the old one. You may have to remove a fender shield to reach in and guide the new cable through a body grommet.
Once the wire is in place, push the new antenna mount through the hole on the fender and secure it. Plug the antenna cable into the radio.