I have a 2006 Monte Carlo SS and have had the misfortune of accidentally snapping off the wedge shaped antenna mast off its base on the roof of the car. It happened while I was scraping snow and ice off after a storm during this brutal winter. Looking at the attached photo, you'll see what looks like something inside the mast being sheared off from the shorter of the 2 bare metal studs. I found no corresponding pieces of metal falling out of the bottom of the mast. Maybe I missed it. I tried to glue the thing back onto the base, but it came off in the car wash yesterday, and couldn't find it. I saw one on Ebay (link follows)-- ACDelco OE Service 20842596 Cellular Phone Antenna | eBay -- but I'm not sure how to attach it. What I'm wondering is, looking at my photo, is there a piece of the bottom of the mast still inside the base? Also, there seems to be a wedge shaped button of some kind (arrow), but it doesn't press down when I push on it with a screwdriver. Before I waste $20 buying the replacement, does anyone know the answer to my question, and how to install a new mast from ebay, or should I just have the dealer do it? Thanks.

 

After doing some research I have found a solution. I went to a nearby dealer and a mechanic came out to my car and unscrewed the bottom portion of the mast still inside the base in the photo in my original post. It's just plastic, with the mast being a slightly flexible rubber fin that is molded to the base. I simply ordered an AC Delco replacement (from the eBay link above) for $20.
To attach it you simply insert the new mast into the hole facing forward as pictured. Then, you simply tighten the mast like a bolt until it bottoms out. The mast will be facing forward as shown when this happens. If you insert the mast any other way before screwing in, it will not be facing forward when it bottoms out. The metal strip on the bottom of the mast engages a metal tab down inside the base when fully screwed in. That's all there is to it.