Have you tried using a screwdriver to remove the piece at all?

 

I'm not sure how. There is no slot or phillips groves to use a screwdriver. I have tried using a pin to try to turn it. It will be easy to go by the Mazda place and ask them; I expect they have seen it before. I'll report back on that as soon as I have some info.

 

Got it fixed at the local Mazda dealer as I couldn't figure out how to get the broken "plug" out. I asked how much it would be.

89 US$ for unscrewing the plugged part and adding the antenna. Forty-five minutes time. Then,

130 US$ to drill out the plug as it will not unscrew. Then,

210 US$ to replace the mast base as it is "cracked." Then,

Two hours labor to drop the headliner in the rear to get to the mast base from the bottom.

I complained. They gave me some relief on the labor so the total cost was 220 US$. Three hours later it is fixed and it works much better on the AM radio.

 

Glad you got it fixed.
To bad you didn't see it before you bought it, the dealer could have had it fixed before delivery.

 

I just snapped off the antenna on my Mazda5. A long antenna like that on top of a tall car is bad design. I tried to unscrew what was left with pliers but could not. I just bought a new base and I was hoping there was a way to replace it without removing the headliner but it looks like I will have to. I might try drilling out the broken plug first. I don't suppose there are directions for how to remove and reinstall the headliner anywhere? Thanks.

 

I figured it out on my own. Photos and directions here: http://cid-a11ab21b76c441bc.skydrive...s&sa=595337876