Buick 2011 Lucerne Owner's Manual page 249

The AM-FM antenna is integrated with the rear window
defogger, located in the rear window. Make sure that the
inside surface of the rear window is not scratched and
that the lines on the glass are not damaged. If the
inside surface is damaged, it could interfere with radio
reception. For proper radio reception, the antenna
connector needs to be properly attached to the post on
the glass.
If a cellular telephone antenna needs to be attached to
the glass, make sure that the grid lines for the AM-FM
antenna are not damaged. There is enough space
between the grid lines to attach a cellular telephone
antenna without interfering with radio reception.
The XM Satellite Radio antenna is located on the roof of
the vehicle. Keep the antenna clear of obstructions for
clear radio reception.
If the vehicle has a sunroof, the performance of the XM
system may be affected if the sunroof is open.
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