Buick REGAL 1997 Manual page 193

Backglass Antenna (If Equipped)
Your AM-FM antenna
is
integrated with your rear
window defogger, located in the rear window. Be 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.
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NOTICE:
Do not try to clear frost or other material from
the inside of the rear window with a razor blade
or anything else that is sharp. This may damage
the rear defogger grid and affect your radio's
ability to pick up stations clearly. The repairs
wouldn't be covered by your warranty.
Because this antenna is built into your rear window,
there is a
reduced risk of damage caused by car washes
and vandals.
If you choose to add a cellular telephone to your vehicle,
and the antenna needs to be attached to the glass, be sure
that you do not damage the grid lines for the AM-FM
antenna. There is enough space between the lines to
attach a cellular telephone antenna without interfering
with radio reception.