"...Some of the earliest antennas in cars were wire loops hidden within the
cloth tops of 1930's sedans, but with the advent of all-steel roofs the
upright mast antenna became the preferred design. About 30 years later,
carmakers tried hiding them again, integrating antennas into windshields or
rear windows by applying wires to the surface or embedding them inside the
glass..."

Interesting article at
http://www.nytimes.com/2005/03/14/au...b43c&ei=5 070