Slot antenna apparatus for the roof of a motor vehicle having a central electrically non-conducting portion comprises a horizontal sheet of electrically conducting material under the central portion of the roof. The sheet includes a looped slot having a total loop length of substantially one wavelength in the commercial FM broadcasting band and dividing the sheet into inner and outer portions. A coaxial feed cable adapted for connection at its lower end to AM-FM radio receiver apparatus is routed up one of the vertical pillers to the roof portion of the body and across the roof portion to the center front of the slot to feed the antenna at its front center relative to the vehicle body. A ground conductor connects the outer portion of the horizontal sheet to a point on the vehicle body comprising a voltage null in the vehicle body standing voltage pattern to provide a DC ground and an RF ground at commercial AM broadcast frequencies. The outer portion of the horizontal sheet overlaps the electrically conducting outer portion of the vehicle roof around substantially its entire periphery to form a capacitive RF ground coupling to the vehicle body at commercial FM broadcast frequencies. A separate feed for AM may be provided at the side of the slot; and the horizontal sheet material may have a sheet conductivity of 1-2 ohms/square for reduced VSWR.