A stripline RF transmission cable has a flat inner conductor surrounded by a dielectric layer that is surrounded by an outer conductor. The outer conductor has a top section and a bottom section which transition to a pair of edge sections that interconnect the top section with the bottom section. The top section, bottom section and the inner conductor may be provided with generally equal widths. An average dielectric constant of the dielectric layer may be lower between the inner conductor edges and the edge sections than between a mid section of the inner conductor and the top and the bottom sections and/or spacing between the inner conductor and the dielectric layer may be reduced proximate a mid section of the inner conductor.