Abstract: There is provided an improved electrical signal transmission cable having at least one signal-carrying center conductor and respective flanking ground conductors. The center conductor is surrounded by a thin layer of polymeric foam insulation. The foam insulated center conductor and the ground conductors are embedded in a solid polymeric insulation. This construction provides for an increased signal propagation velocity as well as for the maintenance of center-to-center distances for the conductors both during the manufacture of and normal use of the cable.