Ribbon cables including a plurality of spaced apart substantially parallel conductors extending along a length of the cable and arranged along a width of the cable, and first and second insulative layers disposed on opposite sides of and substantially coextensive with the plurality of conductors along the length and width of the cable are described. Each insulative layer may be adhered to the conductors and may include alternating substantially parallel thicker and thinner portions extending along the length of the cable. The thicker portions of the first and second insulative layers are substantially aligned in one to one correspondence. Each corresponding thicker portion of the first and second insulative layers have at least one conductor in the plurality of conductors disposed therebetween. The thicker portions may have an effective dielectric constant less than 2.