Before revision: Impedance For a ribbon cable using 26AWG wire, 0.050" spacing and common PVC insulation the resultant impedance for any two adjacent wires within the cable is 110 to 130 ohms.Digital Systems Engineering, William J. Dally, John W. Poulton, page 52 "2.7.2.2 Ribbon cable" The precise number will vary a few percent due to materials.
After revision: Characteristic impedancecharacteristic For a ribbon cable using 26AWG wire, 0.050" spacing and common PVC insulation the resultant impedance for any two adjacent wires within the cable is 110 to 130 ohms.Digital Systems Engineering, William J. Dally, John W. Poulton, page 52 "2.7.2.2 Ribbon cable" The precise number will vary a few percent due to materials.