SCU-38 Passive GPS Antenna The Standard Horizon SCU-38 external receiver allows your compatible Standard Horizon radios internal GPS receiver to operate even when mounted in an area where the internal GPS cannot receive a signal. Simply connect the SCU-38 and mount the antenna where it has a clear view of the sky. Cable measures 5M long. The SCU-38 is compatible with the following Standard Horizon radios: GX1400G, GX1800G, GX1850G, and GX2400 *Please note that the SCU-38 is a passive antenna and will only work with units already equipped with a built-in GPS receiver.