Directional Bridge 10MHz - 26.5GHz The Agilent (now Keysight) 85027B directional bridge is designed to operate with either the Agilent (now Keysight) 8757 in ac or dc detection modes or with the 8756 or 8755 in ac detection mode. This bridge offers high directivity, excellent test port match, and a measurement range of up to 26.5 GHz in coax