Directional Bridge 10MHz - 18GHz The Agilent (now Keysight) 85027C is a Directional Bridge designed to operate with either the 8757 in ac or dc detection modes or with 8755/8756 in ac detection mode. Can detect ac and dc signals (depending on scalar network analyzer used) High directivity Excellent test port match Measurement range: 10 MHz to 18 GHz in coax