The 11666A Reflectometer Bridge can make reflection measurements covering from 40MHz to 18GHz. Operation of this type of directional device is based on principles of the resistive Wheatstone Bridge extended to microwave frequencies. When three bridge arms are 50 ohms, the voltage across corners of the bridge is directly proportional to the reflection coefficient of the device connected in the fourth arm. Equivalent directivity is 30 dB to 26 dB. Equivalent output SWR is 1.25 to 1.52. Input SWR is 1.92. Maximum input power is +15 dBm. Quality HP Bridge…dependable and easy-to-use. This unit is an accessory of the 8755