RF Impedance Test Set The Agilent (now Keysight) 43961A is a RF Impedance Test Kit and provides the capability to measure impedance parameters of 1-port devices with the 4395A option 010 (100 kHz to 500 MHz) or the 4396B option 010 (100 kHz to 1.8 GHz). The test port or the 43961A is a 7-mm connector and can be used with the 16191A,16192A, or 16193A test fixure. The 43961A includes open/short/load calibration standards, and the test fixures such as 16192A are optional.