The HP / Agilent 8508A Vector Voltmeter is a fully automatic tuned receiver that makes RF voltage and phase measurements easy. The 8508A narrowband measuring technique gives a dynamic range of over 90 dB and a sensitivity of 10 microvolts to trace even the smallest signal.
The 8508A also measures the phase difference between its two input channels with at least 0.1 degree resolution over a full +180 to -180 degree range, so they can be used for another complete set of measurements - such as electrical length, phase distortion, or impedance.
There are two input modules from which to choose. The 85081B Input module has rf probes and the 85082A Input module has Type N (f) connectors.