Most VNAs have a low damage threshold (e.g., +20 dBm). If your amplifier outputs more power than this, place a high-power fixed attenuator on the output side before connecting it to the VNA Port 2.
Testing an RF amplifier with a is the gold standard for characterizing gain, impedance matching, and stability. 1. Essential Setup & Safety Basics of RF Amplifier Test with the Vector Net...
By performing a Power Sweep at a fixed frequency, you find the input power level where the gain drops by 1dB. This defines the limit of the linear range. Most VNAs have a low damage threshold (e