modify VNA to make Transistor parameter measurements

There are a number of VNA projects on the internet that produce smith charts for various configurations that use a single directional coupler . HP's application note provides a technique for producing transistor S parameters usine a signal generator and a 8405A Vector Voltmeter. The compelexity of the 8405A Vector Voltmeter can be significantly reduced by the use of an open source VNA most designs use a single directional coupler and a second is required to test transistor output impeadance. I am looking at the NanoVNA2 https://github.com/nanovna-v2 or one based on Henrik Forstén project https://hforsten.com/improved-homemade-vna.html there is also a thesis from Josh Johnson using an AD8302 this is limited to 2.7 Ghz and is sufficent for most applications https://github.com/joshajohnson/vna/