Very good Oristo. Makes sense. I built a tandem coupler prior to getting the vna. Same idea as you outlined. This coupler is very interesting unit as it shows a directivity at HF of nearly 60 dB. Using a signal generator and a portable Oscope it was quite good at capturing mag and phase of the reflection coefficient. Its design is flexible and hence may be a good candidate for a Zo other than 50 ohm.
Alan
