Yes. If we are trying to measure the so called TRUE INSERTION loss... |S21|. And the vna has a reasonable dynamic range, then we could build an appropriate MINIMUM LOSS PAD. It would provide a match between 50 ohms and the UNUN transform ratio. Example, say it was a 9:1. Then I would need a 450 ohm to 50 ohm minimum loss pad. That pad has a minimum loss of ~ 16 dB. Higher loss will result in "nicer R values"... So now measure the pad, then measure the pad + UNUN and find the delta. Yes, something so simple has the devil in the details. And it can be more difficult than first realized!
Alan
