I've observed that reversing just about any Murata 10.7 MHz ceramic filter alters the response and changes the measured distortion in an FM tuner. I believe this means that S11 differs from S22, or S21 differs from S12, or both. Evidently this precludes using a NanoVNA to accurately renormalize from 50 to 330 ohms since it only measures S11 and S21. But if you reverse the filter in the measurement circuit, you can measure S22 and S12. Then if you combine all four measurements, you can use the full renormalization equations for S11, S21, S12, and S22 to get the correct response.
Since the NanoVNA won't do this itself, I've written a little Windows program to do it. You feed it two 50 ohm .s2p files and it generates an .s2p file for whatever renormalization Z you specify. It seems to work. When I get it all documented, I'll post a link.
Brian
