Oristo, I forgot to mention that I use the NanoVna to measure return loss with good dynamic range. First I tested the S21 performance of the NanoVna with an HP 355D and found that I could measure the 10 dB steps nicely down to about 60 dB. Then I attached an HP 8721 directional coupler with the Ch 1 watching the reflected port. With a BNC short across the 8721's test port I did a through cal. I now have a pretty good RL measuring system with the 44 dB directivity that the HP8721 offers. The 50 ohm load from an HP 85032 shows the S21 going into the mud as it should.
