After doing a 2-port cal, only the port 1 extension seems to work. I am using the same length extension coax for both ports. For port 1, I attach the extension coax with an open end and bring the Smith Chart back to infinite ohms and zero J to get the delay time in ps. Clicking on port 2 after I have added the coax extension to it, doesn't seem to do anything. I can put the same value time I get for the port 1 extension in for port 2, but when measureing a S11 load, the Smith Chart value I get is the same no matter what extension time I put in port 2. I am trying to make a shunt VNA measurement on a low resistance <5 ohms.antenna. What should I be doing different? Is my port 2 extension feature bad or should I be doing something else? I have never used the port extension feature before. The only thing I can find in the users manual about the use of port extension is one little thing in section 5. Is there another section that explains it in more detail? I'm also assuming that, since this is a 2-port measurement, port 2 has to have the extension time put in to get the correct measurement.