On Fri, Jul 15, 2022 at 05:58 AM, <dianebonk2@...> wrote:
Hello everyone,
I am a beginner in using the NanoVNA, I have a calibration problem after
connecting a transmission line into the VNA. You can see some pictures of the
result in the attached document after connecting the cable to the VNA in the
attached file.
Could someone tell me how to correct the impedance shift introduced by the
cable? Thanks
I went to the "electrical delay" menu to correct the problem by adding a delay
but it got worse. I don't know what to do.
I want to solder the cable afterwards into a PCB where we have antenna traces.
The most accurate way is to calibrate at the end of the cable using a short, open and a 50 ohm SMD or very small resistor with absolute minimum leads.
The other way is to use the electrical delay to compensate for the length of the cable With a 33 cm (12 inch) cable I had to set the edelay to 3.18 ns to get the open at the far right of the smith chart. Try 0.1 nanoseconds (100 picoseconds) for each cm of cable and then keep adjusting until you get close to the far right on the Smith chart. The velocity factor of the cable you use will have an effect so the 100 picoseconds is just an estimate to get you in the ballpark.
Roger
Roger Need
