I having fits trying to measure lossy "soft" ferrites against the manufacturers curves. Over the range 1 to 300 MHz, I'm not even getting close, looking at either S11 into a short or S21. I've tried a few home-brew fixtures, and they all yield a Z which is much lower than the published data, so I'm thinking it is my fixturing and calibration that are doing me in.
For those that have been successful:
- Do you perform you OSL cal at the input port to the fixture, or the far side?
- Is your preferred method S11 into a short, S11 into 50 ohms, or S21?
Just to set the level of conversation; I'm quite comfortable driving around a Smith Chart and have been involved in RF for a very long time, so feel free to pick me apart!
Brent DeWitt