Hi Roger,
When I do one full turn on the primary (through the first hole and back down the second) I get the results as shown in the attached images.
This is why I removed part of a turn to see what would happen.
When I measure the inductance of one turn I get 7.38uH which is as close as I can get to my calculated value of 4.5uH (using 4 x 50 ohms for the impedance).
If I have a full turn I get about 12.5uH inductance which is about three times too large when compared to the calculated value.
