I am trying to compare the analytical and experimental results of coupling factor and mutual inductance. I can measure L, Q, Rs, and measure total inductance by connecting the two windings in series and getting the highest value to calculate mutual inductance (M) as indicated here: https://electronics.stackexchange.com/questions/127881/how-to-identify-mutual-inductance. I believe all this is correct but then I input a sinusoidal signal on one side and measure the voltage of the other side and try to calculate, again, mutual inductance and coupling factor: M=V2L1/V1 or M=V2/I1 as suggested here: https://www.daycounter.com/LabBook/Mutual-Inductance.phtml. The results do no match. In my case, the copling factor k is very small so I was expecting some error but not that much. I believe the measurement setup is wrong, e.g. the load on L2 should have and effect, etc. Any thoughts or suggestions?