Combining FT240 and FT140 cores And theire AL values

Did you know that an FT140 core fits exactly in an FT240 core?

FT240 - 31 with 2 x5 turns (upper picture left)

FT240 - 43 with 2 x5 turns (upper picture middle)

FT240 - 31 with 2 x5 turns combined with FT140 - 43 (upper picture right)

The AL figure for ferrite cores it is quoted as mH/1000 turns.

Comparison of the common mode rejection

Setup: resistors are 56 Ohms

the setup gives a loss of 4 dB which is calibrated away with the mini VNA

The results: