Not sure how you measured it, but you do realize that the bslun needs
to be terminated in it's appropriate imepdances (load) for you to
measure it's response over frequency. Without the loads, the capacitive
portion will dominate due to the winding cap and it will peak at a very
low frequency. With terminations, the response will broaden out
(remember? s^2+R/Ls+ 1/LCwhere R/L = wo/Q).