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I mounted a length of B & W coil 2 1/4 ” in diameter and 5 5/16″ long, .085″ in wire diameter, with 32 turns, vertically on an aluminum disc 3′ in diameter that I use as a ground plane for testing small coils. I measured the self-resonant frequency of the coil over the ground plane to be 22.7 Mhz.
The use of the Medhurst data gave a calculated resonant frequency of 21.54 MHz, and NEC-2 gave a resonant frequency of 27.84 MHz.
NEC-2 simulation gave an error of + 22.6 % in resonant frequency, compared to the measured value; and the Medhurst method gave an error of only – 5.11 % compared to the measured value. It looks like The Medhurst method gives a more accurate result than NEC-2. The circumference of a loop of the test coil is appreciably smaller than .05 wavelength for all three of the resonant frequencies used (measured, Medhurst, and NEC-2).