Original poster: "K. C. Herrick" <kchdlh-at-juno-dot-com> Here are two handy calculators I found. The first, for physical & electrical parameters of a helical coil & the second for calculation of LC resonant frequency. Thank you, deepfriedneon and engplanet... Ken Herrick http://www.deepfriedneon-dot-com/tesla_f_calchelix.html and http://www.engplanet-dot-com/redirect.html?3853.