Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org> Hi Bart, >Are you sure this isn't henry's instead of mH? The denominator ends in 10^-7 on the web page (is that really mH and your email post is henry's?). Yes, it was in henries. But the formula was wrong as seen in my other posts. Thanks for pointing this out. Dave