John, Roger thanks for the suggestions. I think what will eventuate depends largely on the physical set-up, ie weights, speed etc An EM looks good in my mind's eye and I know there's a practical solution, hopefully one that's flexible enough to have a reasonable tuning range Joe --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .