> A dynamic way would be to set up an ac bridge and measure the > inductivity of each coil directly Peter, I estimate the inductance at 10mH per coil http://www.thekeeser.com/Electronics%20info/measure_an_unknown_inductor.htm Using 1k1 and 45n, peaking at 7600Hz Have you a suggestion for a better filter ? -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist