myasar said:How can P*otel?
HMX said:Some time ago I was searching solution for same problem and I found very old program from @gilent called APPCAD. It contains tool for spiral coils design. Surprisingly 3-pole filter with coils designed by this program works better than expected, on first try and no addidtional tunning needed. Try search for this program in forum, I think I seen it somewhere, but it must be old DOS version.