Hi, John, Thanks for the new info. Do you know what the impedance should be? I get similar DC resistances from input and output, thus expect impedance is the same each way. 73 de Norman KG4SWM John Kolb wrote: > Just measured 2 open filters and a loose bobbin and got wire > diameters about 0.0062 and 0.0070 ("V and Y case filters), > which would be 34 or 35 gauge enameled wire.