It's a good idea to wind and measure the inductance of the toriod before installation.? In my experience not all cores are alike especially the five for a dime variety found on Ebay.? Testing of magnetic material is steeped in theory and the art is well practiced.? Check the litergy on test methods.?
I used a multivibrator design by Al Dutcher, EDN April 12, 2007 that formed a charge/ discharge oscilator and ran at a few Mhz which I viewed on a scope and measured on a frequency counter.? The frequency of oscillation related to the inductance.? A general coverage receiver quite loosely coupled to the large signal of the multivibrator might also work if the oscillation is within range of its rx coverage.? I keep an ancient RS DX302 general coverage receiver on the test bench just for that purpose
Buy the cores from Kits and Parts.? You'll get what you want within a few days of your order rather than waiting 6 weeks or more.? ?Howard, n3fel
