Sal M. Onella wrote:
. . .
Could I set up a test jig to figure out the mixes and frequencies? Yes,
maybe. Give me some ideas for the test circuit. I have a 1GHz spec-an &
tracking generator.

To determine if a core is useful, you need some way to measure the
impedance. And unless you're using the cores for high power or high Q
applications, all you really need to know is the magnitude of the
impedance. An "antenna analyzer" is a really simple and portable way to
check flea market beads if you have one -- just put a short loop of wire
between the terminals and run it through the bead's hole. If you're
measuring at low frequency where the impedance might be low, you can use
more than one turn and calculate the one-turn (one pass through the
hole) impedance as the measured value divided by the square of the
number of turns.

If you really need to know the mix, you'll probably need to be able to
measure the R and X components of the impedance as well as the core
dimensions, then refer to catalogs of various vendors to find a match.

Roy Lewallen, W7EL