Oh, well another thing about the 3X harmonics, the back EMF generated
out of phase could mix inside the signal generator (output circuitry - which
is non linear) and thus create harmonics. A better way is guess what the
inductance would be and place a .1uF or .01uF cap in series and measure
with an oscope across the capacitor or inductance. At the resonate
frequency of the LC network, there wil be a spike or peak. Take this
frequency and use the L= 1/(4*pi^2*F^2*C) equation and it will give the
inductance. Then use the torriod or rod equation and find the permeability.
Also, the permeability will change with frequency - so you will end up with
a frequency versus perm curve, and also current effects the perm. There
are a lot of things to take into account and these are only a few.
There really is no "ferrite' resonate frequency but the inductor you are
making will have a resonate frequency. The distributive capacitance
is what creates this SRF.
Hope this helps some.
v/r Ken Carrigan
PS - capacitors also act like inductors after their SRF is reached. The
leads have about 1nH per inch - so you can calculate the typical SRF
for caps.