I agree that a 259B does not make a good general purpose instrument for
measuring inductor values over the HF range. In fact, there are very few
instruments which are. One of the few I know of is the HP 4191A vector
impedance meter, but it's not likely to be found in many amateur
workshops. Making good impedance measurements at HF is often very much
more difficult than most people realize.

The 259B is, I maintain, a very good instrument for identifying core
materials and for use in the design of inductors, transformers, and
other magnetic components. I've used mine many times for the purpose and
gotten the results I expected. That was, I thought, the subject of this
thread, but it appears to have drifted elsewhere.

Roy Lewallen, W7EL

Owen Duffy wrote:

Roy, with respect, you are describing work-arounds for the inability of
the '259B to make useful measurements on inductors over about 200 ohms
reactance.

Sure, the instrument can be used to characterise a core, and that
information extrapolated to design an inductor with higher reactance, but
you cannot measure the larger inductance directly, or discover reliably,
the properties of the larger inductor like self resonance effects, or
loss.

I won't address defensive posts by others who seem to have chosen to
ignore my qualification "When talking about ferrite or powdered iron
cored inductors of reactance over 200 ohms".

An example of the traps: a chap recently confirmed to me that indeed mu
is frequency sensitive as demonstrated by the '259B measurement of the
inductance of an inductor over HF which showed inductance was highly
frequency dependent. The problem was that the inductive reactance was
over 250 ohms at most frequencies of measurement, and the '259B
calculates inductance without warning that the value is unreliable
because of the magnitude of reactance on which the inductance is
calculated. Try measuring a 30uH coil's inductance over 2-30MHz using a
'259B and you will see what I mean.

Owen