I don't know what you are talking about Jim, are you talking about core
internal resonance? If so, I'm not talking about that.
Not quite.. A strong resistive component is present only around resonance,
and the resonance of a single pass through a #31 or #43 core is in the
range of 150  300 MHz, depending on the dimensions of the core. This is
clearly shown by FairRite data sheets.
The Fairrite data sheets show the reactance of that material and the
resistance crossing at about 3 MHz. This is completely independent of the
number of turns.
For example, a 73 material loss tangent and reactance crosses near the top
of 160 meters. If I take ANY 73 mix core and measure conductor impedance
going through a core window, with external leads calibrated out, R and X
will be equal (Q=1 ) at the high end of 160. This means the core contributes
equal parts reactance and resistance at that frequency, with resistance
progressively increasing in proportion to reactance (Q lowering below 1)
higher up.
43 materials have a Q=1 around mid HF.
If I have a choke that is 100 j100 and worse case series tune the core with
0 j100 from common mode impedance, the result is 100 j0.
I just don't follow what you are saying, because defeating the choke can
only happen if resistance is low.
This is some cores people have used for many years actually DO work, and a
certain mix (and authoritatively dictated impedance) is absolutely not a
requirement. I've worked with this stuff daily for 3040 years, and the
first thing I look at in broadband systems is core Q=1 frequency. This is
where loss and reactance cross. It is also how I sort cores, and verify a
core is labeled correctly. Many of us would be surprised at the number of
cores that get missorted or mislabeled in distribution. I've seen bags of
100's of 73 mix cores, from normal good distribution, that were 61 or 43.
73 Tom
All good topband ops know how to put up a beverage at night.
_________________
Topband Reflector
