Hi Marv,
> permeability, it was likely greater than 100. Thus, the core is
> intercepting relatively little of the magnetic field compared to a tight
> winding. Additionally, rod cores with their open magnetic structure are
> very difficult to saturate compared to a toroid or other closed loop form.
Heating is always more of a problem than saturation, because of
the finite Q of soft-iron cores. The usual exception is pulse duty.
Most off the shelf rods have too much loss tangent at HF. They
look like a resistor in series with an inductor.
If you tell me the core material type number (assuming it is a
standard number), I can tell you the Q or ratio of resistance to
reactance. I'd bet it is pretty poor with an off-the-shelf rod at the
high end of HF.
> Since relatively little RF current flows through this coil, if things
> are working correctly, the DC component probably creates more flux.
The "dc" flowing through the core is time-varying at an RF rate. I'm
afraid no matter what the impedance, you are stuck with a certain
number of ampere-turns that are changing at an RF rate.
> A tuned circuit is a much more demanding application... probably
> requiring something in the neighborhood of 100x the power handling
> capability.
It always translates to volt-turns at a certain impedance, or ampere
turns at a certain frequency. Q of a resonant system multiplies the
problem because of increased VAR power.
I would be skeptical of using random ferrite materials in a HV, high
current application at RF. Ferrites do not get rid of heat well.
73, Tom W8JI
w8ji@contesting.com
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