On Oct 16, 3:40 pm, Roy Lewallen wrote:
....
Regarding the ferrite absorbing energy from the antenna -- the amount
absorbed will be maximum when the ferrite's impedance is the complex
conjugate of the antenna's. For example, if the vertical is resonant and
grounded with no feed system, you'll get maximum ferrite heating when
the ferrite's impedance is around 36 + j0 ohms. If you add more ferrite,
the amount of power absorbed from a passing wave and delivered to the
ferrite will decrease, approaching zero as the ferrite impedance
increases to a large value.
....

I'm puzzling over this, Roy. It seems like this assumes some source
impedance driving the antenna, but maybe I'm missing something in your
analysis.

My thought-process is to treat the antenna as an impedance Z1, the
ferrite an impedance Z2, and the source an impedance Z3, the three of
them being in series. I suppose thinking of the antenna as a constant
impedance as you change its environment with ferrite might not be
quite right, but to the degree that approximation is correct, then I'd
expect maximum ferrite dissipation (absorption) would occur when its
impedance, Z2 is equal to the complex conjugate of (Z1+Z3). On the
other hand, if I feed the antenna with a constant current source, the
ferrite dissipation increases indefinitely as the resistive component
of its impedance increases.

Am I missing something?

Cheers,
Tom