Mark wrote:

thanks for the replies...
so for talking purposes:

Z1 is the antenna feedpoint Z and we will define "antenna" as the
exposed wire after the end of the ferrite tube.

Z2 is the Z of the wire passing though the ferrite

Z3 is the source Z which I will stipulate is 50 Ohms

Ok.

OK as we add ferrite to the antenna, Z1 changes because the antenna is
getting shorter as the ferrite is getting longer. i.e. if there is 7"
of ferrite, then there is only 12" of exposed antenna and it is
elevated over the ground plane so Z1 is going up. In the end case,
when the ferrite is 19" there is no antenna Z1 becomes infinity.

Then looking into the base (thinking as lumped elements), we have Z2 +
Z1. Since Z1 is infinity, the base must look like infinity, but this
does not pass common sense.

Why not? A zero length antenna is an open circuit, which has an infinite
impedance. What would you expect the impedance of a zero length antenna
to be?

In other words, what is the Z looking into a 19" wire that is inside
19" of ferrite. Thinking in lumped element terms, it would be very
high and little power will flow.

That's correct.

Thinking in distributed terms there
will be some relatively low Z looking into the base, power will flow
and the ferrite will dissipate heat.

Can you explain how you reach that conclusion?

The base Z would be related to
some property of the ferrite like the property of free space has a Z
of 377.

The ferrite with wire inside comprises half of a circuit -- I posted
more about this a day or so ago. The only reason current flows into an
open-ended wire like a whip antenna -- that is, the only reason the whip
doesn't have an infinite input impedance -- is that the field created by
the alternating current in the wire couples to some other conductor
which is the other half of the circuit. The field induces a current in
that second conductor which flows into the other terminal. And that
current creates a field which couples into the whip, sustaining current
in it. If you could prevent the field from the wire from coupling to the
ground plane, no further current would flow into the wire and it would
indeed look like an open circuit. The ferrite does essentially just this.

What is that propery and what would a typical Z be?

The ferrite has an intrinsic impedance, as does free space and every
other medium. It's the ratio of E to H fields of a TEM wave in the
material. But what does that have to do with this?

Roy Lewallen, W7EL