Peter O. Brackett wrote:

Hmmmm....

Roy, I don't believe that is a "complete" description of circular
polarization either.

My understanding is that circular polarization is what we call the
polarization of electromagnetic radiation when the electric field vector
E rotates with an angular velocity rather than oscillating back and
forth in a single (linear) direction.

Roy, your description of circular polarization above seems to imply that
the angular velocity of the E vector of a circularly polarized wave is
always "synchronized" with the signal frequency since you stated that it
rotates at one revolution per cycle, or one radian per radian per second.

This of course is the (normal?) situation if the antenna is say a helix
firing along its axis or say crossed dipoles fed with a 90 degree phase
shift, but... to be more complete, we should note that...

Circular polarization does not have to be "synchronous"!

Consider...

What would you call the polarization type of the radiation emitted by
the following radiator?

An ordinary linear dipole fed with RF from a feedline through two slip
rings arranged such that a mechanical drive is able to rotate the dipole
at some arbitrary mechanical angular velocity completely unsynchronized
with the RF carrier.

For example, say it's a 5m dipole driven with 30MHz carrier signal and
mechanically rotated at 1000 revolutions per minute.

Such an arrangement would result in circularly polarized radiation with
the E vector having angular velocity of 1000 revolutions per minute and
a carrier frequency of 30MHz which definitely is not one revolution per
cycle.

Thoughts, comments?

That certainly doesn't fit the classical definition of circular
polarization. Circular and linear polarizations are special cases of
elliptical polarization, which all fields actually have, and which is
universally defined in terms of polarization change over each period.
Whatever you want to call the field your mechanical arrangement is
producing, it's not circular polarization in the sense universally used
in the literature.

Roy Lewallen, W7EL