"Wes Stewart" wrote:
I don't know of anyone who is using true circular
polarization (at VHF) even though their antennas are capable of
generating it.
________________

Most FM broadcast stations in the US use some form of dual polarization,
which they think of as "circular" but usually is not due to differing H&V
pattern distortions from the mounting structure supporting their antennas.
Paper 6 at http://rfry.org discusses this in the form of NEC-2 studies.

In some cases, several FM stations all use a common antenna at a master FM
site. An array of "cavity-backed radiators"* used in these cases can
provide a c-pol axial ratio of 2dB or less for all polarization planes.
Antennas of this design are used as master FM antennas in Houston, Dallas
and St Louis, where they radiate approximately eight FM stations of 100kW
ERP each. Sears Tower in Chicago has a number of them installed in a
vertical stack for use by individual FM stations.

*crossed, wideband dipoles in phase quadrature, installed in a circular,
wire mesh cavity about 1/4-wave deep and less than a wavelength in diameter
and arrayed in groups of three or four around a triangular or square
cross-section tower. Several levels (often 8 or 10) are used to provide
elevation gain for the array.

RF