Alan Peake wrote:


Roy Lewallen wrote:
One of the advantages of a Yagi is its directivity. When mounted
horizontally, its horizontal pattern is quite directional, but the
pattern in the vertical plane is relatively broad -- the vertical
pattern of a typical HF Yagi in the forward direction, in fact, isn't
much different from a single dipole. If you mount the Yagi vertically,
the two patterns swap so the horizontal pattern ends up very much
broader than when mounted vertically.

Roy, are you talking about high gain yagis? I just looked at the
beamwidths of an 11 element DL6WU Yagi on 2m and got 35 degrees
horizontal and 39 degrees vertical in EZNEC. Not much difference there.
Alan



I think he's talking about lower gain (e.g. a 3 element beam for 20m),
where the 3dB beamwidth might be about 50-60 degrees in the Eplane
(parallel to the elements) and 80 degrees in the H plane (perpendicular
to the elements). The 80 is about the same as the 3dB beamwidth of a
dipole.

For higher gain antennas (e.g. your VHF/UHF), the beamwidths will be
pretty close in E and H planes. (since a larger fraction of the overall
antenna gain comes from "array pattern" gain rather than the individual
"element patterns")


Of course, the polarization sensitivity of the ground reflection makes
the horizontal antenna usually a winner overall.