Ulrich G. Kliegis wrote in
:

Will the donut shape suffer from the absorption by the shrouds and
stays, or can that be neglected?

Any metal objects that are a significant portion of a wavelength will re-
radiate all the RF that passes by them, inducing RF current in them. The
Yagi beam antennas use this phenomenon to produce their directional
pattern, as do many other antenna arrays with parasitic elements.

The re-radiated RF from nearby metal objects, such as the sail rigging, has
its own radiation patterns happening at different phases than the radiating
element's output. The vector sum of all these various re-radiated patterns
adds and subtracts from the main antenna's pattern, creating an effective
pattern that looks just awful! There are huge nulls in the donut where the
various patterns cancel each other in certain directions. In other
directions, the combined pattern actually has more signal than the
original. As the boat rotates in azimuth, so does this pattern, making the
signals fade and get stronger as you turn.

Larry
--
While in Mexico, I didn't have to press 1 for Spanish.
While in Iran, I didn't have to press 1 for Farsi, either.
It just isn't fair.