Thanks Jim, all fair comment and noted.

The end application is a four square phased array for the 80m DX window.

The location is at another ham's property, a rural location with ground
ranging from dryish clay to rock.

I do expect noise to be lowish compared to residential precincts.

The excercise is really about a design for a monopole that gives
reasonably good performance if extended to the four square configuration.

Yes, I note your points about the phase sensitivity to components. That
would be a challenge even with buried radials as although we have been in
drought for a long time with 'controlled' low moisture content of the
soil, rain changes that and the soil is no longer as homogenous.

Nothing is as perfect as a modeller's world, but the discussion and some
of the links offered give confidence that a shortened vertical with
capacity hat and three radials, and shunt coil matched should give
similar performance to full quarter wave verticals with 32 buried
radials.

I have just reread Cebik's article on buried radials, and my own models
seem fairly consistent.

As you say, Rudy's work is further confirmation allowing for the
difference in configuration and the |S21| use.

Owen