"Sal" wrote in :

...
This thread got me thinking. If three or four tuned radials were
added, would this be a better approach?

A set of radials helps to decouple the feedline, in this case, you would
place them a quarter wave below the bottom of the sleeve.

Ok, you have noted commercial implemenations of this idea... yes it is
done. The quarter wave between the radials and the bottom of the sleeve
carries significant current, ie it affects the pattern and gain.

And still, decoupling is not perfect, though much better.

Whilst the OP's design looks like it is simple, in my experience it is
not. Whilst I have had a lot of success with coaxial dipoles where the
sleeve was three times or more the diameter of the inner element and
substantially air dielectric, I have had little success the the cheap
and nasty approach of applying braid over a vinyl jacket and trying to
adjust it for low common mode feed line impedance and low VSWR. I am not
saying it is impossible, just not as easy as a ground plane!

Owen