JB wrote:

The 1/4 wave ground plane has a useless pattern. Main lobe at about 30
degrees above horizon, but broad enough to be usable and simple to build. . .

J-poles, vertical dipoles have a more useful pattern below horizon. They
provide useful performance without being too large. . .

A quarter wave ground plane (with or without sloping radials), a J-pole,
and a vertical dipole all have virtually identical patterns provided
that the outside of the feedline can be adequately decoupled. In free
space, the maximum is directed to the horizon. In a real installation,
height above ground and reflections from other objects will modify the
elevation pattern, in the same manner for all those antenna types.

The patterns of all these antennas can be affected by current conducted
to or induced on outside of the feedline. Those with EZNEC or other
modeling program might find it interesting to attach a vertical wire to
the "ground" side of the feedpoint and extending downward to represent
the outside of a feedline. An effective current (choke) balun can be
simulated with a 1k ohm resistive load inserted in the wire. You'll find
considerable current can occur on the wire when it has particular
lengths, the lengths depending on whether the bottom end is grounded or
open, and placement of "baluns". When the current on the wire is high,
considerable pattern distortion can result. I've always supposed that
this is the cause of widely differing reports of the effectiveness of a
J-Pole -- some people get luckier than others with feedline length. A
pair of current baluns, one at or near the feedpoint and another about a
quarter wavelength below, are usually enough to suppress the current on
the outside of the feedline to a low enough value to prevent pattern
distortion.

Roy Lewallen, W7EL