Making a gain antenna that doesn't require a tower usually falls into the area of switched vertical arrays, like a 4-square. Some of the problems are the radial field and the phasing/switching system. We started with 20 meters.
The most straightforward approach was to put together a 2-element vertical array. The Bravo series would be excellent, except for the horizontal resonators make it awkward and potentially a safety issue. The key was to eliminate the horizontal components in the elements. After a year's work, the result is the new Evolution Vertical™. In an attempt to describe it in a few words (like in patent), it is a radical-ratio asymmetric vertical dipole. The feed point is also right where you want it - at boom level.
The first rotatable vertical beam was a 20-meter 2-element. After using 2-element arrays for years on beaches with Team Vertical, it felt powerful to have one that could rotate. This was really breaking new ground and when it was rotated for the first time, it was amazing. This 2-element 20 meter is called the EVA-220, for Evolution Vertical™ Array.