Jim Kelley wrote:

Hi Richard,

I think what you're seeing is the 3-D interference pattern generated by
your sources. I'm not sure that really tells us very much about the
antennas themselves. You'd need to surround each of the antennas with a
uniform field in order to compare them. By uniform, I mean the field
intensity toward the antenna is the same in any direction.

How about polarization?

Roy Lewallen, W7EL